Molecules

16 pages, 1172 KB

Open AccessEditor’s ChoiceArticle

Mechanochemistry to Form Substituted Imidazoles, Imidazolium Salts and NHC–Gold Complexes with Fluorine-Containing Groups

by Chloé Salis, Sabrina Mohammedi, Lucia Turazza, Yuna Blandin, Maritie Garnier, Catherine Hemmert, Michel Baltas and Heinz Gornitzka

Molecules 2025, 30(3), 522; https://doi.org/10.3390/molecules30030522 - 24 Jan 2025

Cited by 3 | Viewed by 3308

Abstract

Synthesis of organometallic compounds has had an enormous impact on medicine. In this context, gold complexes are gaining much interest since the discovery of the cytotoxic effect of cisplatin. On the other hand, in the last two decades, the mechanochemical synthetic approaches have [...] Read more.

Synthesis of organometallic compounds has had an enormous impact on medicine. In this context, gold complexes are gaining much interest since the discovery of the cytotoxic effect of cisplatin. On the other hand, in the last two decades, the mechanochemical synthetic approaches have been developed considerably demonstrating that they could also be a powerful tool enabling environmentally benign and sustainable synthesis of metal complexes. The present work focuses on mechanochemical synthesis of precursors and gold–NHC complexes of type NHCAuCl and [AubisNHC]⁺. The mechanochemical approach has been studied to afford four substituted imidazoles, eight imidazolium salts and six NHCAuCl and one [AubisNHC]⁺. Substituted imidazoles were obtained with yields varying between 29–99%. Five imidazolium salts bearing aliphatic carbon atoms were obtained, with yields from 46–81%. It is important to notice that the reaction can follow the aging process giving rise to imidazolium salts in very good yields. Concerning the gold(I) complexes, for the first time, six mono NHC complexes of type NHCAuCl have been synthesized, five of them with yields varying between 41–83%. Finally, compound 19 [AubisNHC]⁺ has been obtained not only by transmetallation, but most gratifyingly through direct metalation in 73% yield. Full article

(This article belongs to the Section Organometallic Chemistry)

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15 pages, 3196 KB

Open AccessEditor’s ChoiceArticle

Decoration of Silver Nanoparticles on WS₂-WO₃ Nanosheets: Implications for Surface-Enhanced Resonance Raman Spectroscopy Detection and Material Characteristics

by Khaled Al Youssef, Adrien Chauvin, Jean-François Colomer and Carla Bittencourt

Molecules 2025, 30(3), 530; https://doi.org/10.3390/molecules30030530 - 24 Jan 2025

Cited by 1 | Viewed by 2376

Abstract

This study investigates the chemical and structural modifications of vertically aligned tungsten disulfide–tungsten trioxide (WS₂-WO₃) nanosheets decorated with silver nanoparticles (Ag(NPs)) under nitrogen plasma conditions. The synthesized vertically aligned WS₂-WO₃ nanosheets were functionalized through direct-current (DC) [...] Read more.

This study investigates the chemical and structural modifications of vertically aligned tungsten disulfide–tungsten trioxide (WS₂-WO₃) nanosheets decorated with silver nanoparticles (Ag(NPs)) under nitrogen plasma conditions. The synthesized vertically aligned WS₂-WO₃ nanosheets were functionalized through direct-current (DC) magnetron sputtering, forming silver-decorated samples. Structural changes, as well as the size and distribution of Ag(NPs), were characterized using scanning electron microscopy (SEM). Chemical state analysis was conducted via X-ray photoelectron spectroscopy (XPS), while Raman spectroscopy was employed to investigate vibrational modes. The findings confirmed the successful decoration of Ag(NPs) and identified unexpected compound transformations that were dependent on the duration of functionalization. The synthesized and functionalized samples were evaluated for their sensing capabilities towards Rhodamine B (RhB) through surface-enhanced resonance Raman scattering (SERRS). This study discusses the impact of substrate morphology and the shape and size of nanoparticles on the enhancement of SERRS mechanisms, achieving an enhancement factor (EF) of approximately 1.6 × 10⁶ and a limit of detection (LOD) of 10⁻⁹ M. Full article

(This article belongs to the Special Issue Recent Trends of Functional Nanomaterials for Biomedical and Healthcare Applications (2nd Edition))

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15 pages, 3125 KB

Open AccessEditor’s ChoiceArticle

The Graphene Oxide/Gold Nanoparticles Hybrid Layers for Hydrogen Peroxide Sensing—Effect of the Nanoparticles Shape and Importance of the Graphene Oxide Defects for the Sensitivity

by Krystian Pupel, Kacper Jędrzejewski, Sylwia Zoladek, Marcin Palys and Barbara Palys

Molecules 2025, 30(3), 533; https://doi.org/10.3390/molecules30030533 - 24 Jan 2025

Cited by 12 | Viewed by 3052

Abstract

Graphene oxide (GO) and reduced graphene oxides (RGOs) show intrinsic electrocatalytic activity towards the electrocatalytic reduction of H₂O₂. Combining these materials with gold nanoparticles results in highly sensitive electrodes, with sensitivity in the nanomolar range because the electrocatalytic properties [...] Read more.

Graphene oxide (GO) and reduced graphene oxides (RGOs) show intrinsic electrocatalytic activity towards the electrocatalytic reduction of H₂O₂. Combining these materials with gold nanoparticles results in highly sensitive electrodes, with sensitivity in the nanomolar range because the electrocatalytic properties of GO and nanoparticles are synergistically enhanced. Understanding the factors influencing such synergy is crucial to designing novel catalytically active materials. In this contribution, we study gold nanostructures having shapes of nanospheres (AuNSs), nanourchins (AuNUs), and nanobowls (AuNBs) combined with GO or electrochemically reduced graphene oxide (ERGO). We investigate the amperometric responses of the hybrid layers to H₂O₂. The AuNUs show the highest sensitivity compared to AuNBs and AuNSs. All materials are characterized by electron microscopy and Raman spectroscopy. Raman spectra are deconvoluted by fitting them with five components in the 1000–1800 cm⁻¹ range (D*, D, D”, G, and D′). The interaction between nanoparticles and GO is visualized by the relative intensities of Raman bands (ID/IG) and other parameters in the Raman spectra, like various D”, D* band positions and intensities. The ID/IG parameter is linearly correlated with the sensitivity (R² = 0.97), suggesting that defects in the graphene structure are significant factors influencing the electrocatalytic H₂O₂ reduction. Full article

(This article belongs to the Special Issue Advances in Electrochemical Nanocomposites)

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31 pages, 5936 KB

Open AccessEditor’s ChoiceReview

Comparative Phytochemistry of Polyacetylenes of the Genus Artemisia (Asteraceae): Compounds with High Biological Activities and Chemotaxonomic Significance

by Harald Greger

Molecules 2025, 30(3), 537; https://doi.org/10.3390/molecules30030537 - 24 Jan 2025

Cited by 7 | Viewed by 5269

Abstract

In spite of the many chemical reports on polyacetylenes of the genus Artemisia, combined conclusions regarding their distribution and biological functions are widely missing. The aim of the present review was to arrange the diversity of polyacetylenes in the genus following biogenetic [...] Read more.

In spite of the many chemical reports on polyacetylenes of the genus Artemisia, combined conclusions regarding their distribution and biological functions are widely missing. The aim of the present review was to arrange the diversity of polyacetylenes in the genus following biogenetic aspects and group them together into characteristic structural types. The co-occurrence of the dehydrofalcarinol type with the aromatic capillen-isocoumarin type represents a characteristic biogenetic trend, clearly segregating species of the subgenus Dracunculus from those of the subgenera Artemisia and Absinthium, distinguished by the spiroketal enol ether and/or linear triyne type. Various accumulation trends toward specific structures additionally contribute to a more natural species grouping within the subgenera. Biological activities were reported for all four structural types, ranging from antifungal, insecticidal, nematicidal, and cytotoxic properties to allelopathic effects. Of particular interest were their remarkable cytotoxic potencies, from which the very high values of dehydrofalcarin-3,8-diol may be associated with the pronounced affinity of this type to form extremely stable bonds to proteins acting in signaling pathways. The aromatic acetylene capillin inhibited the viability of various tumor cells in a dose- and time-dependent manner. Its potent apoptosis-inducing activity was induced via the mitochondrial pathway. A group of spiroketal enol ethers was identified as inhibitors of PMA-induced superoxide generation. Among them, the epoxide of the isovalerate ester exhibited the highest potency. The ecological impact of acetylene formation was made apparent by the allelopathic effects of DME of the linear triyne type, and the aromatic capillen by inhibiting seed germination and growth of widespread weeds. Full article

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12 pages, 2231 KB

Open AccessEditor’s ChoiceArticle

An In-Plane Heterostructure Ni₃N/MoSe₂ Loaded on Nitrogen-Doped Reduced Graphene Oxide Enhances the Catalyst Performance for Hydrogen Oxidation Reaction

by Abrar Qadir, Peng-Peng Guo, Yong-Zhi Su, Kun-Zu Yang, Xin Liu, Ping-Jie Wei and Jin-Gang Liu

Molecules 2025, 30(3), 488; https://doi.org/10.3390/molecules30030488 - 22 Jan 2025

Viewed by 2271

Abstract

Non-noble metal electrocatalysts for the hydrogen oxidation reaction (HOR) that are both highly active and low-cost are essential for the widespread use of fuel cells. Herein, a simple two-step method for creating an in-plane heterostructure of Ni₃N/MoSe₂ loaded on N-doped [...] Read more.

Non-noble metal electrocatalysts for the hydrogen oxidation reaction (HOR) that are both highly active and low-cost are essential for the widespread use of fuel cells. Herein, a simple two-step method for creating an in-plane heterostructure of Ni₃N/MoSe₂ loaded on N-doped reduced graphene oxide (Ni₃N/MoSe₂@N-rGO) as an effective electrocatalyst for the HOR is described. The process involves hydrothermal treatment of the Ni and Mo precursors with N-doped reduced graphene oxide, followed by the annealing with urea. The Ni₃N/MoSe₂@N-rGO catalyst exhibits high activities for the HOR, with current densities of 2.15 and 3.06 mA cm⁻² at 0.5 V vs. the reversible hydrogen electrode (RHE) in H₂-saturated 0.1 M KOH and 0.1 M HClO₄ electrolytes, respectively, which is comparable to a commercial 20% Pt/C catalyst under similar experimental conditions. Furthermore, the catalyst demonstrates excellent durability, maintaining its performance during accelerated degradation tests for 5000 cycles. This work offers a practical framework for the designing and preparing of non-precious metal electrocatalysts for the HOR in fuel cells. Full article

(This article belongs to the Special Issue Exclusive Contributions by the Editorial Board Members (EBMs) of the Inorganic Chemistry Section of Molecules 2024)

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12 pages, 1252 KB

Open AccessEditor’s ChoiceArticle

The Influence of pH on Long-Range Electron Transfer and Proton-Coupled Electron Transfer in Ruthenium-Modified Azurin

by Nikta Ghazi and Jeffrey J. Warren

Molecules 2025, 30(3), 472; https://doi.org/10.3390/molecules30030472 - 22 Jan 2025

Cited by 2 | Viewed by 2938

Abstract

Long-range electron transfer (ET) is an essential component of all biological systems. Reactions of metalloproteins are important in this context. Recent work on protein “charge ladders” has revealed how the redox state of embedded metal ions can influence the ionization of amino acid [...] Read more.

Long-range electron transfer (ET) is an essential component of all biological systems. Reactions of metalloproteins are important in this context. Recent work on protein “charge ladders” has revealed how the redox state of embedded metal ions can influence the ionization of amino acid residues at protein surface sites. Inspired by these observations, we carried out a variable pH investigation of intramolecular ET reactions in a ruthenium-modified protein system built on azurin from Pseudomonas aeruginosa. We also generate a Pourbaix diagram that describes the variable pH redox behavior of a Ru model complex, Ru(2,2′-bipyridyl)₂(imidazole)₂(PF₆)₂. The intramolecular ET rate constants for the oxidation of azurin-Cu⁺ by flash-quench-generated Ru³⁺ oxidants do not follow the predictions of the semi-classical ET rate expression with fixed values of reorganization energy (λ) and electronic coupling (H_DA). Based on the pH dependence of the Ru^3+/2+ redox couple, we propose a model where pure ET is operative at acidic pH values (≤ 7) and the mechanism changes to proton-coupled electron transfer at pH ≥ 7.5. The implications of this mechanistic proposal are discussed in the context of biological redox reactions and with respect to other examples of intramolecular ET reactions in the literature. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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17 pages, 1664 KB

Open AccessEditor’s ChoiceArticle

Binary Combinations of Essential Oils: Antibacterial Activity Against Staphylococcus aureus, and Antioxidant and Anti-Inflammatory Properties

by Clara Naccari, Giovanna Ginestra, Nicola Micale, Ernesto Palma, Benedetta Galletta, Rosaria Costa, Rossella Vadalà, Antonia Nostro and Mariateresa Cristani

Molecules 2025, 30(3), 438; https://doi.org/10.3390/molecules30030438 - 21 Jan 2025

Cited by 6 | Viewed by 3217

Abstract

Background: The lack of new antimicrobial drugs and increased antimicrobial resistance has focused attention on the employment of essential oils (EOs) in human and veterinary medicine. The aim of this study was to test new binary associations between known and uncommon EOs. [...] Read more.

Background: The lack of new antimicrobial drugs and increased antimicrobial resistance has focused attention on the employment of essential oils (EOs) in human and veterinary medicine. The aim of this study was to test new binary associations between known and uncommon EOs. Methods: EOs from Origanum vulgare L., Juniperus communis L., Cistus ladaniferus L., Citrus aurantium L. var. amara were tested individually and in binary combinations to study, as follows: antibacterial activity against Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) and Escherichia coli; antioxidant capacity via redox-based assays (DPPH, ABTS and FRAP); and anti-inflammatory activity via the bovine serum albumin denaturation inhibition assay. Results: O. vulgare L. showed good antibacterial activity against all strains (MIC = 0.03–0.12%, v/v), followed by C. ladaniferus L., and also had the best antioxidant and anti-inflammatory activities. Synergistic and additive effects were observed for the EO combinations O. vulgare L./C. ladaniferus L. and O. vulgare L./J. communis L. against S. aureus and MRSA, respectively. A reduction in biofilm was noted. Antioxidant and anti-inflammatory activities were also detected. Conclusions: The results suggest that EO combinations may be a promising strategy in veterinary settings for the treatment of infectious diseases caused by S. aureus, including drug-resistant and biofilm-forming strains accompanied by oxidative stress and inflammation. Full article

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19 pages, 3078 KB

Open AccessEditor’s ChoiceArticle

An Efficient Synthesis of 3,5-Bis-Aminated Pyrazolo[1,5-a]Pyrimidines: Microwave-Assisted Copper Catalyzed C-3 Amination of 5-Amino-3-Bromo-Substituted Precursors

by Terungwa H. Iorkula, Bryce A. Tolman, Latifat O. Ganiyu and Matt A. Peterson

Molecules 2025, 30(3), 458; https://doi.org/10.3390/molecules30030458 - 21 Jan 2025

Cited by 3 | Viewed by 3310

Abstract

An efficient method has been developed for the rapid production of diverse arrays of 3,5-bis-aminated pyrazolo[1,5-a]pyrimidines. The method utilizes CuI (5 mol%) and carbazole-based ligand L-1 (N-(9H-carbazol-9-yl)-1H-pyrrole-2-carboxamide) (10 mol%) for efficient Ullmann-type coupling of various amines to 5-amino-3-bromopyrazolo[1,5-a]pyrimidine precursors [...] Read more.

An efficient method has been developed for the rapid production of diverse arrays of 3,5-bis-aminated pyrazolo[1,5-a]pyrimidines. The method utilizes CuI (5 mol%) and carbazole-based ligand L-1 (N-(9H-carbazol-9-yl)-1H-pyrrole-2-carboxamide) (10 mol%) for efficient Ullmann-type coupling of various amines to 5-amino-3-bromopyrazolo[1,5-a]pyrimidine precursors after heating in diethylene glycol (DEG) for only 1 h at 80 °C (microwave heating). 3,5-Bis-aminated products were obtained in good to excellent yields (60–93%, 83% average for 29 examples). 1° and 2° alkylamines, as well as a variety of aryl- or heteroarylamines coupled efficiently, and 1° and 2° alkyl (or aryl) amines at C-5 were well tolerated. The optimized conditions worked well on both the 50 mg and 1.0 g scales and gave products in only two steps from commercially available 3-bromo-5-chloropyrazolo[1,5-a]pyrimidine. Advantages provided by this method include short reaction time, excellent yields, broad substrate scope, and avoidance of toxic reagents commonly utilized for reductive aminations of C-3 NH₂ substituted precursors. Full article

(This article belongs to the Special Issue Advances in the Synthesis of Heterocyclic Compounds and Their Applications)

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15 pages, 2047 KB

Open AccessEditor’s ChoiceArticle

Colorimetric Detection of Dopamine Based on Peroxidase-like Activity of β-CD Functionalized AuNPs

by Sara Anderson, Hamish Shepherd, Kiran Boggavarapu and Janak Paudyal

Molecules 2025, 30(2), 423; https://doi.org/10.3390/molecules30020423 - 20 Jan 2025

Cited by 7 | Viewed by 4176

Abstract

Catalytically active nanomaterials, or nanozymes, have gained significant attention as alternatives to natural enzymes due to their low cost, ease of preparation, and enhanced stability. Because of easy preparation, excellent biocompatibility, and unique optoelectronic properties, gold nanoparticles (AuNPs) have attracted increasing attention in [...] Read more.

Catalytically active nanomaterials, or nanozymes, have gained significant attention as alternatives to natural enzymes due to their low cost, ease of preparation, and enhanced stability. Because of easy preparation, excellent biocompatibility, and unique optoelectronic properties, gold nanoparticles (AuNPs) have attracted increasing attention in many fields, including nanozymes. In this work, we demonstrated the applicability of beta-cyclodextrin functionalized gold nanoparticles (β-CD-AuNPs) as enzyme mimics for different substances, including TMB and DA. We found that β-CD-AuNPs can catalyze the H₂O₂-mediated oxidation of DA. The dopamine signal-off sensor was developed by taking advantage of the peroxidase-like activity of β-CD-AuNPs towards TMB and DA, where both 3,3′,5,5′-tetramethylbenzidine (TMB) and dopamine (DA) may compete for the binding sites with β-CD-AuNPs. As a result, the presence of dopamine can be detected even through the naked eye (up to the concentration of 3.75 µM) and using a spectrophotometer (up to the concentration of 1.0 µM) by monitoring the disappearance of the blue color of the oxidized form of TMB in the presence of dopamine. Furthermore, no obvious disappearance of color was observed at lower concentrations of interferences including ascorbic and uric acid. Given the versatility of cyclodextrin to host large numbers of analyte molecules, we envision that a similar principle can be applied for the detection of other analyte molecules of biological, medical, and environmental significance. Full article

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12 pages, 3229 KB

Open AccessEditor’s ChoiceArticle

Anion-Directed Assembly of a Bimetallic Pd/Ag Nanocluster: Synthesis, Characterization, and HER Activity

by Yu-Rong Ni, Rugma Thekke Pangal, Michael N. Pillay, Tzu-Hao Chiu, Samia Kahlal, Jean-Yves Saillard and C. W. Liu

Molecules 2025, 30(2), 404; https://doi.org/10.3390/molecules30020404 - 18 Jan 2025

Cited by 6 | Viewed by 2235

Abstract

Palladium-doped silver nanoclusters (NCs) have been highlighted for their unique physicochemical properties and potential applications in catalysis, optics, and electronics. Anion-directed synthesis offers a powerful route to control the morphology and properties of these NCs. Herein, we report a novel Pd-doped Ag NC, [...] Read more.

Palladium-doped silver nanoclusters (NCs) have been highlighted for their unique physicochemical properties and potential applications in catalysis, optics, and electronics. Anion-directed synthesis offers a powerful route to control the morphology and properties of these NCs. Herein, we report a novel Pd-doped Ag NC, [Pd(H)Ag₁₃(S){S₂P(OⁱPr)₂}₁₀] (PdHAg₁₃S), synthesized through the inclusion of sulfide and hydride anions. This NC features a unique linear S-Pd-H axis enclosed in a 4-5-4 stacked arrangement of silver atoms. The distinctive hydride environment was characterized by NMR spectroscopy, and the total structure was determined by single-crystal X-ray diffraction (SCXRD) and supported by computational studies. Mass spectrometry and X-ray photoelectron spectroscopy (XPS) further confirmed the assigned composition. This unique construct exhibits promising hydrogen evolution reaction (HER) activity. Our findings highlight the potential of anion-directed synthesis for creating novel bimetallic NCs with tailored structures and catalytic properties. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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23 pages, 1277 KB

Open AccessEditor’s ChoiceReview

The Role of Ionic Liquids in Textile Processes: A Comprehensive Review

by Anastasia Anceschi, Claudia Riccardi and Alessia Patrucco

Molecules 2025, 30(2), 353; https://doi.org/10.3390/molecules30020353 - 16 Jan 2025

Cited by 19 | Viewed by 5836

Abstract

Thanks to their unique physicochemical properties, ionic liquids (ILs) have moved from niche academic interest to critical components in various industrial applications. The textile industry, facing significant environmental and economic pressures, has begun to explore ILs as sustainable alternatives to traditional solvents and [...] Read more.

Thanks to their unique physicochemical properties, ionic liquids (ILs) have moved from niche academic interest to critical components in various industrial applications. The textile industry, facing significant environmental and economic pressures, has begun to explore ILs as sustainable alternatives to traditional solvents and chemicals. This review summarizes research on the use of ILs in various textile processes, including dyeing, finishing, and fiber recycling, where their high thermal stability, tunable solubility, and low volatility are exploited to reduce resource consumption and environmental impact. The discussion also extends to the integration of ILs in textile waste recycling, highlighting innovative approaches to fiber dissolution and regeneration aimed at circular economy goals. Despite these advances, challenges such as high production costs and scalability remain barriers to the widespread adoption of ILs in the textile sector. Addressing these barriers through continued research and development is essential to fully realize the potential of ILs for sustainable transformation in textiles. Full article

(This article belongs to the Special Issue Advances of Ionic Liquids in Organic, Polymer and Material Chemistry: Key Trends in Green Chemistry)

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14 pages, 4018 KB

Open AccessEditor’s ChoiceArticle

Synthesis and Biological Evaluation of New cis-Restricted Triazole Analogues of Combretastatin A-4

by Lidia Prieto, Daniel Gaviña, Marcos Escolano, María Cánovas-Belchí, María Sánchez-Roselló, Carlos del Pozo, Eva Falomir and Santiago Díaz-Oltra

Molecules 2025, 30(2), 317; https://doi.org/10.3390/molecules30020317 - 15 Jan 2025

Cited by 5 | Viewed by 2831

Abstract

The natural products combretastatins A-1 and A-4 are potent antimitotic and vascular-disrupting agents through their binding at the colchicine site in tubulin. However, these compounds suffer from a low water solubility and a tendency to isomerize to the inactive trans stilbenes. In this [...] Read more.

The natural products combretastatins A-1 and A-4 are potent antimitotic and vascular-disrupting agents through their binding at the colchicine site in tubulin. However, these compounds suffer from a low water solubility and a tendency to isomerize to the inactive trans stilbenes. In this study, we have prepared a series of 18 cis-restricted triazole analogues of combretastatin A-4 (CA-4), maintaining, in all cases, the 3,4,5-trimethoxy phenyl ring A, with the aim of investigating the substitution pattern on the B-ring in a systematic way. To this end, cytotoxic activities of the cis-restricted analogues of CA-4 prepared were determined in two tumor cell lines, namely, HT-29 and A-549, as well as in the non-tumor cell line HEK-293, to pre-evaluate the selectivity profile of the compounds for the tumor cell lines. The main conclusion was the essential presence of methoxyl or ethoxyl groups at the para position of the B-ring in order to obtain good antitumor activities. Thus, the more active compounds in our study displayed IC₅₀ values in the nanomolar range for the tumor cell lines but not for the normal cells. Consequently, these triazole analogues of CA-4 could serve as promising alternatives to the natural product, although further studies about their biological activity are essential in order to fully determine their viability as therapeutic agents in the treatment of cancer. Full article

(This article belongs to the Special Issue Design, Synthesis and Evaluation of Small Molecule Drugs)

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24 pages, 9140 KB

Open AccessEditor’s ChoiceArticle

Design, Synthesis, and Antioxidant and Anti-Tyrosinase Activities of (Z)-5-Benzylidene-2-(naphthalen-1-ylamino)thiazol-4(5H)-one Analogs: In Vitro and In Vivo Insights

by Hee Jin Jung, Hye Jin Kim, Hyeon Seo Park, Hye Soo Park, Jeongin Ko, Dahye Yoon, Yujin Park, Pusoon Chun, Hae Young Chung and Hyung Ryong Moon

Molecules 2025, 30(2), 289; https://doi.org/10.3390/molecules30020289 - 13 Jan 2025

Cited by 6 | Viewed by 3158

Abstract

Fifteen compounds (1–15) constructed on a hybrid structure combining a β-phenyl-α,β-unsaturated carbonyl template and a 2-aminothiazol-4(5H)-one scaffold were designed and synthesized as potential novel anti-tyrosinase substances. Two compounds (10 and 15) showed more potent inhibition [...] Read more.

Fifteen compounds (1–15) constructed on a hybrid structure combining a β-phenyl-α,β-unsaturated carbonyl template and a 2-aminothiazol-4(5H)-one scaffold were designed and synthesized as potential novel anti-tyrosinase substances. Two compounds (10 and 15) showed more potent inhibition against mushroom tyrosinase than kojic acid, and the inhibitory activity of 10 (IC₅₀ value: 1.60 μM) was 11 times stronger than that of kojic acid. Lineweaver–Burk plots indicated that these two compounds were competitive inhibitors that bound to the mushroom tyrosinase active site, which was supported by in silico experiments. Compound 10 was an anti-tyrosinase and anti-melanogenic substance in B16F10 cells and was more potent than kojic acid, without cytotoxicity. Compound 15 exhibited the most potent effect on zebrafish larval depigmentation and showed a depigmentation effect comparable to kojic acid, even at a concentration 200 times lower. Compounds 8 and 10 exhibited strong antioxidant capacities, scavenging 2,2-diphenyl-1-picrylhydrazyl, (2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid)⁺ radicals, and reactive oxygen species. Hybrid compounds 10 and 15 are potential therapeutic agents for skin hyperpigmentation disorders. Full article

(This article belongs to the Special Issue Enzyme Inhibitors: Design, Synthesis and Biological Evaluation, 2nd Edition)

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42 pages, 10298 KB

Open AccessEditor’s ChoiceReview

The Current State-of-the-Art of the Processes Involved in the Chemical Recycling of Textile Waste

by Urbain Nshokano Ndagano, Laura Cahill, Ciara Smullen, Jennifer Gaughran and Susan M. Kelleher

Molecules 2025, 30(2), 299; https://doi.org/10.3390/molecules30020299 - 13 Jan 2025

Cited by 37 | Viewed by 15960

Abstract

The textile industry’s rapid growth and reliance on synthetic fibres have generated significant environmental pollution, highlighting the urgent need for sustainable waste management practices. Chemical recycling offers a promising pathway to reduce textile waste by converting used fibres into valuable raw materials, yet [...] Read more.

The textile industry’s rapid growth and reliance on synthetic fibres have generated significant environmental pollution, highlighting the urgent need for sustainable waste management practices. Chemical recycling offers a promising pathway to reduce textile waste by converting used fibres into valuable raw materials, yet technical challenges remain due to the complex compositions of textile waste, such as dyes, additives, and blended fabrics. Full article

(This article belongs to the Special Issue Featured Reviews in Organic Chemistry 2024)

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31 pages, 13503 KB

Open AccessEditor’s ChoiceReview

Iron-Catalyzed Cross-Dehydrogenative Coupling

by Haiyan Diao, Yujia Chen and Feng Liu

Molecules 2025, 30(2), 250; https://doi.org/10.3390/molecules30020250 - 10 Jan 2025

Cited by 7 | Viewed by 4405

Abstract

This review highlights significant advances in iron-catalyzed cross-dehydrogenative coupling (CDC), a method pivotal for forming carbon-carbon (C-C) bonds directly from C-H bonds. This technique uses iron—a naturally abundant, inexpensive, and environmentally benign transition metal—as a catalyst to facilitate the coupling of two unfunctionalized [...] Read more.

This review highlights significant advances in iron-catalyzed cross-dehydrogenative coupling (CDC), a method pivotal for forming carbon-carbon (C-C) bonds directly from C-H bonds. This technique uses iron—a naturally abundant, inexpensive, and environmentally benign transition metal—as a catalyst to facilitate the coupling of two unfunctionalized C-H bonds. This method stands out for avoiding pre-functionalized substrates, reducing both waste and cost in organic synthesis. The discussion includes a variety of CDC methodologies involving combinations of C(sp³)-H with C(sp³)-H, C(sp³)-H with C(sp²)-H, and C(sp³)-H with C(sp)-H bonds. These methods have been successfully applied in synthesizing complex molecules and pharmaceuticals, highlighting the versatility and efficiency of iron catalysis. Full article

(This article belongs to the Special Issue Featured Reviews in Organic Chemistry 2024)

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24 pages, 2864 KB

Open AccessEditor’s ChoiceArticle

o-Halogenation and -Alkoxylation of Phenylglycine Derivatives by Pd-Mediated C-H Functionalization: Scope and Limitations

by Eduardo Laga, Sonia Nieto, Carlos Cativiela and Esteban P. Urriolabeitia

Molecules 2025, 30(2), 236; https://doi.org/10.3390/molecules30020236 - 9 Jan 2025

Viewed by 2177

Abstract

Orthopalladated derivatives from substituted phenylglycines [Pd(μ-Cl)(C₆H₃R₁C(R₂)(R₃)N(R₄)₂]₂ (1) react with halogenating reagents (PhICl₂, Br₂, I₂) (2) to give the [...] Read more.

Orthopalladated derivatives from substituted phenylglycines [Pd(μ-Cl)(C₆H₃R₁C(R₂)(R₃)N(R₄)₂]₂ (1) react with halogenating reagents (PhICl₂, Br₂, I₂) (2) to give the corresponding o-halogenated amino acids C₆H₃(X)R₁C(R₂)(R₃)N(R₄)₂ (3). The reaction is general and tolerates a variety of functional groups (R₁ to R₄) at the aryl ring, the Cα, and the N atom. On the other hand, the reaction of [Pd(μ-Cl)(C₆H₃R₁C(R₂)(R₃)N(R₄)₂]₂ (1) with PhI(OAc)₂ in the presence of a variety of alcohols R₅OH (4) gives the o-alkoxylated phenylglycines C₆H₃(OR₅)R₁C(R₂)(R₃)N(R₄)₂ (5), also as a general process. A partial loss of the enantiomeric excess is observed when the starting phenylglycine is enantiomerically pure, this arising from the formation of bridging azavinylidene (6) and imine intermediate species (7), which were characterized by X-ray diffraction methods. Full article

(This article belongs to the Special Issue Featured Papers in Organometallic Chemistry—2nd Edition)

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20 pages, 4509 KB

Open AccessEditor’s ChoiceArticle

Comparison of In Situ and Postsynthetic Formation of MOF-Carbon Composites as Electrocatalysts for the Alkaline Oxygen Evolution Reaction (OER)

by Linda Sondermann, Laura Maria Voggenauer, Annette Vollrath, Till Strothmann and Christoph Janiak

Molecules 2025, 30(2), 208; https://doi.org/10.3390/molecules30020208 - 7 Jan 2025

Cited by 11 | Viewed by 4212

Abstract

Mixed-metal nickel-iron, Ni_xFe materials draw attention as affordable earth-abundant electrocatalysts for the oxygen evolution reaction (OER). Here, nickel and mixed-metal nickel-iron metal–organic framework (MOF) composites with the carbon materials ketjenblack (KB) or carbon nanotubes (CNT) were synthesized in situ in a [...] Read more.

Mixed-metal nickel-iron, Ni_xFe materials draw attention as affordable earth-abundant electrocatalysts for the oxygen evolution reaction (OER). Here, nickel and mixed-metal nickel-iron metal–organic framework (MOF) composites with the carbon materials ketjenblack (KB) or carbon nanotubes (CNT) were synthesized in situ in a one-pot solvothermal reaction. As a direct comparison to these in situ synthesized composites, the neat MOFs were postsynthetically mixed by grinding with KB or CNT, to generate physical mixture composites. The in situ and postsynthetic MOF/carbon samples were comparatively tested as (pre-)catalysts for the OER, and most of them outperformed the RuO₂ benchmark. Depending on the carbon material and metal ratio, the in situ or postsynthetic composites performed better, showing that the method to generate the composite can influence the OER activity. The best material Ni₅Fe-CNT was synthesized in situ and achieved an overpotential (η) of 301 mV (RuO₂ η = 354 mV), a Tafel slope (b) of 58 mV/dec (RuO₂ b = 91 mV/dec), a charge transfer resistance (R_ct) of 7 Ω (RuO₂ R_ct = 39 Ω), and a faradaic efficiency (FE) of 95% (RuO₂ FE = 91%). Structural changes in the materials could be seen through a stability test in the alkaline electrolyte, and chronopotentiometry over 12 h showed that the derived electrocatalysts and RuO₂ have good stability. Full article

(This article belongs to the Section Inorganic Chemistry)

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12 pages, 3914 KB

Open AccessEditor’s ChoiceArticle

Synthesis of Branched Cyclo-Olefin Copolymers Using Neutral α-Sulfonate-β-Diimine Nickel Catalyst

by Donghui Li, Lixia Pei, Wenbo Du, Xieyi Xiao, Heng Gao, Handou Zheng and Haiyang Gao

Molecules 2025, 30(1), 157; https://doi.org/10.3390/molecules30010157 - 3 Jan 2025

Cited by 6 | Viewed by 2156

Abstract

The homopolymerization of norbornene and the copolymerization of norbornene and ethylene were carried out using the neutral α-sulfonate-β-diimine nickel catalyst SD-Ni. The neutral α-sulfonate-β-diimine catalyst is highly active in the homopolymerization of norbornene, producing vinyl-addition polynorbornene [...] Read more.

The homopolymerization of norbornene and the copolymerization of norbornene and ethylene were carried out using the neutral α-sulfonate-β-diimine nickel catalyst SD-Ni. The neutral α-sulfonate-β-diimine catalyst is highly active in the homopolymerization of norbornene, producing vinyl-addition polynorbornene (PNB) with a high molecular weight. The copolymerization of norbornene (NB) and ethylene (E) using the catalyst SD-Ni was also investigated. The α-sulfonate-β-diimine catalyst SD-Ni shows distinctive catalytic copolymerization properties to produce high-molecular-weight E-NB copolymers with low norbornene incorporation. Importantly, microstructure analyses confirm that the resultant E-NB copolymers are branched cyclo-olefin copolymers (COCs) with branched polyethylene units. Full article

(This article belongs to the Special Issue Organometallic Compounds: Design, Synthesis and Application)

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42 pages, 16381 KB

Open AccessEditor’s ChoiceReview

Synthetic Approaches Toward Phosphorus-Containing BODIPY and Squaraine Dyes: Enhancing Versatility of Small-Molecule Fluorophores

by Jeanne M. Favret and Sergei V. Dzyuba

Molecules 2025, 30(1), 116; https://doi.org/10.3390/molecules30010116 - 31 Dec 2024

Cited by 4 | Viewed by 4787

Abstract

Phosphorus-containing fluorophores provide a versatile framework for tailoring photophysical properties, enabling the design of advanced fluorogenic materials for various applications. Boron dipyrromethene (BODIPY) and squaraine dyes are of interest due to their multifaceted modularity and synthetic accessibility. Incorporating phosphorus-based functional groups into BODIPY [...] Read more.

Phosphorus-containing fluorophores provide a versatile framework for tailoring photophysical properties, enabling the design of advanced fluorogenic materials for various applications. Boron dipyrromethene (BODIPY) and squaraine dyes are of interest due to their multifaceted modularity and synthetic accessibility. Incorporating phosphorus-based functional groups into BODIPY or squaraine scaffolds has been achieved through a plethora of synthetic methods, including post-dye assembly functionalization. These modifications often influence key spectroscopic properties and molecular functionality by expanding their utility in bioimaging, sensing, photosensitization, and theranostic applications. By leveraging the tunable nature of phosphorus-containing moieties, these dyes hold immense promise for addressing current challenges in spectroscopy, imaging, and material designs while unlocking new opportunities for advanced functional systems in chemistry, biology, and medicine. Full article

(This article belongs to the Special Issue Recent Progress in Organophosphorus Chemistry)

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17 pages, 1816 KB

Open AccessEditor’s ChoiceArticle

The Diverse Binding Modes Explain the Nanomolar Levels of Inhibitory Activities Against 1-Deoxy-d-Xylulose 5-Phosphate Reductoisomerase from Plasmodium falciparum Exhibited by Reverse Hydroxamate Analogs of Fosmidomycin with Varying N-Substituents

by Sana Takada, Mona A. Abdullaziz, Stefan Höfmann, Talea Knak, Shin-ichiro Ozawa, Yasumitsu Sakamoto, Thomas Kurz and Nobutada Tanaka

Molecules 2025, 30(1), 72; https://doi.org/10.3390/molecules30010072 - 28 Dec 2024

Cited by 4 | Viewed by 2337

Abstract

It is established that reverse hydroxamate analogs of fosmidomycin inhibit the growth of Plasmodium falciparum by inhibiting 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR), the second enzyme of the non-mevalonate pathway, which is absent in humans. Recent biochemical studies have demonstrated that novel reverse [...] Read more.

It is established that reverse hydroxamate analogs of fosmidomycin inhibit the growth of Plasmodium falciparum by inhibiting 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR), the second enzyme of the non-mevalonate pathway, which is absent in humans. Recent biochemical studies have demonstrated that novel reverse fosmidomycin analogs with phenylalkyl substituents at the hydroxamate nitrogen exhibit inhibitory activities against PfDXR at the nanomolar level. Moreover, crystallographic analyses have revealed that the phenyl moiety of the N-phenylpropyl substituent is accommodated in a previously unidentified subpocket within the active site of PfDXR. In this study, the crystal structures of PfDXR in complex with a series of reverse N-phenylalkyl derivatives of fosmidomycin were determined to ascertain whether the high inhibitory activities of the derivatives are consistently attributable to the utilization of the subpocket of PfDXR. While all reverse fosmidomycin derivatives with an N-substituted phenylalkyl group exhibit potent inhibitory activity against PfDXR, the present crystal structure analyses revealed that their binding modes to the PfDXR are not uniform. In these compounds, the nanomolar inhibitory activities appear to be driven by binding modes distinct from that observed for the inhibitor containing the N-phenylpropyl group. The structural information obtained in this study will provide a basis for further design of fosmidomycin derivatives. Full article

(This article belongs to the Special Issue Synthesis and Evaluation of Bioactivity of Enzyme Inhibitors)

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29 pages, 10314 KB

Open AccessEditor’s ChoiceArticle

Structure–Activity Relationship Studies of Tetracyclic Pyrrolocarbazoles Inhibiting Heterotetrameric Protein Kinase CK2

by Lukas Kröger, Sebastian Borgert, Miriam Lauwers, Michaela Steinkrüger, Joachim Jose, Markus Pietsch and Bernhard Wünsch

Molecules 2025, 30(1), 63; https://doi.org/10.3390/molecules30010063 - 27 Dec 2024

Viewed by 1709

Abstract

The serine/threonine kinase CK2 (formerly known as casein kinase II) plays a crucial role in various CNS disorders and is highly expressed in various types of cancer. Therefore, inhibiting this key kinase could be promising for the treatment of these diseases. The CK2 [...] Read more.

The serine/threonine kinase CK2 (formerly known as casein kinase II) plays a crucial role in various CNS disorders and is highly expressed in various types of cancer. Therefore, inhibiting this key kinase could be promising for the treatment of these diseases. The CK2 holoenzyme is formed by the recruitment of two catalytically active CK2α and/or CK2α′ subunits by a regulatory CK2β dimer. Starting with the lead furocarbazole W16 (4) inhibiting the CK2α/CK2β interaction, analogous pyrrolocarbazoles were prepared and tested for their protein–protein interaction inhibition (PPII). The key step of the synthesis was a multicomponent Levy reaction of 2-(indolyl)acetate 6, benzaldehydes 7, and N-substituted maleimides 8. Targeted modifications were performed by the saponification of the tetracyclic ester 9a, followed by the coupling of the resulting acid 10 with diverse amines. The replacement of the O-atom of the lead furocarbazole 4 by an N-atom in pyrrolocarbazoles retained or even increased the inhibition of the CK2α/CK2β interaction. The large benzyloxazolidinyl moiety of 4 could be replaced by smaller N-substituents without the loss of the PPII. The introduction of larger substituents at the 2-position and/or at p-position of the phenyl moiety at the 10-position to increase the surface for the inhibition of the PPI did not enhance the inhibition of the CK2α/CK2β association. The strong inhibition of the CK2α/CK2β association by the histidine derivative (+)-20a (K_i = 6.1 µM) translated into a high inhibition of the kinase activity of the CK2 holoenzyme (CK2α₂β₂, IC₅₀ = 2.5 µM). Thus, 20a represents a novel lead compound inhibiting CK2 via the inhibition of the association of the CK2α and Ck2β subunits. Full article

(This article belongs to the Special Issue Heterocycles in Medicinal Chemistry III)

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17 pages, 3339 KB

Open AccessEditor’s ChoiceArticle

The Application of a Sodium Benzoate Salt-Nucleating Agent in Recycled Polyethylene Terephthalate: Crystallization Behavior and Mechanism

by Meizhen Wang, Fuhua Lin, Tianjiao Zhao, Yapeng Dong, Xinyu Hao, Dingyi Ning, Yanli Zhang, Kexin Zhang, Dan Zhou, Jun Luo, Xiangyang Li and Bo Wang

Molecules 2025, 30(1), 37; https://doi.org/10.3390/molecules30010037 - 26 Dec 2024

Cited by 5 | Viewed by 3278

Abstract

The molecular chains of recycled polyethylene terephthalate (rPET) show breakage during daily use, causing poor crystallization and leading to mechanical properties that, when blended with the nucleating agent, become an effective method of solving this problem. The salt-nucleating agent sodium benzoate (SB), disodium [...] Read more.

The molecular chains of recycled polyethylene terephthalate (rPET) show breakage during daily use, causing poor crystallization and leading to mechanical properties that, when blended with the nucleating agent, become an effective method of solving this problem. The salt-nucleating agent sodium benzoate (SB), disodium terephthalate (DT), and trisodium 1,3,5benzene tricarboxylic (TBT) were synthesized, and an rPET/nucleating agent blend was prepared. The intrinsic viscosity (η) results showed that the η of the rPET/SB was decreased, which indicated the breakage of the rPET molecular chains. The FTIR results indicated that a chemical reaction occurred between the rPET and Na⁺ of the SB. Moreover, the Na⁺ content of the DT and TBT were higher than that of the SB, which increased the opportunity for low-molecular-weight rPET to reattach to the organic carboxylic acid portion of the nucleating agent, thereby increasing the η of the rPET/DT and rPET/TBT. The salt-nucleating agent sodium benzoate greatly improved the crystallization properties of the rPET, resulting in the half-crystallization time decreasing, the crystallization temperature increasing, and the effect of SB being better than that of DT and TBT. This was because the nucleating agent caused chemical nucleation with rPET, and the ionic groups acted as nucleation sites, while the rPET/DT and rPET/TBT, which had high molecular weights, hindered the improvement of the crystallization properties. The mechanical properties prove that the rPET/SB decreased due to the severe degradation of the rPET molecular chains. The mechanical properties of the rPET/DT and rPET/TBT were effectively improved because of the nucleating agent refining the grain size of the rPET and the high molecular weight. But the stacking of multitudinous rPET molecular chains can form a structure resembling physical cross-linking, causing a slight decrease in the mechanical properties of the rPET/TBT compared to the rPET/DT. Full article

(This article belongs to the Special Issue Molecular Insights into Soft Materials)

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22 pages, 2936 KB

Open AccessEditor’s ChoiceReview

Effects and Impact of Selenium on Human Health, A Review

by Song Bai, Miaohe Zhang, Shouying Tang, Miao Li, Rong Wu, Suran Wan, Lijun Chen, Xian Wei and Shuang Feng

Molecules 2025, 30(1), 50; https://doi.org/10.3390/molecules30010050 - 26 Dec 2024

Cited by 149 | Viewed by 26908

Abstract

Selenium (Se) is an essential trace element that is crucial for human health. As a key component of various enzymes and proteins, selenium primarily exerts its biological functions in the form of selenoproteins within the body. Currently, over 30 types of selenoproteins have [...] Read more.

Selenium (Se) is an essential trace element that is crucial for human health. As a key component of various enzymes and proteins, selenium primarily exerts its biological functions in the form of selenoproteins within the body. Currently, over 30 types of selenoproteins have been identified, with more than 20 of them containing selenocysteine residues. Among these, glutathione peroxidases (GPXs), thioredoxin reductases (TrxRs), and iodothyronine deiodinases (DIOs) have been widely studied. Selenium boasts numerous biological functions, including antioxidant properties, immune system enhancement, thyroid function regulation, anti-cancer effects, cardiovascular protection, reproductive capability improvement, and anti-inflammatory activity. Despite its critical importance to human health, the range between selenium’s nutritional and toxic doses is very narrow. Insufficient daily selenium intake can lead to selenium deficiency, while excessive intake carries the risk of selenium toxicity. Therefore, selenium intake must be controlled within a relatively precise range. This article reviews the distribution and intake of selenium, as well as its absorption and metabolism mechanisms in the human body. It also explores the multiple biological functions and mechanisms of selenium in maintaining human health. The aim is to provide new insights and evidence for further elucidating the role of selenium and selenoproteins in health maintenance, as well as for future nutritional guidelines and public health policies. Full article

(This article belongs to the Special Issue Organosulfur and Organoselenium Chemistry II)

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29 pages, 6531 KB

Open AccessEditor’s ChoiceArticle

Design, Structure–Activity Relationships, and Computational Modeling Studies of a Series of α-Helix Biased, Ultra-Short Glucagon-like Peptide-1 Receptor Agonists

by Jonathon R. Sawyer, Joseph A. Audie, Jon Swanson, David Diller, Solimar Santiago, Valentin K. Gribkoff, Allison Ackerman, Victor J. Hruby, Gianpaolo Gobbo, Michael A. Bellucci, William A. Glauser, Brad L. Pentelute and Tomi K. Sawyer

Molecules 2025, 30(1), 12; https://doi.org/10.3390/molecules30010012 - 24 Dec 2024

Cited by 1 | Viewed by 6946

Abstract

A systematic structure–activity and computational modeling analysis of a series of glucagon-like peptide-1 receptor (GLP-1R) agonists based upon an ultra-short GLP-1 peptide, H-His-Aib-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Bip-Bip-NH2, was conducted. This highly potent 11-mer peptide led to a deeper understanding of the α-helical bias of strategic α-methylation within [...] Read more.

A systematic structure–activity and computational modeling analysis of a series of glucagon-like peptide-1 receptor (GLP-1R) agonists based upon an ultra-short GLP-1 peptide, H-His-Aib-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Bip-Bip-NH2, was conducted. This highly potent 11-mer peptide led to a deeper understanding of the α-helical bias of strategic α-methylation within the linear parent template as well as optimization of GLP-1R agonist potency by 1000-fold. These data were correlated with previously reported co-structures of both full-length GLP-1 analogs and progenitor N-terminal GLP-1 fragment analogs related to such ultra-short GLP-1R agonist peptides. Furthermore, the development of a quantitative structure–activity relationship (QSAR) model to analyze these findings is described in this study. Full article

(This article belongs to the Section Medicinal Chemistry)

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37 pages, 6908 KB

Open AccessEditor’s ChoiceReview

A Concise Review on Porous Adsorbents for Benzene and Other Volatile Organic Compounds

by Jerzy Choma, Barbara Szczęśniak, Adam Kapusta and Mietek Jaroniec

Molecules 2024, 29(23), 5677; https://doi.org/10.3390/molecules29235677 - 30 Nov 2024

Cited by 38 | Viewed by 8996

Abstract

Emissions of volatile organic compounds (VOCs) such as benzene, toluene, xylene, styrene, hexane, tetrachloroethylene, acetone, acetaldehyde, formaldehyde, isopropanol, etc., increase dramatically with accelerated industrialization and economic growth. Most VOCs cause serious environmental pollution and threaten human health due to their toxic and carcinogenic [...] Read more.

Emissions of volatile organic compounds (VOCs) such as benzene, toluene, xylene, styrene, hexane, tetrachloroethylene, acetone, acetaldehyde, formaldehyde, isopropanol, etc., increase dramatically with accelerated industrialization and economic growth. Most VOCs cause serious environmental pollution and threaten human health due to their toxic and carcinogenic nature. Adsorption on porous materials is considered one of the most promising technologies for VOC removal due to its cost-effectiveness, operational flexibility, and low energy consumption. This review aims to provide a comprehensive understanding of VOC adsorption on various porous adsorbents and indicate future research directions in this field. It is focused on (i) the molecular characterization of structures, polarity, and boiling points of VOCs, (ii) the adsorption mechanisms and adsorption interactions in the physical, chemical, and competitive adsorption of VOCs on adsorbents, and (iii) the favorable characteristics of materials for VOCs adsorption. Porous adsorbents that would play an important role in the removal of benzene and other VOCs are presented in detail, including carbon-based materials (activated carbons, active carbon fibers, ordered mesoporous carbons, and graphene-based materials), metal-organic frameworks, covalent organic frameworks, zeolites, and siliceous adsorbents. Finally, the challenges and prospects related to the removal of VOCs via adsorption are pointed out. Full article

(This article belongs to the Special Issue Design and Synthesis of Novel Adsorbents for Pollutant Removal)

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49 pages, 18308 KB

Open AccessEditor’s ChoiceReview

Targeting Vascular Endothelial Growth Factor Receptor 2 (VEGFR-2): Latest Insights on Synthetic Strategies

by Carolina S. Marques, Pedro Brandão and Anthony J. Burke

Molecules 2024, 29(22), 5341; https://doi.org/10.3390/molecules29225341 - 13 Nov 2024

Cited by 36 | Viewed by 8946

Abstract

Vascular endothelial growth factor receptor 2 (VEGFR-2) is a crucial mediator of angiogenesis, playing a pivotal role in both normal physiological processes and cancer progression. Tumors harness VEGFR-2 signaling to promote abnormal blood vessel growth, which is a key step in the metastasis [...] Read more.

Vascular endothelial growth factor receptor 2 (VEGFR-2) is a crucial mediator of angiogenesis, playing a pivotal role in both normal physiological processes and cancer progression. Tumors harness VEGFR-2 signaling to promote abnormal blood vessel growth, which is a key step in the metastasis process, making it a valuable target for anticancer drug development. While there are VEGFR-2 inhibitors approved for therapeutic use, they face challenges like drug resistance, off-target effects, and adverse side effects, limiting their effectiveness. The quest for new drug candidates with VEGFR-2 inhibitory activity often starts with the selection of key structural motifs present in molecules currently used in clinical practice, expanding the chemical space by generating novel derivatives bearing one or more of these moieties. This review provides an overview of recent advances in the development of novel VEGFR-2 inhibitors, focusing on the synthesis of new drug candidates with promising antiproliferative and VEGFR-2 inhibition activities, organizing them by relevant structural features. Full article

(This article belongs to the Special Issue The Design, Synthesis, and Biological Activity of New Drug Candidates)

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17 pages, 1439 KB

Open AccessEditor’s ChoiceReview

Nanoparticle Tracking Analysis: An Effective Tool to Characterize Extracellular Vesicles

by Gabrielle Kowkabany and Yuping Bao

Molecules 2024, 29(19), 4672; https://doi.org/10.3390/molecules29194672 - 1 Oct 2024

Cited by 86 | Viewed by 13107

Abstract

Extracellular vesicles (EVs) are membrane-enclosed particles that have attracted much attention for their potential in disease diagnosis and therapy. However, the clinical translation is limited by the dosing consistency due to their heterogeneity. Among various characterization techniques, nanoparticle tracking analysis (NTA) offers distinct [...] Read more.

Extracellular vesicles (EVs) are membrane-enclosed particles that have attracted much attention for their potential in disease diagnosis and therapy. However, the clinical translation is limited by the dosing consistency due to their heterogeneity. Among various characterization techniques, nanoparticle tracking analysis (NTA) offers distinct benefits for EV characterization. In this review, we will discuss the NTA technique with a focus on factors affecting the results; then, we will review the two modes of the NTA techniques along with suitable applications in specific areas of EV studies. EVs are typically characterized by their size, size distribution, concentration, protein markers, and RNA cargos. The light-scattering mode of NTA offers accurate size, size distribution, and concentration information in solution, which is useful for comparing EV isolation methods, storage conditions, and EV secretion conditions. In contrast, fluorescent mode of NTA allows differentiating EV subgroups based on specific markers. The success of fluorescence NTA heavily relies on fluorescent tags (e.g., types of dyes and labeling methods). When EVs are labeled with disease-specific markers, fluorescence NTA offers an effective tool for disease detection in biological fluids, such as saliva, blood, and serum. Finally, we will discuss the limitations and future directions of the NTA technique in EV characterization. Full article

(This article belongs to the Special Issue Nanostructured Materials: Synthesis, Functionalization and Applications in Biomedicine)

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56 pages, 2136 KB

Open AccessEditor’s ChoiceReview

Unlocking the Potential of Hydrosols: Transforming Essential Oil Byproducts into Valuable Resources

by Heloísa H. S. Almeida, Isabel P. Fernandes, Joana S. Amaral, Alírio E. Rodrigues and Maria-Filomena Barreiro

Molecules 2024, 29(19), 4660; https://doi.org/10.3390/molecules29194660 - 30 Sep 2024

Cited by 47 | Viewed by 11117

Abstract

The global demand for sustainable and non-toxic alternatives across various industries is driving the exploration of naturally derived solutions. Hydrosols, also known as hydrolates, represent a promising yet underutilised byproduct of the extraction process of essential oils (EOs). These aqueous solutions contain a [...] Read more.

The global demand for sustainable and non-toxic alternatives across various industries is driving the exploration of naturally derived solutions. Hydrosols, also known as hydrolates, represent a promising yet underutilised byproduct of the extraction process of essential oils (EOs). These aqueous solutions contain a complex mixture of EO traces and water-soluble compounds and exhibit significant biological activity. To fully use these new solutions, it is necessary to understand how factors, such as distillation time and plant-to-water ratio, affect their chemical composition and biological activity. Such insights are crucial for the standardisation and quality control of hydrosols. Hydrosols have demonstrated noteworthy properties as natural antimicrobials, capable of preventing biofilm formation, and as antioxidants, mitigating oxidative stress. These characteristics position hydrosols as versatile ingredients for various applications, including biopesticides, preservatives, food additives, anti-browning agents, pharmaceutical antibiotics, cosmetic bioactives, and even anti-tumour agents in medical treatments. Understanding the underlying mechanisms of these activities is also essential for advancing their use. In this context, this review compiles and analyses the current literature on hydrosols’ chemical and biological properties, highlighting their potential applications and envisioning future research directions. These developments are consistent with a circular bio-based economy, where an industrial byproduct derived from biological sources is repurposed for new applications. Full article

(This article belongs to the Special Issue Featured Reviews in Applied Chemistry 2.0)

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17 pages, 4803 KB

Open AccessEditor’s ChoiceArticle

Comparative Investigation of Water-Based CMC and LA133 Binders for CuO Anodes in High-Performance Lithium-Ion Batteries

by Nischal Oli, Sunny Choudhary, Brad R. Weiner, Gerardo Morell and Ram S. Katiyar

Molecules 2024, 29(17), 4114; https://doi.org/10.3390/molecules29174114 - 30 Aug 2024

Cited by 9 | Viewed by 4021

Abstract

Transition metal oxides are considered to be highly promising anode materials for high-energy lithium-ion batteries. While carbon matrices have demonstrated effectiveness in enhancing the electrical conductivity and accommodating the volume expansion of transition metal oxide-based anode materials in lithium-ion batteries (LIBs), achieving an [...] Read more.

Transition metal oxides are considered to be highly promising anode materials for high-energy lithium-ion batteries. While carbon matrices have demonstrated effectiveness in enhancing the electrical conductivity and accommodating the volume expansion of transition metal oxide-based anode materials in lithium-ion batteries (LIBs), achieving an optimized utilization ratio remains a challenging obstacle. In this investigation, we have devised a straightforward synthesis approach to fabricate CuO nano powder integrated with carbon matrix. We found that with the use of a sodium carboxymethyl cellulose (CMC) based binder and fluoroethylene carbonate additives, this anode exhibits enhanced performance compared to acrylonitrile multi-copolymer binder (LA133) based electrodes. CuO@CMC electrodes reveal a notable capacity ~1100 mA h g⁻¹ at 100 mA g⁻¹ following 170 cycles, and exhibit prolonged cycling stability, with a capacity of 450 mA h g⁻¹ at current density 300 mA g⁻¹ over 500 cycles. Furthermore, they demonstrated outstanding rate performance and reduced charge transfer resistance. This study offers a viable approach for fabricating electrode materials for next-generation, high energy storage devices. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Energy Storage Devices)

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20 pages, 4858 KB

Open AccessEditor’s ChoiceReview

Overcoming Cancer Drug Resistance with Nanoparticle Strategies for Key Protein Inhibition

by Hyeonji Yoo, Yeonjin Kim, Jinseong Kim, Hanhee Cho and Kwangmeyung Kim

Molecules 2024, 29(17), 3994; https://doi.org/10.3390/molecules29173994 - 23 Aug 2024

Cited by 38 | Viewed by 4875

Abstract

Drug resistance remains a critical barrier in cancer therapy, diminishing the effectiveness of chemotherapeutic, targeted, and immunotherapeutic agents. Overexpression of proteins such as B-cell lymphoma 2 (Bcl-2), inhibitor of apoptosis proteins (IAPs), protein kinase B (Akt), and P-glycoprotein (P-gp) in various cancers leads [...] Read more.

Drug resistance remains a critical barrier in cancer therapy, diminishing the effectiveness of chemotherapeutic, targeted, and immunotherapeutic agents. Overexpression of proteins such as B-cell lymphoma 2 (Bcl-2), inhibitor of apoptosis proteins (IAPs), protein kinase B (Akt), and P-glycoprotein (P-gp) in various cancers leads to resistance by inhibiting apoptosis, enhancing cell survival, and expelling drugs. Although several inhibitors targeting these proteins have been developed, their clinical use is often hampered by systemic toxicity, poor bioavailability, and resistance development. Nanoparticle-based drug delivery systems present a promising solution by improving drug solubility, stability, and targeted delivery. These systems leverage the Enhanced Permeation and Retention (EPR) effect to accumulate in tumor tissues, reducing off-target toxicity and increasing therapeutic efficacy. Co-encapsulation strategies involving anticancer drugs and resistance inhibitors within nanoparticles have shown potential in achieving coordinated pharmacokinetic and pharmacodynamic profiles. This review discusses the mechanisms of drug resistance, the limitations of current inhibitors, and the advantages of nanoparticle delivery systems in overcoming these challenges. By advancing these technologies, we can enhance treatment outcomes and move towards more effective cancer therapies. Full article

(This article belongs to the Special Issue Featured Reviews in Nanochemistry)

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21 pages, 4153 KB

Open AccessEditor’s ChoiceArticle

Tuning Ferulic Acid Solubility in Choline-Chloride- and Betaine-Based Deep Eutectic Solvents: Experimental Determination and Machine Learning Modeling

by Tomasz Jeliński, Maciej Przybyłek, Rafał Różalski, Karolina Romanek, Daniel Wielewski and Piotr Cysewski

Molecules 2024, 29(16), 3841; https://doi.org/10.3390/molecules29163841 - 13 Aug 2024

Cited by 23 | Viewed by 4281

Abstract

Deep eutectic solvents (DES) represent a promising class of green solvents, offering particular utility in the extraction and development of new formulations of natural compounds such as ferulic acid (FA). The experimental phase of the study undertook a systematic investigation of the solubility [...] Read more.

Deep eutectic solvents (DES) represent a promising class of green solvents, offering particular utility in the extraction and development of new formulations of natural compounds such as ferulic acid (FA). The experimental phase of the study undertook a systematic investigation of the solubility of FA in DES, comprising choline chloride or betaine as hydrogen bond acceptors and six different polyols as hydrogen bond donors. The results demonstrated that solvents based on choline chloride were more effective than those based on betaine. The optimal ratio of hydrogen bond acceptors to donors was found to be 1:2 molar. The addition of water to the DES resulted in a notable enhancement in the solubility of FA. Among the polyols tested, triethylene glycol was the most effective. Hence, DES composed of choline chloride and triethylene glycol (TEG) (1:2) with added water in a 0.3 molar ration is suggested as an efficient alternative to traditional organic solvents like DMSO. In the second part of this report, the affinities of FA in saturated solutions were computed for solute-solute and all solute-solvent pairs. It was found that self-association of FA leads to a cyclic structure of the

C_{2}^{8}

type, common among carboxylic acids, which is the strongest type of FA affinity. On the other hand, among all hetero-molecular bi-complexes, the most stable is the FA-TEG pair, which is an interesting congruency with the high solubility of FA in TEG containing liquids. Finally, this work combined COSMO-RS modeling with machine learning for the development of a model predicting ferulic acid solubility in a wide range of solvents, including not only DES but also classical neat and binary mixtures. A machine learning protocol developed a highly accurate model for predicting FA solubility, significantly outperforming the COSMO-RS approach. Based on the obtained results, it is recommended to use the support vector regressor (SVR) for screening new dissolution media as it is not only accurate but also has sound generalization to new systems. Full article

(This article belongs to the Special Issue Advances of Ionic Liquids in Organic, Polymer and Material Chemistry: Key Trends in Green Chemistry)

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22 pages, 1115 KB

Open AccessFeature PaperEditor’s ChoiceReview

A Phenotypic Approach to the Discovery of Potent G-Quadruplex Targeted Drugs

by Stephen Neidle

Molecules 2024, 29(15), 3653; https://doi.org/10.3390/molecules29153653 - 1 Aug 2024

Cited by 21 | Viewed by 5957

Abstract

G-quadruplex (G4) sequences, which can fold into higher-order G4 structures, are abundant in the human genome and are over-represented in the promoter regions of many genes involved in human cancer initiation, progression, and metastasis. They are plausible targets for G4-binding small molecules, which [...] Read more.

G-quadruplex (G4) sequences, which can fold into higher-order G4 structures, are abundant in the human genome and are over-represented in the promoter regions of many genes involved in human cancer initiation, progression, and metastasis. They are plausible targets for G4-binding small molecules, which would, in the case of promoter G4s, result in the transcriptional downregulation of these genes. However, structural information is currently available on only a very small number of G4s and their ligand complexes. This limitation, coupled with the currently restricted information on the G4-containing genes involved in most complex human cancers, has led to the development of a phenotypic-led approach to G4 ligand drug discovery. This approach was illustrated by the discovery of several generations of tri- and tetra-substituted naphthalene diimide (ND) ligands that were found to show potent growth inhibition in pancreatic cancer cell lines and are active in in vivo models for this hard-to-treat disease. The cycles of discovery have culminated in a highly potent tetra-substituted ND derivative, QN-302, which is currently being evaluated in a Phase 1 clinical trial. The major genes whose expression has been down-regulated by QN-302 are presented here: all contain G4 propensity and have been found to be up-regulated in human pancreatic cancer. Some of these genes are also upregulated in other human cancers, supporting the hypothesis that QN-302 is a pan-G4 drug of potential utility beyond pancreatic cancer. Full article

(This article belongs to the Special Issue Bioorganic Chemistry in Europe)

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19 pages, 4692 KB

Open AccessEditor’s ChoiceArticle

Phytochemical Investigation of Carex praecox Schreb. and ACE-Inhibitory Activity of Oligomer Stilbenes of the Plant

by Csilla Zsuzsanna Dávid, Norbert Kúsz, Orinamhe Godwin Agbadua, Róbert Berkecz, Annamária Kincses, Gabriella Spengler, Attila Hunyadi, Judit Hohmann and Andrea Vasas

Molecules 2024, 29(14), 3427; https://doi.org/10.3390/molecules29143427 - 22 Jul 2024

Cited by 7 | Viewed by 2784

Abstract

Phenolic compounds are the main special metabolites of Cyperaceae species from phytochemical, pharmacological, and chemotaxonomical points of view. The present study focused on the isolation, structure determination, and pharmacological investigation of constituents from Carex praecox. Twenty-six compounds, including lignans, stilbenes, flavonoids, megastigmanes, [...] Read more.

Phenolic compounds are the main special metabolites of Cyperaceae species from phytochemical, pharmacological, and chemotaxonomical points of view. The present study focused on the isolation, structure determination, and pharmacological investigation of constituents from Carex praecox. Twenty-six compounds, including lignans, stilbenes, flavonoids, megastigmanes, chromenes, and phenylpropanoids, were identified from the methanol extract of the plant. Five of these compounds, namely, carexines A–E, are previously undescribed natural products. All compounds were isolated for the first time from C. praecox. The ACE-inhibitory activity of seven stilbenoid compounds was tested, and (–)-hopeaphenol proved to be the most active (IC₅₀ 7.7 ± 0.9 μM). The enzyme–kinetic studies revealed a mixed-type inhibition; therefore, domain-specific studies were also conducted. The in silico docking of (–)-hopeaphenol to the ACE affirmed some favorable interactions. In addition, the antiproliferative and antibacterial effects of some compounds were also evaluated. Full article

(This article belongs to the Special Issue Bioactive Compounds from Natural Sources III)

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20 pages, 639 KB

Open AccessEditor’s ChoiceReview

Recent Advances in the Determination of Major and Trace Elements in Plants Using Inductively Coupled Plasma Optical Emission Spectrometry

by Marin Senila

Molecules 2024, 29(13), 3169; https://doi.org/10.3390/molecules29133169 - 3 Jul 2024

Cited by 65 | Viewed by 8975

Abstract

Interest in measuring major and trace elements in plants has increased in recent years because of growing concerns about the elements’ contribution to daily intakes or the health risks posed by ingesting vegetables contaminated by potentially toxic elements. The recent advances in using [...] Read more.

Interest in measuring major and trace elements in plants has increased in recent years because of growing concerns about the elements’ contribution to daily intakes or the health risks posed by ingesting vegetables contaminated by potentially toxic elements. The recent advances in using inductively coupled plasma atomic emission spectrometry (ICP-OES) to measure major and trace elements in plant samples are reviewed in the present work. The sample preparation before instrumental determination and the main advantages and limitations of ICP-OES are described. New trends in element extraction in liquid solutions using fewer toxic solvents and microextractions are observed in recently published literature. Even though ICP-OES is a well-established and routine technique, recent innovations to increase its performance have been found. Validated methods are needed to ensure the obtaining of reliable results. Much research has focused on assessing principal figures of merit, such as limits of detection, quantification, selectivity, working ranges, precision in terms of repeatability and reproducibility, and accuracy through spiked samples or certified reference materials analysis. According to the published literature, the ICP-OES technique, 50 years after the release of the first commercially available equipment, remains a powerful and highly recommended tool for element determination on a wide range of concentrations. Full article

(This article belongs to the Special Issue Advanced Analytical Techniques in Environmental Chemistry, 2nd Edition)

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18 pages, 1322 KB

Open AccessEditor’s ChoiceReview

Zinc Toxicity: Understanding the Limits

by Hannah Schoofs, Joyce Schmit and Lothar Rink

Molecules 2024, 29(13), 3130; https://doi.org/10.3390/molecules29133130 - 1 Jul 2024

Cited by 190 | Viewed by 59748

Abstract

Zinc, a vital trace element, holds significant importance in numerous physiological processes within the body. It participates in over 300 enzymatic reactions, metabolic functions, regulation of gene expression, apoptosis and immune modulation, thereby demonstrating its essential role in maintaining overall health and well-being. [...] Read more.

Zinc, a vital trace element, holds significant importance in numerous physiological processes within the body. It participates in over 300 enzymatic reactions, metabolic functions, regulation of gene expression, apoptosis and immune modulation, thereby demonstrating its essential role in maintaining overall health and well-being. While zinc deficiency is associated with significant health risks, an excess of this trace element can also lead to harmful effects. According to the World Health Organization (WHO), 6.7 to 15 mg per day are referred to be the dietary reference value. An excess of the recommended daily intake may result in symptoms such as anemia, neutropenia and zinc-induced copper deficiency. The European Food Safety Authority (EFSA) defines the tolerable upper intake level (UL) as 25 mg per day, whereas the Food and Drug Administration (FDA) allows 40 mg per day. This review will summarize the current knowledge regarding the calculation of UL and other health risks associated with zinc. For example, zinc intake is not limited to oral consumption; other routes, such as inhalation or topical application, may also pose risks of zinc intoxication. Full article

(This article belongs to the Special Issue Featured Review Papers in Bioorganic Chemistry)

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15 pages, 3065 KB

Open AccessEditor’s ChoiceArticle

Energetic Aspects and Molecular Mechanism of 3-Nitro-substituted 2-Isoxazolines Formation via Nitrile N-Oxide [3+2] Cycloaddition: An MEDT Computational Study

by Ewa Dresler, Aneta Wróblewska and Radomir Jasiński

Molecules 2024, 29(13), 3042; https://doi.org/10.3390/molecules29133042 - 26 Jun 2024

Cited by 24 | Viewed by 5022

Abstract

Regioselectivity and the molecular mechanism of the [3+2] cycloaddition reaction between nitro-substituted formonitrile N-oxide 1 and electron-rich alkenes were explored on the basis of the wb97xd/6-311+G(d) (PCM) quantum chemical calculations. It was established that the thermodynamic factors allow for the formation of stable [...] Read more.

Regioselectivity and the molecular mechanism of the [3+2] cycloaddition reaction between nitro-substituted formonitrile N-oxide 1 and electron-rich alkenes were explored on the basis of the wb97xd/6-311+G(d) (PCM) quantum chemical calculations. It was established that the thermodynamic factors allow for the formation of stable cycloadducts along all considered models. The analysis of the kinetic parameters of the main processes show that all [3+2] cycloadditions should be realized with full regioselectivity. In all cases, the formation of 5-substituted 3-nitro-2-isoxazolidines is clearly preferred. It is interesting that regiodirection is not determined by the local electrophile/nucleophile interactions but by steric effects. From a mechanistic point of view, all considered reactions should be treated as polar, one-step reactions. All attempts to locate the hypothetical zwitterionic intermediates along the cycloaddition paths were, however, not successful. Full article

(This article belongs to the Special Issue Advances in the Synthesis of Heterocyclic Compounds and Their Applications)

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22 pages, 1325 KB

Open AccessEditor’s ChoiceArticle

Comparing Nutritional Values and Bioactivity of Kefir from Different Types of Animal Milk

by Chiara La Torre, Paolino Caputo, Erika Cione and Alessia Fazio

Molecules 2024, 29(11), 2710; https://doi.org/10.3390/molecules29112710 - 6 Jun 2024

Cited by 31 | Viewed by 9303

Abstract

The growing interest in fermented dairy products is due to their health-promoting properties. The use of milk kefir grains as a starter culture made it possible to obtain a product with a better nutritional and biological profile depending on the type of milk. [...] Read more.

The growing interest in fermented dairy products is due to their health-promoting properties. The use of milk kefir grains as a starter culture made it possible to obtain a product with a better nutritional and biological profile depending on the type of milk. Cow, buffalo, camel, donkey, goat, and sheep milk kefirs were prepared, and the changes in sugar, protein, and phenol content, fatty acid composition, including conjugated linoleic acids (CLAs), as well as antioxidant activity, determined by ABTS and FRAP assays, were evaluated and compared. The protein content of cow, buffalo, donkey, and sheep milk increased after 24 h of fermentation. The fatty acid profile showed a better concentration of saturated and unsaturated lipids in all fermented milks, except buffalo milk. The highest content of beneficial fatty acids, such as oleic, linoleic, and C18:2 conjugated linoleic acid, was found in the cow and sheep samples. All samples showed a better antioxidant capacity, goat milk having the highest value, with no correlation to the total phenolic content, which was highest in the buffalo sample (260.40 ± 5.50 μg GAE/mL). These findings suggested that microorganisms living symbiotically in kefir grains utilize nutrients from different types of milk with varying efficiency. Full article

(This article belongs to the Special Issue New Frontiers in Fermented Products – 2nd Edition)

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17 pages, 1416 KB

Open AccessEditor’s ChoiceArticle

Exploring Phenolic Compounds Extraction from Saffron (C. sativus) Floral By-Products Using Ultrasound-Assisted Extraction, Deep Eutectic Solvent Extraction, and Subcritical Water Extraction

by Valentina Masala, Stela Jokić, Krunoslav Aladić, Maja Molnar and Carlo Ignazio Giovanni Tuberoso

Molecules 2024, 29(11), 2600; https://doi.org/10.3390/molecules29112600 - 1 Jun 2024

Cited by 30 | Viewed by 4704

Abstract

Saffron (Crocus sativus) floral by-products are a source of phenolic compounds that can be recovered and used in the nutraceutical, pharmaceutical, or cosmetic industries. This study aimed to evaluate the phenolic compounds’ extraction using green extraction techniques (GETs) in saffron floral [...] Read more.

Saffron (Crocus sativus) floral by-products are a source of phenolic compounds that can be recovered and used in the nutraceutical, pharmaceutical, or cosmetic industries. This study aimed to evaluate the phenolic compounds’ extraction using green extraction techniques (GETs) in saffron floral by-products and to explore the influence of selected extraction techniques on the phytochemical composition of the extracts. Specifically, ultrasound-assisted extraction (UAE), subcritical water extraction (SWE), and deep eutectic solvents extraction (DESE) were used. Phenolic compounds were identified with (HR) LC-ESI-QTOF MS/MS analysis, and the quantitative analysis was performed with HPLC-PDA. Concerning the extraction techniques, UAE showed the highest amount for both anthocyanins and flavonoids with 50:50% v/v ethanol/water as solvent (93.43 ± 4.67 mg/g of dry plant, dp). Among SWE, extraction with 96% ethanol and t = 125 °C gave the best quantitative results. The 16 different solvent mixtures used for the DESE showed the highest amount of flavonoids (110.95 ± 5.55–73.25 ± 3.66 mg/g dp), while anthocyanins were better extracted with choline chloride:butane-1,4-diol (16.0 ± 0.80 mg/g dp). Consequently, GETs can be employed to extract the bioactive compounds from saffron floral by-products, implementing recycling and reduction of waste and fitting into the broader circular economy discussion. Full article

(This article belongs to the Special Issue Waste and By-Products from Agricultural Production for Innovative Health Applications)

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10 pages, 1812 KB

Open AccessEditor’s ChoiceArticle

SiOx/C Composite Anode for Lithium-Ion Battery with Improved Performance Using Graphene Quantum Dots and Carbon Nanoparticles

by Sung Won Hwang

Molecules 2024, 29(11), 2578; https://doi.org/10.3390/molecules29112578 - 30 May 2024

Cited by 16 | Viewed by 4145

Abstract

In this study, a composite was manufactured by mixing graphene quantum dots, silicon oxide, and carbon nanoparticles, and the characteristics of the anode materials for secondary batteries were examined. To improve the capacity of the graphene quantum dot (GQD) anode material, the added [...] Read more.

In this study, a composite was manufactured by mixing graphene quantum dots, silicon oxide, and carbon nanoparticles, and the characteristics of the anode materials for secondary batteries were examined. To improve the capacity of the graphene quantum dot (GQD) anode material, the added silicon oxide content was varied among 0, 5, 10, 15, and 30 wt%, and carbon nanoparticles were added as a structural stabilizer to alleviate silicon oxide volume expansion. The physical properties of the prepared GQD/SiOx/C composite were investigated through XRD, SEM, EDS, and powder resistance analysis. Additionally, the electrochemical properties of the manufactured composite were observed through an analysis of the charge–discharge cycle, rate, and impedance of a lithium secondary battery. In the GQD/SiOx/C composite, by adding carbon nanoparticles, an internal cavity was formed that can alleviate the volume expansion of silicon oxide, and the carbon nanoparticles and silicon oxide particles were uniformly distributed. The formed internal cavity had a silicon oxide content of 5 wt%. Low initial efficiency was observed, and above 30 wt%, low cycle stability was observed. The GQD/SiOx/C composite with 15 wt% of silicon oxide added showed an initial discharge capacity of 595 mAh/g, a capacity retention rate of 92%, and a rate characteristic of 81 at 2 C/0.1 C. Silicon oxide was added to improve the capacity of the anode material, and carbon nanoparticles were added as a structural stabilizer to buffer the volume change of the silicon oxide. To use GQD/SiOx/C composite as a highly efficient anode material, the optimal silicon oxide content and carbon nanoparticle mechanism as a structural stabilizer were discussed. Full article

(This article belongs to the Section Applied Chemistry)

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22 pages, 5743 KB

Open AccessEditor’s ChoiceArticle

Potential Large-Scale CO₂ Utilisation for Salicylic Acid Production via a Suspension-Based Kolbe–Schmitt Reaction in Toluene

by Omar Mohammad, Jude A. Onwudili and Qingchun Yuan

Molecules 2024, 29(11), 2527; https://doi.org/10.3390/molecules29112527 - 27 May 2024

Cited by 12 | Viewed by 6673

Abstract

Conversion of CO₂ into organic chemicals offers a promising route for advancing the circularity of carbon capture, utilisation, and storage in line with the international 2050 Net Zero agenda. The widely known commercialised chemical fixation of CO₂ into organic chemicals is [...] Read more.

Conversion of CO₂ into organic chemicals offers a promising route for advancing the circularity of carbon capture, utilisation, and storage in line with the international 2050 Net Zero agenda. The widely known commercialised chemical fixation of CO₂ into organic chemicals is the century-old Kolbe–Schmitt reaction, which carboxylates phenol (via sodium phenoxide) into salicylic acid. The carboxylation reaction is normally carried out between the gas–solid phases in a batch reactor. The mass and heat transfer limitations of such systems require rather long reaction times and a high pressure of CO₂ and are often characterised by the low formation of undesirable side products. To address these drawbacks, a novel suspension-based carboxylation method has been designed and carried out in this present study, where sodium phenoxide is dispersed in toluene to react with CO₂. Importantly, the addition of phenol played a critical role in promoting the stoichiometric conversion of phenoxide to salicylic acid. Under the optimal conditions of a phenol/phenoxide molar ratio of 2:1 in toluene, a reaction temperature of 225 °C, a CO₂ pressure of 30 bar, a reaction time of 2 h, and stirring at 1000 rpm, an impressive salicylic acid molar yield of 92.68% has been achieved. The reaction mechanism behind this has been discussed. This development provides us with the potential to achieve a carboxylation reaction of phenoxide with CO₂ more effectively in a continuous reactor. It can also facilitate the large-scale fixing of CO₂ into hydroxy aromatic carboxylic acids, which can be used as green organic chemical feedstocks for making various products, including long-lived polymeric materials. Full article

(This article belongs to the Special Issue Recent Advances on Biomass Conversion and CO₂ Valorization: Steeping towards a Circular Economy)

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23 pages, 3000 KB

Open AccessEditor’s ChoiceArticle

Comparative Study of Microwave, Pulsed Electric Fields, and High Pressure Processing on the Extraction of Antioxidants from Olive Pomace

by Maria Tsevdou, Athina Ntzimani, Maria Katsouli, George Dimopoulos, Dimitrios Tsimogiannis and Petros Taoukis

Molecules 2024, 29(10), 2303; https://doi.org/10.3390/molecules29102303 - 14 May 2024

Cited by 34 | Viewed by 3199

Abstract

Olive oil production is characterized by large amounts of waste, and yet is considerably highly valued. Olive pomace can serve as a cheap source of bioactive compounds (BACs) with important antioxidant activity. Novel technologies like Pulsed Electric Fields (PEF) and High Pressure (HP) [...] Read more.

Olive oil production is characterized by large amounts of waste, and yet is considerably highly valued. Olive pomace can serve as a cheap source of bioactive compounds (BACs) with important antioxidant activity. Novel technologies like Pulsed Electric Fields (PEF) and High Pressure (HP) and microwave (MW) processing are considered green alternatives for the recovery of BACs. Different microwave (150–600 W), PEF (1–5 kV/cm field strength, 100–1500 pulses/15 µs width), and HP (250–650 MPa) conditions, in various product/solvent ratios, methanol concentrations, extraction temperatures, and processing times were investigated. Results indicated that the optimal MW extraction conditions were 300 W at 50 °C for 5 min using 60% v/v methanol with a product/solvent ratio of 1:10 g/mL. Similarly, the mix of 40% v/v methanol with olive pomace, treated at 650 MPa for the time needed for pressure build-up (1 min) were considered as optimal extraction conditions in the case of HP, while for PEF the optimal conditions were 60% v/v methanol with a product/solvent ratio of 1:10 g/mL, treated at 5000 pulses, followed by 1 h extraction under stirring conditions. Therefore, these alternative extraction technologies could assist the conventional practice in minimizing waste production and simultaneously align with the requirements of the circular bioeconomy concept. Full article

(This article belongs to the Special Issue Virgin Olive Oil: Processing, Byproducts, Quality Control, and Nutraceutical Profile II)

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37 pages, 2176 KB

Open AccessEditor’s ChoiceReview

Can Plant Extracts Help Prevent Hair Loss or Promote Hair Growth? A Review Comparing Their Therapeutic Efficacies, Phytochemical Components, and Modulatory Targets

by Joon Yong Choi, Min Young Boo and Yong Chool Boo

Molecules 2024, 29(10), 2288; https://doi.org/10.3390/molecules29102288 - 13 May 2024

Cited by 49 | Viewed by 54650

Abstract

This narrative review aims to examine the therapeutic potential and mechanism of action of plant extracts in preventing and treating alopecia (baldness). We searched and selected research papers on plant extracts related to hair loss, hair growth, or hair regrowth, and comprehensively compared [...] Read more.

This narrative review aims to examine the therapeutic potential and mechanism of action of plant extracts in preventing and treating alopecia (baldness). We searched and selected research papers on plant extracts related to hair loss, hair growth, or hair regrowth, and comprehensively compared the therapeutic efficacies, phytochemical components, and modulatory targets of plant extracts. These studies showed that various plant extracts increased the survival and proliferation of dermal papilla cells in vitro, enhanced cell proliferation and hair growth in hair follicles ex vivo, and promoted hair growth or regrowth in animal models in vivo. The hair growth-promoting efficacy of several plant extracts was verified in clinical trials. Some phenolic compounds, terpenes and terpenoids, sulfur-containing compounds, and fatty acids were identified as active compounds contained in plant extracts. The pharmacological effects of plant extracts and their active compounds were associated with the promotion of cell survival, cell proliferation, or cell cycle progression, and the upregulation of several growth factors, such as IGF-1, VEGF, HGF, and KGF (FGF-7), leading to the induction and extension of the anagen phase in the hair cycle. Those effects were also associated with the alleviation of oxidative stress, inflammatory response, cellular senescence, or apoptosis, and the downregulation of male hormones and their receptors, preventing the entry into the telogen phase in the hair cycle. Several active plant extracts and phytochemicals stimulated the signaling pathways mediated by protein kinase B (PKB, also called AKT), extracellular signal-regulated kinases (ERK), Wingless and Int-1 (WNT), or sonic hedgehog (SHH), while suppressing other cell signaling pathways mediated by transforming growth factor (TGF)-β or bone morphogenetic protein (BMP). Thus, well-selected plant extracts and their active compounds can have beneficial effects on hair health. It is proposed that the discovery of phytochemicals targeting the aforementioned cellular events and cell signaling pathways will facilitate the development of new targeted therapies for alopecia. Full article

(This article belongs to the Special Issue Antioxidant Activity of Natural Products: 2nd Edition)

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28 pages, 2743 KB

Open AccessEditor’s ChoiceReview

Innovative Solid-Phase Extraction Strategies for Improving the Advanced Chromatographic Determination of Drugs in Challenging Biological Samples

by Mohammadreza Mahdavijalal, Carmine Petio, Giovanni Staffilano, Roberto Mandrioli and Michele Protti

Molecules 2024, 29(10), 2278; https://doi.org/10.3390/molecules29102278 - 12 May 2024

Cited by 44 | Viewed by 7770

Abstract

In the past few decades, considerable scientific strides have been made in the subject of drug analysis in human biological samples. However, the risk caused by incorrect drug plasma levels in patients still remains an important concern. This review paper attempts to investigate [...] Read more.

In the past few decades, considerable scientific strides have been made in the subject of drug analysis in human biological samples. However, the risk caused by incorrect drug plasma levels in patients still remains an important concern. This review paper attempts to investigate the advances made over the last ten years in common sample preparation techniques (SPT) for biological samples based on solid sorbents, including solid-phase extraction (SPE) and solid-phase micro-extraction (SPME), and in particular in the field of molecularly imprinted polymers (MIPs), including non-stimuli-responsive and stimuli-responsive adsorbents. This class of materials is known as ‘smart adsorbents’, exhibiting tailored responses to various stimuli such as magnetic fields, pH, temperature, and light. Details are provided on how these advanced SPT are changing the landscape of modern drug analysis in their coupling with liquid chromatography-mass spectrometry (LC-MS) analytical techniques, a general term that includes high-performance liquid chromatography (HPLC) and ultra-high performance liquid chromatography (UHPLC), as well as any variation of MS, such as tandem (MS/MS), multiple-stage (MSⁿ), and high-resolution (HRMS) mass spectrometry. Some notes are also provided on coupling with less-performing techniques, such as high-performance liquid chromatography with ultraviolet (HPLC-UV) and diode array detection (HPLC-DAD) detection. Finally, we provide a general review of the difficulties and benefits of the proposed approaches and the future prospects of this research area. Full article

(This article belongs to the Special Issue Mass Spectrometry in Life Sciences: A Theme Issue Dedicated to Professor Gérard Hopfgartner)

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52 pages, 22828 KB

Open AccessEditor’s ChoiceReview

Indole-Based Compounds in the Development of Anti-Neurodegenerative Agents

by Elisabetta Barresi, Emma Baglini, Valeria Poggetti, Jacopo Castagnoli, Doralice Giorgini, Silvia Salerno, Sabrina Taliani and Federico Da Settimo

Molecules 2024, 29(9), 2127; https://doi.org/10.3390/molecules29092127 - 3 May 2024

Cited by 49 | Viewed by 9592

Abstract

Neurodegeneration is a gradual decay process leading to the depletion of neurons in both the central and peripheral nervous systems, ultimately resulting in cognitive dysfunctions and the deterioration of brain functions, alongside a decline in motor skills and behavioral capabilities. Neurodegenerative disorders (NDs) [...] Read more.

Neurodegeneration is a gradual decay process leading to the depletion of neurons in both the central and peripheral nervous systems, ultimately resulting in cognitive dysfunctions and the deterioration of brain functions, alongside a decline in motor skills and behavioral capabilities. Neurodegenerative disorders (NDs) impose a substantial socio-economic strain on society, aggravated by the advancing age of the world population and the absence of effective remedies, predicting a negative future. In this context, the urgency of discovering viable therapies is critical and, despite significant efforts by medicinal chemists in developing potential drug candidates and exploring various small molecules as therapeutics, regrettably, a truly effective treatment is yet to be found. Nitrogen heterocyclic compounds, and particularly those containing the indole nucleus, which has emerged as privileged scaffold, have attracted particular attention for a variety of pharmacological applications. This review analyzes the rational design strategy adopted by different research groups for the development of anti-neurodegenerative indole-based compounds which have the potential to modulate various molecular targets involved in NDs, with reference to the most recent advances between 2018 and 2023. Full article

(This article belongs to the Special Issue Heterocyclic Compounds: Synthesis and Medicinal Chemistry Applications)

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32 pages, 8970 KB

Open AccessEditor’s ChoiceReview

Defects and Defect Passivation in Perovskite Solar Cells

by Zhanwei Wang, Hongli Gao, Dandan Wu, Junhua Meng, Jinxiang Deng and Min Cui

Molecules 2024, 29(9), 2104; https://doi.org/10.3390/molecules29092104 - 2 May 2024

Cited by 115 | Viewed by 23058

Abstract

Perovskite solar cells have made significant strides in recent years. However, there are still challenges in terms of photoelectric conversion efficiency and long-term stability associated with perovskite solar cells. The presence of defects in perovskite materials is one of the important influencing factors [...] Read more.

Perovskite solar cells have made significant strides in recent years. However, there are still challenges in terms of photoelectric conversion efficiency and long-term stability associated with perovskite solar cells. The presence of defects in perovskite materials is one of the important influencing factors leading to subpar film quality. Adopting additives to passivate defects within perovskite materials is an effective approach. Therefore, we first discuss the types of defects that occur in perovskite materials and the mechanisms of their effect on performance. Then, several types of additives used in perovskite solar cells are discussed, including ionic compounds, organic molecules, polymers, etc. This review provides guidance for the future development of more sustainable and effective additives to improve the performance of solar cells. Full article

(This article belongs to the Special Issue Fabrication and Application of Nano-Semiconductor Optoelectronic Materials/Devices)

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14 pages, 5110 KB

Open AccessEditor’s ChoiceArticle

Sc-Modified C₃N₄ Nanotubes for High-Capacity Hydrogen Storage: A Theoretical Prediction

by Shuli Liu, Xiao Tang, Chang He, Tingting Wang, Liying Shang, Mengyuan Wang, Shenbo Yang, Zhenjie Tang and Lin Ju

Molecules 2024, 29(9), 1966; https://doi.org/10.3390/molecules29091966 - 25 Apr 2024

Cited by 16 | Viewed by 2379

Abstract

Utilizing hydrogen as a viable substitute for fossil fuels requires the exploration of hydrogen storage materials with high capacity, high quality, and effective reversibility at room temperature. In this study, the stability and capacity for hydrogen storage in the Sc-modified C₃N [...] Read more.

Utilizing hydrogen as a viable substitute for fossil fuels requires the exploration of hydrogen storage materials with high capacity, high quality, and effective reversibility at room temperature. In this study, the stability and capacity for hydrogen storage in the Sc-modified C₃N₄ nanotube are thoroughly examined through the application of density functional theory (DFT). Our finding indicates that a strong coupling between the Sc-3d orbitals and N-2p orbitals stabilizes the Sc-modified C₃N₄ nanotube at a high temperature (500 K), and the high migration barrier (5.10 eV) between adjacent Sc atoms prevents the creation of metal clusters. Particularly, it has been found that each Sc-modified C₃N₄ nanotube is capable of adsorbing up to nine H₂ molecules, and the gravimetric hydrogen storage density is calculated to be 7.29 wt%. It reveals an average adsorption energy of −0.20 eV, with an estimated average desorption temperature of 258 K. This shows that a Sc-modified C₃N₄ nanotube can store hydrogen at low temperatures and harness it at room temperature, which will reduce energy consumption and protect the system from high desorption temperatures. Moreover, charge donation and reverse transfer from the Sc-3d orbital to the H-1s orbital suggest the presence of the Kubas effect between the Sc-modified C₃N₄ nanotube and H₂ molecules. We draw the conclusion that a Sc-modified C₃N₄ nanotube exhibits exceptional potential as a stable and efficient hydrogen storage substrate. Full article

(This article belongs to the Section Physical Chemistry)

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20 pages, 2188 KB

Open AccessEditor’s ChoiceArticle

Comparison among Different Green Extraction Methods of Polyphenolic Compounds from Exhausted Olive Oil Pomace and the Bioactivity of the Extracts

by Valter F. R. Martins, Tânia B. Ribeiro, Ana I. Lopes, Manuela E. Pintado, Rui M. S. C. Morais and Alcina M. M. B. Morais

Molecules 2024, 29(9), 1935; https://doi.org/10.3390/molecules29091935 - 24 Apr 2024

Cited by 21 | Viewed by 3863

Abstract

The use of by-products as a source of bioactive compounds with economic added value is one of the objectives of a circular economy. The olive oil industry is a source of olive pomace as a by-product. The olive pomace used in the present [...] Read more.

The use of by-products as a source of bioactive compounds with economic added value is one of the objectives of a circular economy. The olive oil industry is a source of olive pomace as a by-product. The olive pomace used in the present study was the exhausted olive pomace, which is the by-product generated from the air drying and subsequent hexane extraction of residual oil from the olive pomace. The objective was to extract bioactive compounds remaining in this by-product. Various types of green extraction were used in the present study: solvent extraction (water and hydroalcoholic); ultrasound-assisted extraction; Ultra-Turrax-assisted extraction; and enzyme-assisted extraction (cellulase; viscoenzyme). The phenolic profile of each extract was determined using HPLC-DAD and the total phenolic content (TPC) and antioxidant activity (ABTS, DPPH, and ORAC) were determined as well. The results showed significant differences in the yield of extraction among the different methods used, with the enzyme-assisted, with or without ultrasound, extraction presenting the highest values. The ultrasound-assisted hydroethanolic extraction (USAHE) was the method that resulted in the highest content of the identified phenolic compounds: 2.021 ± 0.29 mg hydroxytyrosol/100 mg extract, 0.987 ± 0.09 mg tyrosol/100 mg extract, and 0.121 ± 0.005 mg catechol/100 mg extract. The conventional extraction with water at 50 °C produced the best results for TPC and antioxidant activity of the extracts. The extracts from the USAHE were able to inhibit Gram-positive bacteria, especially Bacillus cereus, showing 67.2% inhibition at 3% extract concentration. Full article

(This article belongs to the Special Issue Plant Sourced Compounds: Extraction, Identification and Bioactivity)

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11 pages, 2444 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Novel and Sensitive Touchdown Polymerase Chain Reaction Assays for the Detection of Goat and Sheep Milk Adulteration with Cow Milk

by Ariadni Kourkouli, Nikolaos Thomaidis, Marilena Dasenaki and Athina Markou

Molecules 2024, 29(8), 1820; https://doi.org/10.3390/molecules29081820 - 17 Apr 2024

Cited by 11 | Viewed by 3405

Abstract

Milk is the most consumed liquid food in the world due to its high nutritional value and relatively low cost, characteristics that make it vulnerable to adulteration. One of the most common types of milk adulteration involves the undeclared addition of cow’s milk [...] Read more.

Milk is the most consumed liquid food in the world due to its high nutritional value and relatively low cost, characteristics that make it vulnerable to adulteration. One of the most common types of milk adulteration involves the undeclared addition of cow’s milk to milk from other mammalian species, such as goats, sheep, buffalo or donkeys. The incidence of such adulteration not only causes a crisis in terms of commercial market and consumer uncertainty but also poses a risk to public health, as allergies can be triggered by proteins in undeclared cow’s milk. In this study, a specific qualitative touchdown (TD) PCR method was developed to detect the undeclared addition of cow’s milk in goat and sheep milk based on the discrimination of the peak areas of the melting curves after the modification of bovine-specific primers. The developed methodology has high specificity for the DNA templates of other species, such as buffalos and donkeys, and is able to identify the presence of cow’s milk down to 1%. Repeatability was tested at low bovine concentrations of 5% and 1% and resulted in %RSD values of 1.53–2.04 for the goat–cow assay and 2.49–7.16 for the sheep–cow assay, respectively. The application of this method to commercial goat milk samples indicated a high percentage of noncompliance in terms of labeling (50%), while a comparison of the results to rapid immunochromatographic and ELISA kits validated the excellent sensitivity and applicability of the proposed PCR methodology that was able to trace more adulterated samples. The developed assays offer the advantage of multiple detection in a single run, resulting in a cost- and time-efficient method. Future studies will focus on the applicability of these assays in dairy products such as cheese and yogurt. Full article

(This article belongs to the Special Issue State-of-the-Art Analytical Technologies for Food Safety, Quality and Authenticity Assessment)

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13 pages, 9466 KB

Open AccessEditor’s ChoiceArticle

ZnO-CeO₂ Hollow Nanospheres for Selective Determination of Dopamine and Uric Acid

by Yaru Zhang, Xiaoxia Yan, Yifan Chen, Dongmei Deng, Haibo He, Yunyi Lei and Liqiang Luo

Molecules 2024, 29(8), 1786; https://doi.org/10.3390/molecules29081786 - 15 Apr 2024

Cited by 24 | Viewed by 2761

Abstract

ZnO-CeO₂ hollow nanospheres have been successfully synthesized via the hard templating method, in which CeO₂ is used as the support skeleton to avoid ZnO agglomeration. The synthesized ZnO-CeO₂ hollow nanospheres possess a large electrochemically active area and high electron transfer [...] Read more.

ZnO-CeO₂ hollow nanospheres have been successfully synthesized via the hard templating method, in which CeO₂ is used as the support skeleton to avoid ZnO agglomeration. The synthesized ZnO-CeO₂ hollow nanospheres possess a large electrochemically active area and high electron transfer owing to the high specific surface area and synergistic effect of ZnO and CeO₂. Due to the above advantages, the resulting ZnO-CeO₂ hollow spheres display high sensitivities of 1122.86 μA mM⁻¹ cm⁻² and 908.53 μA mM⁻¹ cm⁻² under a neutral environment for the selective detection of dopamine and uric acid. The constructed electrochemical sensor shows excellent selectivity, stability and recovery for the selective analysis of dopamine and uric acid in actual samples. This study provides a valuable strategy for the synthesis of ZnO-CeO₂ hollow nanospheres via the hard templating method as electrocatalysts for the selective detection of dopamine and uric acid. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Catalysis, Electrochemistry and Environmental Applications)

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16 pages, 10772 KB

Open AccessEditor’s ChoiceArticle

Study on the Synthesis, Surface Activity, and Self-Assembly Behavior of Anionic Non-Ionic Gemini Surfactants

by Zhiqiang Man and Wenxiang Wu

Molecules 2024, 29(8), 1725; https://doi.org/10.3390/molecules29081725 - 11 Apr 2024

Cited by 15 | Viewed by 3415

Abstract

The use of surfactants in oil recovery can effectively improve crude oil recovery rate. Due to the enhanced salt and temperature resistance of surfactant molecules by non-ionic chain segments, anionic groups have good emulsifying stability. Currently, there are many studies on anionic non-ionic [...] Read more.

The use of surfactants in oil recovery can effectively improve crude oil recovery rate. Due to the enhanced salt and temperature resistance of surfactant molecules by non-ionic chain segments, anionic groups have good emulsifying stability. Currently, there are many studies on anionic non-ionic surfactants for oil recovery in China, but there is relatively little systematic research on introducing EOs into hydrophobic alkyl chains, especially on their self-assembly behavior. This article proposes a simple and effective synthesis method, using 3-aminopropane sulfonic acid, fatty alcohol polyoxyethylene ether, and epichlorohydrin as raw materials, to insert EO into hydrophobic alkyl chains and synthesize a series of new anionic non-ionic Gemini surfactants (CnEO-5, n = 8, 12, 16). The surface activity, thermodynamic properties, and self-assembly behavior of these surfactants were systematically studied through surface tension, conductivity, steady-state fluorescence probes, transmission electron microscopy, and molecular dynamics simulations. The surface tension test results show that CnEO-5 has high surface activity and is higher than traditional single chain surfactants and structurally similar anionic non-ionic Gemini surfactants. Additionally, thermodynamic parameters (e.g., ΔG°_mic ΔH°_mic ΔS°_mic et al. indicate that CnEO-5 molecules are exothermic and spontaneous during the micellization process. DLS, p-values, and TEM results indicate that anionic non-ionic Gemini surfactants with shorter hydrophobic chains (such as C8EO-5) tend to form larger vesicles in aqueous solutions, which are formed in a tail to tail and staggered manner; Negative non-ionic Gemini surfactants with longer hydrophobic chains (such as C12EO-5, C16EO-5) tend to form small micelles. The test results indicate that CnEO-5 anionic non-ionic Gemini surfactants have certain application prospects in improving crude oil recovery. Full article

(This article belongs to the Special Issue Research Progress of Surfactants)

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