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From Natural to Synthetic Small-Molecule Antioxidants: New Candidates in Drug Discovery—Second Edition

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A special issue of Antioxidants (ISSN 2076-3921). This special issue belongs to the section "Natural and Synthetic Antioxidants".

Deadline for manuscript submissions: closed (31 August 2024) | Viewed by 9344

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Special Issue Editors

Dr. Gabriele Carullo

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Department of Life Sciences, University of Siena, 53100 Siena, Italy
Interests: HDAC; vasorelaxant agents; antioxidant and anti-inflammatory nutraceuticals; leukemia; Pseudomonas aeruginosa; hybrid compounds; retinitis pigmentosa
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Dr. Roberta Ibba

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Department of Medicine, Surgery and Pharmacy, University of Sassari, Via Muroni 23A, 07100 Sassari, Italy
Interests: medicinal chemistry; drug design; anticancer drugs; antiviral; VEGFR-2; natural compounds; antioxidants; fragment-based drug design
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Dr. Valeria Tudino

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Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
Interests: medicinal chemistry; HIV; anticancer compounds; antimicrobial agents; nitrogen-based compounds; Pseudomonas aeruginosa
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Dr. Maria Dichiara

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Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
Interests: medicinal chemistry; drug design; anticancer drugs; infectious diseases; de novo synthetic compounds; neurological disorders
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Special Issue Information

Dear Colleagues,

In view of the great response we received with the previous Special Issue, "From Nature to Synthetic Small Molecule Antioxidants: New Candidates in Drug Discovery", we decided to continue addressing this topic through a Second Edition.

Natural compounds are well known for their invaluable contribution to pharmacological research in several therapeutic areas. Over the years, natural product collections have offered a wide variety of pharmacophores. These have been exploited in drug discovery to provide new lead compounds that are able to tackle even the most difficult screened targets.

This Special Issue, entitled “From Natural to Synthetic Small-Molecule Antioxidants: New Candidates in Drug Discovery—Second Edition”, aims to welcome both original articles and extensive reviews related to natural products, their derivatives, and de novo designed compounds in drug discovery efforts. Oxidative-stress-related conditions, reactive oxygen species, oxidative damage, and inflammatory stimuli are topics of great interest for modern medicinal chemistry, and therefore, they will be welcome in this Special Issue. For publication, we will consider the following topics: the bioactivity of medicinal plant extracts, the development of natural-derived compounds, biological applications and synthetic strategies for natural metabolites and/or analogues, and the rational or computer-aided design and development of synthetic small-molecule derivatives with pharmacological interest. Furthermore, applications looking at different disorders, from cancers to infectious diseases, as well as cardiovascular, neurological, and other human conditions, will also be considered.

Dr. Gabriele Carullo
Dr. Roberta Ibba
Dr. Valeria Tudino
Dr. Maria Dichiara
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Antioxidants is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

natural products
nutraceuticals
antioxidants
de novo synthetic compounds
GPCRs
ion channels
anticancer compounds
cardiovascular diseases
neurological disorders
infectious diseases

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Published Papers (7 papers)

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Research

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26 pages, 3745 KiB

Open AccessArticle

Exploring the 3,5-Dibromo-4,6-dimethoxychalcones and Their Flavone Derivatives as Dual α-Glucosidase and α-Amylase Inhibitors with Antioxidant and Anticancer Potential

by Jackson K. Nkoana, Malose J. Mphahlele, Garland K. More and Yee Siew Choong

Antioxidants 2024, 13(10), 1255; https://doi.org/10.3390/antiox13101255 - 17 Oct 2024

Viewed by 320

Abstract

The rising levels of type 2 diabetes mellitus (T2DM) and the poor medical effects of the commercially available antidiabetic drugs necessitate the development of potent analogs to treat this multifactorial metabolic disorder. It has been demonstrated that targeting two or more biochemical targets associated with the onset and progression of diabetes along with oxidative stress and/or cancer could be a significant strategy for treating complications related to this metabolic disorder. The 3,5-dibromo-4,6-dimethoxychalcones (2a–f) and the corresponding flavone derivatives (3a–f) were synthesized and characterized using spectroscopic (NMR, HR-MS and FT-IR) techniques. The inhibitory effect of both series of compounds against α-glucosidase and α-amylase was evaluated in vitro through enzymatic assays. Selected compounds were also evaluated for potential to activate or inhibit superoxide dismutase. Compound 3c was selected as a representative model for the flavone series and evaluated spectrophotometrically for potential to coordinate Cu(II) and/or Zn(II) ions implicated in the metal-catalyzed free radical generation. A plausible mechanism for metal-chelation of the test compounds is presented. Furthermore, the most active compounds from each series against the test carbohydrate-hydrolyzing enzymes were selected and evaluated for their antigrowth effect on the human breast (MCF-7) and lung (A549) cancer cell lines and for cytotoxicity against the African Green Monkey kidney (Vero) cell line. The parent chalcone 2a and flavone derivatives 3a, 3c and 3e exhibited relatively high inhibitory activity against the MCF-7 cells with IC₅₀ values of 4.12 ± 0.55, 8.50 ± 0.82, 5.10 ± 0.61 and 6.96 ± 0.66 μM, respectively. The chalcones 2a and 2c exhibited significant cytotoxicity against the A549 cells with IC₅₀ values of 7.40 ± 0.67 and 9.68 ± 0.80 μM, respectively. Only flavone 3c exhibited relatively strong and comparable cytotoxicity against the MCF-7 and A549 cell lines with IC₅₀ values of 6.96 ± 0.66 and 6.42 ± 0.79 μM, respectively. Both series of compounds exhibited strong activity against the MCF-7 and A549 cell lines compared to the analogous quercetin (IC₅₀ = 35.40 ± 1.78 and 35.38 ± 1.78 μM, respectively) though moderate compared to nintedanib (IC₅₀ = 0.53 ± 0.11 and 0.74 ± 0.15 μM, respectively). The test compounds generally exhibited reduced cytotoxicity against the Vero cells compared to this anticancer drug. Molecular docking revealed strong alignment of the test compounds with the enzyme backbone to engage in hydrogen bonding interaction/s and hydrophobic contacts with the residues in the active sites of α-glucosidase and α-amylase. The test compounds possess favorable drug-likeness properties, supporting their potential as therapeutic candidates against T2DM. Full article

(This article belongs to the Special Issue From Natural to Synthetic Small-Molecule Antioxidants: New Candidates in Drug Discovery—Second Edition)

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28 pages, 10692 KiB

Open AccessArticle

Design, Synthesis, and Anti-Melanogenic Activity of 2-Mercaptomethylbenzo[d]imidazole Derivatives Serving as Tyrosinase Inhibitors: An In Silico, In Vitro, and In Vivo Exploration

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

Antioxidants 2024, 13(10), 1248; https://doi.org/10.3390/antiox13101248 - 16 Oct 2024

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Abstract

2-Mercaptomethylbenzo[d]imidazole (2-MMBI) derivatives were designed and synthesized as tyrosinase (TYR) chelators using 2-mercaptomethylimidazole scaffolds. Seven of the ten 2-MMBI derivatives exhibited stronger inhibition of mushroom TYR activity than kojic acid. Their ability to chelate copper ions was demonstrated through experiments using the copper chelator pyrocatechol violet and assays measuring TYR activity in the presence or absence of exogenous CuSO₄. The inhibition mechanisms of derivatives 1, 3, 8, and 9, which showed excellent TYR inhibitory activity, were elucidated through kinetic studies and supported by the docking simulation results. Derivatives 3, 7, 8, and 10 significantly inhibited cellular TYR activity and melanin production in B16F10 cells in a dose-dependent manner, with stronger potency than kojic acid. Furthermore, in situ, derivatives 7 and 10 showed stronger inhibitory effects on B16F10 cell TYR activity than kojic acid. Six derivatives, including 8, showed highly potent depigmentation in zebrafish larvae, outpacing kojic acid even at 200–670 times lower concentrations. Additionally, all derivatives could scavenge for reactive oxygen species without causing cytotoxicity in epidermal cells. These results suggested that 2-MMBI derivatives are promising anti-melanogenic agents. Full article

(This article belongs to the Special Issue From Natural to Synthetic Small-Molecule Antioxidants: New Candidates in Drug Discovery—Second Edition)

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23 pages, 4913 KiB

Open AccessArticle

7-O-tyrosyl Silybin Derivatives as a Novel Set of Anti-Prostate Cancer Compounds

by Valeria Romanucci, Rita Pagano, Kushal Kandhari, Armando Zarrelli, Maria Petrone, Chapla Agarwal, Rajesh Agarwal and Giovanni Di Fabio

Antioxidants 2024, 13(4), 418; https://doi.org/10.3390/antiox13040418 - 29 Mar 2024

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Abstract

Silybin is a natural compound extensively studied for its hepatoprotective, neuroprotective and anticancer properties. Envisioning the enhancement of silybin potential by suitable modifications in its chemical structure, here, a series of new 7-O-alkyl silybins derivatives were synthesized by the Mitsunobu reaction starting from the silybins and tyrosol-based phenols, such as tyrosol (TYR, 3), 3-methoxytyrosol (MTYR, 4), and 3-hydroxytyrosol (HTYR, 5). This research sought to explore the antioxidant and anticancer properties of eighteen new derivatives and their mechanisms. In particular, the antioxidant properties of new derivatives outlined by the DPPH assay showed a very pronounced activity depending on the tyrosyl moiety (HTYR > MTYR >> TYR). A significant contribution of the HTYR moiety was observed for silybins and 2,3-dehydro-silybin-based derivatives. According to the very potent antioxidant activity, 2,3-dehydro-silybin derivatives 15ab, 15a, and 15b exerted the most potent anticancer activity in human prostate cancer PC-3 cells. Furthermore, flow cytometric analysis for cell cycle and apoptosis revealed that 15ab, 15a, and 15b induce strong G1 phase arrest and increase late apoptotic population in PC-3 cells. Additionally, Western blotting for apoptotic marker cleaved caspase-3 confirmed apoptosis induction by these silybin derivatives in PC-3 cells. These findings hold significant importance in the investigation of anticancer properties of silybin derivatives and strongly encourage swift investigation in pre-clinical models and clinical trials. Full article

(This article belongs to the Special Issue From Natural to Synthetic Small-Molecule Antioxidants: New Candidates in Drug Discovery—Second Edition)

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28 pages, 5016 KiB

Open AccessArticle

Exploring Metabolic and Gut Microbiome Responses to Paraquat Administration in Male Wistar Rats: Implications for Oxidative Stress

by Julia Hernandez-Baixauli, Gertruda Chomiciute, Harry Tracey, Ignasi Mora, Antonio J. Cortés-Espinar, Javier Ávila-Román, Nerea Abasolo, Hector Palacios-Jordan, Elisabet Foguet-Romero, David Suñol, Mar Galofré, Juan María Alcaide-Hidalgo, Laura Baselga-Escudero, Josep M. del Bas and Miquel Mulero

Antioxidants 2024, 13(1), 67; https://doi.org/10.3390/antiox13010067 - 1 Jan 2024

Cited by 1 | Viewed by 2513

Abstract

In this study, we examined the metabolic and gut microbiome responses to paraquat (PQ) in male Wistar rats, focusing on oxidative stress effects. Rats received a single intraperitoneal injection of PQ at 15 and 30 mg/kg, and various oxidative stress parameters (i.e., MDA, SOD, ROS, 8-isoprostanes) were assessed after three days. To explore the omic profile, GC-qTOF and UHPLC-qTOF were performed to assess the plasma metabolome; ¹H-NMR was used to assess the urine metabolome; and shotgun metagenomics sequencing was performed to study the gut microbiome. Our results revealed reductions in body weight and tissue changes, particularly in the liver, were observed, suggesting a systemic effect of PQ. Elevated lipid peroxidation and reactive oxygen species levels in the liver and plasma indicated the induction of oxidative stress. Metabolic profiling revealed changes in the tricarboxylic acid cycle, accumulation of ketone body, and altered levels of key metabolites, such as 3-hydroxybutyric acid and serine, suggesting intricate links between energy metabolism and redox reactions. Plasma metabolomic analysis revealed alterations in mitochondrial metabolism, nicotinamide metabolism, and tryptophan degradation. The gut microbiome showed shifts, with higher PQ doses influencing microbial populations (e.g., Escherichia coli and Akkermansia muciniphila) and metagenomic functions (pyruvate metabolism, fermentation, nucleotide and amino acid biosynthesis). Overall, this study provides comprehensive insights into the complex interplay between PQ exposure, metabolic responses, and gut microbiome dynamics. These findings enhance our understanding of the mechanisms behind oxidative stress-induced metabolic alterations and underscore the connections between xenobiotic exposure, gut microbiota, and host metabolism. Full article

(This article belongs to the Special Issue From Natural to Synthetic Small-Molecule Antioxidants: New Candidates in Drug Discovery—Second Edition)

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22 pages, 7026 KiB

Open AccessArticle

Anti-Browning Effect of 2-Mercaptobenzo[d]imidazole Analogs with Antioxidant Activity on Freshly-Cut Apple Slices and Their Highly Potent Tyrosinase Inhibitory Activity

by Jieun Lee, Hye Soo Park, Hee Jin Jung, Yu Jung Park, Min Kyung Kang, Hye Jin Kim, Dahye Yoon, Sultan Ullah, Dongwan Kang, Yujin Park, Pusoon Chun, Hae Young Chung and Hyung Ryong Moon

Antioxidants 2023, 12(10), 1814; https://doi.org/10.3390/antiox12101814 - 29 Sep 2023

Cited by 3 | Viewed by 1406

Abstract

Ten 2-mercaptobenzimidazole (2-MBI) analogs were synthesized as potential tyrosinase inhibitors because mercapto-containing compounds can bind to copper ions at the active site of tyrosinase to inhibit enzyme activity. Nine 2-MBI analogs showed sub-micromolar IC₅₀ values for mushroom tyrosinase monophenolase activity; analog 4 was 280-fold more potent than kojic acid, and in diphenolase activity, 6 was 970-fold more potent than kojic acid. The inhibition mode of the 2-MBI analogs was investigated using kinetic studies supported by docking simulations. Benzimidazoles without the 2-mercapto substituent of the 2-MBI analogs lost their tyrosinase inhibitory activity, implying that the 2-mercapto substituent plays an important role in tyrosinase inhibition. The 2-MBI analogs exerted potent antioxidant effects against 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and reactive oxygen species (ROS). The results obtained from apple slices and human embryonic kidney cells (HEK-293) suggest that most 2-MBI analogs are sufficiently safe candidates to delay the browning of apple slices effectively. Thus, these results support the potential use of 2-MBI analogs as anti-browning agents in foods such as mushrooms, vegetables, and fruits. Full article

(This article belongs to the Special Issue From Natural to Synthetic Small-Molecule Antioxidants: New Candidates in Drug Discovery—Second Edition)

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Review

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13 pages, 1042 KiB

Open AccessReview

Exploring Angiotensin II and Oxidative Stress in Radiation-Induced Cataract Formation: Potential for Therapeutic Intervention

by Vidya P. Kumar, Yali Kong, Riana Dolland, Sandra R. Brown, Kan Wang, Damian Dolland, David Mu and Milton L. Brown

Antioxidants 2024, 13(10), 1207; https://doi.org/10.3390/antiox13101207 - 8 Oct 2024

Viewed by 574

Abstract

Radiation-induced cataracts (RICs) represent a significant public health challenge, particularly impacting individuals exposed to ionizing radiation (IR) through medical treatments, occupational settings, and environmental factors. Effective therapeutic strategies require a deep understanding of the mechanisms underlying RIC formation (RICF). This study investigates the roles of angiotensin II (Ang II) and oxidative stress in RIC development, with a focus on their combined effects on lens transparency and cellular function. Key mechanisms include the generation of reactive oxygen species (ROS) and oxidative damage to lens proteins and lipids, as well as the impact of Ang II on inflammatory responses and cellular apoptosis. While the generation of ROS from water radiolysis is well established, the impact of Ang II on RICs is less understood. Ang II intensifies oxidative stress by activating type 1 receptors (AT1Rs) on lens epithelial cells, resulting in increased ROS production and inflammatory responses. This oxidative damage leads to protein aggregation, lipid peroxidation, and apoptosis, ultimately compromising lens transparency and contributing to cataract formation. Recent studies highlight Ang II’s dual role in promoting both oxidative stress and inflammation, which accelerates cataract development. RICs pose a substantial public health concern due to their widespread prevalence and impact on quality of life. Targeting Ang II signaling and oxidative stress simultaneously could represent a promising therapeutic approach. Continued research is necessary to validate these strategies and explore their efficacy in preventing or reversing RIC development. Full article

(This article belongs to the Special Issue From Natural to Synthetic Small-Molecule Antioxidants: New Candidates in Drug Discovery—Second Edition)

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21 pages, 1510 KiB

Open AccessReview

An Update on Recent Studies Focusing on the Antioxidant Properties of Salvia Species

by Domenico Iacopetta, Jessica Ceramella, Domenica Scumaci, Alessia Catalano, Maria Stefania Sinicropi, Rosa Tundis, Stefano Alcaro and Fernanda Borges

Antioxidants 2023, 12(12), 2106; https://doi.org/10.3390/antiox12122106 - 13 Dec 2023

Cited by 2 | Viewed by 2077

Abstract

Nutrition has crucial effects and a significant role in disease prevention. Recently, nutraceuticals have attracted much attention in scientific research due to their pleiotropic effects and relatively non-toxic behavior. Among the biological effects displayed by plants belonging to the Lamiaceae family, such as antibacterial, anticancer, anti-inflammatory, and anticholinesterase, sage is well known for its antioxidant properties and is a rich source of numerous compounds that are biologically active, amongst them polyphenols, with more than 160 types identified. In this review we summarized some of the significant studies published in the last decade reporting the most employed extraction methods and the different assays that are useful for establishing the antioxidant properties of some sage species. Even though the scientific literature contains plenty of data regarding the antioxidant properties of many sage species, further studies are needed in order to gain a deeper understanding of the mechanism of action and the compounds responsible for their antioxidant activity. Finally, it should be taken into account that the data on the antioxidant properties of sage extracts are often difficult to compare with each other, since a series of variables in the extraction procedures, the type of assay used, and standardization may affect the final result. Full article

(This article belongs to the Special Issue From Natural to Synthetic Small-Molecule Antioxidants: New Candidates in Drug Discovery—Second Edition)

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