Search Results (970)

Deuterium-labelled amino acids have found extensive applications in such research areas as pharmaceutical, bioanalytical, neutron diffraction, inelastic neutron scattering, in analysis of drug metabolism using mass spectrometry (MS), and, structuring of biomolecules by NMR. For these reasons, interest in new methodologies for the deuterium labelling of amino acids and the extent of their applications are equally rising. The ideal method will be able to label target compounds rapidly and cost-effectively by the direct exchange of a hydrogen atom by a deuterium atom. Most of these exchange reactions can often be carried out directly on the final target compound or a late intermediate in the synthesis, and often D₂O can be used as the deuterium source. This review aims to provide a high-level overview of the chemical deuteration of amino acids in various groups (aromatic, heterocyclic, and non-aromatic α-amino acids). It primarily focuses on metal-catalyzed H/D exchange under hydrothermal conditions, with some attention given to studies on stereoselectivity and chemically synthesized perdeuteration and selective deuteration. In addition, we present different methods tested, manipulated, and developed for versatile new scalable protocols for preparation of selective and perdeuterated biologically important amino acids and their enzymatic and kinetic resolution to give pure enantiomers. Different methods for the synthesis of stereocontrolled selective and perdeuterated amino acids, including synthetic, and methods for preparing optically pure amino acids are presented. Full article

Background: Trimetazidine is a clinically established cardioprotective agent with anti-ischemic and antioxidant properties, widely used in the management of coronary artery disease. Combining its metabolic and cytoprotective effects with the potent anti-inflammatory activity of profens presents a promising therapeutic strategy. Methods: Five novel trimetazidine–profen hybrid compounds were synthesized using N,N′-dicyclohexylcarbodiimide-mediated coupling and structurally characterized by NMR and high-resolution mass spectrometry. Their antioxidant activity was evaluated by hydroxyl radical scavenging assays (HRSA), and the anti-inflammatory potential was assessed via the inhibition of albumin denaturation (IAD). Lipophilicity was determined chromatographically. Molecular docking and 100 ns molecular dynamics simulations were performed to investigate the binding modes and stability in human serum albumin (HSA) binding sites. The acute toxicity of the hybrid molecules was predicted in silico using GUSAR software. Results: All synthesized hybrids demonstrated varying degrees of biological activity, with compound 3c exhibiting the most potent antioxidant (HRSA IC₅₀ = 71.13 µg/mL) and anti-inflammatory (IAD IC₅₀ = 108.58 µg/mL) effects. Lipophilicity assays indicated moderate membrane permeability, with compounds 3c and 3d showing favorable profiles. Docking studies revealed stronger binding affinities of S-enantiomers, particularly 3c and 3d, to Sudlow sites II and III in HSA. Molecular dynamics simulations confirmed stable ligand–protein complexes, highlighting compound 3c as maintaining consistent and robust interactions. The toxicity results indicate that most hybrids, particularly compounds 3b–3d, exhibit a favorable safety profile compared to the parent trimetazidine. Conclusion: The hybrid trimetazidine–profen compounds synthesized herein, especially compound 3c, demonstrate promising dual antioxidant and anti-inflammatory therapeutic potential. Their stable interaction with serum albumin and balanced physicochemical properties support further development as novel agents for managing ischemic heart disease and associated inflammatory conditions. Full article

Chirality is a prevalent characteristic of natural systems that plays a significant role in the biological activities of living organisms, and the enantiomers typically exhibit different pharmacological activities. Consequently, developing methods with high selectivity and sensitivity for chiral analysis is of great importance for pharmaceutical engineering, biomedicine, and food safety. Electrochemical chiral recognition has garnered significant attention owing to its unique advantages, including simplicity of operation, rapid response, and cost-effectiveness. The biomaterials, such as amino acids, proteins, nucleic acids, and polysaccharides, possess inherent chiral sites, excellent biocompatibility, and abundant modifiable groups, rendering them ideal candidates for constructing electrochemical chiral sensors. This review focuses on the research progress of electrochemical chiral recognition based on different biomaterials from 2019 to 2024. In addition, the distinct chiral recognition mechanisms and electrochemical analysis methods, as well as the research challenges and prospects of electrochemical chiral sensors based on biomaterials in enantiomer recognition are discussed. This review can provide a reference for further study in related fields. Full article

Several carrier proteins are involved in nuclear translocation from the cytoplasm to the nucleus in eukaryotic cells. We have previously demonstrated the binding of several intact folded and disordered proteins to the human isoform importin α3 (Impα3); furthermore, disordered peptides, corresponding to their nuclear localization signals (NLSs), also interact with Impα3. These proteins and their isolated NLSs also bind to the truncated importin species ∆Impα3, which does not contain the N-terminal disordered importin binding domain (IBB). In this work, we added a further ‘layer’ of conformational disorder to our studies, testing whether the isolated D-enantiomers of NLSs of selected proteins, either folded or unfolded, were capable of binding to both Impα3 and ∆Impα3. The D-enantiomers, like their L-form counterparts, were monomeric and disordered in isolation, as shown by nuclear magnetic resonance (NMR). We measured the ability of such D-enantiomeric NLSs to interact with both importin species by using fluorescence, biolayer interferometry (BLI), isothermal titration calorimetry (ITC), and molecular simulations. In all cases, the binding affinities were within the same range as those measured for their L-isomer counterparts for either Impα3 or ∆Impα3, and the binding locations corresponded to the major NLS binding site of the protein. Thus, the stereoisomeric nature is not important in defining the binding of proteins to the main component of classical cellular translocation machinery, although the primary structure of the hot-spot site for NLS binding of importin is well defined. Full article

First-line treatment for localized prostate cancer (PCa) includes radical prostatectomy (RP) for high-risk disease. However, in many cases, patients experience biochemical recurrence (BCR), heralded by rising prostate specific antigen (PSA) levels in the serum. Our goal was to identify metabolic pathways that are disrupted in BCR to determine potential targets of therapy. We conducted metabolomic analysis in prostate tissue from the tumors of 74 patients who underwent prostatectomy as treatment for localized PCa and correlated levels of metabolites with clinical and non-clinical factors. Cholesterol and triglycerides were upregulated in Hispanic vs. non-Hispanic and in obese vs. non-obese individuals, respectively. Both lipids and non-lipids were altered with increasing Gleason grades and clinical stages. High post-RP PSA (>0.1 ng/mL) indicated recurrence (p = 0.0094) and correlated with alterations in 141 metabolites including 114 lipids and 26 non-lipid molecules. The largest increase with high post-RP PSA was in 2-hydroxyglutaric acid (2-HG), a product of the tricarboxylic acid (TCA) cycle, that had previously been established as an oncometabolite in other cancers. 2-HG was highly selective and specific for high post-RP PSA (AUC = 0.8526; p = 0.0002) while Kaplan–Meier curves indicated that among patients who recurred, high 2-HG in the tumor reduced time-to-recurrence from 84 months (for those with low 2-HG) to 38 months (for those with high 2-HG). The addition of D2HG, an enantiomer of 2-HG, increased the growth rate of LNCaP and C4 cells, and also increased Akt and ERK phosphorylation. 2-HG is upregulated in PCa tumors from patients who experience high post-RP PSA indicative of recurrence. Future studies may target this metabolite to prevent recurrent disease. Full article

Chiral liquid chromatography (cLC) using chiral stationary phases (CSPs) has become a crucial technique for separating enantiomers. Understanding enantiomeric discrimination is essential for improving chromatographic conditions and elucidating chiral molecular recognition; the computational methods are extremely helpful for this. To assess the relevance of the association of these two approaches and to analyze the current trends, in this review, a systematic analysis of the scientific literature was performed, covering recently published works (from 2015 to January 2025) on enantioseparation by cLC using CSPs and computational studies. CSPs based on polysaccharides and Pirkle-type were the most described (accounting for 52% and 14% of the studies, respectively). Regarding the computational methods, molecular docking and molecular dynamics (MD) were the most reported (accounting for 50% and 25% of the studies, respectively). In the articles surveyed, a significant growth in research concerning both cLC enantioseparation and computational studies is evident, emphasizing the benefit of the synergy between these two approaches. Full article

The separation of three proton pump inhibitors (omeprazole, lansoprazole, and rabeprazole) as exemplified molecules containing chiral sulfoxide groups was investigated in polar organic liquid chromatographic mode on seven different polysaccharide stationary phases (Chiralcel OD and OJ; Chiralpak AD, AS, and IA; Lux Cellulose-2 and -4). Different alcohols, such as methanol, ethanol, 1-propanol, 2-propanol, and their combinations, were used as eluents. After method optimization, semi-preparative enantioseparation was successfully applied for the three proton pump inhibitors to collect the individual enantiomers. A detailed investigation was conducted into elution order reversal, thermodynamic parameters, the effect of eluent mixtures, and the hysteresis of retention time and selectivity. Using Chiralpak AS, containing the amylose tris[(S)-α-methylbenzylcarbamate] chiral selector, the separation of the investigated enantiomers was achieved in all four neat eluents, with methanol providing the best results. In many cases, a reversal of the enantiomer elution order was observed. In addition to chiral-selector-dependent reversal, eluent-dependent reversal was also observed. Notably, even replacing methanol with ethanol altered the enantiomer elution order. Both enthalpy- and entropy-controlled enantioseparation were also observed in several cases; however, temperature-dependent elution order reversal was not. The hysteresis of retention and selectivity was further investigated on amylose-type columns in methanol–2-propanol and methanol–ethanol eluent mixtures. The phenomenon was observed on all amylose columns regardless of the eluent mixtures employed. Hystereticity ratios were calculated and used to compare the hysteresis behaviors of different systems. Multivariate statistical analysis revealed that Chiralpak AS exhibited the most distinct enantioselective behavior among the tested columns, likely due to the absence of a direct connection between the carbamate moiety and the aromatic substituent. The present study aided in understanding the mechanisms leading to enantiomer recognition, which is crucial for developing new chiral stationary phases and chiral HPLC method development in general. Full article

The paper proposes a putative prebiotic scenario leading to homochirality in the RNA world. In this scenario, racemic ribose, the only chiral moiety in RNA, was enantioseparated (in its pyranose form) on a chiral surface formed by the adsorption of (prochiral) nucleobases (NBs) on a mineral or metal. Purine bases (adenine and guanine) are more likely candidates for this process than pyrimidine bases because they have more H-bond donors and acceptors. Another possible candidate surface for the enantioseparation of ribose would be formed by the adsorption of nucleobase pairs, e.g., guanine–cytosine (GC). Interactions of ribose molecules with hydrogen bond donors and acceptors of NBs or NB pairs (located on the surface) enforced the orientation of ribose molecules in two directions perpendicular to each other and parallel to the surface. Consequently, the energy of interactions of enantiomers of the sugar with the surface was not the same. Thus, a solvent moving along the surface caused the enantiomers of ribose to move with different rates, resulting in the enantioseparation of ribose in a chromatography-like process. The same process would also separate ribose from other monosaccharides in the mix. Hydrogen bonding between nucleobases was also pivotal in the formation of large homochiral domains on the surfaces. Full article

The growing need for developing safer and more effective methods for obtaining enantiomers of chiral compounds, particularly those with pharmacological activity, highlights the potential of biocatalysis as an appropriate pharmaceutical research direction. However, low catalytic activity and stability of free enzymes are often among the substantial limitations to the wide application of biocatalysis. Therefore, to overcome these obstacles, new technological procedures are being designed. In this study, we present optimized protocols for the immobilization of Candida antarctica lipase B (CALB) on an octyl- agarose support, ensuring high enantioselectivity in an organic reaction medium. The immobilization procedures (with drying step), including buffers with different pH values and concentrations, as well as the study of the influence of temperature and immobilization time, were presented. It was found that the optimal conditions were provided by citrate buffer with a pH of 4 and a concentration of 300 mM. The immobilized CALB on the octyl-agarose support exhibited high catalytic activity in the kinetic resolution of (R,S)-1-phenylethanol via enantioselective transesterification with isopropenyl acetate in 1,2-dichloropropane (DCP), as a model reaction for lipase activity monitoring on an analytical scale. HPLC analysis demonstrated that the (R)-1-phenylethyl acetate was obtained in an enantiomeric excess of ee_p > 99% at a conversion of approximately 40%, and the enantiomeric ratio was E > 200. Thermal and storage stability studies performed on the immobilized CALB octyl-agarose support confirmed its excellent stability. After 7 days of thermal stability testing at 65 °C in a climatic chamber, the (R)-1-phenylethyl acetate was characterized by enantiomeric excess of ee_p > 99% at a conversion of around 40% (similar values of catalytic parameters to those achieved using a non-stored lipase). The documented high catalytic activity and stability of the developed CALB-octyl-agarose support allow us to consider it as a useful tool for enantioselective transesterification in organic medium. Full article

Chirality plays a key role in the effectiveness and toxicity of bioactive compounds. Usnic acid (UA), a lichen metabolite, exists as two enantiomers. Despite numerous studies on its biological properties, enantioselective aspects remain poorly recognized. This study assessed the cytotoxicity of UA enantiomers against colon, prostate, thyroid, brain, and breast cancer cell lines, as well as non-cancerous cells. Cell viability was determined by the MTT assay after 24, 48, and 72 h. Colon cancer HCT116 cells were the most sensitive (IC₅₀ ~10 µg/mL, 72 h), with no enantiomeric dominance. In prostate cancer PC3 cells, (+)-UA was more effective. Moderate cytotoxic effect was noted for thyroid cancer cells; however, this was evaluated for the first time. MDA-MB-231 breast cancer cells were strongly affected (IC₅₀ 15.8 and 20.2 µg/mL for (+)- and (−)-UA, 72 h), as compared to MCF7 cells. Brain cancer cells were the least affected, as so were normal astrocytes. UA had no effect on normal colon epithelial cells but showed moderate toxicity in prostate, thyroid, and breast cells. To conclude, the overall cytotoxicity of (+)-UA was stronger than its (−)-enantiomer, while the latter compound was more toxic to normal cells. These findings highlight the advantage of (+)-UA, especially in chemopreventive strategies. Full article

The bis-thiourea chiral solvating agent (CSA) BTDA enables the NMR-based determination of absolute configuration in N-3,5-dinitrobenzoyl (DNB) amino acid derivatives without requiring covalent derivatization. A reliable trend of the sense of nonequivalence and absolute configuration is found in both ¹H and ¹³C NMR spectra. A dual-enantiomer approach, using (R,R)- and (S,S)-BTDA, generates diastereomeric complexes with the enantiopure substrate, and distinct spatial arrangements are reflected in consistent and interpretable Δδ values. The observed chemical shift differences correlate reliably with the stereochemistry of the chiral center and are further supported by ROESY (Rotating-frame Overhauser Enhancement SpectroscopY) experiments and binding constants’ measurements, confirming the formation of stereoselective non-covalent complexes. This methodology extends the logic of Mosher’s analysis to solvating agents and remains effective even in samples containing single pure enantiomers of the amino acid derivative. The BTDA-based dual-CSA system thus represents a robust, non-derivatizing strategy for stereochemical assignment by NMR, combining operational simplicity with broad applicability to DNB derivatives of amino acids with free carboxyl function. Full article

Penicyclone A is a polyketide compound with a unique and intriguing structure recently isolated from the fungus Penicillium sp. F23-2 during an OSMAC (one-strain-many-compounds) campaign. The compound demonstrated significant antimicrobial activity without exhibiting any cytotoxic effects, which prompted us to pursue total synthesis of the reported enantiomer. Upon completion of the synthesis, we observed that our synthetic compound lacked antimicrobial activity. Further analysis suggested that the natural product may have, in fact, been the opposite enantiomer to that reported. This observation led us to synthesize the antipodal enantiomer using our previously developed synthetic sequence and to evaluate the biological activity (via antibacterial and cytotoxicity assays) of both the final compound and the selected intermediates from both enantiomeric series. Full article

The reaction of either the L (2S3R) or D (2R3S) enantiomers of H₂N-C*H(R)CO₂⁻ (R = -C*H(OH)CH₃ or -C*H(OH)CH(CH₃)₂) and the L (2S) or D (2R) enantiomers of H₂N-C*H(C(CH3)₂OH)CO₂⁻ with imidazole-4-carboxaldehyde and nickel(II) acetate in methanol yields a single stereoisomer of an oxazolidine. There is retention of chirality on ring positions 4 and 5 (if C_β is chiral) of the oxazolidine, C_α and C_β of the parent amino acid, and transfer of chirality to the newly generated stereogenic centers, ring positions 3, the amino acid nitrogen atom, N_AA, and 2, the aldehyde carbon atom, C_ald. Specifically, when C_α has an S configuration, both N_AA and C_ald are formed as R. Likewise, a C_α which is R results in both N_AA and C_ald being formed as S. For example, the reaction of L threonine (C_α is S and C_β is R) with 4-imidazolecarboxaldehyde in the presence of nickel(II) gives the facial Λ NiL₂, where L is (2R, 3R, 4S, 5R) 4-carboxylato-5-methyl-2-(4-imidazolyl)-1,3-oxazolidine. The same reaction with D threonine produces the enantiomeric Δ complex of (2S, 3S, 4R, 5S) 4-carboxylato-5-methyl-2-(4-imidazoyl)-1,3-oxazolidine. The high stereospecificity is thought to be based on the fused three-ring structure of the characterized nickel complexes in which the hydrogen atoms of C_α, N_AA, and C_ald must be cis to one another. Identical reactions occur with 2-pyridine carboxaldehyde and LT or DT. In contrast, the reactions of L allo threonine (2S3S) and the primary alcohols, L or D serine, give the conventional meridionally coordinated aldimine product. Full article

Root and crown rot in strawberries caused by Neopestalotiopsis rosae (N. rosae) results in yield losses of approximately 70%. The main method of control is based on the application of fungicides; however, the excessive use of these products can induce resistance by pathogens to the active ingredients. The use of secondary metabolites is an alternative to disease management. Usnic acid (UA), a secondary metabolite produced by lichens, has shown antimicrobial and antifungal activities that could be useful for the management of phytopathogens, particularly the (+) enantiomer. To provide alternatives to fungicides, the potential of UA as an alternative for N. rosae management was evaluated under in vitro and in vivo conditions. Using the “poisoned medium” technique, concentrations of 0 (UA0), 100 (UA1), 200 (UA2), and 400 (UA4) µg/mL UA at a dose of 2.5 mL/L PDA were evaluated on N. rosae mycelial growth and the number of spores. The UA at 400 µg/mL exhibited a fungistatic effect, reducing the mycelial growth of isolates of N. rosae in 50–60%. In the in vivo assay, sprayed UA (400 µg/mL) reduced hydrogen peroxide (48.59%) and malonaldehyde (77.62%) contents in “Albion” strawberry seedlings inoculated with 466 and FREC2 strains, respectively. These findings suggest that UA could be a potential tool for N. rosae management and could help mitigate the oxidative stress induced by infection. However, field trials are required to evaluate and validate this response. Full article

Carnitine (CA) is a chiral amino acid and mostly comes from meat and dairy products. CA cannot be found in fruits, vegetables, or other plants, so vegetarians are deficient in CA. CA exists in the form of D-carnitine (D-CA) and L-carnitine (L-CA); only L-carnitine has biological activity. L-CA promotes the oxidation of fatty acids and then causes the effect of weight loss. In this study, the fluorescence probe was established by using graphene oxide-modified cadmium telluride (CdTe) QDs (GO-CdTe QDs) for the chiral recognition of carnitine enantiomers. GO-CdTe QDs present fluorescence. D-CA enhances the fluorescence spectral signal of the GO-CdTe QDs system, while L-CA weakens its spectral signal. Based on this phenomenon, we determined D-carnitine and L-carnitine. Full article