Elucidating the Antiglycation Potential of Plumbagin Against Methylglyoxal-Induced Glycation of Bovine Liver Catalase.

Galangin and Caffeic acid inhibit Methylglyoxal-induced Advanced Glycation End Product formation in Bovine Serum Albumin

Meloxicam Inhibited the Glycation Phenomenon via Scavenging Di-Carbonyl Moieties

Senescence or aging is often associated with onset of morbidities, which have been attributed to the harmful phenomenon of glycation. To date, no drug is available to combat this deleterious process. The drug repurposing is a robust and cost-effective approach to identify potential candidate molecules for drug discovery programs. In present study, Meloxicam (MEL) was evaluated for its capacity to be repurposed against glycation. Using the Fructose-BSA model, the anti-glycation effect was evaluated by measuring intrinsic fluorescence of Advanced Glycation End Products (AGEs). The fructoseamine load and free lysine availability was estimated using NBT and TNBSA assays respectively. The BSA secondary structure was assessed by Thioflavin-T, Congo red and Circular Dichroism tests. Finally, lysine blockade and carbonyl entrapment was evaluated as a possible mode of anti-glycation action. Our data showed that MEL (0.5, 1, and 2mM) has significantly reduced the AGEs formation (IC50 = 0.25mM). The load of fructosamine adducts along with free lysine availability was found to be reduced. The secondary structure of BSA was preserved. Regarding mode of action, MEL did not block lysine residues, which was also supported by computational data. However, it was found to entrap carbonyl intermediates. In conclusion, the present study demonstrate that MEL possess anti-glycation potential, which can be attributed to entrapment of carbonyl intermediates. Hence, MEL, a clinically used NSAIDs, present itself as promising candidate to be repurposed against deleterious phenomenon of glycation.

Preferential formation of Nω-(carboxyethyl)arginine from methylglyoxal and its accumulation in human lens proteins.

Unveiling the Role of Mg2+ and Mn2+ in Theaflavin-Mediated Inhibition of Advanced Glycation End Products Formation: Mechanistic Insights from Intermolecular Interaction

Advanced glycation end products (AGEs) are implicated in the pathogenesis of chronic diseases. This study investigated the inhibitory effect of theaflavin (TA) on AGE formation in a human serum albumin (HSA)-fructose model system, both in the absence and presence of non-cytotoxic Mg2+ or Mn2+. The underlying mechanism was elucidated using multiple spectroscopic techniques and molecular docking. TA significantly inhibited AGE formation, with the enhancement by metal ions following the order: 1.5 μM Mn2+ > 1.5 μM Mg2+ > 1 mM Mg2+. This trend aligned with the binding affinity between HSA and TA derived from molecular interaction studies. Site marker competition and docking results revealed that TA binds preferentially within subdomain IIA of HSA. Furthermore, the conformational changes in HSA following glycation and inhibition were monitored, along with the influence of metal ions on the antioxidant activity of TA. By integrating the results, it was concluded that free radical scavenging contributes more significantly to AGE inhibition than does blocking the glycation sites on HSA. Overall, this study elucidates the influence of metal ions on the inhibitory effect of TA against AGE formation and the corresponding mechanism, providing insights for the prevention and management of chronic diseases.

Molecular insights into the anti-browning effect of protocatechualdehyde.

Polyphenol oxidase (PPO) is a vital polyphenol-metabolizing enzyme responsible for the enzymatic browning of fruits and vegetables. This study assessed the anti-PPO activity of protocatechualdehyde (PCA), yielding an IC50 value of 94 μM (95% CI: 91.8 to 96.4 μM). Kinetic analysis revealed that PCA acted as a reversible and competitive inhibitor of PPO. Molecular docking indicated that hydrogen bonding and hydrophobic interactions were the main driving forces for PCA-PPO binding. Fluorescence spectroscopy further demonstrated that PCA binding altered the microenvironments around tyrosine and tryptophan residues, leading to conformational rearrangements and partial unfolding of the enzyme, evidenced by significant fluorescence quenching. Molecular dynamics simulation demonstrated that PCA perturbed the secondary structure of PPO and caused stretching of its overall structure, thereby inhibiting the catalytic activity of the enzyme. Furthermore, PCA demonstrated excellent anti-browning activity by regulating phenolic metabolism, reducing membrane lipid peroxidation, enhancing the ascorbic acid-glutathione cycle, and modulating cell wall metabolism to delay cellular senescence. Collectively, these findings offer some valuable insights into the development of PPO inhibitor and anti-browning agent, and provide a theoretical foundation for the potential application of PCA in the area of food preservation.

Inhibitory Effects of Grape Seed Extract and Epicatechin on Malondialdehyde-Mediated Protein Lipoxidation.

Malondialdehyde (MDA) is one of the principal and most studied reactive carbonyl species derived from polyunsaturated fatty acid peroxidation. This aldehyde is a chemically reactive molecule and should not be considered merely as a marker of lipid peroxidation. Its interaction with proteins, commonly termed protein lipoxidation, modifies protein structure and functions, thus extending the hazards of lipid peroxidation. In this study, a simplified model mimicking MDA-mediated protein oxidation in bovine serum albumin (BSA) was established to simulate protein lipoxidation in food systems. Grape seed extract (GSE, 50-200 mg/L) and epicatechin (EC, 145-580 mg/L) significantly inhibited MDA-mediated protein lipoxidation in BSA, as evidenced by a marked decrease in lipofuscin-like fluorescence and confirmed via Western blot analysis of MDA-protein adduct formation. Nevertheless, concentration-dependent dual effects were observed by protein conformational changes (reduced sulfhydryl, surface hydrophobicity, and altered microstructure) at high concentrations of GSE and EC, although they exhibited potent inhibitory effects in MDA-mediated protein lipoxidation. HPLC quantification demonstrated that GSE scavenged 10-60% of MDA while EC scavenged 70-95%, indicating their direct contribution to MDA removal. Molecular docking simulations further implied a possible binding mode in which EC associates with BSA more favorably (lower free energy) than MDA, which may competitively block the sites accessible to MDA. Collectively, these findings support a mitigation strategy in which phenolic nucleophiles can be employed to counteract MDA-mediated protein lipoxidation.