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

Non-enzymatic glycosylation of proteins leads to the formation of advanced glycation end products (AGEs), implicated in oxidative stress and the progression of several chronic diseases. Among the reactive carbonyl compounds, methylglyoxal (MGO) is highly potent in inducing glycoxidative damage by modifying proteins. Herein, we investigated the protective effect of plumbagin, a naphthoquinone derived from Plumbago zeylanica, to counteract MGO-induced glycation of catalase, employing integrated biophysical and computational approaches. AGE-specific fluorescence at 335 and 370 nm, ThT dye fluorescence, and microscopic visualizations confirmed that plumbagin markedly reduces AGEs formation and aggregation. Fluorescence quenching experiments revealed a stable catalase-plumbagin complex formation having binding affinity (Ka): 0.205 × 106 M-1 and a stoichiometry of one binding site (n ≈ 1.1), suggesting a single, specific binding pocket. Isothermal titration calorimetry (ITC) confirmed an exothermic, enthalpy-driven interaction. Molecular dynamics simulations (MDS) analysis displayed a more compact and ordered conformation of complex, as evidenced by reduced Rg, SASA, and RMSF values. H-bonds stabilized the complex without altering the catalytic residues (His74, Asn147, Tyr357). PCA and FEL showed complex remained confined to a single deep energy minimum, indicating enhanced thermodynamic stability. These findings highlight plumbagin as a potent multifunctional compound capable of mitigating MGO-induced glycation.