Molecular characteristics of gallocatechin gallate affecting protein glycation

Abstract

As one of the most reactive dicarbonyl compounds, methylglyoxal (MGO) can react with protein to form advanced glycation end products (AGEs), then promoting the development of diabetic complications. Hence, it is significant for preventing protein glycation mediated by MGO. Here, the anti-glycation potential and mechanism of gallocatechin gallate (GCG) as an active ingredient of green tea were investigated. It was found that GCG exhibit good scavenging activities of O2.- and .OH radicals of lysine–MGO system by 92.9% and 15.6%, respectively. The inhibitions (%) of GCG at 354.0 μg/mL for AGEs, dityrosine and N-formylkynurenine in bovine serum albumin (BSA)–MGO system were 96.7%, 97.3% and 98.2%, respectively. GCG (17.8–354.0 μg/mL) trapped MGO in a dose-dependent manner, 82.5% of MGO was trapped and the trapping efficiency reached 46.6% within 12 h when the concentration of GCG was 354.0 μg/mL. Two GCG–mono-MGO adducts were found when the molar ratios of MGO to GCG were 1:3 and 1:6. The efficacy of GCG in recovering the amino groups content, tryptophan residues and hydrophobic pockets of BSA was weak. The binding constant between GCG and BSA was in the order of magnitude of 104 L/mol, and the simulation analysis showed that the GCG–BSA complex was stable. It was inferred that the molecular mechanism of GCG against protein glycation induced by MGO may be due to its scavenging activity of O2.- and .OH radicals, MGO trapping capability and BSA binding interaction. These results suggested that GCG may be a potential inhibitor of MGO-induced glycation and provide new insights into GCG as a dietary supplement in functional foods for ameliorating the diabetic complications of MGO-derived AGEs.