Molecular insights into α-glucosidase inhibition and antiglycation properties affected by the galloyl moiety in (−)-epigallocatechin-3-gallate

BACKGROUND Diabetes mellitus poses a substantial threat to public health due to rising morbidity and mortality. α-Glucosidase is one of the key enzymes affecting diabetes. Herein, (−)-epigallocatechin-3-gallate (EGCG) and (−)-epigallocatechin (EGC) were applied to clarify the role of the galloyl moiety of tea polyphenols in the inhibition of glycation and α-glucosidase activity. The structure–activity relationship of the galloyl moiety in EGCG on α-glucosidase was investigated in terms of inhibition kinetics, spectroscopy, atomic force microscopy and molecular docking. A bovine serum protein–fructose model was employed to determine the effect of the galloyl moiety on glycation. RESULTS The results indicated that the introduction of a galloyl moiety enhanced the capacity of EGCG to inhibit glycation and α-glucosidase activity. The IC 50 value of EGC is approximately 2400 times higher than that of EGCG. Furthermore, the galloyl moiety in EGCG altered the microenvironment and secondary structure of α-glucosidase, resulting in a high binding affinity of EGCG to α-glucosidase. The binding constant of EGCG to α-glucosidase at 298 K is approximately 28 times higher than that of EGC. CONCLUSION Overall, the galloyl moiety of EGCG plays a crucial role in inhibiting glycation and α-glucosidase activity, which helps to enhance the molecular understanding of the structure and function of the polyphenol galloyl moiety in the science of food and agriculture. © 2023 Society of Chemical Industry.