A study of the mechanism of α-glucosidase inhibition by rapeseed polyphenols

Type II diabetes mellitus is a non-communicable disease with high morbidity in today's world, and the inhibition of α-glucosidase is an effective modality for its amelioration and treatment. In the present study, some rapeseed polyphenols were identified using HPLC fingerprinting techniques. The inhibitory activities of procyanidin B2, caffeic acid, sinapic acid, and sinapine were evaluated through UV, fluorescence, infrared, and circular dichroism spectroscopy. Additionally, molecular docking and molecular dynamics simulation were employed to elucidate the inhibitory mechanism. The IC50 value of procyanidin B2 and its Ki were determined to be 0.09 ± 0.01 mg/mL and 1.13 ± 0.07 mg/mL, respectively. The calculated binding energy from AutoDock was -9.0 kcal/mol, and the end-state free energy was -29.05 ± 8.31 kcal/mol, indicating strong inhibitory activity. Consequently, procyanidin B2 is a promising anti-diabetic component. Notably, key residues such as ASP327, ASP443, ASP542, and ARG526 were identified, which interact with the inhibitor through hydrogen bonding and van der Waals forces, thereby affecting substrate binding.