Spectroscopy and molecular docking analysis reveal structural specificity of flavonoids in the inhibition of α-glucosidase activity.

The inhibition of α-glucosidase activity is a prospective approach to prevent postprandial hyperglycemia. As two flavonoids extracted from citrus fruits, eriocitrin and eriodictyol have similar structures and show multiple pharmacological activities. In order to investigate the effects of flavonoids structure on enzyme inhibition, spectroscopy and molecular docking analysis were used. Saccharomyces cerevisiae α-glucosidase (GH13) was used for studying the inhibitory mechanism by multi-spectroscopic analysis. Results indicated that they could quench the intrinsic fluorescence of α-glucosidase, the binding constants at 298 K were (7.02 ± 0.22) × 10 and (4.57 ± 0.16) × 10 L mol, respectively. The interaction between them with α-glucosidase were mainly driven by hydrophobic interaction, they induced conformational changes of α-glucosidase. The human α-glucosidase (C-terminal maltase-glucoamylase, GH31) was used in the molecular docking analysis to determine the interaction of eriocitrin and eriodictyol with the α-glucosidase. The results revealed that they could bind with α-glucosidase and might cause the decrease of α-glucosidase activity. The inhibitory effect of eriocitrin was stronger than that of eriodictyol, which might be due to the position and amount of hydroxyl groups. This work confirmed two novel α-glucosidase inhibitors and provided the structure-function relationship of flavonoids in inhibition of α-glucosidase activity.