Inhibition of .ALPHA.-Glucosidase and .ALPHA.-Amylase by Flavonoids

The inhibitory activity of six groups of flavonoids against yeast and rat small intestinal alpha-glucosidases and porcine pancreatic alpha-amylase was compared, and chemical structures of flavonoids responsible for the inhibitory activity were evaluated. Yeast alpha-glucosidase was potently inhibited by the anthocyanidin, isoflavone and flavonol groups with the IC50 values less than 15 microM. The following structures enhanced the inhibitory activity: the unsaturated C ring, 3-OH, 4-CO, the linkage of the B ring at the 3 position, and the hydroxyl substitution on the B ring. Rat small intestinal alpha-glucosidase was weakly inhibited by many flavonoids, and slightly by the anthocyanidin and isoflavone groups.…