Inhibitory Activities of Rubi Fructus on Digestive Enzymes

Control of postprandial glucose level is important in the management of diabetes. Thus, carbohydrate-hydrolyzing enzymes have been the targets to delay absorption of glucose. In this study, water extracts of Rubi Fructus (WERF) showed inhibition on both alpha-glucosidase from baker's yeast and alpha-amylase from porcine pancreas. The IC50 value of WERF on alpha-amylase was 59.4 mu g/mL. The inhibitory activities of WERF were considerably decreased during incubation at 25, 37, and 45 degrees C for 24 hr. For the assessment of the active components tannin fraction was separated from WERF using Sephadex LH-20. Whereas LH-unbound fraction showed minimal inhibition on alpha-amylase LH-bound fraction containing enriched tannins showed higher inhibition (IC50 8.9 mu g/mL) than WERF (IC50 59.41 mu g/mL). These results suggested that tannin enriched fraction of WERF contributed to the inhibitory activity of WERF on alpha-amylase.