Potential Antihyperglycemic Effects of Adzuki (<i>Vigna angularis</i>) Polyphenols on Mice and Caco-2 Cells

Background/Purpose Some health-beneficial foods, including adzuki beans ( Vigna angularis), can show antihyperglycemic effects. Adzuki bean-derived polyphenols, such as (+)-catechin 7- O- β-d-glucopyranoside (C7G) and (+)-epicatechin 7- O- β-d-glucopyranoside (E7G), could be potential inhibitors of α-amylase and α-glucosidase, however, few studies of the activity of adzuki polyphenols have been performed in vivo. Thus, we evaluated the antihyperglycemic effects of crude adzuki bean extract containing polyphenols (ABP), and purified C7G or E7G using mice and Caco-2 cells. Methods Six-week-old male ICR mice were orally administered ABP (100 or 250 mg/kg), C7G or E7G (15 or 40 mg/kg), and sucrose (2 g/kg). Blood samples were taken from the lateral tail vein to measure the blood glucose levels at various times over 0–120 min. Cultured caco-2 cells, an intestinal model, were treated with ABP, C7G, or E7G. The glucose concentration in the medium was measured to examine the activity of α-glucosidase. Results Administration of adzuki polyphenols decreased blood glucose levels, especially E7G administration significantly showed antihyperglycemic effects in vivo. In Caco-2 cells, α-glucosidase activity was significantly decreased by ABP, C7G, or E7G addition in a dose-dependent manner without cytotoxicity. Conclusion These results suggest that C7G and E7G in adzuki bean extract inhibited sucrose-degrading enzymes to elicit antihyperglycemic effects in vivo, which supports the results of previous studies using adzuki beans, and may contribute to health promotion.