α-Glucosidase inhibiting activity and bioactive compounds of six red wine grape pomace extracts

Grape pomace contains considerable amounts of polyphenols and it has been reported to exhibit specific inhibitory activity against mammalian intestinal α-glucosidases. This study aims to investigate the anti-diabetes potential of Chambourcin, Merlot, Norton, Petit Verdot, Syrah and Tinta Cão red wine grape pomaces by assessing their rat intestinal α-glucosidase inhibitory activity in relation to their total phenolic content and individual identified phenolic compounds by HPLC. Among the selected pomaces, Tinta Cão, Syrah and Merlot extracts showed higher potency in inhibiting α-glucosidase, and appeared to have higher respective total phenolic contents. Fifteen phenolic compounds were identified in the pomace samples, however, none of them showed significant inhibition of intestinal α-glucosidases. Red grape pomace, namely Tinta Cão, appears to be a promising functional food for the potential future development of a food-derived α-glucosidase inhibitor for preventing and treating diabetes.