Discovery of a new tannin compound as an α‐glucosidase inhibitor from Carya cathayensis Sarg. kernels and its inhibitory kinetics

Abstract

SummaryInhibition of α‐glucosidases is recognised as an effective approach towards managing postprandial hyperglycaemia. This study aimed to identify a specific compound in Carya cathayensis Sarg. kernels (CCSKs) exhibiting strong inhibitory activities against α‐glucosidase and elucidate the inhibitory kinetic mechanism. Employing a bioassay‐guided approach, an α‐glucosidase inhibitor was isolated from CCSKs through sequential chromatography protocol involving AB‐8 macroporous adsorptive resin, Sephadex LH‐20 and C18‐reversed phase silica gel. The resulting inhibitor was a novel tannin compound, identified as rugosin C ethyl ester. Rugosin C ethyl ester displayed superior inhibitory activity (IC50 of 2.60 μg/mL) compared to acarbose (IC50 of 105.95 μg/mL). The kinetic analysis indicated that rugosin C ethyl ester had a mixed‐type reversible inhibition against α‐glucosidase. The inhibition constants (Ki and Kis) were determined to be 3.119 and 0.856 μg/mL, respectively. The findings indicated that rugosin C ethyl ester might serve as a promising functional ingredient in low‐glycemic index foods.