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

Summary: Inhibition 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. [ABSTRACT FROM AUTHOR]