In vitro and in vivo postprandial hypoglycemic effects and comprehensive metabolite profiling of Dangjo chili pepper (Capsicum annuum L. cv. Dangjo)

Abstract

The Dangjo chili pepper (DJ) has been reported to contain various compounds with α-glucosidase inhibitory activity. However, the hypoglycemic effect of DJ and the active ingredients responsible have not been fully investigated. Herein, the current study aimed to examine DJ as a novel α-glucosidase inhibitor for the prevention of hyperglycemia. The identification of metabolites and the assessment of α-glucosidase inhibitory activity was conducted in three chili pepper species. Glucose uptake inhibition by DJ ethanol extract (DJE) was evaluated in Caco-2 cells. Furthermore, an oral carbohydrate tolerance test was performed in C57BL/6 mice. A total of 18 metabolites were identified in Dangjo, Green, and Cucumber chili peppers. Among these, quercitrin was one the most abundant flavonoid in DJ. The DJ showed the highest inhibition of α-glucosidase activity against both maltose and sucrose compared to other peppers. In addition, isoorientin, quercitrin, and DJE had similar inhibitory activities for both substrates. Glucose uptake was significantly inhibited in the DJE group compared to the control group. The mice were orally administered freeze-dried DJ at 150 and 300 mg/kg body weight (B.W.), and blood glucose levels were measured. Under glucose loading, both groups had significantly reduced blood glucose concentration compared to the control group (p = 0.001). Under maltose loading, the blood glucose concentration was decreased in the 150 mg/kg B.W. group compared to the control group (p = 0.025). These results indicate that Dangjo chili pepper has the potential to function as a postprandial hypoglycemic agent by inhibiting the α-glucosidase activity.