In Vitro and In Vivo α-Glucosidase and α-Amylase Inhibitory Effects of the Water Extract of Leaves of Pepper (Capcicum Annuum L. Cultivar Dangjo ) and the Active Constituent Luteolin 7-O-Glucoside

Abstract

This study was conducted to evaluate the in vitro and in vivo hypoglycemic potential of the water extract of pepper (Capcicum annuum L. cultivar Dangjo) leaves (WEPL) and the active constituent luteolin 7-O-glucoside (LG) isolated from WEPL. WEPL showed in vitro α-glucosidase and α-amylase inhibitory activity. LG also showed a similar α-glucosidase and α-amylase inhibitory activity, suggesting that the ability of WEPL to inhibit both enzymes may be due to the presence of LG and other polyphenols in WEPL. Supporting this observation, both WEPL and LG significantly reduced blood glucose levels in streptozocin-induced diabetic mice when challenged with oral administration of sucrose, but not after oral glucose challenge. Hence, inhibition of α-glucosidase and α-amylase may possibly be one of the mechanisms for WEPL and LG to exert hypoglycemic activity, indicating that pepper leaves may be considered as a potential candidate for the management of type 2 diabetes mellitus. Practical Applications Leaves of pepper cultivars, including Dangjo pepper, are commonly consumed as food in Korea. The findings of this study demonstrate that the water extract of pepper leaves exhibits the capacity to inhibit carbohydrate hydrolyzing enzymes (α-glucosidase and α-amylase) in vitro and in vivo and these beneficial effects appear to be due to some specific bioactive compounds in pepper leaves, in particular luteolin 7-O-glucoside. Our preliminary observation provides a rationale for a possible use of pepper leaves for the management of postprandial hyperglycemia.