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 a-glucosidase and a-amylase inhibitory activity.LG also showed a similar a-glucosidase and a-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 a-glucosidase and a-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 APPLICATIONSLeaves 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 (a-glucosidase and a-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.

Alpha Glucosidase Inhibitory Activities of Plants with Focus on Common Vegetables

“…Similarly, ethanol and water crude extracts from fruits of some pepper cultivars consumed in Korea exhibited close to full inhibitory activity against yeast AGs, compared to acarbose that showed 50% inhibition at 25 mM [50]. Luteolin-7-O-glucoside flavonoid isolated from pepper leaves showed a similar level of inhibitory activity (IC 50 : 15 µM) compared to acarbose [51]. Recently, methanolic extracts of several potato tubers exhibited AG inhibition with IC 50 values ranging from 42.42 ± 0.94 to 78.65 ± 0.48 µg/mL, which is less potent than acarbose (IC 50 : 15.65 µg/mL) [52].…”

“…"Dangjo" and "Wongi No. 1" are two well-known Korean pepper varieties that have been specifically developed for higher AGI activity [51,74]. Since a range of bioactive Schematic diagram of the procedure through which AGI activity is measured in plant extracts using different substrates; pNPG (A) and maltose/sucrose (B).…”

“…"Dangjo" and "Wongi No. 1" are two well-known Korean pepper varieties that have been specifically developed for higher AGI activity [51,74]. Since a range of bioactive compounds have been reported to possess AG inhibitory activity, as described above, increasing the amount of such inhibitors in vegetables can be a critical step for the production of vegetables with higher AGI activity.…”

Alpha-Glucosidase Inhibitory Activity in Different Pepper Cultivars (Capsicum annuum L.)

“…Taken together, these results suggest that the MI extract contains a higher concentration of an unknown AGI compound. Park et al (2016) reported that LG7, a compound in the extract of pepper leaves, inhibits α-glucosidase and α-amylase activity, and reduces blood glucose levels in diabetic mice. Extracts of MI and SG were analyzed using an HPLC system to determine LG7 levels, but no significant difference in LG7 concentrations were found between the two samples ( Fig.…”

“…A previous study found that phenolic compounds from pepper leaves, including polyamine phenolic conjugates, chlorogenic acid derivatives, anthocyanin, and flavone glycosides, have antioxidant activities (Kim et al, 2014). Recently, Park et al (2016) reported that pepper (C. annuum L. cv. Dangjo) leaf extract inhibited the activities of α-glucosidase and α -amylase-possibly caused by the presence of luteolin 7-O-glucoside (L7G), a flavonoid glucoside.…”