Antioxidant and Postprandial Glucose-lowering Potential of the Hydroethanolic Extract of Nypa fruticans Seed Mesocarp

Abstract

Postprandial hyperglycemia and oxidative stress are implicated in the pathophysiology of type 2 diabetes. An alternative treatment should target both conditions. The present study aimed to evaluate the antioxidant and postprandial glucose-lowering potential of a polyphenolic rich extract of Nypa fruticans nuts. Hydroethanolic extract (HEE) was prepared; polyphenol and fl avonoid content was determined. In vitro antioxidant activity was done through molybdenum (VI) reduction and ABTS and DPPH radical-scavenging capacities. The glucose-lowering potential of the extract was evaluated through in vitro glucose-binding capacity, the regulatory ability of the extract on the pancreas of normal Wistar rats (oral glucose tolerance test), and digestion of carbohydrates (starch and sucrose) by normal Wistar rats. Starch (1 g/kg of the body weight (BW) and sucrose (2 g/kg BW) solution were used as substrates for alpha amylase and invertase inhibition test, respectively. Acarbose (3 mg/kg BW) was used as the reference. Polyphenolic-rich extract (400 mg/kg BW) was administered to treated rats. Results showed that HEE of N. fruticans nuts has antioxidant activity through the scavenging of ABTS (EC50 of 1.75 mg/mL) and DPPH (2.96 mg/mL) radicals and the reduction of Mo (VI). The extract signifi cantly reduced glucose concentrations at t30 compared to glibenclamide, but glibenclamide maintained lower glycemia than the extract thereafter to the end of the study. From the administration of sucrose, the extract maintained lower plasma glucose levels compared to acarbose throughout the study. However, no inhibition was observed in glycemia following starch administration in HEE-treated group as glycemia remained higher compared to the acarbose group throughout the study. Thus, N. fruticans seed mesocarp is a rich source of dietary polyphenols with a strong antioxidant capacity. Its HEE has glucose-lowering potential and possible inhibitory action on the last phase of carbohydrate digestion.