Antidiabetic and antioxidant activities of Nypa fruticans Wurmb.vinegar sample from Malaysia

摘要

Objective: To study the antidiabetic and antioxidant activities of nipa palm vinegar(NPV) used in traditional Malay medicine for treating diabetes. Methods: NPV was extracted using liquid-liquid extraction method and the obtained samples were subjected to antidiabetic studies using normal and streptozotocin-induced diabetic rat models whereas antidoxidant activities were investigated via in vitro antioxidant tests namely 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azinobis-3-ethylbenzothiozoline-6-sulfonic acid free radicals scavenging activities and the reducing power assay. Results: Single administration of NPV and its extracts were not effective in both normal and diabetic rats. In intraperitoneal glucose tolerance test, NPV and its aqueous extract showed significant blood glucose lowering effect. In the sub-acute study, compared with the diabetic control, aqueous extract of NPV showed the most notable blood glucose lowering effect(56.6%) and a significant improvement in serum insulin levels(79.8%, P<0.05). To assess NPV's antioxidant activity, three in vitro antioxidant tests were employed: 2,2-diphenyl-1-picryhydrazyl and 2,2'-azinobis-3-ethylbenzothiozoline-6-sulfonic acid free radical-scavenging assays, and the reducing power assay. Ethyl acetate extract had the greatest antioxidant potential and content of phenolic and flavonoid compounds. A linear positive correlation between the antioxidant parameters was observed. Chemical profiling analysis of aqueous extract of NPV revealed the presence of acetic acid(35.25%), the main active constituent which significantly contributed to the observed antidiabetic activity. Conclusions: Aqueous extract of NPV possesses antihyperglycaemic activities comparable to the metformin, while the ethyl acetate extract precipitated significant antioxidant effects attributable to its high phenolic content. These findings suggest that antioxidant compounds of NPV do not contribute much towards the overall observed antidiabetic effect.