An in vitro evaluation of the antioxidant and antidiabetic potential of Sutherlandia montana E. Phillips R.A. Dyer leaf extracts

摘要

Objective: To evaluate the antioxidant and antidiabetic activities of Sutherlandia montana E. Phillips & R.A. Dyer leaf extracts using the in vitro model.Methods: The antioxidant activities of aqueous, decoction, ethanol and hydro-ethanol extracts of the plant were determined using seven different assays; the antidiabetic potential was evaluated through the inhibition of key carbohydrate hydrolysing enzymes（aamylase and a-glucosidase）, while the modes of the enzymes inhibition were assessed using enzyme kinetic analysis.Results: The ethanol extract exhibited the best scavenging activity(IC50: 0.47, 0.36,0.20, 0.29 and 0.01 mg/m L) against the tested radicals like 1,1-diphenyl-2-picrylhydrazyl,2, 20-azinobis（3-ethylbenzothiazoline-6-sulfonic acid）, nitric oxide, hydroxyl and superoxide anion, respectively. It also showed the best reducing power efficiency when compared with the standard（silymarin）, while the decoction extract displayed the strongest metal chelating potential(IC50: 0.71 mg/m L). The ethanol(IC50: 5.52 mg/m L)and decoction(IC50: 0.05 mg/m L) extracts exhibited mild and strong inhibitory effects on the specific activities of a-amylase and a-glucosidase respectively, through an uncompetitive and non-competitive mode of action.Conclusions: The observed properties might be linked to the presence of active principles as shown by the results of the phytochemical analyses of the extracts. This research has validated the folkloric application of Sutherlandia montana as a potential antidiabetic agent, which is evident from the inhibition of specific activities of key enzymes involved in carbohydrate metabolism.