Inhibitory effect of Gymnema Montanum leaves on α-glucosidase activity and α-amylase activity and their relationship with polyphenolic content

The present study was attempted to investigate the effect of G. montanum leaf extract on inhibition of alpha-glucosidase and alpha-amylase activity. The ethanol extract of G. montanum (GLEt) at various concentrations (1-10 mu g/ml) was tested for its inhibition pattern against alpha-glucosidase and alpha-amylase activity in vitro and compared with the commercially available alpha-glucosidase inhibitor, acarbose. The GLEt showed competitive inhibition against yeast alpha-glucosidase and noncompetitive inhibition against salivary alpha-amylase in a concentration-dependent manner. Further, we investigated the effect of extract on levels of blood glucose and plasma insulin in neonatal streptozotocin-induced type 2 diabetic rats. Long-term administration (12 weeks) of the GLEt effectively reduced the blood glucose level and also increased the insulin level. In a preliminary phytochemical analysis, G. montanum leaves were rich in phenolic composition and found to be positively correlated with the inhibitory effect of alpha-glucosidase and alpha-amylase activity. These results suggest that the GLEt might exert its antidiabetic effect by suppressing carbohydrate absorption from the intestine and thereby reducing hyperglycemia.