Regular paper In vitro α-glucosidase and α-amylase enzyme inhibitory effects of Andrographis paniculata extract and andrographolide

There has been an enormous interest in the development of alternative medicines for type 2 diabetes, specifically screening for phytochemicals with the ability to delay or prevent glucose absorption. The goal of the present study was to provide in vitro evidence for potential inhibition of α-glucosidase and α-amylase enzymes, followed by a confirmatory in vivo study on rats to generate a stronger biochemical rationale for further studies on the ethanolic extract of Andrographis paniculata and andrographolide. The extract showed appreciable α-glucosidase inhibitory effect in a concentration-dependent manner (IC50 = 17.2 ± 0.15 mg/ml) and a weak α-amylase inhibitory activity (IC50 = 50.9 ± 0.17 mg/ml). Andrographolide demonstrated a similar (IC50 = 11.0 ± 0.28 mg/ml) α-glucosidase and α-amylase inhibitory activity (IC50 = 11.3 ± 0.29 mg/ml). The positive in vitro enzyme inhibition tests paved way for confirmatory in vivo studies. The in vivo studies demonstrated that A. paniculata extract significantly (P < 0.05) reduced peak blood glucose and area under curve in diabetic rats when challenged with oral administration of starch and sucrose. Further, andrographolide also caused a significant (P < 0.05) reduction in peak blood glucose and area under the curve in diabetic rats. Hence α-glucosidase inhibition may possibly be one of the mechanisms for the A. paniculata extract to exert antidiabetic activity and indicates that AP extract can be considered as a potential candidate for the management of type 2 diabetes mellitus.