Evaluation of Traditional Indian Antidiabetic Medicinal Plants for Human Pancreatic Amylase Inhibitory Effect In Vitro

Pancreatic alpha-amylase inhibitors offer an effective strategy to lower the levels of post prandial hyperglycemia via control of starch breakdown. Eleven Ayurvedic Indian medicinal plants with known hypoglycemic properties were subjected to sequential solvent extraction and tested for alpha-amylase inhibition, in order to assess and evaluate their inhibitory potential on pancreatic alpha-amylase. Analysis of 91 extracts, showed that 10 exhibited strong Human Pancreatic Amylase (HPA) inhibitory potential. Of these, 6 extracts showed concentration dependent inhibition with IC50 values, namely, cold and hot water extracts from Ficus bengalensis bark (4.4 and 125 mu gmL(-1)), Syzygium cumini seeds (42.1 and 4.1 mu gmL(-1)), isopropanol extracts of Cinnamomum verum leaves (1.0 mu gmL(-1)) and Curcuma longa rhizome (0.16 mu gmL(-1)). The other 4 extracts exhibited concentration independent inhibition, namely, methanol extract of Bixa orellana leaves (49 mu gmL(-1)), isopropanol extract from Murraya koenigii leaves (127 mu gmL(-1)), acetone extracts from C. longa rhizome (7.4 mu gmL(-1)) and Tribulus terrestris seeds (511 mu gmL(-1)). Thus, the probable mechanism of action of the above fractions is due to their inhibitory action on HPA, thereby reducing the rate of starch hydrolysis leading to lowered glucose levels. Phytochemical analysis revealed the presence of alkaloids, proteins, tannins, cardiac glycosides, flavonoids, saponins and steroids as probable inhibitory compounds.