α-Glucosidase Inhibitor Activity of Terminalia Species

Terminalia arjuna, Terminalia ballerica, Terminalia chebula, Terminalia catappa, Terminalia kaerbachii and Terminalia microcarpa leaves were tested for their alpha-glucosidase inhibitory activity in vitro. The alpha-glucosidase activity was determined by measuring the p-nitrophenol release from pNPG at 400 nm. Terminalia kaerbachii has the highest alpha-glucosidase inhibitor activity with IC50 value of 0.27 +/- 0.17 mu g mL(-1) and is a promising antidiabetic herbal medicine candidate. However, most of the Terminalia species are also potential as antidiabetic medicine candidates as the IC50 values are approximately 5 mu g mL(-1), which is near the IC50 value of 1-deoxynojirimycin, the reference compound, except for Terminalia microcarpa, which has IC50 value of 25.15 +/- 0.04 mu g mL(-1) (above 21 mu g mL(-1)). From the phytochemical screening, Terminalia kaerbacchi contains alkaloids, flavonoids and cathechic tannins, but does not contain saponin, quinon, steroid/terpenoids and gallic tannins. It is estimated that there is a correlation between a-glucosidase inhibitory activity and its phytochemical content.