α-Amylase inhibitory activity of some traditionally used medicinal species of Labiatae

BACKGROUND Natural α-amylase inhibitors of herbal origin are an attractive therapeutic approach to control post-prandial hyperglycemia via reducing the glucose release from starch and delaying carbohydrate absorption. These compounds are able to inhibit the activity of the carbohydrate hydrolyzing enzymes in the small intestine and potentially useful in control of diabetes. The enlarged Lamiaceae (Labiatae) family contains about 6,900 to 7,200 species worldwide and many species of this family possess medicinal properties and have been used traditionally for treatment of chronic illnesses including diabetes. METHODS In the present study particular species of Labiatae family from the genera, Phlomis, Satureja, Salvia, Scutellarua, Stachys and Hymenocrater, which are growing wildly in Iran, selected to evaluate for possible in vitro α-amylase inhibitory activity, compared to acarbose as a positive control. RESULTS The inhibitory activities of all the herbal extracts were varied from 1.9 to 18.6 (IC50, μg/mL). Additionally, the ethyl acetate extract of P. bruguieri (IC50 = 1.9 μg/mL) and the butanol extract of P. persica (IC50 = 3.6 μg/mL) exhibited the lowest IC50 values among all the species as the most potent herbal extracts, while the inhibitory activity of S. sahendica and S. macrosiphon (ethyl acetate extracts) as well as P. caucasica (butanol extract) on α-amylase enzyme was observed as weak and did not reach at least to the 50% of the enzyme inhibition level. CONCLUSIONS Taking together, P. bruguieri and P. persica among the Phlomis species can be the promising sources of α-amylase inhibitors. However, P. rigida, S. bizantina and H. bituminosus that exhibited moderate activity can be stand on second level of interest.