Influence of Three Morus Species Extracts on α-Amylase Activity

Diabetes mellitus is one of the most common endocrine diseases and its type II is the major form of diabetes, accounting for 90% of cases worldwide. The inhibition of carbohydrate hydrolyzing enzymes such as α-amylase can be an important strategy in the control of blood glucose levels in patients with type II diabetes. In this investigation, three Morus species, M. alba, M. alba var. nigra and M. nigra, were studied for their possible effects on the starch breakdown by α-amylase in vitro. M. alba var. nigra [IC₅₀=13.26 (12.86-13.66) mg/ml] and M. alba [IC₅₀=17.60 (17.39-17.80) mg/ml] revealed appreciable α-amylase inhibitory activities in a concentration-dependent manner. Furthermore, the most active extract (i.e. M. alba var. nigra,) was partitioned by stepwise solvent-solvent extraction process and the inhibitory activities of each of the fractions on the enzyme were studied. According to the results, all the fractions (n-hexane, chloroform, ethyl acetate and aqueous fractions) had potent inhibitory effects on the α-amylase activity. However, the lowest inhibitory potency was observed for the aqueous fraction.