Inhibition mechanism of ethyl acetate extract of Ononis natrix subsp. angustissima (Lam.) Širj against α-amylase

Inhibition of the activity of carbohydrate digestive enzymes prevents the rise of postprandial glucose level, slows down monosaccharide absorption rates, and reduces postprandial hyperglycemia. This has potential as a management and/or therapeutic approach for type 2 diabetes. Many studies have shown that phenolic extracts and pure polyphenols can retard starch digestion in vitro, and the retarding effect depen*ds on the phenolic composition and molecular structure. In this study, the mechanism of inhibition of α-amylase by the ethyl acetate extract (EAc) of Ononis natrix subsp. angustissima (Lam.) Širj, acarbose, catechin and gallic acid (used independently) were determined.The Km and Vmax values of α-amylase determined by Lineweaver-Burk representation were 0.974 mmol/L and 0.5 mmol/min, respectively. Uncompetitive inhibition was observed in presence of EAc extract and gallic acid through the decrease in the Km 0.234, 0.429 mmol/L, respectively and Vmax values 0.2, 0.256 mmol/min, respectively. This indicates the presence of natural inhibitors metabolites in the EAc extract whose performance was superior to that of acarbose (Km 7.304 mmol/L). A non-competitive inhibition was recorded in the presence of catechin by the decrease in the value of Vmax (0.286 mmol/min). In non-competitive and uncompetitive inhibitions, the inhibitor binds to broad regions of the enzyme other than the active site.As an uncompetitive inhibitor, the EAc extract can exhibit higher affinity for the enzyme under substrate-saturated conditions, including conditions that mimic the postprandial state.