alpha-Glucosidase enzyme inhibitors are clinically used for the treatment of Type 2 diabetes mellitus. We tested alpha-glucosidase inhibitory effects of Potentilla astracanica Jacq. extracts (1, 2), two compounds isolated from these extracts, prunetin 5-O-beta-glucopyranoside (3) and genistein 5-O-beta-glucopyranoside (4), and their aglycon forms (5 and 6). All the tested materials possessed remarkable alpha-glucosidase inhibitor activity compared to the positive control, acarbose. Genistein (6) showed the highest activity with an IC50 value of 1.47 (+/- 0.11) mu g/ml. An enzyme kinetics analysis revealed that 3 and 6 were uncompetitive, 5 was noncompetitive, and 4 was competitive inhibitors. Using molecular modeling techniques we tried to provide insight into molecular mechanisms of their activity and how allosteric binding of 6 affected binding interactions between the agonist (maltose) and the enzyme. (C) 2017 Elsevier B.V. All rights reserved.