α-glucosidase inhibition by methanol extract from aerial parts of Salvia saffroticosa Montbr. & Auch. ex Benth. and Hypericum scabrum L.

Controlling post-meal hyperglycemia with α-glucosidase inhibitors is an important strategy in the management of diabetes and the reduction of chronic complications associated with this disease. Based on the results of previous studies, the methanolic extracts of the shoots of Salvia suffruticosa Montbr. & Auch. ex Benth. and Hypericum scabrum L. have significant inhibitory effects on α-glucosidase activity. In this study, to determine the plant parts of S. suffruticosa and H. scabrum with the highest α-glucosidase inhibitory effect, after preparing the methanolic extract from different organs of the plants, the inhibitory effect of all extracts in different concentrations was investigated at 405 nm wavelength using a microplate reader. The highest α-glucosidase inhibitory activity in S. suffruticosa was related to the concentration 160 mg.mL-1 of the flower extract (100% inhibition and IC50 = 8.91 mg.mL-1), and the highest inhibitory activity of H. scabrum was related to the concentration 10 mg.mL-1 of the flower (96.49% inhibition and IC50 = 1.04 mg.mL-1) and leaf extracts (86% inhibition and IC50 = 3.98 mg.mL-1). According to the results of the kinetic study of enzymatic inhibition, S. suffruticosa flower and leaf extracts follow a noncompetitive-uncompetitive mixed pattern of inhibition and H. scabrum flower extract follows the competitive-noncompetitive one. Methanolic extract of flowers in S. suffruticosa and H. scabrum had a significant inhibitory effect on the activity of α-glucosidase. So, the flowers of these species are good natural sources for extracting compounds with potent medicinal properties to control postprandial blood sugar levels.