Kinetics of α-glucosidase inhibition by different fractions of three species of Labiatae extracts: a new diabetes treatment model

Context: Glucosidases are a group of enzymes playing crucial roles in digestion of carbohydrates. Glucosidase inhibitors can reduce carbohydrate digestion rate and have the potential to prevent development of type 2 diabetes. The Labiatae is one of the largest plant families grown globally and many studies that have isolated new pharmaceutical compounds. In folk medicine, some of Labiatae plants such as Zataria multiflora Boiss, Salvia mirzayanii Rech. F. & Esfand, and Otostegia persica Boiss are consumed for the treatment of diabetes. Objectives: This study investigates the inhibitory effects of different fractions of three mentioned species extracts on α-glucosidase. Materials and methods: Ethanol extracts of these plants leaves were fractionated using petroleum ether, chloroform, ethyl acetate, and n-butanol solutions. The duration of this study was 12 months. To measure enzyme inhibition, 5 μL of the enzyme, 20 μL of substrate and samples were used and for evaluation mode of inhibition, constant amounts of α-glucosidase were incubated with rising concentrations of substrate (PNPG). Results: The results revealed that the ethyl acetate fraction of Zataria multiflora (IC(50) = 0.35 ± 0.01 mg/mL) and petroleum ether fraction of Salvia mirzayanii (IC(50) = 0.4 ± 0.11 mg/mL) were the most potent inhibitors of α-glucosidase in comparison with the other samples and acarbose as the standard (IC(50) = 7 ± 0.19 mg/mL). All of the samples exhibited noncompetitive-uncompetitive inhibition. Discussion and conclusion: It can be inferred from this study that α-glucosidase inhibitory potential of the studied extracts may be a marker of antidiabetic potential of these extracts.