Introduction: Diabetes is a chronic disease caused by an inherited or acquired defect in insulin secretion or a decrease in the response of the organs to the secreted insulin. This defect raises blood glucose levels, which can have side effects on the systems of the body, including blood vessels, and it can also destroy the nerves. There are approximately 180 million people worldwide with diabetes, and it is estimated that this number will reach 400 million by 2025. Managing blood glucose levels is a vital strategy in controlling the complications of diabetes. Inhibition of enzymes involved in the process of carbohydrate digestion and absorption can significantly decrease postprandial blood glucose levels. There are key enzymes in carbohydrate digestion such as α-Amylase and α-glucosidase. α- Amylase function is to convert complex carbohydrate in the food into oligosaccharides and disaccharides, and finally the α-Glucosidase breaks them down into monosaccharide that is absorbed by the intestinal tract, and it causes hyperglycemia after eating. Post-meal hyperglycemic control is considered as an important strategy in management of diabetes, especially type II diabetes, and the reduction of chronic complications associated with the disease. Thus inhibitors of carbohydrate degrading enzymes could be useful in the treatment of type II diabetes. Objectives: The aim of this study was to evaluate the α-glucosidase inhibitory activity of methanolic extracts from some plants used in traditional medicine in Sulaymaniyah province on the α-glucosidase enzyme activity.Methods: Eight plant species recommended by authentic spiceries from Sulaymaniyah for treatment of diabetics were collected from various regions of Sulaymaniyah province of Kurdistan region of Iraq. The plants were completely dried and grounded to fine powder. Enzyme assay was conducted in four different extract concentrations including (1, 0.1, 0.01 and 0.001 g/l) for all plant samples. However, the inhibition kinetic analysis and determination of the type of inhibition for extracts with higher inhibitory potency were done using three different concentrations of plants’ extracts (1, 0.5 and 0.1 g/l). Results: The results showed that among studied plants, the leaf extract of Rubus idaeus L., root extract of Rheum ribes R. and leaf extract of Salix alba L. had the highest inhibition activities toward α- glucosidase enzyme. With 1 mg/ml of extract the leaf extract of Rubus idaeus L. showed 99.13% inhibitory effect with IC50 of 0.046 g/l, root extract of Rheum ribes R. showed 95.39% inhibitory effect with IC50 of 0.085 g/l, and leaf extract of Salix alba L. showed 85.46% inhibitory effect with IC50 0.046 g/l. Kinetic study of methanolic extract of leaf and root organs of both plants Rubus idaeus L., Rheum ribes R. on α-glucosidase activity showed mixed type of inhibition (Uncompetitive-Noncompetitive) while the leaf organ of Salix alba L. showed Uncompetitive type of inhibition.
