Glycosidase inhibitory activity and antioxidant properties of a polysaccharide from the mushroom inonotus obliquus

From the paper

Abstract

A water-soluble polysaccharide from Inonotus obliquus (IOPS) was isolated from the mushroom Inonotus obliquus (Fr.) Pilat. The chemical compositions, molecular weight and inhibitory activities on glycosidase and antioxidant properties of IOPS were investigated. The results indicated that IOPS was an acid protein-bound polysaccharide, with a molecular weight of 1.7 x 10⁴ Da and the contents of neutral sugar, protein and uronic acids being 42.5, 18.5 and 6.1%, respectively. IOPS exhibited an inhibitory activity against α-glucosidase with the IC₅₀ value of 93.3 μg/mL, whereas it had no effective inhibition on α-amylase. Results of antioxidant activity assays revealed that IOPS had inhibitory activity on the concentration-dependent quenching of 1,1-Diphenyl-2-picrylhydrazyl and hydroxyl radicals. Furthermore, IOPS inhibited the formation of thiobarbituric acid-reactive substances in Fe²⁺/ascorbate-induced lipid peroxidation in rat liver tissue. These results clearly demonstrated that IOPS was one of the main bioactive components of I. obliquus that contributed to hypoglycemic activity and antioxidant activity. Diabetes mellitus is one of the primary threats to human health because of its increasing prevalence, chronic course and disabling complications. Postprandial hyperglycemia plays an important role in the development of type 2 diabetes mellitus and complications associated with the disease. One therapeutic approach to decrease postprandial hyperglycemia is to retard the absorption of glucose through inhibition of carbohydrate-hydrolyzing enzymes in the digestive organs. In this study, a polysaccharide isolated from the mushroom Inonotus obliquus (IOPS) was shown to have notable glycosidase inhibitory effects and antioxidant activities. This research will benefit for the investigation of effective and safe α-glucosidase inhibitors from natural materials. IOPS could be a good candidate for application in food and medicinal fields. It might be developed for functional food or lead compounds for use in antidiabetes.