Effects of selenizing modification on characteristics and antioxidant activities of Inonotus obliquus polysaccharide

Abstract

Excessive reactive oxygen species is implicated in the etiology and pathology of many acute and chronic diseases. Selenium acts as an antioxidant and stimulates the creation of more antioxidants. Selenizing modification polysaccharides potentiate the physiological and pharmacological activities of selenium and polysaccharide. In this study, Inonotus obliquus polysaccharide (IOP) extracted from cultured mycelia was modified into Se-IOP by HNO3-Na2SeO3 method. The characteristics and antioxidant activity of IOP and Se-IOP were comparatively investigated. The result showed that polysaccharide content of purified IOP was 98.9%. The selenium content of Se-IOP was 0.71 mg/g. Both IOP and Se-IOP were homogeneous polysaccharides with a molecular weight of 37.354 and 28.071 kDa, respectively depicted in high performance gel permeation chromatogram (HPGPC). Moreover, both IOP and Se-IOP were composed of Man, Glu, and Gal with a molar ratio of 7.7:32.6:23.3 and 8.3:32.1:22.7, respectively determined by high performance liquid chromatography (HPLC). The characteristic absorption peak of O-Se-O, Se=O and C-O-Se appeared at 1026.75, 772.82, and 652.29 cm-1 respectively in FT-IR spectrum of Se-IOP indicating the success of selenylation. NMR spectrum further confirmed the anomeric carbon signals and chemical shifts in IOP and Se-IOP. These variations induced by selenylation may lead to a higher antioxidant activity of Se-IOP on scavenging hydroxyl, 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and superoxide radical than that of IOP. Furthermore, Se-IOP treatment could also reduce oxidant damage by decreasing the level of malondialdehyde (MDA) and increasing the activities of superoxidedismutase (SOD) and GSH-Px in mice.