Abstract: Inonotus obliquus is a kind of edible fungus containing a variety of bioactive substances, among which its polysaccharides exhibit notable antioxidant activity. In this paper, extracellular crude polysaccharide was obtained from the liquid fermentation broth of I. obliquus, and the antioxidant ability of extracellular polysaccharide from I. obliquus before and after deproteinization was detected. The content of crude polysaccharide in liquid fermentation broth of I. obliquus measured by phenol-sulfuric acid colorimetric method was 1.28 mg/mL. The deproteinization rate reached 51.5%, but the loss rate of polysaccharide was 25.4% with Sevag method after four rounds of deproteinization. In vitro antioxidant studies, the concentration was 0.8 mg/mL, the clearance rates of ·OH^-, O₂^-·and DPPH were 33.1%, 33.4% and 32.1%, but after deproteinization the clearance rates for ·OH^-, O₂^-·and DPPH were 29.9%, 30.6% and 25.6%, respectively. It is concluded that extracellular polysaccharide of I. obliquus has certain antioxidant ability in vitro.

Key words: Inonotus obliquus, extracellular polysaccharide, free radicals, antioxidant activity, Sevag method