Isolation, purification and antioxidant activities of polysaccharides from Grifola frondosa

► The water-insoluble polysaccharides were isolated from Grifola frondosa. ► Three main fractions were purified from the G. frondosa polysaccharides. ► Different in vitro assay systems were used. ► The G. frondosa polysaccharides have effective antioxidant activities. ► I helpful for the comprehensive utilization of G. frondosa resources. The crude polysaccharides (GFP) were isolated from the fruiting bodies of Grifola frondosa and purified by DEAE cellulose-52 chromatography and Sephadex G-100 size-exclusion chromatography in that order. Three main fractions, GFP-1, GFP-2 and GFP-3, were obtained through the isolation and purification steps. Then the antioxidant activities of these three fractions were investigated in vitro. The results showed that GFP-1, GFP-2 and GFP-3 possessed significant inhibitory effects on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical and superoxide radical; their reducing power, ferrous ions chelating effect and the inhibition ability of the rat liver lipid oxidation where also strong. These results suggest that G. frondosa polysaccharides could be a suitable natural antioxidant and may be the functional foods for humans.