Antioxidant effects of a water-soluble proteoglycan isolated from the fruiting bodies of Pleurotus ostreatus

A water-soluble protein-bound polysaccharide (POPPS-a) was isolated from the fruiting bodies of Pleurotus ostreatus by hot water extraction and ethanol precipitation, and further purified by DEAE-cellulose ion exchange chromatography and Sepharose CL-6B gel-filtration chromatography using ÄKTA explore 100 purification system. The molecular weight of POPPS-a was 33 kDa by HPGPC analysis. Gas chromatography of absolute acid hydrolysate of POPPS-a suggested that it was composed of arabinose, mannose, galactose, glucose and galacturonic acid in molar ratios of 1:0.9:1.7:5:0.6. The in vitro antioxidant activities of POPPS-a were studied by various antioxidant assays, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, superoxide radical scavenging activity and hydroxyl radical scavenging activity. The results show that water-soluble protein-bound polysaccharide (POPPS-a) had a significant antioxidant activity in a concentration-dependent manner. This study suggested that POPPS-a could be considered as a potential natural antioxidants.