Abstract: Water extraction followed by fractional ethanol precipitation was used to purify water-soluble polysaccharides from portabella mushroom Agaricus bisporus (WPPA). The polysaccharide fractions WPPA60, WPPA70 and WPPA80 were obtained using three ethanol concentrations: 60%, 70% and 80%. Their antioxidant activity in vitro was assessed in terms of reducing power, scavenging activity against superoxide anion hydroxyl free radicals and inhibitory activity against H2O2-induced erythrocyte hemolysis. The results showed that WPPA60, WPPA70 and WPPA80 revealed strong reducing power, scavenging capacity against superoxide anion and hydroxyl free radicals and inhibitory effect on erythrocyte hemolysis and MDA generation. The polysaccharide fractions were ranked in decreasing order of antioxidant activity as follows: WPPA70, WPPA80 and WPPA60.

Key words: reducing power, portabella mushroom Agaricus bisporus, polysaccharide, antioxidation