Characterization and Antioxidant Activity of Polysaccharides From <i>Agaricus bisporus</i> by Gradient Ethanol Precipitation

In this present work, the polysaccharides from Agaricus bisporus were extracted and fractioned with gradient ethanol precipitation method for the first time. Five fractions (ABP40, ABP50, ABP60, ABP70, and ABP80) were obtained with ethanol concentrations of 40%, 50%, 60%, 70%, and 80%, respectively, and their characteristics and antioxidant activities in vitro were investigated. The five fractions presented significant differences in total sugar, protein, and uronic acid content, with a marked discrepancy in the molar ratio of the monosaccharide composition. The molecular weights of the polysaccharides decreased with increasing ethanol concentration. Compared to the other four fractions, ABP70, which has the highest uronic acid content, showed more conspicuous radical-scavenging activities against hydroxyl (89.9 ± 0.33%) and DPPH radicals (80.1 ± 0.01%). Moreover, it was found that the total sugar content and antioxidant activities of polysaccharides increased with the extension of precipitation time, with the highest antioxidant activities at 24 h. Therefore, ABP70, precipitated for 24 h, may have a potential application value for the development of antioxidants. This study provides valuable information for the further commercial applications of polysaccharides from Agaricus bisporus.