Analyses of active antioxidant polysaccharides from four edible mushrooms

Four water-soluble polysaccharides were extracted from Pleurotus eryngii, Flammulina velutipes, Pleurotus ostreatus and white Hypsizygus marmoreus. Using anion exchange and gel permeation chromatography, a neutral and an acidic fraction were purified from each water-soluble polysaccharide. Their molecular weights were all around 20 kDa except that the acidic polysaccharide from Pleurotus ostreatus (named WPOPA) had a lower molecular weight of 5 kDa. Four neutral polysaccharides were mainly composed of galactose (42.7%-69.1%), followed by Man (19.4%-39.3%) and Glc (1.1%-15.9%). Four acidic polysaccharides contained glucose (59.0%-81.8%) as major sugar and minor glucuronic acid (4.5%-9.5%). Acidic polysaccharides exhibited stronger antioxidant activities than neutral fractions, and WPOPA showed the best antioxidant effects. Structural analysis indicated WPOPA had beta-(1 -> 6)-glucan backbone branched at O-3 by beta-1,3-D-Glcp, t-beta-D-Glcp and t-beta-D-GlcpA. This investigation would be useful for screening natural antioxidants and significant in developing mushroom polysaccharides as functional foods. (C) 2018 Elsevier B.V. All rights reserved.