Antioxidant and immunological activity in vitro of polysaccharides from Phellinus nigricans mycelia

•Three novel polysaccharide fractions were isolated from Phellinus nigricans mycelium.•PNMP2 and PNMP3 possessed better antioxidant activity in vitro than PNMP1.•Lymphocyte proliferation was significantly increased by PNMP.

Three polysaccharide fractions, namely, PNMP 1, PNMP2, and PNMP3, were isolated from Phellinus nigricans mycelia. The average molecular weights of PNMP1, PNMP2, and PNMP3 were approximately 28.4, 31.5, and 26.1 kDa, respectively. PNMP2 and PNMP3 comprised six monosaccharides: arabinose, fucose, glucose, galactose, mannose, and xylose. PNMP1 comprised only four monosaccharides: glucose, galactose, mannose, and xylose. In vitro antioxidant tests showed that PNMP2 and PNMP3 significantly scavenged superoxide radical, hydroxyl radical, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. PNMP1 effectively inhibited DPPH radical. Lymphocyte proliferation was significantly increased by PNMP1, PNMP2, and PNMP3, particularly by PNMP2 and PNMP3 in the presence of concanavalin A or lipopolysaccharide as mitogens for lymphocytes.