In this study, one water-soluble polysaccharide (RVP) was isolated from the fruiting bodies of Russula virescens. Its molecular weight (Mw) was similar to 3.9 x 10(4) Da, as determined by high-performance size-exclusion chromatography (HPSEC). The RVP was composed of D-galactose and D-mannose in a ratio of 2:1, as detected by gas chromatography (GC). The structural features of RVP were investigated by partial hydrolysis with acid, periodate oxidation and Smith degradation, acetylation, methylation analysis, and NMR spectroscopy (H-1, C-13). The results revealed that RVP had a backbone consisting of (1 -> 6)-linked-alpha-D-galactopyranosyl and (1 -> 2, 6)-linked-alpha-D-galactopyranosyl residues that terminated in a single non-reducing terminal (1 -> )-alpha-D-mannopyranosyl residue at the O-2 position of each (1 -> 2, 6)-linked-alpha-D-galactopyranosyl residues along the main chain in the ratio of 1:1:1. Preliminary, in vitro antioxidant activity tests showed that RVP could dose-dependently enhance the scavenging effect on hydroxyl radicals at concentrations from 20 to 160 mu g/ml. These results indicated that RVP was mainly composed of water-soluble galactomannan, and it had a significant effect on scavenging of hydroxyl radicals in vitro. (C) 2010 Elsevier Ltd. All rights reserved.