Purification, structural analysis and hydroxyl radical-scavenging capacity of a polysaccharide from the fruiting bodies of Russula virescens

In this study, one water-soluble polysaccharide (RVP) was isolated from the fruiting bodies of Russula virescens. Its molecular weight (Mw) was ∼3.9 ×104 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 (1H, 13C). The results revealed that RVP had a backbone consisting of (1 → 6)-linked-α-d-galactopyranosyl and (1 → 2, 6)-linked-α-d-galactopyranosyl residues that terminated in a single non-reducing terminal (1 → )-α-d-mannopyranosyl residue at the O-2 position of each (1 → 2, 6)-linked-α-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 μg/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.