Structural characterization of an active polysaccharide from Phellinus ribis

A water-soluble polysaccharide named as PRP was isolated from the fruiting bodies of Phellinus ribis by hot water extraction, DEAE-cellulose and Superdex 30 column chromatography. Its structural characteristics were investigated by FT-IR, NMR spectroscopy, GLC-MS, methylation analysis, periodate oxidation and Smith degradation. Based on the data obtained, PRP was found to be a β-d-glucan containing a (1 → 4), (1 → 6)-linked backbone, with a single β-d-glucose at the C-3 position of (1 → 6)-linked glucosyl residue every eight residues, along the main chain. The glucan has a weight-average molecular weight of about 8.59 kDa by HPGPC determination using dextran samples as the standards. Preliminary activity tests in vitro revealed that PRP could stimulate the proliferation of spleen lymphocyte.