Structural characterization and hydroxyl radicals scavenging capacity of a polysaccharide from the fruiting bodies of Auricularia polytricha

One low molecular-weight polysaccharide (APP) of 2.8 × 104 Da was isolated from the fruiting body of Auricularia polytricha. Partial hydrolysis with acid, periodate oxidation–Smith degradation, acetylation, methylation analysis and NMR spectroscopy (1H, 13C) were conducted to elucidate its structure and the repeating unit of APP was established as: the backbone was composed of (1 → 3)-linked-β-d-mannopyranosyl, (1 → 3)-linked-β-d-galactopyranosyl and (1 → 3,6)-linked-β-d-mannopyranosyl residues in the ratio of 3:2:1, and terminated with one single terminal (1→)-β-d-glucopyranosyl at the O-6 position of (1 → 3,6)-linked-β-d-mannopyranosyl along the main chain. Preliminary antioxidant activity test in vitro showed APP could potentialize scavenging effect on hydroxyl radicals in a dose dependent manner.