A novel branched αβ-glucan isolated from the basidiocarps of the edible mushroom Pleurotus florida

As polysaccharides of the mushroom genus Pleurotus can act as biological response modifiers, we now describe the chemical characterization of a new water-soluble αβ-glucan from the fruiting bodies of the edible mushroom Pleurotus florida. It was obtained via successive aq. extraction, freeze-thawing, precipitation with Fehling solution, and dialysis through a membrane with Mr 1000 kDa cut-off. It was analyzed using NMR spectroscopy, HPSEC, monosaccharide composition, methylation analysis, and a controlled Smith degradation. It was a branched glucan (Mw 1.1 × 106 g/mol), with a main-chain of (1→3)-linked-α-d-Glcp residues, partially substituted at O-6 by single-unit β-d-Glcp, and a minor proportion by side-chains with 3-O-substituted β-d-Glcp groups.