Polysaccharides of Pleurotus ostreatus: Isolation and structure of pleuran, an alkali-insoluble β- d-glucan

An alkali-insoluble skeletal β- d-glucan has been isolated from the fruit bodies of Pleurotus ostreatus. The polysaccharide has a branched structure consisting of a backbone of (1 → 3)-linked β- d-glucopyranosyl residues, every fourth being substituted at 0–6 with single d-glucopyranosyl groups. The polysaccharide contained a small proportion (7%) of (1 → 6)- and (1 → 4)-linked interior residues. The β- d-glucan (pleuran) demonstrated efficacy in promoting the survival of mice susceptible to bacterial infections.