A water soluble β-glucan of an edible mushroom Termitomyces heimii: Structural and biological investigation

A water soluble beta-glucan (PS-I) with an average molecular weight similar to 1.48 x 10(5) Da was isolated from the alkaline extract of an edible mushroom Termitomyces heimii. PS-I contained (1 -> 3)-, (1 -> 6)-, (1 -> 3, 6)-linked and terminal beta-D-glucopyranosyl moieties in a ratio of nearly 2:1:1:1. Based on the total hydrolysis, methylation analysis, periodate oxidation, Smith degradation, partial hydrolysis and 1D/2D NMR experiments the structure of the PS-I was elucidated. On the basis of these experiments, the repeating unit of the polysaccharide was found to consist of a backbone chain of two (1 -> 6)-beta-D-glucopyranosyl residues, one of which was branched at O-3 position with the side chain consisting of two (1 -> 3)-beta-D-glucopyranosyl and a terminal beta-D-glucopyranosyl residue. Cytotoxic effect of PS-I on human blood lymphocytes at varied concentrations was studied. Moreover, it also exhibited potent antioxidant activities by diminishing the ROS and NO in the nicotine stimulated lymphocytes up to 200 mu g/ml. (C) 2015 Elsevier Ltd. All rights reserved.