Structural characterization of a heteroglycan from an edible mushroom Termitomyces heimii

A water soluble heteroglycan (THPS) of an average molecular weight ~1.98 × 10⁵ Da was isolated from the aqueous extract of the fruit bodies of an edible mushroom Termitomyces heimii. Structural characterization of THPS was carried out using acid hydrolysis, methylation analysis, periodate oxidation, Smith degradation and 1D/2D NMR studies. Sugar analysis indicated the presence of glucose, mannose, galactose, and fucose in a molar ratio of nearly 6:2:2:1. The repeating unit of the THPS had a backbone consisting of four (1 → 3)-β-d-glucopyranosyl, one (1 → 6)-β-d-glucopyranosyl, two (1 → 3)-α-D-manopyranosyl, and two (1 → 6)-α-D-galactopyranosyl residues, out of which one (1 → 3)-β-d-glucopyranosyl residue was branched at O-6 position with terminal β-d-glucopyranosyl residue and one (1 → 6)-α-D-galactopyranosyl residue was branched at O-2 position with terminal α-L-fucopyranosyl residue.