Heteroglycan of an edible mushroom Termitomyces clypeatus: structure elucidation and antioxidant properties

•A water-soluble heteroglycan was isolated from the mushroom Termitomyces clypeatus (R. Heim).•Its structure was composed with d-glucose, d-galactose, d-mannose, and l-fucose.•The structure was established by chemical and 1D/2D NMR analysis.•The heteroglycan exhibited antioxidant properties.

A water-soluble heteroglycan (PS) of an average molecular weight ∼1.98 ×105 Da was isolated from the aqueous extract of an edible mushroom Termitomyces clypeatus (R. Heim). The structure of the polysaccharide (PS) was established using total hydrolysis, methylation analysis, Smith degradation, and 1D/2D NMR experiments. Total hydrolysis indicated the presence of d-glucose, d-galactose, d-mannose, and l-fucose in a molar ratio of 4.10:1.95:1.0:0.95, respectively. The chemical and NMR analysis indicated the presence of a repeating unit with a backbone consisting of one each of the residues (1→3)-α-d-galactopyranosyl, (1→3)-α-d-mannopyranosyl, (1→3)-α-d-glucopyranosyl, (1→3)-β-d-glucopyranosyl, (1→6)-β-d-glucopyranosyl, and (1→6)-α-d-galactopyranosyl, respectively. The (1→3)-α-d-mannopyranosyl residue was found branched at O-2 with terminal α-l-fucopyranosyl moiety and (1→3)-β-d-glucopyranosyl residue was branched at O-6 with terminal α-d-glucopyranosyl residue. The PS exhibited antioxidant properties.

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