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A water-soluble heteroglycan (PS-II) with average molecular weight similar to 7.27 x 10(4) Da, was isolated from the fruiting bodies of an edible truffle mushroom Tuber rufum (Pico) var. by hot water extraction. The structural investigation of PS-II has been carried out using acid hydrolysis, methylation analysis, periodate oxidation, and 10/2D NMR experiments. It was composed of D-glucose, D-galactose, L-fucose in a molar ratio of nearly 4:3:1 respectively. On the basis of these experiments, the repeating unit of the PS-II was found to contain a backbone of two (1 -> 6)-alpha-D-galactopyranosyl, one (1 -> 4)-alpha-D-glucopyranosyl, two (1 -> 6)-beta-D-glucopyranosyl, and one (1 -> 4)-beta-D-glucopyranosyl residues, out of which (1 -> 4)-alpha-D-glucopyranosyl residue was branched at O-2 position with terminal alpha-L-fucopyranosyl residue and at O-6 position with terminal alpha-D-galactopyranosyl residue. Ameliorative activities of the PS-II was observed at different concentrations (25, 50, 100, 200, 400 mu g/ml) and it maintained the redox balance as well as reduced the lipid peroxidation to protect the cell damage. (C) 2016 Elsevier B.V. All rights reserved.