Structural characterization and antioxidant activity of a glucan from Meripilus giganteus

•A branched glucan was isolated from the mushroom Meripilus giganteus..•Structure of the glucan was established by chemical and 1D/2D NMR experiments.•This glucan showed antioxidant activities. A new water soluble glucan (MGPS), with a molecular weight ∼1.48×105Da, was isolated from the fruit bodies of Meripilus giganteus by hot water extraction followed by purification through dialysis tubing cellulose membrane and sepharose 6B column chromatography. Its structural characteristics were investigated by acid hydrolysis, methylation analysis, Smith degradation and 1D/2D NMR experiments. The monosaccharide composition analysis showed that MGPS contain only glucose. The backbone of MGPS was composed of two (1→3)-β-d-glucopyranosyl, two (1→6)-β-d-glucopyranosyl, two (1→6)-α-d-glucopyranosyl, and one (1→4)-α-d-glucopyranosyl residues, out of which one (1→3)-β-d-glucopyranosyl residue was branched at O-6 position with terminal α-d-glucopyranosyl residue and one (1→4)-α-d-glucopyranosyl residue branched at O-6 position with terminal β-d-glucopyranosyl residue. In vitro antioxidant studies showed that the MGPS exhibited hydroxide radical scavenging activity (IC50=390μg/mL), superoxide radical scavenging activity (IC50=70μg/mL), and ferrous ion chelating activity (IC50=290μg/mL).