Sulfated modification, characterization and property of a water-insoluble polysaccharide from Ganoderma atrum

Sulfated modification was carried out to modify a water-insoluble polysaccharide from Ganoderma atrum (AGAP). The effects of sulfation on structure, physicochemical and functional properties of AGAP were investigated. Three sulfated derivatives were prepared, designated as S-1, S-2 and S-3 with degree of substitution (DS) of 0.35, 0.74 and 1.14, respectively. AGAP was elucidated as an alpha-(1 -> 3)-glucan with few branches terminated by single mannose or xylose residues. The molecular weight (M-w) and radius of gyration (R-g) were estimated to be 1665 kDa and 65.49 nm, respectively. After sulfated modification, nonselective sulfation occurred preferably at O-6, partially at O-2 and O-4 positions of the glucosyl residues. The water-solubility of the derivatives was significantly improved in a DS-dependent manner. M-w of the derivatives showed a sharp decrease, and the chain conformation was estimated to be expanded stiff in phosphate buffer. In vitro tests showed that sulfated modification improved its antioxidant activities and anti-proliferative ability against S-180 tumor cells. This study suggested that sulfated modification was an effective approach to improve the water-solubility and functional properties of insoluble polysaccharides. (C) 2015 Elsevier B.V. All rights reserved.