Structural characterization and immunostimulatory activity of a novel protein-bound polysaccharide produced by Hirsutella sinensis Liu, Guo, Yu & Zeng

HS002-II, a novel protein-bound polysaccharide with 44 kDa molecular weight, was fractionated from submerged cultures of Hirsutella sinensis Liu, Guo, Yu & Zeng by DEAE-Sepharose and Sephacryl S200 chromatography. Based on the results of infrared spectroscopy, high performance liquid chromatography, methylation, amino acid analysis, NMR spectroscopy and atomic force microscopy, the polysaccharide moieties of HS002-II mainly contained a long backbone of (1 -> 3)-linked alpha-D-ribofuranosyl units (1 -> 4)-linked alpha-D-xylopyranosyl units and (1 -> 4)-linked beta-D-glucopyranosyl units, which was substituted at C-6. The two branches were beta-D-mannopyranosyl residues and beta-D-galactopyranosyl residues terminated with alpha-L-arabinopyranosyl residues, respectively. HS002-II consisted of 57.9% polysaccharide and 42.1% protein with the existence of N-type carbohydrate-protein linkage. In terms of the pro-inflammatory cytokines assay (NO, TNF-alpha, IL-beta and NF-kappa B) using murine macrophages cell line (RAW264.7), HS002-II exhibited significant immunomodulatory activity by stimulating the I kappa B-NF-kappa B pathway. (C) 2013 Elsevier Ltd. All rights reserved.