Structural characterization and immunomodulatory activity of Grifola frondosa polysaccharide via toll-like receptor 4-mitogen-activated protein kinases-nuclear factor kappa B pathways

We isolated a neutral polysaccharide from the fruiting body of a mushroom Grifola frondosa (GFP-A). The aim of this study was to characterize a neutral alpha-D-polysaccharide derived from G. frondosa and evaluate its immunomodulatory effect on toll-like receptor 4, mitogen-activated protein kinases and nuclear factor kappa B pathways of protein expression in macrophages. The structural features of GFP-A were characterized by physicochemical and instrumental analyses. Its molecular weight was found to be 8.48 x 10(2) kDa. The main chain of GFP-A consisted of (1 -> 4)-linked and (1 -> 6)-linked alpha-D-glucopyranosyl, and (1. 3,6)-linked alpha-D-mannopyranosyl residues, which branched at C-3. The branches consisted of (1 -> 6)-linked alpha-D-galactopyranosyl and t-L-rhamnopyranosyl residues. An in vitro immunomodulatory assay for pro-inflammatory cytokines (interleukin-1 beta, interleukin-2, tumor necrosis factor alpha, etc.) using the macrophage cell line, RAW 264.7, revealed that GFP-A exhibited significant immunomodulatory activity by stimulating the toll-like receptor 4, mitogen-activated protein kinases to nuclear factor kappa B/pathway.