Structure characterization of a novel polysaccharide from Hericium erinaceus fruiting bodies and its immunomodulatory activities

A novel polysaccharide fraction (HEP-S) was extracted and isolated from the fruiting bodies of Hericium erinaceus. Structural characterization revealed that HEP-S had an average molecular weight of 1.83 x 104 Da and consisted of rhamnose, fucose, mannose, glucose and galactose at a molar ratio of 1.47 : 0.93 : 1.36 : 8.68 : 4.08. Periodate oxidation-Smith degradation and NMR analysis showed that the main linkage types of HEP-S were composed of (1 ->)-alpha-D-Glc, (1 -> 3,4)-alpha-D-Glc, (1 -> 6)-alpha-D-Gal, (1 -> 3,4)-beta-D-Man, (1 -> 3,6)-alpha-Rha and (1 -> 2)-beta-L-Fuc. The immunomodulatory assay indicated that HEP-S could significantly enhance the pinocytic and phagocytic capacity and promote the secretion of nitric oxide and pro-inflammatory cytokines by activating the corresponding mRNA and protein expression in RAW 264.7 cells involving a toll-like receptor 2 membrane receptor. Besides, HEP-S was also found to improve the adaptive immune function by enhancing T and B lymphocyte proliferation and increasing the interleukin-2, interleukin-4 and interferon-. secretion in spleen lymphocytes. These results suggested that HEP-S could be used as a potential immunoregulatory agent in functional foods.