Structural characteristics, anti-proliferative and immunomodulatory activities of a purified polysaccharide from Lactarius volemus Fr.

Lactarius volemus Fr. is an edible mushroom widely consumed in China. Polysaccharide is an important nutri-tional component of L. volemus. This research aimed to isolate the polysaccharide from L. volemus and study its structure and bioactivities. A purified polysaccharide was identified and named as LVF-I whose primary structure was proposed considering the comprehensive results of monosaccharide composition, periodate oxidation-smith degradation, methylation analysis, FT-IR and 1D/2D NMR spectroscopy. Then the immunomodulation of LVF-I and its inhibition effect on H1299 and MCF-7 cells were investigated. Results showed that LVF-I (12,894 Da) contained fucose, mannose, glucose and galactose. It had a backbone consisting of -> 4)-alpha-D-Glcp-(1 ->, -> 6)-beta-D-Manp-(1 ->, -> 6)-alpha-D-Galp-(1 -> and -> 4)-beta-D-Manp-(1 ->. And its side chains were branched at C2 of -> 4)-beta-D-Manp-(1 -> by -> 6)-alpha-D-Galp-(1 ->, alpha-D-Glcp-(1 ->, alpha-D-Galp-(1 -> and alpha-L-Fucp-(1 ->. LVF-I (250-1000 mu g/mL) could inhibit the proliferation of H1299 and MCF-7 cells, while enhance the proliferative response of splenocyte and the phagocytic ability of RAW264.7. Furthermore, LVF-I (250-1000 mu g/mL) significantly induced the secretion of nitric oxide, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) by up-regulating their mRNA expression in macrophages. These results suggested that LVF-I had the potential to be developed as antitumor or immunomodulatory agents by inhibiting the proliferation of tumor cells and stimulating macrophages-mediated immune responses.