Structural characterization and immunomodulatory activity of a water-soluble polysaccharide from Poria cocos.

In order to investigate the structural characteristics and immunomodulatory effects of Poria cocos polysaccharides, a water-soluble homogeneous polysaccharide (PCP-2) was isolated by water extraction and alcohol precipitation and further purified by Cellulose DEAE-52 and Sephacryl S-100HR column chromatography. PCP-2 is a heteropolysaccharide composed of glucose, galactose, mannose, and fucose in a molar ratio of 42.0: 35.0: 13.9: 9.1. It exhibits a narrow molecular weight distribution at 2.35 kDa with a branching degree of 37.1 %. The main chain types of PCP-2 include 1,3-β-D-Glc and 1,6-β-D-Glc as the backbone glucans and 1,6-α-D-Gal as the backbone heterogalactan. In vitro experiments demonstrate that PCP-2 directly stimulate RAW264.7 cell proliferation and secretion of inflammatory factors such as NO and TNF-α. In cyclophosphamide (CTX)-induced mice, it promotes the development of thymus and spleen immune organs, elevates the blood levels of IgG, IgA, IgM and CD3+CD4+ T cells, increases the intestinal villus height/ crypt depth ratio and improves gut barrier dysfunctions. These findings suggest that PCP-2 is a natural fungal polysaccharide with broad spectrum of immunoenhancing effects, which can significantly ameliorate the immunocompromised state.