Structure Characterization of a Novel Polysaccharide from Dictyophora indusiata and Its Macrophage Immunomodulatory Activities

A novel polysaccharide, here named DP1, was isolated from the fruiting body of Dictyophora indusiata using a water extraction method. Structure characterization revealed that DP1 had an average molecular weight of 1132 kDa and consisted of glucose (56.2%), galactose (14.1%), and mannose (29.7%). The main linkage type of DP1 were proven to be (1 -> 3)-linked a-l-Man, (1 -> 2,6)-linked a-d-Glc, (1 -> 6)-linked beta-d-Glc, (1 -> 6)-linked beta-d-Gal, and (1 -> 6)-linked beta-d-Man by periodate oxidation-Smith degradation and nuclear magnetic resonance analysis. The immunostimulating assay indicated that DP1 could significantly promote macrophage NO, TNF-a, and IL-6 secretion in murine RAW 264.7 cells involving complement receptor 3 (CR3). The immune activities of DP1 were quite stable under thermal processing (100, 121, and 145 degrees C). Besides, DP1 retained stability after acidic/alkline treatment (pH 4.0-10.0), which enabled it to be an ideal complementary medicine or functional food for therapeutics of hypoimmunity and immunodeficiency diseases.