Structure characterization and immunoactivity on dendritic cells of two neutral polysaccharides from Dictyophora rubrovalvata

Dictyophora rubrovalvata is a valuable fungus homologous to food and medicine, and its polysaccharide have been gaining increasing attention because of its plentiful activity. However, the structure and activity of its homogeneous polysaccharide have not been studied enough. In this study, two polysaccharides DRP-I and DRP-II were purified from D. rubrovalvata . Their structures were characterized by chemical composition, monosaccharide composition analysis, methylation analysis and nuclear magnetic resonance spectroscopy. The results showed that DRP-I and DRP-II were neutral heteropolysaccharides with molecular weights of 5.79 × 10 3 and 1.25 × 10 4  Da, respectively, which were composed of mannose, galactose, glucose, xylose and fucose. The main chains were → 6)- α -D-Gal p -(1 → 6)- α -D-Gal p -(2,1 → 6)- α -D-Man p -(2,1 → 6)- α -D-Gal p -(1, and branch chains were β -D-Xyl p -(1 → 3)- α -L-Fuc p -(1 → 4)- α -D-Man p -(1 → and α -D-Gal p -(1 → 3)- α -D-Gal p -(1 → . The in vitro immunoactivity assays on dendritic cells showed that DRP-I and DRP-II could up-regulate the expression of IL-10 and IL-6 and inhibit the expression of TNF-α in a concentration-dependent manner. This research indicated that DRP-I and DRP-II possessed immunoactivity by balancing the excessive inflammation, and molecular weight is an important factor affecting immunoactivity. Graphical Abstract