Effects of Simulated Digestion on the Structure and Macrophages and Dendritic Cells Activation of Grifola frondosa Polysaccharides

The present work was analyzed the effects of simulated digestion on the structure of a multibranched polysaccharide (PM) from Grifola frondosa. Additionally, the activation effect of PM on macrophages and dendritic cells was compared before and after simulated digestion. The PM was composed of glucose, glucuronic acid, xylose, mannose, arabinose, and galactose in molar ratios of 81.6: 6.1: 5.4: 3.5: 2.5: 1.0, with an average molecular weight of 3.04 × 104 g/mol. The PM main chain is alternately linked by →3-β-D-Glcp-1→, →3-β-D-GlcpA-1→, →6-β-D-Glcp-1→, and →3, 6)-β-D-Glcp-(1→, accompanied by multiple branched chains. PM significantly promotes macrophage proliferation, phagocytosis, and secretion of IL-6, IL-1β, and TNF-α, while reducing dendritic cell phagocytosis. During digestion, the branched chains linked with →3,4)-β-D-Xylp-(1→ and →3,4)-α-D-Manp-(1→ were mainly hydrolyzed in the gastric phase, while the glycosidic bonds and linkage sequences composing the main chain were not significantly changed. Meanwhile, the digested PM showed a slight enhancement in macrophages and dendritic cell activation. These results provide insight into the structural and immunoreactivity changes in G. frondosa polysaccharides after digestion and their potential role in intestinal immunity through activation of macrophages and dendritic cells.