Structural characterization and immunomodulatory effect of a starch-like Grifola frondosa polysaccharides on cyclophosphamide-induced immunosuppression in mice

In this study, a pure Grifola frondosa polysaccharide (GFP-1) was extracted and purified from Grifola frondosa. By HPLC, GC-MS, FT-IR, and NMR analysis, GFP-1 was determined to be a starch-like polysaccharide with an average molecular weight of 3370 kDa. It included three monosaccharides, i.e., glucose, galactose, and mannose. The backbone of GFP-1 consisted of-*4)-alpha-Glcp-(1-* and-*4,6)-alpha-Glcp-(1-* . The side branches were composed of-*6)-alpha-Galp-(1-*, alpha-Glcp-(1-*, and a small amount of alpha-Manp-(1-* . By using a cyclophosphamide (CTX)-induced immunosuppressed mice model, we evaluated the immunomodulatory activity of GFP-1. The results showed that GFP-1 increased the thymic and spleen indices, promoted the level of IgG and IgA in serum, and activated the mitogen-activated protein kinase (MAPK) pathway in CTX-induced mice. Also, GFP-1 significantly promoted the mRNA expression of intestinal barrier factors and protected intestinal structural integrity in immunosuppressed mice. In conclusion, the data presented here suggested that GFP-1 might be a potential immune-enhancing supplement.