Brassica rapa L. (Tibetan Turnip) polysaccharide improves the immune function and regulates intestinal microbiota in immunosuppressive mice.

In this paper, active polysaccharides were extracted from Brassica rapa L. polysaccharide (BRP), and structural characterization was preliminarily investigated. Its immunomodulatory activity and molecular biological mechanisms in cyclophosphamide-induced immunosuppressed mice were also explored, as well as its effects on intestinal microbiota. Results indicate that BRP is an acidic heteropolysaccharide with the main components of Ara, GalA, and GlcA and has α- and β-glycosidic linkages with pyranose bonds. The results of the study showed that BRP could effectively improve the thymus and spleen indices and repair Cy-induced immune tissue damage in immunosuppressed mice. Meanwhile, BRP increased the immune cell activity and antioxidant levels in mice. In addition, BRP increased the secretion of cytokines (IL-1β, IL-6, IL-10, and TNF-α) and immunoglobulins (IgA, IgG) in mouse serum. It also regulates the relative expression of genes related to the TLR4/NF-κB signaling pathways as well as regulates the diversity and composition of mouse intestinal microbiota. In conclusion, BRP was able to regulated the immune function in immunosuppressed mice, providing a theoretical basis for the development of immunomodulators.