Immunomodulatory Function and Action Mechanism of a Small-Molecular-Weight Saccharide Fraction from Fruits of Schisandra chinensis (Turcz.) Baill

Schisandra chinensis (Turcz.) Baill. is a classic medicine-food homologous plant rich in saccharides, but research on its small-molecule saccharides is scarce. In this study, a small-molecular-weight saccharide fraction ( SFSC ) was isolated from S. chinensis using macroporous resin adsorption and ultrafiltration, and its structure was characterized by LC-MS/MS. To assess biological effects, in vivo experiments demonstrated that SFSC restored immune function in cyclophosphamide (CTX)-induced immunosuppressed mice. In vitro assays showed that SFSC enhanced the proliferation of RAW264.7 macrophages and further induced M1 polarization, as well as the secretion of immunologically active mediators via TLR4-dependent MAPK and NF-κB signaling pathways. Further fractionation revealed that both acidic and neutral subfractions jointly contribute to SFSC ’s immunomodulatory activity, with the acidic subfraction specifically mediating macrophage proliferation. Thus, this study clarifies both the mechanism and material basis of SFSC, providing a basis for the development of natural immunomodulators.