Structural characterization and immune-enhancing effects of a novel polysaccharide extracted from Sargassum fusiforme

To alleviate the adverse effects of chemotherapy and bolster immune function, a novel polysaccharide derived from Sargassum fusiforme named as SFP-alpha II. The structural composition of SFP-alpha II predominantly consisted of guluronic and mannuronic acids in a molar ratio of 33.8:66.2, with an average molecular weight of 16.5 kDa. Its structure was primarily characterized by-*4)- alpha-GulA-(1-* and-*4)- beta-ManA-(1-* linkages confirmed by FT-IR, methylation, and NMR analyses. The absence of a triple-helix structure was in SFP-alpha II was confirmed using circular dichroism and Congo red dye assays. The dimensions varied with lengths ranging from 20 nm up to 3 mu m revealed by atomic force microscopy (AFM). SFP-alpha II has been found to enhance immunomodulatory activity in cyclophosphamide (CTX)-induced immunosuppressed mice. This was evidenced by improvements in immune organ indices, cytokine levels, and the release of nitric oxide (NO). Specifically, SFP-alpha II mitigated immunosuppression by upregulating the secretion of IL-18 (167.3 %) and TNF-alpha (227.1 %) at a dose of 400 mg/kg, compared with the CTX group in macrophages. Ultimately, SFP-alpha II may serve as a mechanism for immune enhancement through modulation of TLR4-mediated NF-cB and MAPK signaling pathways. This integration of traditional Chinese and Western medicine, leveraging SFP-alpha II as a potential functional food could be pivotal in alleviating immunosuppressive side effects in CTX treatment.