Structural characterization and immunomodulatory activity of the polysaccharide from halophyte Suaeda salsa:...

Suaeda salsa is a halophyte that tolerates harsh environments and contributes to soil desalination. To mitigate the expansion of saline-alkali land and improve resource use efficiency, extraction of functional components from S. salsa was performed to promote sustainable development. In this study, a polysaccharide (SGP) was extracted from Suaeda salsa via water extraction and alcohol precipitation. SGP-C was subsequently isolated and purified using DEAE-52 cellulose and Sephadex G-200 columns. Its relative molecular mass was estimated to be 1.47 × 10³ kDa by high-performance liquid chromatography. Structural analysis was performed through monosaccharide composition analysis, methylation analysis, GC/MS, and 1D/2D NMR spectroscopy. SGP-C primarily consists of arabinose, galacturonic acid, and glucose, with rhamnose and mannose as minor components. In vitro immunomodulatory assays demonstrated that SGP-C concentration-dependently promoted macrophage proliferation and enhanced phagocytosis, NO production, and cytokine secretion in RAW 264.7 cells. qRT-PCR results indicated that SGP-C up-regulated the mRNA expression of cytokines such as TNF-α, IL-10, IL-1β, and IL-6, suggesting its potential to further regulate immune cell activity. Western blot analysis revealed that SGP-C coordinately activated key proteins in the TLR4-PI3K/AKT-NF-κB signaling pathway and induced nuclear translocation of the p65 subunit. The experiments indicate that Suaeda salsa shows great potential for the amelioration of saline-alkali soils, and its bioactive polysaccharides exhibit significant immunomodulatory activity. These findings provide a theoretical basis for ecological restoration and the development of functional products.