Three-phase extraction of polysaccharide from : Process optimization, structural characterization and bioactivities.

The isolation of polysaccharide (SRP) by three-phase extraction was optimized, and its structure and biological activities were identified. The optimal extraction conditions were: mass fraction of ammonium sulfate, 20%; volume ratio of sample solution to t-butanol, 1:1.5; extraction temperature, 35°C. Under these conditions, the yield of SRP was 6.85% ± 0.13%. SRP was found to be composed of glucose (35.79%), galactose (26.80%), glucuronic acid (9.92%), fructose (8.65%), xylose (7.92%), fucose (4.19%), arabinose (3.46%) and rhamnose (3.26%), with the molecular weight of 27.52 kDa. The results of DPPH, hydroxyl, ABTS radical scavenging and reducing power tests showed that SRP had good antioxidant capacities. SRP had no cytotoxic effect on RAW264.7 macrophages at the concentrations of 25-200 μg/mL, and could significantly promote phagocytosis activity and cell migration according to CCK-8 assay, phagocytosis assay and cell scratch experiment. SRP can significantly stimulate the transcript expression levels of TNF-α, IL-1β and IL-6, as determined by RT-PCR and Western blot assays. SRP activated the TLR4/NF-κB signaling pathway, and autophagy also occurred. These results suggest that SRP is a safe antioxidant and immunomodulator, and that it can be used in the development of functional foods and/or pharmaceuticals.