Purification, characterization and immunostimulating activity of water-soluble polysaccharide isolated from Capsosiphon fulvescens

A water-soluble polysaccharide (SPS-CF) was isolated and purified from Korean Capsosiphon fulvescens by dilute acid extraction, ethanol precipitation, and DEAE-cellulose ion exchange chromatography. The purified SPS-CF was shown to be a glucuronogalactomannan with a molecular mass of 385 kDa and the monosaccharide composition of the SPS-CF was determined to be mannose (55.4% in mole percentage), galactose (25.3%), glucuronic acid (16.3%), and arabinose (0.8%). Fourier-transform infrared and elemental analysis indicated that the purified SPS-CF is a sulfated polysaccharide containing significant amount of sulfate esters (5.7% in mass). Enzyme Linked Immunosorbent Assay showed that the SPS-CF significantly stimulates the release of the pro-inflammatory cytokines, TNF-alpha and IL-6, in a dose-dependent manner. RT-PCR analysis demonstrated that the SPS-CF also induced a more than two-fold increase in the expression of iNOS and COX-2, responsible for the induction of NO and PGE2, respectively, at 5 microg/ml in RAW264.7 murine macrophages. These results suggest that the sulfated SPS-CF isolated from C. fulvescens has potent immunostimulating activity.