Anti-inflammatory activity of a sulfated polysaccharide from the brown alga Sargassum cristaefolium

We screened the anti-inflammatory activities of polysaccharides from three algae species, such as Porphyra tenera (red algae), Monostroma nitidum (green algae), and Sargassum cristaefolium (brown algae) by measuring inhibition of LPS-induced nitric oxide (NO) production in murine RAW264.7 macrophages. In addition, we investigated the effects of sulfate content and molecular size of the S. cristaefolium polysaccharide on NO inhibitory activity. Among the three tested alga polysaccharide extracts, the S. cristaefolium extract had the highest NO inhibitory effect. The three polysaccharides with 1193.2, 864.4, 386.1 kDa in S. cristaefolium extract, in combination with their 4 acid-degraded polysaccharides with 106.3, 55.9, 15.4, and 1.9 kDa were prepared by Sephacryl S-400HR gel permeation chromatography, and the 386.1 kDa sample had the highest NO inhibitory effect. Three polysaccharide samples with sulfate contents of 0.84%, 9.42%, and 50.83% were obtained by NaBH4 desulfating or SO3–DMF sulfurization of the original S. cristaefolium polysaccharide with 386.1 kDa and 31.1% sulfate content. The highest NO inhibitory activity was observed in the polysaccharide with 9.42% sulfate content. The polysaccharide with 386.10 kDa significantly inhibited inducible nitric oxide synthase expression mediated by inhibiting the phosphorylation of the signal proteins of p-38, ERK and JNK, and nuclear factor-κB activation in lipopolysaccharide-stimulated RAW264.7 cells.