Bioassay-Guided Extraction of Crude Fucose-Containing Sulphated Polysaccharides from Sargassum fusiforme with Response Surface Methodology

The response surface methodology（RSM） combined with bioassays was employed to optimize the extraction process of crude fucose-containing sulphated polysaccharides（c FCSP） from Sargassum fusiforme. The central composite design（CCD） was used with four variables, five levels, and four responses. The four variables were p H value of hydrochloric acid solution, extraction temperature（℃）, ratio of liquid to raw material(m L g-1), and extraction time（h）, respectively. Chemical and bioassay indices were used in combination as the response parameters, which included the yield of c FCSP, fucose content, proliferation rate of spleen cells, and lipopolysaccharide-induced proliferation of splenocytes. The experimental data were fitted to a second-order polynomial equation using multiple regression analysis, and examined using the appropriate statistical methods. The best extraction conditions were as follows: the p H value of hydrochloric acid solution was 3.50; the extraction temperature was 100℃; the ratio of liquid to raw material was 15.00 m L g-1 and the extraction time was 2.50 h. The experimental yield was close to the predicted from the model. The extract could promote spleen lymphocyte proliferation, especially the lipopolysaccharide-induced lymphocyte proliferation in vitro, which suggested that its immunomodulatory effect on B lymphocytes. Therefore, c FCSP extracted from S. fusiforme could be utilized as an immunostimulant in functional foods and pharmaceutical industry in future.