Purification, antitumor and antioxidant activities in vitro of polysaccharides from the brown seaweed Sargassum pallidum

Supercritical CO2 extraction, ultrasonic-aid extraction and membrane separation technology were applied to prepare Sargassum pallidum polysaccharides (SP). Three main fractions, SP-1, SP-2 and SP-3, were obtained by membranes of 1.0 × 10−4 mm pore size and normal molecular-weight cut-off of 50 kDa. The resulting three preparations were further purified by DEAE Cellulose-52 chromatography to afford seven polysaccharide fractions. Furthermore, the antitumor and antioxidant activities, in vitro, of the polysaccharide fractions were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical-scavenging assay, respectively. SP-3-1 and SP-3-2 showed significantly higher antitumor activity against the HepG2 cells, A549 cells, and MGC-803 cells. SP-3 had the highest sulfate content (22.6%). These results indicate that the higher antitumor activity of SP-3-1 and SP-3-2 from SP-3 with lower molecular weights may be related to their molecular weights and sulfate contents. The antioxidant activities of SP-1, SP-2 and SP-3 were low at the tested concentration.