The Purification, Structure And Immunological Activity Of Polysaccharides From Sargassum Horneri

Sargassum horneri is one of the abundant edible seaweed resources, which contains rich nutritive materials, especially the polysaccharides with a variety of biological activities. In the present research, the polysaccharides were isolated from Sargassum horneri by water extraction and alcohol precipitation, and then primarily fractionated by column chromatographies. Chemical approaches and instrumental analysis methods were used to figure out the structural characteristics of the purified fractions. The experiments on mouse were carried out in vivo and in vitro to investigate the immunological activities of these polysaccharide fractions.Five crude polysaccharides of Sargassum horneri, including two crude laminaran fractions(CSHL and HSHL), and two fucoidan fractions(CSHP and HSHP) extracted by cold and hot water and one algin fraction(SHA) extracted by Na2CO3 solution, were obtained, respectively. DEAE-Cellulose and DEAE-Sepharose Fast Flow anion-exchange columns and Sephacryl S-400 filtration chromatography were applied to fractionate laminarans and fucoidans, while SHA was purified by dissolution with alkali and precipitation with acid. The percentages of CSHP22 and HSHP11 are higher than the other fractions of 16 components obtained from Sargassum horneri. Further study of these polysaccharides were conducted and the results are as follows: the highest content of sugar, uronic acid, protein and sulfate are 87.86%(HSHP11), 29.70%(SHA), 4.27%(HSHP13, in addition to SHA) and 26.60%(CSHP21). The molecular weight of polysaccharides was estimated to range from 4.6×103 Da(HSHP13) to 6.8×105 Da(CSHP). Monosaccharide compositions show that most polysaccharide fractions mainly consisted of fucose.To figure out the fine structural features of CSHP22, one primary fraction of fucoidans, the methods of periodate oxidation, Smith degradation and methylation, combined with IR, GC-MS and NMR, were conducted. The results indicate that with branches and complex structure, the main chain of CSHP22 is composed of 1,3-linked Fuc and inserted by small amount of 1,6-Gal. C-2 and C-4 of 1,3-linked Fuc may be the branch points or the positions of sulfate constitution. Analyzed by 1H and 13 C NMR, the two fragments, →2)-α-L-Fucp4SO3--(1→ and →3)-α-L-Fucp4SO3--(1→, are thought to exist in CSHP22.The effections of CSHP, CSHP22, HSHP and HSHP11 on immune cells in vitro and the effections of CSHP on immune cells in vivo were studied on ICR mice, which indicated that fucoidans of Sargassum horneri significantly enhanced the proliferation of splenic lymphocytes, the killing activity of NK cells, and phagocytosis and cytotoxic activities of peritoneal macrophages to perform immunological activities. The results of experiences in vitro also indicated that different polysaccharide fractions had different immune activities.