| Fucoidan is a kind of heteropolysaccharides. It's generally found in brown seaweeds and some echinoderms, Recent researches in the marine drugs area show it has many biological activities, such as anticoagulant, anti-tumor, antiviral and anti-ulcer etc.. And the study on fucoidan is more and more concerned by researchers in recent years. Fucoidans extracted from different sources generally have different structure and constituents.Kelp (Laminaria japonica), a kind of large seaweed, is rich in protein, vitamins and minerals. It also contains fucoidans. China has become the largest country in the cultivation of kelp. Its annual production of kelp takes a share of over 80 percent of the whole world. But the kelp industry of China has never grown big. The main problem is that the production line is too simple. The entire industry is still on a low level. To accelate the development of the kelp industry of China, more effort should be conducted on the study of new high value products.Recently, many biological activities of fucoidans from Laminaria japonica have been studied, but reports on their structure are seldom seen. This paper tries to elucidate the structure of fucoidans from Laminaria japonica.1. Crude fucoidans were extracted from Laminaria japonica and then separated by anion-exchange chromatography on Q-Sepharose FF into three fractions, F-0, F-1 and F-2. Where F-l was the fractions with high uronic acids, and F-2 was high with sulfate ester. The yield ratios were 13.4%, 34.8%, and 28.6% respectively. Chemical composition analysis shows the contents of sulfate ester in the three fractions are 7.6%, 16.1%, and 30.5%. And the contents of uronic acids are 20.8%, 21.4%, 8.4%. QC analysis shows monosaccharides constituents in the three fractions are fucose, galactose, glucose, mannose, rhamnose, and xylose. Where fucose contents are the the highest, i.e. 40.7%, 52.9%, and 62.5% respectively. HPSEC shows the average molecular weights are 150,700 for F-l, and 160,000 for F-2.2. By comparing the hydrolysis products by methods of H2SO4, H2O2, and enzyme, H2O2 was found to be the best choice for the preparation of oligo-fucoidans. Through orthogonal experiments, the best hydrolysis condition was found to be 9%H2C>2, 60 °C, and 6h. Fucoidans were hydrolyzed with H2O2, separated by 5,000 Da. ultra-filtration membrane, and then purified by Bio-P4, and P2. The products were named F-lb, F-lc, F-2b, and F-2c. Comparison of the contents of sulfate ester in the products of acid degradation and H2O2 degradation showed the latter was higher.3. Anticoagulant experiments on the H2O2 degraded products with different molecular weights shows F-2 has strong anticoagulant, activity. And the 5,000~15,000 fraction of F-2 also shows strong activity, while the lower fraction does not. Compared with F-2, the F-l and its products are all less active. And the lower fraction of F-l even shows no activity at all.4. The structure of F-2, desulfated F-2, and F-2b were analyzed by IR, methylation, GC-MS, and NMR. The IR spectrum revealed that disulfated fucose exists in F-2. F-2 and its desulfated derivative were subjected to methylation analysis by GC-MS. The result showed that 1—>3-linkage is the major linkage pattern in fucose residues. Sulfate groups are substituted mainly at C-4 positions, lessly at C-2 of fucose residues, and some of fucose residues are disulfated at C-2, 4 positions. NMR showed F-2b is 1—>3 linked tetra-saccharides. It has fucose residues of two configurations, a and (3. And sulfate groups are substituted at C-4. The structure model of F-2b is -?a-L-Fucp-4(SO4))-(l->3)-(/3-L-Fucp-4(SO4))-(l-?3)-a-L-Flicp-(l-?3)-...
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