| Fucoidan, existed between brown algae's cells, consists amount number of sulphate radicals and L-fucose, as well as xylose, glucose, arabinose, galactose and uronic acid et al, whose contents are different with different fucoidan. Liking other sulphated polysaccharides, fucoidan has many bio-activities, such as anti-virus, anticoagulant, killing tumor cells and adjusting immune function. Many literatures reported that the bio-activities of fucoidan are related with it's structure, including the quality of sulphate radical and it's binding site, the kinds of single sugar and ratio, branched structure and molecular weight. So, people have done a lot of studies on related fields. When analyzing fuciodan's structure, researchers gradually cultivated the habit of considering how structure can effect on polysaccharide's bio-activities. This can explain the mechanism of fucoidan's bio-activities more reasonable. Kelp is one of important members in brown seaweed family. China is one of the main countries planting kelp, and kelp plays an important role in seaside provinces'economic corps in China, especially in Fu Jian province. Deep proceeding is an important appropriation for promoting kelp production's value and improving the structure of kelp industry. The high bio-activities of fucoidan provide a wonderful future for utilizing fucoidan to make healthy food and new drugs.Recent years, the antioxidant activity of fucoidan is being taken attention by researchers, and being one of hot studying point on fucoidan. In this article, we have done some research works on fucoidan as follows:1,On the process of extracting fucoidan from kelp, we have studied some factors affecting on extracting fucoidan, including the quality of adding water used as extracting media, pH, extracting time, and temperature. Though setting up orthogonal experiment, and though orthogonal analysis, we acquired the best process. The result showed, the extracting ratio of fucoidan was desirable on the condition of temperature 80℃, the quality of adding water 1:25, time 3 hours and pH 4. And, the extracting ratio was 5.51%, the content of L-fucose in crude fucoidan was 15.02%, and the content of sulphate radical was 18.25%.2,We have analyzed the physics and chemistry properties of crude fucoidan. The content of protein in fucoidan was determined with the method of kjeldahl; the ash content was also analyzed and the salt and small molecular materials in fucoidan were separated by ultrafiltration equipment; the As and Hg were measured with HG-AFS; the single sugar composition in fucoidan was checked with GC. The results indicated that the protein content was 6.9%, ash was 27.96%, As and Hg were 2.78mg/Kg and 0.125 mg/Kg, respectively, before desalination, contrast with 2.26 mg/Kg and 0.119 mg/Kg after desalination; and L(-)-fucose, D-xylose, D-mannose, D-glucose, D-galactose were checked out, and their contents were 40.62%, 2.76%, 25.88%, 22.10%, 8.64%, respectively.3,The effect of competitive chelators EDTA and phytic acid on depriving heavy metals binding with fucoidan has been studied, as well as the effect of different acid concentration and ultrafilitration on the regular of depriving heavy metals. The results illustrated that it was effective to reduce the residue of metal elements, such as Mg, Ca, Mn, Zn, As, Ag, Cd, Pb, when the competitive chelators EDTA and phytic acid were added during the extraction process. However, it was not very satisfied as to Hg, Fe, Cu and Ba. In addition, the effect of adding EDTA was better than adding phytic acid.4,Fucoidan was purified with DEAE-Cellulose52, and two fractions were gotten, which were named HF1 and HF2, respectively. Low molecular weight fucoidan were made with acid degradation. The contents of uronic acid in fraction HF1and HF2 were 18.834±1.144% and 5.878±0.402%, respectively; and the contents of sulphate radical in fraction HF1and HF2 were 27.631±0.229 and 26.328±0.665, respectively; the L-fucose's contents in HF1and HF2 were 44.197% and 81.119%, respectively. The content of L-fucose in low molecular weight fucoidan was much lower than thant in the fucoidan which had not been broken down by acid, and their contents were 13.033% and 40.624%, respectively. The binding sites of sulphate radical in L-fucose in low molecular weight fucoidan and HF1 were both in C-2 and C-4, however, HF2's mainly existed in the site of C-4.5,During the experiment of anti-oxidation in vitro, we fond that HF1, HF2 and high molecular weight fucoidan had anti-hydroxyl radical activity, and their IC50 were 7.6mg/mL, 5.2mg/mL, and 8.9mg/mL,respectively. And the low molecular weight fucoidan had no this activity. And these four fractions did not show the activity of anti-lipid peroxidation. These four fractions showed different activity on extent in inhibiting oxidation of linoleic acid at low concentration, without any activity at high concentration. And, the low molecular fucoidan's activity of inhibiting oxidation of linoleic acid could have longer time than the one of high molecular weight; and the fraction consisting higher content of uronic acid had better inhibiting result than the one consiting lower content of uronic acid.
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