| In this article, we summerize the chemical characters and biological activities of fucoidan from brown algae, and prove that fucoidan is a kind of natural active polysacchardes containing sulfate group and possesses excellent biological properties, including anticoagulant, anti-thrombosis and anti-tumor, antivirus activities and so on. It is a very excellent natural resource for functional food and medicine. While, there are few reports on the produce and biological activities of fucoidan from Laminaria japonica, especially the low molecular weight fucoidan. The yield of Laminaria japonica, which contents a lot of fucoidan, in our country is the highest in the world, while most of the fucoidan, being a by-product of traditional industry from Laminaria japonica, is thrown away. In this article, we produced different molecular weight fucoidan fractions in Laminaria japonica and made a study of the chemical characters of fucoidan frations and their antioxidant, hepatoprotective, anticoagulant, and ACE inhibitory activities. The aim of the article is to provide a valuable scientific basis for the produce of high-valued functional food and medicine from Laminaria japonica.1. In this study, two large molecular weight fucoidan fractions F-A(16.5% SO42-) and F-B (33.5% SO42-) were isolated from Laminariajaponica and separated by anion-exchange chromatographyQ-Sepharose FF. Then low molecular weight fractions F-A1 (MW1.5KD), F-A2 (MW 8.7KD), F-B1 (MW 1.5KD), and F-B2 (MW8.5KD), were obtained from F-A and F-B separately by mild acid hydrolysis and ultra-filtration. In comparison with F-A and F-B, low molecular weight fucoidan fractions had little lower proportions of sulfate, but similar proportions of uronic acid. The neutral sugar compositions varied with the sulfate content and molecular weight.2. The antioxidant activities of fucoidans with different molecular weight and sulfate content were studied using three active oxygen radical assays, DPPH assay and low-density lipoprotein oxidation system in vitro. The aim is to characterize the relationship between chemical composition and antioxidant activities.2.1 The scavenging effects of fucoidans on superoxide, hydroxyl radical and hypochlorous acid were studied by the method of chemiluminescence and Escherichia.coli. protection system. The results show that all the fucoidan fractions had scavenging effects on superoxide, hydroxyl radical and hypochlorous acid, except that the high sulfated fractions F-B1 and F-B2 with low molecular weight had little scavenging activities on the three oxygen free radicals. The antioxidant activities decreased with the increasing of sulfate content, and the influence of sulfate content plays an important role especially on the anitoxidant activities of low molecular weight fucoidans.2.2Low molecular weight fucoidan fractions had scavenging effects on DPPH, but the effects of fucoidans on DPPH were much lower than Vc and probucol.2.3 The antioxidant effects of fucoidan fractions on Cu2+-induced oxidation of human low-density lipoprotein (LDL) were evaluated by monitoring cholesteryl ester hydroperoxides (CHE-OOH) formation kinetics by HPLC analysis. Low molecular weight fucoidan fractions had much better antioxidant activities on Cu2+-induced LDLoxidation than large molecular weight fractions and the activities increased with the increase of sulfate content.3. The hepatoprotective effect of F-A2 was studied using two acute liver injury mice models induced by carbon tetrachloride (CCl4) and D-galactosamine (D-GalN). Addition of F-A2 significantly lowered the content of serum malonaldehyde and markedly increased the activities of superoxide dismutase and glutathione peroxidase, compared with the model groups in both kinds of liver injury mice. Moreover, administration of F-A2 significantly inhibited the elevation of glutamate pyruvate transaminase induced by CCl4 and D-GalN in mice. The results suggest that the antioxidant activity o...
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