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A sulfated polysaccharide, named fucoidan, from the marine alga Cladosiphon okamuranus is comprised of carbohydrate units containing glucuronic acid and sulfated fucose residues. Here we found this compound potently inhibits dengue virus type 2 (DEN2) infection. Viral infection was inhibited when DEN2, but not other serotypes, was pretreated with fucoidan. A carboxy-reduced fucoidan derivative in which glucuronic acid was converted to glucose did not inhibit viral infection. Elimination of the sulfated function group from fucoidan significantly attenuated the inhibitory activity on DEN2 infection with <1% fucoidan. DEN2 particles bound exclusively to fucoidan, indicating that fucoidan interacts directly with envelope glycoprotein (EGP) on DEN2. Structure-based analysis suggested that Arg323 of DEN2 EGP, which is conformationally proximal to one of the putative heparin binding residues, Lys310, is critical for the interaction with fucoidan. In conclusion, both the sulfated group and glucuronic acid of fucoidan account for the inhibition of DEN2 infection.

Our previous study indicated that the interleukin (IL)-6/STAT-3 signal was up-regulated in inflammatory bowel disease (IBD) in both humans and animal models. We also discovered phosphorylated STAT-3 in the nucleus of the colonic epithelial cells in IBD mice. Intestinal epithelial cells (IEC) have been shown to secrete IL-6. Therefore, the secretion of IL-6 from IEC may be one of the mechanisms of STAT-3 phosphorylation in IEC during the pathogenesis of IBD, and inhibition of IL-6 production by IEC may be beneficial in preventing IBD. We examined the preventative effect of various types of fucoidans on IL-6 production in a lipopolysaccharide (LPS)-stimulated murine colonic epithelial cells line, CMT-93, in vitro. We also determined in vivo the effect of fucoidans on murine chronic colitis induced with dextran sodium sulphate. Among fucoidans, those from Cladosiphon okamuranus Tokida and Kjellmaniella crassifolia inhibited IL-6 production in CMT-93 cells with the down-regulation of NF-kappaB nuclear translocation. Analysis of the effect of fucoidan on murine colitis in vivo showed that the disease activity index and myeloperoxidase activity decreased in mice fed Cladosiphon fucoidan, but not Fucus fucoidan. Cytokine profiles in colonic lamina propria indicated that the synthesis of interferon (IFN)-gamma and IL-6 decreased and that of IL-10 and transforming growth factor (TGF)-beta increased in mice fed Cladosiphon fucoidan, compared with mice fed a standard diet or Fucus fucoidan. The levels of IL-6 mRNA in colonic epithelial cells was lower in colitis-induced Balb/c mice fed Cladosiphon fucoidan than those fed a standard diet. Fucoidan improves murine chronic colitis by down-regulating the synthesis of IL-6 in the colonic epithelial cells. Fucoidan derived from C. o. Tokida may be useful as a dietary substance for the patients with inflammatory bowel disease.

Background: Recently, the acquisition by Helicobacter pylori of resistance to antibiotics has become a serious problem. Therefore, nonantibiotic substances are required to diminish H. pylori-induced gastric lesions. In the present study, the effects of Cladosiphon fucoidan were examined in terms of H. pylori attachment to porcine gastric mucin in vitro and Helicobacter pylori-induced gastritis in vivo., Methods: The inhibitory effect of Cladosiphon fucoidan and other polysaccharides on H. pylori attachment to porcine gastric mucin was assayed in vitro with mucin-coated microtiter plates. The effect of Cladosiphon fucoidan on H. pylori-induced gastritis was examined in vivo using Mongolian gerbils. H. pylori-inoculated gerbils were given fucoidan in drinking water. Six weeks after H. pylori-inoculation, gerbils were sacrificed for macroscopic and microscopic examination of gastric lesions and counting of viable H. pylori in the gastric mucosa., Results: Cladosiphon fucoidan inhibited the H. pylori attachment to porcine gastric mucin at pH 2.0 and 4.0. Two other sulfated polysaccharides, Fucus fucoidan and dextran sulfate sodium, also inhibited the attachment but only at pH 2.0. Inhibitory effects of these three sulfated polysaccharides were not observed at pH 7.2 and nonsulfated polysaccharides, such as mannan and dextran, exerted no influence at any pH. In the in vivo experiment, the H. pylori-induced gastritis and the prevalence of H. pylori infected animals were markedly reduced by fucoidan in a dose-dependent manner, at doses of 0.05 and 0.5% in the drinking water., Conclusion: Cladosiphon fucoidan may deserve particular attention as a safe agent that can prevent H. pylori infection and reduce the risk of associated gastric cancer.

This study attempted to enhance the anti-ulcer activity of fucoidan from Cladosiphon okamuranus TOKIDA by chemical modification with a hydrophobic group. The suitable number of fucose residues in the effective compound was also clarified to obtain a compound of constant quality. Degraded fucoidans were coupled with several hydrophobic groups via Schiff bases, and their anti-ulcer activities were determined by acetic acid-induced ulcer models in rats. Size-fractionated oligofucose was also modified and assayed for anti-ulcer activity. Among the modified oligofucoses, only the oligofucose-dodecylaniline combination (OFDA) significantly promoted ulcer healing. The effective dose was 0.2 mg/kg/d. The most suitable number of fucose residues in the compound for the anti-ulcer activity was determined to be around 12. We succeeded in enhancing the anti-ulcer activity of Cladosiphon fucoidan by modification with dodecylaniline. The activity of this compound was comparable or greater than that of typical anti-ulcer agents. By determination of the optimal OF chain length for the anti-ulcer activity of OFDA, it became possible to obtain OFDA of constant quality.

To elucidate the anti-ulcer potential of Cladosiphon fucoidan, anti-peptic activity, bFGF stabilizing activity and inflammatory properties of this and related substances were investigated. Anti-peptic activity was observed with this and other sulfated polysaccharides such as dextran sulfate, carrageenan, and Fucus fucoidan. However, non-sulfated polysaccharides such as mannan and dextran did not exert the anti-peptic activity. The loss of bFGF bioactivity was prevented by all sulfated polysaccharides tested except chondroitin sulfate, at pH 7.4 and at pH 4.0. At pH 2.0, only heparin protected the bFGF activity. The generation of superoxide by macrophages and PMNs was stimulated by dextran sulfate, carrageenan, and Fucus fucoidan, whereas Cladosiphon fucoidan, heparin and chondroitin did not. Dextran sulfate, carrageenan, and Fucus fucoidan also stimulated the secretion of TNFalpha from macrophages, while Cladosiphon fucoidan did not. Thus, Cladosiphon fucoidan is a sulfated polysaccharide without inflammatory action. These results suggest that Cladosiphon fucoidan is a safe substance with potential for gastric protection.

We studied the inhibitory effect of Cladosiphon fucoidan on the attachment of Helicobacter pylori (H. pylori), a gastroduodenal pathogen, to human gastric cell lines. The bacterial binding in these cell lines was inhibited more by Cladosiphon fucoidan (IC50 = 16-30 mg/mL), than by the fucoidan from Fucus (IC50 > 30 mg/mL). Dextran sulfate, another sulfated polysaccharide, did not inhibit the binding at all. Pre-incubating the bacterial suspension with fucoidans reinforced the inhibitory ability of these components, and reduced the IC50 value of Cladosiphon fucoidan to approximately 1 mg/mL. However, the binding was not inhibited by pre-treatment of gastric cells with these components. It was also shown that this fucoidan blocks both Leb- and sulfatide-mediated attachment of H. pylori to gastric cells. Furthermore, fucoidan-binding proteins were found on the H. pylori cell surface by Western blot analysis. Thus, the inhibitory effect exerted by Cladosiphon fucoidan on binding between H. pylori and gastric cells might result from the coating with this component of the bacterial surface.

A structural study was carried out on a fucoidan isolated from the brown seaweed Cladosiphon okamuranus. The polysaccharide contained fucose, glucuronic acid and sulfate in a molar ratio of about 6.1 : 1.0 : 2.9. The results of Smith degradation showed that this polysaccharide has a linear backbone of 1-->3-linked alpha-fucopyranose with a half sulfate substitution at the 4-positions, and a portion of the fucose residues was O-acetylated. The data obtained from partial acid hydrolysis, a methylation analysis and NMR spectra indicated that the alpha-glucuronic acid residue is linked to the 2-positions of the fucose residues, which were not substituted by a sulfate group. These results indicated that the average structure of this fucoidan is as follows: -[(-->3Fuc-4(+/-OSO3-)alpha1-)5-->3[GlcA alpha1-->2]Fuc alpha1-]n-. (Half of each fucose residue was sulfated. One O-acetyl ester was present in every 6 fucose residues.)

A structural study was carried out on a galactose-rich polysaccharide fraction isolated from cell walls of Bifidobacterium catenulatum YIT4016 after N-acetylmuramidase digestion. The polysaccharide contained galactose and glucosamine in a molar ratio of 16.9:1.0. Data obtained by 13C NMR spectroscopy showed that the backbone chain of this polysaccharide is composed of galactofuranose residues, while the branches consist of galactopyranosyl residues. Furthermore, the data obtained from NaIO4 oxidation, partial methanolysis and methylation analysis indicated that this polysaccharide consists of a trisaccharide repeating unit having the following structure: [sequence: see text]

The isolation and analysis of the polysaccharide-peptidoglycan complexes of Lactobacillus casei YIT9018 are presented. Two polysaccharide-peptidoglycan complexes, PS-PG1 and PS-PG2, were solubilized from the heat-killed cell by treatment with N-acetylmuramidase. PS-PG1 was composed of glucose, rhamnose, and small amount of galactose and glucosamine. PS-PG2 was composed of glucose, rhamnose, galactosamine, and glucosamine. The ratio by weight of these fractions was about 1:8. PS-PG2 was analyzed in detail. Smith degradation and deamination of this complex yielded oligosaccharide units. The results of methylation analysis of these units and intact PS-PG2 led to the most probable structure of PS-PG2: (formula; see text)

A water-soluble polysaccharide-peptidoglycan complex (PSPG) was prepared from heat-killed Lactobacillus casei by digesting the bacteria with N-acetylmuramidase. The molecular weight of PSPG was over 30,000, and the polysaccharide portion of PSPG, its main component was composed of rhamnose, glucose, galactose, glucosamine and galactosamine. Mice pretreated intraperitoneally with PSPG survived after a lethal infection with Listeria monocytogenes or Pseudomonas aeruginosa. The growth of infecting bacteria (L. monocytogenes, P. aeruginosa, Salmonella typhimurium, Escherichia coli) in both the peritoneal cavity and the liver was inhibited markedly in the mice that had been treated with PSPG. It was suggested that macrophages may be the main effector for the anti-infectious effect of PSPG since treatment of mice with carrageenan, a selective macrophage blocker, markedly reduced the anti-infectious effect of PSPG.