Fucose Units Research Articles

Synthesis of the oligosaccharides related to branching sites of fucosylated chondroitin sulfates from sea cucumbers.

Natural anionic polysaccharides fucosylated chondroitin sulfates (FCS) from sea cucumbers attract great attention nowadays due to their ability to influence various biological processes, such as blood coagulation, thrombosis, angiogenesis, inflammation, bacterial and viral adhesion. To determine pharmacophore fragments in FCS we have started systematic synthesis of oligosaccharides with well-defined structure related to various fragments of these polysaccharides. In this communication, the synthesis of non-sulfated and selectively O-sulfated di- and trisaccharides structurally related to branching sites of FCS is described. The target compounds are built up of propyl β-d-glucuronic acid residue bearing at O-3 α-l-fucosyl or α-l-fucosyl-(1→3)-α-l-fucosyl substituents. O-Sulfation pattern in the fucose units of the synthetic targets was selected according to the known to date holothurian FCS structures. Stereospecific α-glycoside bond formation was achieved using 2-O-benzyl-3,4-di-O-chloroacetyl-α-l-fucosyl trichloroacetimidate as a donor. Stereochemical outcome of the glycosylation was explained by the remote participation of the chloroacetyl groups with the formation of the stabilized glycosyl cations, which could be attacked by the glycosyl acceptor only from the α-side. The experimental results were in good agreement with the SCF/MP2 calculated energies of such participation. The synthesized oligosaccharides are regarded as model compounds for the determination of a structure-activity relationship in FCS.

Ultrasound Effects on the Degradation Kinetics, Structure, and Antioxidant Activity of Sea Cucumber Fucoidan

The effects of ultrasound on the molecular weight, structure, and antioxidant potential of a fucoidan found in Isostichopus badionotus were investigated. The results showed the molecular weight (Mw) of fucoidan decreased obviously after ultrasound treatment. Higher ultrasonic intensity, lower temperature, and lower fucoidan concentrations led to a more effective sonochemical effect. The kinetic model for fucoidan degradation fitted to 1/M(wt)-1/M(w0) = kt at the tested temperature. The optimized degradation conditions by response surface methodology (RSM) were temperature, 12 °C, and intensity, 508 W/cm². Structural analysis by FTIR and NMR indicated the fucoidan kept the linear tetrasaccharide repeating units as the original polysaccharides after the ultrasound treatment, with only slight destruction of the middle nonsulfated fucose units. Antioxidant activity assay showed the antioxidant activity was slightly improved by the ultrasound treatment. The results suggested that ultrasound treatment is an effective approach to decrease the M(w) of fucoidan with only minor structural destruction.

Water soluble exo-polysaccharide from Syncephalastrum racemosum, a strong inducer of plant defence reactions

This study examines the production, characterization and bioactivity on plant cell cultured in vitro of exopolysaccharides (EPS) from Syncephalastrum racemosum CBS 443.59. Firstly, the influence of the fungus culture condition in shake flasks (pH, temperature and different carbon and nitrogen sources) on EPS and biomass production was evaluated. In order to enhance EPS production, a new protocol based on two-stage pH fermentation in a 3L stirred fermentor was developed. Under this condition, EPS production increased by 3.55 times, compared to a constant pH process, reaching a maximal EPS concentration of 2.62g/L. Structurally, the EPS contains a polyglucuronic acid backbone, linked essentially with mannose and fucose units and some galactose and glucose units. The bioactivity of EPS as inducer of defence reactions in plant suspension-cultured cells was also studied. Our results show, for first time, that EPS from S. racemosum CBS 443.59 induces, depending on the concentration, PAL activation and H2O2 synthesis in Arabidopsis thaliana cell suspensions.

Structure of N-linked oligosaccharides attached to chlorovirus PBCV-1 major capsid protein reveals unusual class of complex N-glycans

The major capsid protein Vp54 from the prototype chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1) contains four Asn-linked glycans. The structure of the four N-linked oligosaccharides and the type of substitution at each glycosylation site was determined by chemical, spectroscopic, and spectrometric analyses. Vp54 glycosylation is unusual in many ways, including: (i) unlike most viruses, PBCV-1 encodes most, if not all, of the machinery to glycosylate its major capsid protein; (ii) the glycans are attached to the protein by a β-glucose linkage; (iii) the Asn-linked glycans are not located in a typical N-X-(T/S) consensus site; and (iv) the process probably occurs in the cytoplasm. The four glycoforms share a common core structure, and the differences are related to the nonstoichiometric presence of two monosaccharides. The most abundant glycoform consists of nine neutral monosaccharide residues, organized in a highly branched fashion. Among the most distinctive features of the glycoforms are (i) a dimethylated rhamnose as the capping residue of the main chain, (ii) a hyperbranched fucose unit, and (iii) two rhamnose residues with opposite absolute configurations. These glycoforms differ from what has been reported so far in the three domains of life. Considering that chloroviruses and other members of the family Phycodnaviridae may have a long evolutionary history, we suggest that the chlorovirus glycosylation pathway is ancient, possibly existing before the development of the endoplasmic reticulum and Golgi pathway, and involves still unexplored mechanisms.

Preparation and characterization of O-acylated fucosylated chondroitin sulfate from sea cucumber.

Fucosylated chondroitin sulfate (FuCS), a kind of complex glycosaminoglycan from sea cucumber, has potent anticoagulant activity. In order to understand the relationship between structures and activity, the depolymerized FuCS (dFuCS) was chosen to prepare its derivates by selective substitution at OH groups. Its O-acylation was carried out in a homogeneous way using carboxylic acid anhydrides. The structures of O-acylated derivatives were characterized by NMR. The results indicated that the 4-O-sulfated fucose residues may be easier to be acylated than the other ones in the sulfated fucose branches. But the O-acylation was always accompanied by the β-elimination, and the degree of elimination was higher as that of acylation was higher. The results of clotting assay indicated that the effect of partial O-acylation of the dFuCS on their anticoagulant potency was not significant and the O-acylation of 2-OH groups of 4-O-sulfated fucose units did not affect the anticoagulant activity.

Structure and effect of sulfated fucose branches on anticoagulant activity of the fucosylated chondroitin sulfate from sea cucumber Thelenata ananas.

Fucosylated chondroitin sulfate (FuCS) is a glycosaminoglycan from sea cucumber, made up of alternating β-d-glucuronic acid and N-acetyl-β-d-galactosamine units. The β-d-glucuronic acid residues have branches of sulfated fucose, while the fucose branches may have distinguishable patterns and proportions of sulfate substitution. The structure of the sulfated fucose branches of the fucosylated chondroitin sulfate from the sea cucumber Thelenata ananas has been characterized by mild acid hydrolysis and NMR technology. The results showed that the fucose residues are made up of 3-,4-mono-O-sulfated fucose and 2,4-di-O-sulfated fucose with about 25:22:53, respectively. The sulfated fucose branches are essential for the anticoagulant action of FuCS, and this potent effect is possibly related to the occurrence of 2,4-di-O-sulfated fucose units. Furthermore, these branches could constitute the structural requirement for the binding of the glycosaminoglycan to coagulant enzymes, such as thrombin by HCII, factor X by the intrinsic tenase complex.

Effects of polysaccharides enriched in 2,4-disulfated fucose units on coagulation, thrombosis and bleeding

Sulfated polysaccharides from marine invertebrates have well-defined structures and constitute a reliable class of molecules for structure-activity relationship studies. We tested the effects of two of these polysaccharides, namely a sulfated fucan and a fucosylated chondroitin sulfate, on coagulation, thrombosis and bleeding. The compounds share similar 2,4-disulfated fucose units, which are required for high anticoagulant activity in this class of polymer. These residues occur either as branches in fucosylated chondroitin sulfate or as components of the linear chain in the sulfated fucan. These polysaccharides possess anticoagulant activity but differ significantly in their mechanisms of action. The fucosylated chondroitin sulfate inhibits thrombin by heparin cofactor II, whereas sulfated fucan inhibits thrombin by both antithrombin and heparin cofactor II. In addition, these polysaccharides also have serpin-independent anticoagulant activities. Fucosylated chondroitin sulfate, but not sulfated fucan, activates factor XII. As a result of the complex anticoagulant mechanism, the invertebrate polysaccharides differ in their effects on experimental thrombosis. For instance, the sulfated fucan inhibits venous thrombosis at lower doses than fucosylated chondroitin sulfate. In contrast, fucosylated chondroitin sulfate is significantly more potent than sulfated fucan in arterial thrombosis. Finally, fucosylated chondroitin sulfate increases bleeding, while sulfated fucan has only a discrete effect. In conclusion, the location of 2,4-disulfated fucose units in the polysaccharide chains dictates the effects on coagulation, thrombosis and bleeding.

Stereoselective Synthesis of Di- and Trisaccharide Fucoidan Fragments Bearing α-D-Glucuronic Acid Residue*

The first stereoselective synthesis of disaccharide α -d-GlcA-(1 → 2)-α-l-Fuc-OPr (1), trisaccharide (1 → 3)-α-l-Fuc-[α -d-GlcA-(1 → 2)]-α -l-Fuc-OPr (3), and their selectively O-sulfated derivatives 2 and 4 bearing sulfo-groups at O(4) of the fucose units has been performed. Compounds 1– 4 represent the fragments of the chain of the fucoidan from Cladosiphon okamuranus brown seaweed. Glucuronylation by a series of selectively O-acetylated glucuronyl bromides was studied to obtain the target products. It has been found that 3-O-acetylated donor 6 is the most efficient agent for α -glycoside bond formation that can be connected with intramolecular remote participation of 3-O-acetyl group favoring α-stereoselectivity.

Electrospray ionization mass spectrometry of oligosaccharides derived from fucoidan of Ascophyllum nodosum

Algal fucoidan is a complex sulfated polysaccharide whose structural characterization requires powerful spectroscopic methodologies. While most of the structural investigations reported so far have been performed using NMR as the main spectroscopic method, we report herein data obtained by negative electrospray ionization mass spectrometry. MS analysis has been carried out on oligosaccharides obtained by partial hydrolysis of fucoidan from the brown algae Ascophyllum nodosum. Oligosaccharide mixtures were fractionated by size exclusion chromatography, which allowed the analysis of oligomers ranging from monosaccharide to pentasaccharide. Monosaccharides were detected as monosulfated as well as disulfated forms. Besides, part of the oligosaccharides exhibited a high content of sulfate, evidencing that fucoidan contains disulfated fucosyl units. Fragmentation experiments yielded characteristic fragment ions indicating that the fucose units are mainly 2-O-sulfated. This study demonstrates that highly sulfated oligosaccharides from fucoidan can be analyzed by ESIMS which gives additional information about the structure of this highly complex polysaccharide.

Extraction of novel sulfated polysaccharides from Aphanothece sacrum (Sur.) Okada, and its spectroscopic characterization

Abstract We extracted polysaccharides (PS) from Aphanothece sacrum using a hot alkaline solution which degraded other biopolymers such as proteins and nucleotides. The spectroscopy and elemental analyses indicated the PS contain carboxyls and sulfate groups. The degree of sulfation was estimated as about 10 mol %. 1H NMR studies demonstrated that the PS of A. sacrum had a dimethylated fucose unit. The combination of sulfate group and fucose in the prokaryotic PS was first evidenced by the direct spectroscopic studies. The PS showed efficient gelation behavior, binding to metal ions abundant in soil, and the swelling volume of the gel was approximately 250 times the dry volume. These results imply that PS of A. sacrum, which has been mass cultivated in Japan for a long time, may have potential as an environmentally benign water absorbent.

Structural investigation of a fucoidan containing a fucose-free core from the brown seaweed, Hizikia fusiforme

A fucoidan, obtained from the hot-water extract of the brown seaweed, Hizikia fusiforme, was separated into five fractions by DEAE Sepharose CL-6B and Sepharose CL-6B column chromatography. All five fractions contained predominantly fucose, mannose and galactose and also contained sulfate groups and uronic acid. The fucoidans had MWs from 25 to 950 kDa. The structure of fraction F32 was investigated by desulfation, carboxyl-group reduction, partial hydrolysis, methylation analysis and NMR spectroscopy. The results showed that the sugar composition of F32 was mainly fucose, galactose, mannose, xylose and glucuronic acid; sulfate was 21.8%, and the MW was 92.7 kDa. The core of F32 was mainly composed of alternating units of →2)-α- d-Man(1→ and →4)-β- d-GlcA(1→, with a minor portion of →4)-β- d-Gal(1→ units. The branch points were at C-3 of →2)-Man-(1→, C-2 of →4)-Gal-(1→ and C-2 of →6)-Gal-(1→. About two-thirds of the fucose units were at the nonreducing ends, and the remainder were (1→4)-, (1→3)- and (1→2)-linked. About two-thirds of xylose units were at the nonreducing ends, and the remainder were (1→4)-linked. Most of the mannose units were (1→2)-linked, and two-thirds of them had a branch at C-3. Galactose was mainly (1→6)-linked. The absolute configurations of the sugar residues were α- d-Man p, α- l-Fuc p, α- d-Xyl p, β- d-Gal p and β- d-Glc pA. Sulfate groups in F32 were at C-6 of →2,3)-Man-(1→, C-4 and C-6 of →2)-Man-(1→, C-3 of →6)-Gal-(1→, C-2, C-3 or C-4 of fucose, while some fucose had two sulfate groups. There were no sulfate groups in either the GlcA or xylose residues.

Selective cleavage and anticoagulant activity of a sulfated fucan: stereospecific removal of a 2-sulfate ester from the polysaccharide by mild acid hydrolysis, preparation of oligosaccharides, and heparin cofactor II-dependent anticoagulant activity.

A linear sulfated fucan with a regular repeating sequence of [3)-alpha-L-Fucp-(2SO4)-(1-->3)-alpha-L-Fucp-(4SO4)-(1-->3)-alpha-L-Fucp-(2,4SO4)-(1-->3)-alpha-L-Fucp-(2SO4)-(1-->]n is an anticoagulant polysaccharide mainly due to thrombin inhibition mediated by heparin cofactor II. No specific enzymatic or chemical method is available for the preparation of tailored oligosaccharides from sulfated fucans. We employ an apparently nonspecific approach to cleave this polysaccharide based on mild hydrolysis with acid. Surprisingly, the linear sulfated fucan was cleaved by mild acid hydrolysis on an ordered sequence. Initially a 2-sulfate ester of the first fucose unit is selectively removed. Thereafter the glycosidic linkage between the nonsulfated fucose residue and the subsequent 4-sulfated residue is preferentially cleaved by acid hydrolysis, forming oligosaccharides with well-defined size. The low-molecular-weight derivatives obtained from the sulfated fucan were employed to determine the requirement for interaction of this polysaccharide with heparin cofactor II and to achieve complete thrombin inhibition. The linear sulfated fucan requires significantly longer chains than mammalian glycosaminoglycans to achieve anticoagulant activity. A slight decrease in the molecular size of the sulfated fucan dramatically reduces its effect on thrombin inactivation mediated by heparin cofactor II. Sulfated fucan with approximately 45 tetrasaccharide repeating units binds to heparin cofactor II but is unable to link efficiently the plasma inhibitor and thrombin. This last effect requires chains with approximately 100 or more tetrasaccharide repeating units. We speculate that the template mechanism may predominate over the allosteric effect in the case of the linear sulfated fucan inactivation of thrombin in the presence of heparin cofactor II.

Differential recognition of animal type beta4-galactosylated and alpha3-fucosylated chito-oligosaccharides by two family 18 chitinases from Trichoderma harzianum.

We report the purification of two glycosyl hydrolase family 18 chitinases, Chit33 and Chit42, from the filamentous fungus Trichoderma harzianum and characterization using a panel of different soluble chitinous substrates and inhibitors. We were particularly interested in the potential of these (alpha/beta)(8)-barrel fold enzymes to recognize beta-1,4-galactosylated and alpha-1,3-fucosylated oligosaccharides, which are animal-type saccharides of medical relevance. Three-dimensional structural models of the proteins in complex with chito-oligosaccharides were built to support the interpretation of the hydrolysis data. Our kinetic and inhibition studies are indicative of the substrate-assisted catalysis mechanism for both chitinases. Both T. harzianum chitinases are able to catalyze some transglycosylation reactions and cleave both simple chito-oligosaccharides and synthetically modified, beta-1,4-galactosylated and alpha-1,3-fucosylated chito-oligosaccharides. The cleavage data give experimental evidence that the two chitinases have differences in their substrate-binding sites, Chit42 apparently having a deeper substrate binding groove, which provides more tight binding of the substrate at subsites (-2-1-+1+2). On the other hand, some flexibility for the sugar recognition at subsites more distal from the cleavage point is allowed in both chitinases. A galactose unit can be accepted at the putative subsites -4 and -3 of Chit42, and at the subsite -4 of Chit33. Fucose units can be accepted as a branch at the putative -3 and -4 sites of Chit33 and as a branch point at -3 of Chit42. These data provide a good starting point for future protein engineering work aiming at chitinases with altered substrate-binding specificity.

Sulfated fucan oligosaccharides elicit defense responses in tobacco and local and systemic resistance against tobacco mosaic virus.

Sulfated fucans are common structural components of the cell walls of marine brown algae. Using a fucan-degrading hydrolase isolated from a marine bacterium, we prepared sulfated fucan oligosaccharides made of mono- and disulfated fucose units alternatively bound by alpha-1,4 and alpha-1,3 glycosidic linkages, respectively. Here, we report on the elicitor activity of such fucan oligosaccharide preparations in tobacco. In suspension cell cultures, oligofucans at the dose of 200 microg ml(-1) rapidly induced a marked alkalinization of the extracellular medium and the release of hydrogen peroxide. This was followed within a few hours by a strong stimulation of phenylalanine ammonia-lyase and lipoxygenase activities. Tobacco leaves treated with oligofucans locally accumulated salicylic acid (SA) and the phytoalexin scopoletin and expressed several pathogenesis-related (PR) proteins, but they displayed no symptoms of cell death. Fucan oligosaccharides also induced the systemic accumulation of SA and the acidic PR protein PR-1, two markers of systemic acquired resistance (SAR). Consistently, fucan oligosaccharides strongly stimulated both local and systemic resistance to tobacco mosaic virus (TMV). The use of transgenic plants unable to accumulate SA indicated that, as in the SAR primed by TMV, SA is required for the establishment of oligofucan-induced resistance.

Is there a correlation between structure and anticoagulant action of sulfated galactans and sulfated fucans?

We attempted to identify the specific structural features in sulfated galactans and sulfated fucans that confer anticoagulant activity. For this study we employed a variety of invertebrate polysaccharides with simple structures composed of well-defined units of oligosaccharides. Our results indicate that a 2-O-sulfated, 3-linked alpha-L-galactan, but not a alpha-L-fucan with a similar molecular size, is a potent thrombin inhibitor mediated by antithrombin or heparin cofactor II. The difference between the activities of these two polysaccharides is not very pronounced when factor Xa replaced thrombin. The occurrence of 2,4-di-O-sulfated units is an amplifying motif for 3-linked alpha-fucan-enhanced thrombin inhibition by antithrombin. If we replace antithrombin by heparin cofactor II, then the major structural requirement for the activity becomes single 4-O-sulfated fucose units. The presence of 2-O-sulfated fucose residues always had a deleterious effect on anticoagulant activity. Overall, our results indicate that the structural requirements for interaction of sulfated galactans and sulfated fucans with coagulation cofactors and their target proteases are stereospecific and not merely a consequence of their charge density and sulfate content.

Drug design, synthesis, and evaluation of a non-sugar-based selectin antagonist

We have designed a series of simple rigid compounds ( 2) having a phenyl ring attached to three essential groups necessary for selectin binding, i.e., a fucose unit, a carboxylic acid, and the hydrophobic part. In this series of compound 2, 2a exhibited strong inhibitory activity in in vitro P-selectin mediated cell adhesion assay. The novel type of compound 2a would be a potential lead compound for selectin antagonist.

Analysis of retted and non retted flax fibres by chemical and enzymatic means

Flax fibres ( Linum usitatissimum L.) were subjected to chemical and enzymatic analysis in order to determine the compositional changes brought about by the retting process and also to determine the accessibility of the fibre polymers to enzymatic treatment. Chemical analysis involved subjecting both retted and non retted fibres to a series of sequential chemical extractions with 1% ammonium oxalate, 0.05 M KOH, 1 M KOH and 4 M KOH. Retting was shown to cause minimal weight loss from the fibres but caused significant changes to the pectic polymers present. Retted fibres were shown to have significantly lower amounts of rhamnogalacturonan as well as arabinan and xylan. In addition the average molecular mass of the pectic extracts was considerably lowered. Enzyme treatment of the 1 M KOH extracts with two different enzymes demonstrated that the non retted extract contained a relatively high molecular weight xylan not found in the retted extract. Treatment of the 1 M KOH extracts and the fibres with Endoglucanase V from Trichoderma viride demonstrated that while this enzyme solubilised cellulose as well as xylan and xyloglucan oligomers from the extract, it had limited access to these polymers on the fibre. MALDI-TOF MS analysis of the material solubilised from the extract suggested that the xylan was randomly substituted with 4-O-methyl glucuronic acid moieties. The xyloglucan was shown to be of the XXXG type and was substituted with galactose and fucose units. The enzyme treatments of the fibres demonstrated that the xylan and xyloglucan polymers in the fibres were not accessible to the enzyme but that material which was entrapped by the cellulose could be released by the hydrolysis of this cellulose.

Pharmacokinetic Analysis of Lectin-dependent Biodistribution of Fucosylated Bovine Serum Albumin: A Possible Carrier for Kupffer Cells

To examine the potential utility of fucosylation of drug carriers for targeted drug delivery to Kupffer cells, the pharmacokinetics of 111In-labeled fucosylated bovine serum albumin (Fuc-BSA) with different numbers of fucose residues (11, 16, 25, 31 or 41) was studied. After intravenous injection in mice, all 111In-Fuc-BSAs were mainly delivered to the liver and their hepatic uptake became saturated when the dose was increased. Of these derivatives, only 111In-Fuc41-BSA showed a slow plasma elimination at low doses, suggesting an interaction with blood components. Examination of binding conditions as well as electrophoretic analysis of the binding components indicated that the serum-type mannan binding protein (MBP) is responsible. Kupffer cells, which possess fucose receptors, showed the highest uptake of 111In-Fuc41-BSA, followed by endothelial cells and hepatocytes. The hepatic uptake of 111In-Fuc41-BSA was inhibited by co-injection of Gal42-BSA, but not by Man46-BSA. On the other hand, excess Fuc41BSA inhibited the hepatic uptake of 111In-Man46-BSA, while 111In-Gal42-BSA did not: These findings suggest that not only the fucose receptors on Kupffer cells but also other lectins are involved in the biodistribution of Fuc-BSAs. To understand how the degree of fucose modification affects the binding affinity of Fuc-BSA with hepatic lectins and serum MBP, a pharmacokinetic analysis was performed based on a physiological model. The Michaelis constant of the hepatic uptake of 111in-Fuc-BSA decreased with an increasing number of fucose units, and the intrinsic hepatic clearance of 111In-Fuc25-, 111In-Fuc31- and 111 In-Fuc41-BSAs was close to, or much greater than, the hepatic plasma flow rate, indicating efficient hepatic uptake of these derivatives. These results suggest that fucosylation is a potentially useful method making drug carriers selective for Kupffer cells, although extensive modification might result in retarded delivery due to binding to other lectins like MBP.

Synthesis and structural studies of “branched” 2‐linked trisaccharides related to h‐type 2 blood group determinants

AbstractA series of fucosylated trisaccharides l‐Fuc‐(1→2)‐ß‐d‐Gal‐(1→4)‐ß‐X‐OMe (1‐6, X = d‐GlcNAc, d‐Qui (6‐deoxy‐Glc), d‐Xyl) related to H type 2 blood group determinant have been synthesized both as their α‐ and ß‐ L‐Fuc anomers together with the component disaccharide starting compounds (7‐11). The conformational properties of the trisaccharides together with their parent disaccharides have been investigated by NMR spectroscopy (proton and carbon chemical shifts and proton NOEs) in combination with computer modeling using the Monte Carlo approach and the HSEA force field using the GEGOP program with the main focus on the α‐linked fucose series.The series of compounds allow for the investigation of interaction between the sugar units in the—in principle—linear structures, which in practice behave as branched trisaccharides.The interaction between the terminal fucose unit and the unit at the reducing end has been probed by substitution of the bulky CH2OH group with CH3 and H substituents, respectively. Compounds with severe steric interactions can be identified by the non‐additivity of their carbon chemical shifts and subsequently confirmed by the detailed conformational assessment by NOEs and computer modeling. The most severe contacts arise in the GlcNAc and Qui trisaccharide series, whereas the Xyl‐containing trisaccharide derivatives only exhibit weak steric interaction as probed by the NMR parameters.

Further data on the structure of brown seaweed fucans: relationships with anticoagulant activity

The composition, molecular weight (MW), anticoagulant activity and nuclear magnetic resonance spectra of various low-molecular-weight fucans (LMWFs) obtained by partial hydrolysis or radical depolymerization of a crude fucoidan extracted from the brown seaweed Ascophyllum nodosum are compared. Fucose units were found mainly sulfated at O-2, to a lesser extent at O-3, and only slightly at O-4, contrary to previously published results for fucoidans from other brown seaweeds, and fucose 2, 3- O-disulfate residues were observed for the first time. As the sulfation pattern excluded an α-(1→2)-linked fucose backbone and a high proportion of α-(1→4) linkages was found, it would appear that the concept of fucoidan structure needs to be revised. Anticoagulant activity is apparently related not only to MW and sulfation content, as previously determined, but also (and more precisely) to 2- O-sulfation and 2,3- O-disulfation levels.