A 2-sulfated, 3-linked alpha-L-galactan is an anticoagulant polysaccharide

Mitigation of Hepatic Impairment with Polysaccharides from Red Alga Albidum corallinum Supplementation through Promoting the Lipid Profile and Liver Homeostasis in Tebuconazole-Exposed Rats

Sulfated polysaccharides from seaweed are highly active natural substances with valuable applications. In the present paper, attempts have been made to discuss the physicochemical and structural features of polysaccharides isolated from red marine alga Alsidium corallinum (ACPs) and their protective effect in hepatic impairments induced by tebuconazole (TEB) in male adult rats. Structural features were determined using high-performance liquid chromatography, Fourier-transformed infrared, and solid-state 1H and 13C-Nuclear magnetic resonance analysis. ACPs are found to be hetero-sulfated-anionic polysaccharides that contain carbohydrates, sulfate groups, and uronic acids. In vitro biological activities suggested the effective antioxidant and antimicrobial capacities of ACPs. For antioxidant testing in vivo, the biochemical analysis and plasma profiles displayed that oral administration of ACPs could mitigate blood lipid indicators, including total cholesterol, triglyceride, low and high-density lipoprotein cholesterol, and bilirubin. Liver function indexes involving alanine aminotransferase and aspartate aminotransferase showed that ACPs possessed prominent antioxidant activities. Additionally, the intervention of ACPs potentially inhibited lipid peroxidation, protein oxidation, key enzymes of lipid metabolism (<0.001), and improved antioxidant status (<0.05). Histomorphological observation confirmed that ACPs intervention could partially repair liver injuries caused by TEB. The computational results showed that A. corallinum monosaccharides bound 1JIJ, 1HD2, and 1WL4 receptors with acceptable affinities, which, together with deep embedding and molecular interactions, support the antioxidant, antimicrobial, and hypolipidemic outlined effects in the in vitro and in vivo findings. Given their prominent antioxidant effects, ACPs are promising candidates for liver diseases and must be considered in pharmaceutical applications.

Designing Smaller, Synthetic, Functional Mimetics of Sulfated Glycosaminoglycans as Allosteric Modulators of Coagulation Factors

Natural glycosaminoglycans (GAGs) are arguably the most diverse collection of natural products. Unfortunately, this bounty of structures remains untapped. Decades of research has realized only one GAG-like synthetic, small-molecule drug, fondaparinux. This represents an abysmal output because GAGs present a frontier that few medicinal chemists, and even fewer pharmaceutical companies, dare to undertake. GAGs are heterogeneous, polymeric, polydisperse, highly water soluble, synthetically challenging, too rapidly cleared, and difficult to analyze. Additionally, GAG binding to proteins is not very selective and GAG-binding sites are shallow. This Perspective attempts to transform this negative view into a much more promising one by highlighting recent advances in GAG mimetics. The Perspective focuses on the principles used in the design/discovery of drug-like, synthetic, sulfated small molecules as allosteric modulators of coagulation factors, such as antithrombin, thrombin, and factor XIa. These principles will also aid the design/discovery of sulfated agents against cancer, inflammation, and microbial infection.

Comparative study on the mechanisms of anti-lung cancer activities of three sulfated galactofucans

Sulfated galactofucans, as the active compositions of fucoidan, were reported to exhibit antitumor activity. In the current study, a sulfated galactofucan (SGF) from Sargassum thunbergii and its three derivatives (SGF-H, SGF-L, and SGF-S) were prepared for structural analysis. Structural analysis showed that SGF-H was a high molecular weight sulfated galactofucan (51.5/17.8 kDa) with a high molar ratio of galactose (Gal) to fucose (Fuc) (0.66 : 1), SGF-L was a low molecular weight sulfated galactofucan (17.7 kDa) with a low molar ratio of Gal to Fuc (0.20 : 1), and SGF-S was a mixture (1.7 kDa) of sulfated galacto-fuco-oligomers or fuco-oligomers. It was noteworthy that the linkage of Gal residues in SGF-H was a β-linkage while SGF-L was an α-linkage. A comparative study on the anti-lung cancer activity in vitro and in vivo, antimetastatic effects, the metastasis-associated protein expression, and binding abilities to fibroblast growth factors (FGFs) of SGF, SGF-H, and SGF-L was performed to understand the structure-activity relationship. To some extent, SGF-L showed the strongest activity in the inhibition of human lung cancer cells A549 cell proliferation, while SGF-H exhibited the strongest activity in the inhibition of human bronchial epithelial cells BEAS-2B cell proliferation. SGF-L showed the strongest antimetastatic activity, followed by SGF-H and SGF. The expression of metastasis-associated proteins showed only a small difference. The in vivo tumor inhibition of SGF, SGF-H, and SGF-L was 45%, 41%, and 31%, respectively. SPR analysis showed SGF-H binds preferentially to FGF1 and FGF2, while SGF-L preferentially binds to FGF7 and FGF10, suggesting that the anti-lung cancer activity from sulfated galactofucan could involve the FGF-FAK/mTOR pathway.

Antithrombotics from the Sea: Polysaccharides and Beyond

Marine organisms exhibit some advantages as a renewable source of potential drugs, far beyond chemotherapics. Particularly, the number of marine natural products with antithrombotic activity has increased in the last few years, and reports show a wide diversity in scaffolds, beyond the polysaccharide framework. While there are several reviews highlighting the anticoagulant and antithrombotic activities of marine-derived sulfated polysaccharides, reports including other molecules are sparse. Therefore, the present paper provides an update of the recent progress in marine-derived sulfated polysaccharides and quotes other scaffolds that are being considered for investigation due to their antithrombotic effect.

Anticoagulant and Antithrombotic Properties of Three Structurally Correlated Sea Urchin Sulfated Glycans and Their Low-Molecular-Weight Derivatives

The anticoagulant and antithrombotic properties of three structurally correlated sea urchin-derived 3-linked sulfated α-glycans and their low molecular-weight derivatives were screened comparatively through various in vitro and in vivo methods. These methods include activated partial thromboplastin time, the inhibitory activity of antithrombin over thrombin and factor Xa, venous antithrombosis, the inhibition of platelet aggregation, the activation of factor XII, and bleeding. While the 2-sulfated fucan from Strongylocentrotus franciscanus was observed to be poorly active in most assays, the 4-sulfated fucan from Lytechinus variegatus, the 2-sulfated galactan from Echinometra lucunter and their derivatives showed multiple effects. All marine compounds showed no capacity to activate factor XII and similar low bleeding tendencies regardless of the dose concentrations used to achieve the highest antithrombotic effect observed. The 2-sulfated galactan showed the best combination of results. Our work improves the background about the structure-function relationship of the marine sulfated glycans in anticoagulation and antithrombosis. Besides confirming the negative effect of the 2-sulfated fucose and the positive effect of the 2-sulfated galactose on anticoagulation in vitro, our results also demonstrate the importance of this set of structural requirements on antithrombosis in vivo, and further support the involvement of high-molecular weight and 4-sulfated fucose in both activities.

Heparin mimetics with anticoagulant activity

Heparin, a sulfated polysaccharide belonging to the glycosaminoglycan family, has been widely used as an anticoagulant drug for decades and remains the most commonly used parenteral anticoagulant in adults and children. However, heparin has important clinical limitations and is derived from animal sources which pose significant safety and supply problems. The ever growing shortage of the raw material for heparin manufacturing may become a very significant issue in the future. These global limitations have prompted much research, especially following the recent well-publicized contamination scandal, into the development of alternative anticoagulants derived from non-animal and/or totally synthetic sources that mimic the structural features and properties of heparin. Such compounds, termed heparin mimetics, are also needed as anticoagulant materials for use in biomedical applications (e.g., stents, grafts, implants etc.). This review encompasses the development of heparin mimetics of various structural classes, including synthetic polymers and non-carbohydrate small molecules as well as sulfated oligo- and polysaccharides, and fondaparinux derivatives and conjugates, with a focus on developments in the past 10 years.

Polysaccharides from Sargassum thunbergii: Monthly variations and anti-complement and anti-tumour activities

Monthly variations of polysaccharides from Sargassum thunbergii and their anti-complement and anti-tumour activities were investigated. It was observed that an increase in fucose and total sugar contents occurred during the growth period (from early April to mid-June), accompanied by a decrease in molar ratios of other monosaccharides to fucose. The highest yields were obtained from early July to early September, which was in accordance with the significant increase in molar ratio of glucose to fucose and decrease in molar ratio of other monosaccharides to fucose. And the above results suggested that S. Thunbergii synthesized large amount of laminaran, the storage substance of brown algae, during the senescence period. However, sulfate contents were relatively stable in the life cycle of S. thunbergii. These results suggested that S. thunbergii synthesized complex sulfated heteropolysacchairdes during inactive period, while during other periods, it synthesized more sulfated galactofucan. All polysaccharides showed anti-complement activity, suggesting that the harvesting time did not influence the anti-complement activities. In the anti-tumour assay in vitro, the polysaccharides taken during the senescence period had much lower anti-tumour activity, suggesting that fucoidan, but not laminaran, determined the anti-tumour activities. Therefore, polysaccharides from S. thunbergii might have great potential in anti-complement and anti-tumour application.

FROZEN PRE-COOKED SEMI-PRODUCTS WITH IODINE-CONTAINING STUFFING

The article shows the necessity of healthy foods development and introduction into population`s food ration, which are enriched with scarce micronutrients, especially with iodine, to strengthen health and prevent diseases. There is a review of Laminarium chemical composition and proved the possibility of using these algae as iodine-containing ingredient to produce foodstuffs aimed to prevent iodine deficient disorders. The correlation of iodine and selenium in Laminarium algae is unique and is (1,0:0,7). This is that correlation what is necessary for human`s thyroid gland to provide normal functioning and optimal producing of the most important hormones – Thyroxine (T6) and Triiodothyronin (T3). While the development of pancakes with Laminarium stuffing, it was made a number of physical and chemical indicators of the stuffings compositions: humidity, active and titrated acidity. The important criteria for the stuffing formulation development was the product organoleptic estimation. It was found the optimal correlation of the formulation`s components of the Laminarium stuffing with the degree of homogenization considering. The application of modern research methods and experimental design, the study of organoleptic, physical, and chemical indicators of Laminarium and stuffing for pancakes with it allowed us to determine the optimum additive content in the stuffing and to optimize technological parameters of pancakes production. The Laminarium algae introduction in the recipe will enrich pancakes with a large number of macro-and microelements, vitamins and organic compounds. It has been found that the new product – pancakes with Laminarium stuffing characterized by high iodine content, has a high nutritional value and good consumer`s indicators. This allows to recommend it for using in preventive nutrition.

The Sea as a Rich Source of Structurally Unique Glycosaminoglycans and Mimetics

Glycosaminoglycans (GAGs) are sulfated glycans capable of regulating various biological and medical functions. Heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate and hyaluronan are the principal classes of GAGs found in animals. Although GAGs are all composed of disaccharide repeating building blocks, the sulfation patterns and the composing alternating monosaccharides vary among classes. Interestingly, GAGs from marine organisms can present structures clearly distinct from terrestrial animals even considering the same class of GAG. The holothurian fucosylated chondroitin sulfate, the dermatan sulfates with distinct sulfation patterns extracted from ascidian species, the sulfated glucuronic acid-containing heparan sulfate isolated from the gastropode Nodipecten nodosum, and the hybrid heparin/heparan sulfate molecule obtained from the shrimp Litopenaeus vannamei are some typical examples. Besides being a rich source of structurally unique GAGs, the sea is also a wealthy environment of GAG-resembling sulfated glycans. Examples of these mimetics are the sulfated fucans and sulfated galactans found in brown, red and green algae, sea urchins and sea cucumbers. For adequate visualization, representations of all discussed molecules are given in both Haworth projections and 3D models.

Oligosaccharides from the 3-linked 2-sulfated alpha-L-fucan and alpha-L-galactan show similar conformations but different dynamics

Here we have performed an nuclear magnetic resonance-based study on the ring and chain conformations as well as dynamics of oligosaccharides generated by acid hydrolysis on two structurally related glycans, a 3-linked 2-sulfated alpha-L-galactan and a 3-linked 2-sulfated alpha-L-fucan. Results derived from scalar couplings have confirmed the ¹C₄ chair configuration to both alpha-L-fucose and alpha-L-galactose, and a similar solution 3D structure for the oligosaccharide chains of both sulfated glycans as seen on the basis of NOE patterns. Measurements of spin-relaxation rates have suggested, however, a slight difference dynamical property to these glycans. The fucose-based oligosaccharides showed an enhanced dynamical property if compared to the galactose-based oligosaccharides of same anomericity, sugar configuration, glycosidic bond and sulfation type. This distinction solely on the dynamical aspect has been driven therefore by the different sugar composition of the two studied sulfated glycans.

Carbohydrate-Carbohydrate Interactions Mediated by Sulfate Esters and Calcium Provide the Cell Adhesion Required for the Emergence of Early Metazoans

Early metazoans had to evolve the first cell adhesion mechanism addressed to maintain a distinctive multicellular morphology. As the oldest extant animals, sponges are good candidates for possessing remnants of the molecules responsible for this crucial evolutionary innovation. Cell adhesion in sponges is mediated by the calcium-dependent multivalent self-interactions of sulfated polysaccharides components of extracellular membrane-bound proteoglycans, namely aggregation factors. Here, we used atomic force microscopy to demonstrate that the aggregation factor of the sponge Desmapsamma anchorata has a circular supramolecular structure and that it thus belongs to the spongican family. Its sulfated polysaccharide units, which were characterized via nuclear magnetic resonance analysis, consist preponderantly of a central backbone composed of 3-α-Glc1 units partially sulfated at 2- and 4-positions and branches of Pyr(4,6)α-Gal1→3-α-Fuc2(SO3)1→3-α-Glc4(SO3)1→3-α-Glc→4-linked to the central α-Glc units. Single-molecule force measurements of self-binding forces of this sulfated polysaccharide and their chemically desulfated and carboxyl-reduced derivatives revealed that the sulfate epitopes and extracellular calcium are essential for providing the strength and stability necessary to sustain cell adhesion in sponges. We further discuss these findings within the framework of the role of molecular structures in the early evolution of metazoans.

Perspective on the use of sulfated polysaccharides from marine organisms as a source of new antithrombotic drugs

Thromboembolic diseases are increasing worldwide and always require anticoagulant therapy. We still need safer and more secure antithrombotic drugs than those presently available. Sulfated polysaccharides from marine organisms may constitute a new source for the development of such drugs. Investigation of these compounds usually attempts to reproduce the therapeutic effects of heparin. However, we may need to follow different routes, focusing particularly in the following aspects: (1) defining precisely the specific structures required for interaction of these sulfated polysaccharides with proteins of the coagulation system; (2) looking for alternative mechanisms of action, distinct from those of heparin; (3) identifying side effects (mostly pro-coagulant action and hypotension rather than bleeding) and preparing derivatives that retain the desired antithrombotic action but are devoid of side effects; (4) considering that sulfated polysaccharides with low anticoagulant action on in vitro assays may display potent effects on animal models of experimental thrombosis; and finally (5) investigating the antithrombotic effect of these sulfated polysaccharides after oral administration or preparing derivatives that may achieve this effect. If these aspects are successfully addressed, sulfated polysaccharides from marine organisms may conquer the frontier of antithrombotic therapy and open new avenues for treatment or prevention of thromboembolic diseases.

Molecular characterization and immunomodulatory activity of sulfated fucans from Agarum cribrosum

The sulfated-fucans, known as fucoidans, were isolated from Agarum cribrosum and fractionated using ion-exchange chromatography to determine their molecular characteristics and in vitro immunomodulatory activity. The crude and fractionated fucoidans (F1 and F2) consisted mostly of carbohydrates (52.4-56.0%), sulfates (12.7-23.0%) and uronic acid (14.1-21.8%), with a small amount of proteins (3.9-9.3%), and included various levels of fucose (44.0-46.7%), mannose (18.9-26.8%), galactose (16.8-33.0%), xylose (10.7-17.0%) and glucose (3.5-9.5%). The crude and fractionated fucans contained one or two subfractions with average molecular weights (Mw) ranging from 110.1 × 10(3) to 2420 × 10(3)g/mol. The fractionated fucoidan, especially the F1 fraction, strongly stimulated murine macrophages (Raw 264.7 cells), producing a considerable amount of nitric oxide (NO) and inducing expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2) and interleukin-10 (IL-10) transcripts by activation of nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) pathways. The maximally immunoenhancing F1 fraction was mainly composed of (1 → 3)-linked fucose, (1 → 2)-linked mannose and (1 → 4)-linked glucuronic acid with sulfates at C-2 or both the C-2 and C-4 positions in (1 → 2,3)- and (1 → 2,3,4)-linked fucose residues.

Marine sulfated glycans with serpin-unrelated anticoagulant properties

Marine organisms are a rich source of sulfated polysaccharides with unique structures. Fucosylated chondroitin sulfate (FucCS) from the sea cucumber Ludwigothurea grisea and sulfated galactan from the red alga Botryocladia occidentalis are one of these unusual molecules. Besides their uncommon structures, they also exhibit high anticoagulant and antithrombotic effects. Earlier, it was considered that the anticoagulant activities of these two marine glycans were driven mainly by a catalytic serpin-dependent mechanism likewise the mammalian heparins. Its serpin-dependent anticoagulant action relies on promoting thrombin and/or factor Xa inhibition by their specific natural inhibitors (the serpins antithrombin and heparin cofactor II). However, as opposed to heparins, these two previously mentioned marine glycans were proved still capable in promoting coagulation inhibition using serpin-free plasmas. This puzzle observation was further investigated and clearly demonstrated that the cucumber FucCS and the red algal sulfated galactan have an unusual serpin-independent anticoagulant effect by inhibiting the formation of factor Xa and/or thrombin through the procoagulants tenase and prothrombinase complexes, respectively. These marine polysaccharides with unusual anticoagulant effects open clearly new perspectives for the development of new antithrombotic drugs as well as push the glycomics project.

Specific sulfation and glycosylation-a structural combination for the anticoagulation of marine carbohydrates

Based on considered achievements of the last 25 years, specific combinations of sulfation patterns and glycosylation types have been proved to be key structural players for the anticoagulant activity of certain marine glycans. These conclusions were obtained from comparative and systematic analyses on the structure-anticoagulation relationships of chemically well-defined sulfated polysaccharides of marine invertebrates and red algae. These sulfated polysaccharides are known as sulfated fucans (SFs), sulfated galactans (SGs) and glycosaminoglycans (GAGs). The structural combinations necessary for the anticoagulant activities are the 2-sulfation in α-L-SGs, the 2,4-di-sulfation in α-L-fucopyranosyl units found as composing units of certain sea-urchin and sea-cucumber linear SFs, or as branching units of the fucosylated chondroitin sulfate, a unique GAG from sea-cucumbers. Another unique GAG type from marine organisms is the dermatan sulfate isolated from ascidians. The high levels of 4-sulfation at the galactosamine units combined with certain levels of 2-sulfation at the iduronic acid units is the anticoagulant structural requirements of these GAGs. When the backbones of red algal SGs are homogeneous, the anticoagulation is proportionally dependent of their sulfation content. Finally, 4-sulfation was observed to be the structural motif required to enhance the inhibition of thrombin via heparin cofactor-II by invertebrate SFs.

Bioactivity and applications of sulphated polysaccharides from marine microalgae

Marine microalgae have been used for a long time as food for humans, such as Arthrospira (formerly, Spirulina), and for animals in aquaculture. The biomass of these microalgae and the compounds they produce have been shown to possess several biological applications with numerous health benefits. The present review puts up-to-date the research on the biological activities and applications of polysaccharides, active biocompounds synthesized by marine unicellular algae, which are, most of the times, released into the surrounding medium (exo- or extracellular polysaccharides, EPS). It goes through the most studied activities of sulphated polysaccharides (sPS) or their derivatives, but also highlights lesser known applications as hypolipidaemic or hypoglycaemic, or as biolubricant agents and drag-reducers. Therefore, the great potentials of sPS from marine microalgae to be used as nutraceuticals, therapeutic agents, cosmetics, or in other areas, such as engineering, are approached in this review.

Anticoagulant activity of a unique sulfated pyranosic (1->3)-β-L-arabinan through direct interaction with thrombin

A highly sulfated 3-linked β-arabinan (Ab1) with arabinose in the pyranose form was obtained from green seaweed Codium vermilara (Bryopsidales). It comprised major amounts of units sulfated on C-2 and C-4 and constitutes the first polysaccharide of this type isolated in the pure form and fully characterized. Ab1 showed anticoagulant activity by global coagulation tests. Less sulfated arabinans obtained from the same seaweed have less or no activity. Ab1 exerts its activity through direct and indirect (antithrombin- and heparin cofactor II-mediated) inhibition of thrombin. Direct thrombin inhibition was studied in detail. By native PAGE, it was possible to detect formation of a complex between Ab1 and human thrombin (HT). Ab1 binding to HT was measured by fluorescence spectroscopy. CD spectra of the Ab1 complex suggested that ligand binding induced a small conformational change on HT. Ab1-thrombin interactions were studied by molecular dynamic simulations using the persulfated octasaccharide as model compound. Most carbohydrate-protein contacts would occur by interaction of sulfate groups with basic amino acid residues on the surface of the enzyme, more than 60% of them being performed by the exosite 2-composing residues. In these interactions, the sulfate groups on C-2 were shown to interact more intensely with the thrombin structure. In contrast, the disulfated oligosaccharide does not promote major conformational modifications at the catalytic site when complexed to exosite 1. These results show that this novel pyranosic sulfated arabinan Ab1 exerts its anticoagulant activity by a mechanism different from those found previously for other sulfated polysaccharides and glycosaminoglycans.

Fucanomics and galactanomics: current status in drug discovery, mechanisms of action and role of the well-defined structures

BACKGROUND

With the recent advent of glycomics, many medically relevant glycans have been discovered. Sulfated fucans (SFs) and sulfated galactans (SGs) are one of these classes of glycans with increasing interest to both glycomics and medicine. Besides having very unique structures, some of these molecules exhibit a broad range of pharmacological actions. In certain cases, high levels of effectiveness may be reached when the proper structural requirements are found.

SCOPE OF REVIEW

Here, we cover the fundamental biochemical mechanisms of some of these medicinal properties. We particularly focus on the beneficial activities of SFs and SGs in inflammation, hemostasis, vascular biology, and cancer.

MAJOR CONCLUSIONS

In these clinical systems, intermolecular complexes directly driven by electrostatic interactions of SFs and SGs with P- and L-selectins, chemokines, antithrombin, heparin cofactor II, thrombin, factor Xa, bFGF, and VEGF, overall govern the resultant therapeutic effects. In spite of that, the structural features of SFs and SGs have shown to be essential determinants for formation and stability of those molecular complexes, which consequently account to the differential levels of the biomedical responses.

GENERAL SIGNIFICANCE

Accurate structure-function relationships have mostly been achieved when SFs and SGs of well-defined structures are used for study. Therefore, these types of glycans have become of great usefulness to identify the chemical requirements needed to achieve satisfactory clinical responses.

Structure-function relationship of anticoagulant and antithrombotic well-defined sulfated polysaccharides from marine invertebrates

Marine sulfated polysaccharides (MSPs), such as sulfated fucans (SFs), sulfated galactans (SGs), and glycosaminoglycans (GAGs) isolated from invertebrate animals, are highly anionic polysaccharides capable of interacting with certain cationic proteins, such as (co)-factors of the coagulation cascade during clotting-inhibition process. Primarily, these molecular complexes between MSPs and coagulation-related proteins seem to be driven mostly by electrostatic interactions. However, through a systematic comparison using several novel well-defined sulfated polysaccharides composed of repetitive oligosaccharides with clear sulfation patterns, it was proved that those molecular interactions are essentially regulated by the stereochemistry of the glycans (which depends on a conjunction of anomeric configurations, sugar types, conformational preferences, glycosylation, and sulfation sites), rather than just a mere consequence of the electronegative density charges (mainly from number of sulfate groups). Here, we present an overview about the structure-function relationship of the invertebrate MSPs with regular structures as potential anticoagulant and antithrombotic agents, as pathologies related to the cardiovascular system are one of the major causes of mortality in the world.

Fucose-containing sulfated polysaccharides from brown seaweeds inhibit proliferation of melanoma cells and induce apoptosis by activation of caspase-3 in vitro

Fucose-containing sulfated polysaccharides (FCSPs) extracted from seaweeds, especially brown macro-algae, are known to possess essential bioactive properties, notably growth inhibitory effects on tumor cells. In this work, we conducted a series of in vitro studies to examine the influence of FCSPs products from Sargassumhenslowianum C. Agardh (FSAR) and Fucus vesiculosus (FVES), respectively, on proliferation of melanoma B16 cells and to investigate the underlying apoptosis promoting mechanisms. Cell viability analysis showed that both FCSPs products, i.e., FSAR and FVES, decreased the proliferation of the melanoma cells in a dose-response fashion, with FSAR being more potent at lower dosages, and FVES being relatively more anti-proliferative than FSAR at higher dosages. Flow cytometric analysis by Annexin V staining of the melanoma cells exposed to the FCSPs products confirmed that both FSAR and FVES induced apoptosis. The FCSPs-induced apoptosis was evidenced by loss of plasma membrane asymmetry and translocation of the cell membrane phospholipids and was accompanied by the activation of caspase-3. The FCSPs bioactivity is proposed to be attributable to distinct structural features of the FCSPs, particularly the presence of sulfated galactofucans (notably in S.henslowianum) and sulfated fucans (notably in F. vesiculosus). This study thus indicates that unfractionated FCSPs may exert bioactive effects on skin cancer cells via induction of apoptosis through cascades of reactions that involve activation of caspase-3.

Important determinants for fucoidan bioactivity: a critical review of structure-function relations and extraction methods for fucose-containing sulfated polysaccharides from brown seaweeds

Seaweeds—or marine macroalgae—notably brown seaweeds in the class Phaeophyceae, contain fucoidan. Fucoidan designates a group of certain fucose-containing sulfated polysaccharides (FCSPs) that have a backbone built of (1→3)-linked α-l-fucopyranosyl or of alternating (1→3)- and (1→4)-linked α-l-fucopyranosyl residues, but also include sulfated galactofucans with backbones built of (1→6)-β-d-galacto- and/or (1→2)-β-d-mannopyranosyl units with fucose or fuco-oligosaccharide branching, and/or glucuronic acid, xylose or glucose substitutions. These FCSPs offer several potentially beneficial bioactive functions for humans. The bioactive properties may vary depending on the source of seaweed, the compositional and structural traits, the content (charge density), distribution, and bonding of the sulfate substitutions, and the purity of the FCSP product. The preservation of the structural integrity of the FCSP molecules essentially depends on the extraction methodology which has a crucial, but partly overlooked, significance for obtaining the relevant structural features required for specific biological activities and for elucidating structure-function relations. The aim of this review is to provide information on the most recent developments in the chemistry of fucoidan/FCSPs emphasizing the significance of different extraction techniques for the structural composition and biological activity with particular focus on sulfate groups.

Functional properties of brown algal sulfated polysaccharides, fucoidans

Marine algae are potentially prolific sources of highly bioactive components that might represent useful leads in the development of new pharmaceutical agents and functional foods. This chapter discusses the current literature on biological activities of sulfated polysaccharides, fucoidans, from brown seaweeds. The profound functional properties of fucoidans could be employed in pharmaceutical, nutraceutical functional food, and cosmeceutical applications. Therefore, the chapter deals with the functional properties of the sulfated polysaccharides, fucoidans, with reference to its industrial applications as a functional ingredient.

Anticoagulant activity of a sulfated galactan: serpin-independent effect and specific interaction with factor Xa

An algal sulfated galactan has high anticoagulant and antithrombotic activities. Its serpin-dependent anticoagulant action is due to promoting thrombin and factor (F)Xa inhibition by antithrombin and heparin cofactor II. Here, we evaluated the anticoagulant effect of the algal sulfated galactan using serpin-free plasma. In contrast to heparin, the sulfated galactan is still able to prolong coagulation time and delay thrombin and FXa generation in serpin-free plasma. We further investigated this effect using purified blood coagulation proteins, discovering that sulfated galactan inhibits the intrinsic tenase and prothrombinase complexes, which are critical for FXa and thrombin generation, respectively. We also investigated the mechanism by which sulfated galactan promotes FXa inhibition by antithrombin using specific recombinant mutants of the protease. We show that sulfated galactan interacts with the heparin-binding exosite of FXa and Arg-236 and Lys-240 of this site are critical residues for this interaction, as observed for heparin. Thus, sulfated galactan and heparin have similar high-affinity and specificity for interaction with FXa, though they have differences in their chemical structures. Similar to heparin, the ability of sulfated galactan to potentiate FXa inhibition by antithrombin is calcium-dependent. However, in contrast to heparin, this effect is not entirely dependent on the conformation of the gamma-carboxyglutamic acid-rich domain of the protease. In conclusion, sulfated galactan and heparin have some similar effects on blood coagulation, but also differ significantly at the molecular level. This sulfated galactan opens new perspective for the development of antithrombotic drugs.

Anticoagulant activity of a sulfated polysaccharide from the green alga Arthrospira platensis

BACKGROUND

The polysaccharide of culture medium from Arthrospira platensis was extracted by ultrafiltration, partially characterized and assayed for anticoagulant activity.

METHODS

The crude polysaccharidic fraction was fractionated by anion exchange chromatography on DEAE-cellulose, subjected to acetate cellulose electrophoresis and characterized by physicochemical procedures. The anticoagulant effect of the ultrafiltrated polysaccharide was checked by several coagulation tests.

RESULTS

Anion exchange chromatography revealed in the whole ultrafiltrated polysaccharidic fraction the occurrence of a sulfated spirulan-like component designated PUF2. The average molecular weight of PUF2 was determined by size exclusion chromatography combined with multi-angle light scattering (SEC-MALS) and viscosimetry and was 199 kDa and the sulfate content was 20% weight/dry weight. The physicochemical characterization indicated the occurrence of rhamnose (49.7%), galacturonic and glucuronic acid (32% of total sugar). The anticoagulant effect of this sulfated polysaccharide was mainly due to the potentiation of thrombin inhibition by heparin cofactor II and was 4-times higher than that of the porcine dermatan sulfate whereas it had no effect on anti-Xa activity.

CONCLUSIONS

An ultrafiltrated sulfated polysaccharide, likely a calcium spirulan was obtained from the culture medium of A. platensis and showed an anticoagulant activity mediated by heparin cofactor II.

GENERAL SIGNIFICANCE

Old culture medium of A. platensis may represent an important source for the spirulan-like PUF2 which was endowed with potentially useful anticoagulant properties whereas its obtention by ultrafiltration may represent an extraction procedure of interest.

A unique 2-sulfated {beta}-galactan from the egg jelly of the sea urchin Glyptocidaris crenularis: conformation flexibility versus induction of the sperm acrosome reaction

Sulfated polysaccharides from the egg jelly of sea urchins act as species-specific inducers of the sperm acrosome reaction, which is a rare molecular mechanism of carbohydrate-induced signal-transduction event in animal cells. The sea urchin polysaccharides differ in monosaccharide composition (l-fucose or l-galactose), glycosylation, and sulfation sites, but they are always in the alpha-anomeric configuration. Herein, structural analysis of the polysaccharide from the sea urchin Glyptocidaris crenularis surprisingly revealed a unique sulfated beta-d-galactan composed by (3-beta-d-Galp-2(OSO(3))-1-->3-beta-d-Galp-1)(n) repeating units. Subsequently, we used the G. crenularis galactan to compare different 2-sulfated polysaccharides as inducers of the acrosome reaction using homologous and heterologous sperm. We also tested the effect of chemically over-sulfated galactans. Intriguingly, the anomeric configuration of the glycosidic linkage rather than the monosaccharide composition (galactose or fucose) is the preferential structural requirement for the effect of these polysaccharides on sea urchin fertilization. Nuclear magnetic resonance and molecular dynamics indicate that sulfated alpha-galactan or alpha-fucan have less dynamic structural behavior, exhibiting fewer conformational populations, with an almost exclusive conformational state with glycosidic dihedral angles Phi/Psi = -102 degrees /131 degrees . The preponderant conformer observed in the sulfated alpha-galactan or alpha-fucan is not observed among populations in the beta-form despite its more flexible structure in solution. Possibly, a proper spatial arrangement is required for interaction of the sea urchin-sulfated polysaccharides with the specific sperm receptor.

Structure, biology, evolution, and medical importance of sulfated fucans and galactans

Sulfated fucans and galactans are strongly anionic polysaccharides found in marine organisms. Their structures vary among species, but their major features are conserved among phyla. Sulfated fucans are found in marine brown algae and echinoderms, whereas sulfated galactans occur in red and green algae, marine angiosperms, tunicates (ascidians), and sea urchins. Polysaccharides with 3-linked, beta-galactose units are highly conserved in some taxonomic groups of marine organisms and show a strong tendency toward 4-sulfation in algae and marine angiosperms, and 2-sulfation in invertebrates. Marine algae mainly express sulfated polysaccharides with complex, heterogeneous structures, whereas marine invertebrates synthesize sulfated fucans and sulfated galactans with regular repetitive structures. These polysaccharides are structural components of the extracellular matrix. Sulfated fucans and galactans are involved in sea urchin fertilization acting as species-specific inducers of the sperm acrosome reaction. Because of this function the structural evolution of sulfated fucans could be a component in the speciation process. The algal and invertebrate polysaccharides are also potent anticoagulant agents of mammalian blood and represent a potential source of compounds for antithrombotic therapies.

Synthesis and characterization of a new polysaccharide-graft-polymethacrylate copolymer for three-dimensional hybrid hydrogels

Hybrid materials constituted by hydrophobic and hydrophilic biocompatible macromolecules are useful for biomedical applications. In this context, a well-known acrylic monomer (methyl methacrylate) was polymerized and grafted onto the polysaccharide dextran by the use of ceric ammonium nitrate as a redox initiator in aqueous nitric acid medium. The effects of concentrations of dextran, acrylic monomer, and ceric ions on the copolymerization yields were investigated in detail. The obtained polymers were studied by solubility measurements, Fourier transform infrared spectrometry, (13)C nuclear magnetic resonance spectroscopy, and viscosimetric analysis. Interestingly, we found conditions to form transparent and homogeneous thin films or 3D structures with hybrid properties. Indeed, the copolymer, but not dextran or PMMA, could be dissolved in water/THF (20/80 v/v). The thermomechanical properties of the resulting copolymer analyzed by differential scanning calorimetry and dynamic mechanical analysis showed the occurrence of a single glass-transition temperature and a marked difference with the two homopolymers. The cytocompatibility of the copolymer with human endothelial cells was evidenced by the normal cell adhesion, proliferation, and morphology after 5 days in culture on these gels. In conclusion, this type of copolymer with hybrid properties of two biocompatible macromolecules could be of great interest as a 3D scaffold or for coating in biomedical applications.

Fucoidan: structure and bioactivity

Fucoidan refers to a type of polysaccharide which contains substantial percentages of L-fucose and sulfate ester groups, mainly derived from brown seaweed. For the past decade fucoidan has been extensively studied due to its numerous interesting biological activities. Recently the search for new drugs has raised interest in fucoidans. In the past few years, several fucoidans' structures have been solved, and many aspects of their biological activity have been elucidated. This review summarizes the research progress on the structure and bioactivity of fucoidan and the relationships between structure and bioactivity.

Sulfated galactan is a catalyst of antithrombin-mediated inactivation of alpha-thrombin

Novel compounds presenting anticoagulant activity, such as sulfated polysaccharides, open new perspectives in medicine. Elucidation of the molecular mechanism behind this activity is desirable by itself, as well as because it allows for the design of novel compounds. In the present study, we investigated the action of an algal sulfated galactan, which potentiates alpha-thrombin inactivation by antithrombin. Our results indicate the following: 1) both the sulfated galactan and heparin potentiate protease inactivation by antithrombin at similar molar concentrations, however they differ markedly in the molecular size required for their activities; 2) this galactan interacts predominantly with exosite II on alpha-thrombin and, similar to heparin, catalyzes the formation of a covalent complex between antithrombin and the protease; 3) the sulfated galactan has a higher affinity for alpha-thrombin than for antithrombin. We propose that the preferred pathway of sulfated galactan-induced inactivation of alpha-thrombin by antithrombin starts with the polysaccharide binding to the protease through a high-affinity interaction. Antithrombin is then added to the complex and the protease is inactivated by covalent interactions. Finally, the antithrombin-alpha-thrombin covalent complex dissociates from the polysaccharide chain. This mechanism resembles the action of heparin with low affinity for antithrombin, as opposed to heparin with high affinity for serpin.

Effect of drying on the biological activities of a red microalgal polysaccharide

The red microalga Porphyridium sp. produces a polysaccharide exhibiting a variety of biological activities with potential for medical and cosmetic uses. For this reason, it is important that the drying process, which is the end point of production, should not destroy the natural characteristics of the material. The objective of this study was to evaluate the effect of drying at temperatures ranging from 40 to 140 degrees C on the bioactivities of the polysaccharide. Drying the polysaccharide at temperatures above 90 degrees C caused a significant decline in its biological activities (antiviral and anti-cell proliferation) and reduced elasticity, viscosity, and intrinsic viscosity relative to lyophilized polysaccharide and to the starting product. The relationship between molecular weight and intrinsic viscosity indicated that the polysaccharide takes a rigid coil conformation, which stiffens as a result of drying. FTIR analysis revealed that drying caused both significant conformational alterations in the polymer chains and changes in the interaction between the polysaccharide and the glycoprotein to which it is noncovalently associated. Differential scanning calorimetry analysis of the water adsorbed on the charged groups of the polysaccharide showed that drying at higher temperatures increased the bound water content due to dissociation of the polymer chains. Thus, it is recommended that the polysaccharide be dried in a two-step process in which free water is removed by convection and bound freezing water is removed by lyphophilization.

Galactan sulfate of Grateloupia indica: Isolation, structural features and antiviral activity

Natural compounds offer interesting pharmacological perspectives for antiviral drug development with regard to broad-spectrum antiviral properties and novel modes of action. In this study, we have analyzed polysaccharide fractions isolated from Grateloupia indica. The crude water extract (GiWE) as well as one fraction (F3) obtained by anion exchange chromatography had potent anti-HSV activity. Their inhibitory concentration 50% (IC50) values (0.12-1.06 microg/ml) were much lower than cytotoxic concentration 50% values (>850 microg/ml). These fractions, which were effective antiviral inhibitors if added only during the adsorption period, had very low anticoagulant activity. Furthermore, they had no direct inactivating effect on virions in a virucidal assay. Chemical, chromatographic and spectroscopic methods showed that the active polysaccharide, which has an apparent molecular mass of 60 kDa and negative specific rotation [alpha]D(32) -16 degrees (c 0.2, H2O), contains alpha-(1-->4)- and alpha-(1-->3)-linked galactopyranose residues. Sulfate groups, if present, are located mostly at C-2/6 of (1-->4)- and C-4/6 of (1-->3)-linked galactopyranosyl units, and are essential for the anti herpetic activity of this polymer.

Conformation of sulfated galactan and sulfated fucan in aqueous solutions: implications to their anticoagulant activities

The discovery of sulfated galactans and sulfated fucans in marine invertebrates with simple and ordered structures opened new perspectives to investigate the biological activity of these molecules and to determine whether different structures confer high affinity for a particular protein. We undertook a conformational analysis of a 2-sulfated, 3-linked alpha-L-galactan and of a alpha-L-fucan with similar structure. Through comparison between theoretical and NMR derived coupling constants, we observed that the pyranose rings are predominantly in the (1)C(4) conformation in these polysaccharides. Additionally, the geometry of the glycosidic linkages was determined based on force field calculations, indicating that the two polysaccharides have similar conformations in solution. Since the sulfated alpha-L-galactan, but not the alpha-L-fucan potentiates antithrombin (AT) inhibition of thrombin, the solution conformations of the compounds were docked into AT and the complexes obtained were refined through molecular dynamics calculations. The obtained results indicates extremely different orientations for the two polysaccharides, which well correlates and explain their distinct anticoagulant activities. Finally, the molecular mechanism of a selective 2-desulfation reaction, observed among sulfated fucans, was explained as a consequence of an intramolecular hydrogen bond capable of assisting in the removal of the charged group.

Structure and anticoagulant activity of a sulfated galactan from the red alga, Gelidium crinale. Is there a specific structural requirement for the anticoagulant action?

Marine red algae are an abundant source of sulfated galactans with potent anticoagulant activity. However, the specific structural motifs that confer biological activity remain to be elucidated. We have now isolated and purified a sulfated galactan from the marine red alga, Gellidium crinale. The structure of this polysaccharide was determined using NMR spectroscopy. It is composed of the repeating structure -4-alpha-Galp-(1-->3)-beta-Galp1--> but with a variable sulfation pattern. Clearly 15% of the total alpha-units are 2,3-di-sulfated and another 55% are 2-sulfated. No evidence for the occurrence of 3,6-anhydro alpha-galactose units was observed in the NMR spectra. We also compared the anticoagulant activity of this sulfated galactan with a polysaccharide from the species, Botryocladia occidentalis, with a similar saccharide chain but with higher amounts of 2,3-di-sulfated alpha-units. The sulfated galactan from G. crinale has a lower anticoagulant activity on a clotting assay when compared with the polysaccharide from B. occidentalis. When tested in assays using specific proteases and coagulation inhibitors, these two galactans showed significant differences in their activity. They do not differ in thrombin inhibition mediated by antithrombin, but in assays where heparin cofactor II replaces antithrombin, the sulfated galactan from G. crinale requires a significantly higher concentration to achieve the same inhibitory effect as the polysaccharide from B. occidentalis. In contrast, when factor Xa instead of thrombin is used as the target protease, the sulfated galactan from G. crinale is a more potent anticoagulant. These observations suggest that the proportion and/or the distribution of 2,3-di-sulfated alpha-units along the galactan chain may be a critical structural motif to promote the interaction of the protease with specific protease and coagulation inhibitors.