Comparison of hydrothermal depolymerization and oligosaccharide profile of fucoidan and fucosylated chondroitin sulfate from Holothuria floridana

Fermented Gracilaria lemaneiformis polysaccharides alleviate food allergy by regulating Treg cells and gut microbiota

Food allergy has a significant impact on the health and well-being of individuals, affecting both their physical and mental states. Research on natural bioactive compounds, such as polysaccharides extracted from seaweeds, holds great promise in the treatment of food allergies. In this study, fermented Gracilaria lemaneiformis polysaccharides (F-GLSP) were prepared using probiotic fermentation. Probiotic fermentation of Gracilaria lemaneiformis reduces the particle size of polysaccharides. To compare the anti-allergic activity of F-GLSP with unfermented Gracilaria lemaneiformis polysaccharides (UF-GLSP), an OVA-induced mouse food allergy model was established. F-GLSP exhibited a significant reduction in OVA-specific IgE and mMCP levels in allergic mice. Moreover, it significantly inhibited Th2 differentiation and IL-4 production and significantly promoted Treg differentiation and IL-10 production in allergic mice. In contrast, UF-GLSP only reduced OVA-specific IgE and mMCP in the serum of allergic mice. Furthermore, F-GLSP demonstrated a more pronounced regulation of intestinal flora abundance compared to UF-GLSP, significantly influencing the populations of Firmicutes, Bacteroidetes, Lactobacillus, and Clostridiales in the intestines of mice with food allergy. These findings suggest that F-GLSP may regulate food allergies in mice through multiple pathways. In summary, this study has promoted further development of functional foods with anti-allergic properties based on red algae polysaccharides.

Marine-Derived Sulfated Glycans Inhibit the Interaction of Heparin with Adhesion Proteins of Mycoplasma pneumoniae

Mycoplasma pneumoniae, a notable pathogen behind respiratory infections, employs specialized proteins to adhere to the respiratory epithelium, an essential process for initiating infection. The role of glycosaminoglycans, especially heparan sulfate, is critical in facilitating pathogen-host interactions, presenting a strategic target for therapeutic intervention. In this study, we assembled a glycan library comprising heparin, its oligosaccharide derivatives, and a variety of marine-derived sulfated glycans to screen the potential inhibitors for the pathogen-host interactions. By using Surface Plasmon Resonance spectroscopy, we evaluated the library's efficacy in inhibiting the interaction between M. pneumoniae adhesion proteins and heparin. Our findings offer a promising avenue for developing novel therapeutic strategies against M. pneumoniae infections.

Exploring the prebiotic potential of hydrolyzed fucoidan fermented in vitro with human fecal inocula: Impact on microbiota and metabolome

Fucoidan is widely applied in food and pharmaceutical industry for the promising bioactivities. Low-molecular weight hydrolyzed fucoidan has gained attention for its beneficial health effects. Here, the modulation on microbiome and metabolome features of fucoidan and its acidolyzed derivatives (HMAF, 1.5-20 kDa; LMAF, <1.5 kDa) were investigated through human fecal cultures. Fucose is the main monosaccharide component in fucoidan and LMAF, while HMAF contains abundant glucuronic acid. LMAF fermentation resulted in the highest production of short-chain fatty acids, with acetate and propionate reaching maximum levels of 13.46 mmol/L and 11.57 mmol/L, respectively. Conversely, HMAF exhibited a maximum butyrate production of 9.28 mmol/L. Both fucoidan and acidolyzed derivatives decreased the abundance of Escherichia-Shigella and Klebsiella in human fecal cultures. Fucoidan and HMAF prefer to improve the abundance of Bacteroides. However, LMAF showed positive influence on Bifidobacterium, Lactobacillus, and Megamonas. Untargeted metabolome indicated that fucoidan and its derivatives mainly altered the metabolic level of lipids, indole, and their derivatives, with fucoidan and HMAF promoting higher level of indole-3-propionic acid and indole-3-carboxaldehyde compared to LMAF. Considering the chemical structural differences, this study suggested that hydrolyzed fucoidan can provide potential therapeutic applications for targeted regulation of microbial communities.

Marine sulfated glycans inhibit the interaction of heparin with S-protein of SARS-CoV-2 Omicron XBB variant

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a worldwide COVID-19 pandemic, leading to 6.8 million deaths. Numerous variants have emerged since its outbreak, resulting in its significantly enhanced ability to spread among humans. As with many other viruses, SARS‑CoV‑2 utilizes heparan sulfate (HS) glycosaminoglycan (GAG) on the surface of host cells to facilitate viral attachment and initiate cellular entry through the ACE2 receptor. Therefore, interfering with virion-HS interactions represents a promising target to develop broad-spectrum antiviral therapeutics. Sulfated glycans derived from marine organisms have been proven to be exceptional reservoirs of naturally existing HS mimetics, which exhibit remarkable therapeutic properties encompassing antiviral/microbial, antitumor, anticoagulant, and anti-inflammatory activities. In the current study, the interactions between the receptor-binding domain (RBD) of S-protein of SARS-CoV-2 (both WT and XBB.1.5 variants) and heparin were applied to assess the inhibitory activity of 10 marine-sourced glycans including three sulfated fucans, three fucosylated chondroitin sulfates and two fucoidans derived from sea cucumbers, sea urchin and seaweed Saccharina japonica, respectively. The inhibitory activity of these marine derived sulfated glycans on the interactions between RBD of S-protein and heparin was evaluated using Surface Plasmon Resonance (SPR). The RBDs of S-proteins from both Omicrion XBB.1.5 and wild-type (WT) were found to bind to heparin, which is a highly sulfated form of HS. All the tested marine-sourced sulfated glycans exhibited strong inhibition of WT and XBB.1.5 S-protein binding to heparin. We believe the study on the molecular interactions between S-proteins and host cell glycosaminoglycans provides valuable insight for the development of marine-sourced, glycan-based inhibitors as potential anti-SARS-CoV-2 agents.

Conventional extraction of fucoidan from Irish brown seaweed Fucus vesiculosus followed by ultrasound-assisted depolymerization

Fucoidan has attracted considerable attention from scientists and pharmaceutical companies due to its antioxidant, anticoagulant, anti-inflammatory, anti-tumor, and health-enhancing properties. However, the extraction of fucoidan from seaweeds often involves the use of harsh chemicals, which necessitates the search for alternative solvents. Additionally, the high viscosity and low cell permeability of high molecular weight (Mw) fucoidan can limit its effectiveness in drug action, while lower Mw fractions exhibit increased biological activity and are also utilized as dietary supplements. The study aimed to (1) extract fucoidan from the seaweed Fucus vesiculosus (FV) using an environmentally friendly solvent and compare it with the most commonly used extraction solvent, hydrochloric acid, and (2) assess the impact of ultrasound-assisted depolymerization on reducing the molecular weight of the fucoidan extracts and examine the cytotoxic effect of different molecular weight fractions. The findings indicated that the green depolymerization solvent, in conjunction with a brief ultrasound treatment, effectively reduced the molecular weight. Moreover, a significant decrease in cell viability was observed in selected samples, indicating potential anticancer properties. As a result, ultrasound was determined to be an effective method for depolymerizing crude fucoidan from Fucus Vesiculosus seaweed.

Distinct mechanisms underlying the therapeutic effects of low-molecular-weight heparin and chondroitin sulfate on Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder influenced by various factors, including age, genetics, and the environment. Current treatments provide symptomatic relief without impeding disease progression. Previous studies have demonstrated the therapeutic potential of exogenous heparin and chondroitin sulfate in PD. However, their therapeutic mechanisms and structure-activity relationships remain poorly understood. In this study, low-molecular-weight heparin (L-HP) and chondroitin sulfate (L-CS) exhibited favorable therapeutic effects in a mouse model of PD. Proteomics revealed that L-HP attenuated mitochondrial dysfunction through its antioxidant properties, whereas L-CS suppressed neuroinflammation by inhibiting platelet activation. Two glycosaminoglycan (GAG)-binding proteins, manganese superoxide dismutase (MnSOD2) and fibrinogen beta chain (FGB), were identified as potential targets of L-HP and L-CS, and we investigated their structure-activity relationships. The IdoA2S-GlcNS6S/GlcNAc6S unit in HP bound to SOD2, whereas the GlcA-GalNAc4S and GlcA-GalNAc4S6S units in CS preferred FGB. Furthermore, N-S and 2-O-S in L-HP, and 4-O-S, 6-O-S, and -COOH in L-CS contributed significantly to the binding process. These findings provide new insights and evidence for the development and use of glycosaminoglycan-based therapeutics for PD.

Sulfated Glycans Inhibit the Interaction of MERS-CoV Receptor Binding Domain with Heparin

Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic virus with high contagion and mortality rates. Heparan sulfate proteoglycans (HSPGs) are ubiquitously expressed on the surface of mammalian cells. Owing to its high negatively charged property, heparan sulfate (HS) on the surface of host cells is used by many viruses as cofactor to facilitate viral attachment and initiate cellular entry. Therefore, inhibition of the interaction between viruses and HS could be a promising target to inhibit viral infection. In the current study, the interaction between the receptor-binding domain (RBD) of MERS-CoV and heparin was exploited to assess the inhibitory activity of various sulfated glycans such as glycosaminoglycans, marine-sourced glycans (sulfated fucans, fucosylated chondroitin sulfates, fucoidans, and rhamnan sulfate), pentosan polysulfate, and mucopolysaccharide using Surface Plasmon Resonance. We believe this study provides valuable insights for the development of sulfated glycan-based inhibitors as potential antiviral agents.

Advances in oligosaccharides production from algal sources and potential applications

In recent years, algal-derived glycans and oligosaccharides have become increasingly important in health applications due to higher bioactivities than plant-derived oligosaccharides. The marine organisms have complex, and highly branched glycans and more reactive groups to elicit greater bioactivities. However, complex and large molecules have limited use in broad commercial applications due to dissolution limitations. In comparison to these, oligosaccharides show better solubility and retain their bioactivities, hence, offering better applications opportunity. Accordingly, efforts are being made to develop a cost-effective method for enzymatic extraction of oligosaccharides from algal polysaccharides and algal biomass. Yet detailed structural characterization of algal-derived glycans is required to produce and characterize the potential biomolecules for improved bioactivity and commercial applications. Some macroalgae and microalgae are being evaluated as in vivo biofactories for efficient clinical trials, which could be very helpful in understanding the therapeutic responses. This review discusses the recent advancements in the production of oligosaccharides from microalgae. It also discusses the bottlenecks of the oligosaccharides research, technological limitations, and probable solutions to these problems. Furthermore, it presents the emerging bioactivities of algal oligosaccharides and their promising potential for possible biotherapeutic application.

The Sea Cucumber Thyonella gemmata Contains a Low Anticoagulant Sulfated Fucan with High Anti-SARS-CoV-2 Actions against Wild-Type and Delta Variants

In this work, we isolated two new sulfated glycans from the body wall of the sea cucumber Thyonella gemmata: one fucosylated chondroitin sulfate (TgFucCS) (17.5 ± 3.5% kDa) and one sulfated fucan (TgSF) (383.3 ± 2.1% kDa). NMR results showed the TgFucCS backbone composed of [→3)-β-N-acetylgalactosamine-(1→4)-β-glucuronic acid-(1→] with 70% 4-sulfated and 30% 4,6-disulfated GalNAc units and one-third of the GlcA units decorated at the C3 position with branching α-fucose (Fuc) units either 4-sulfated (65%) or 2,4-disulfated (35%) and the TgSF structure composed of a tetrasaccharide repeating unit of [→3)-α-Fuc2,4S-(1→2)-α-Fuc4S-(1→3)-α-Fuc2S-(1→3)-α-Fuc2S-(1→]n. Inhibitory properties of TgFucCS and TgSF were investigated using SARS-CoV-2 pseudovirus coated with S-proteins of the wild-type (Wuhan-Hu-1) or the delta (B.1.617.2) strains and in four different anticoagulant assays, comparatively with unfractionated heparin. Molecular binding to coagulation (co)-factors and S-proteins was investigated by competitive surface plasmon resonance spectroscopy. Among the two sulfated glycans tested, TgSF showed significant anti-SARS-CoV-2 activity against both strains together with low anticoagulant properties, indicating a good candidate for future studies in drug development.

SPR Sensor-Based Analysis of the Inhibition of Marine Sulfated Glycans on Interactions between Monkeypox Virus Proteins and Glycosaminoglycans

Sulfated glycans from marine organisms are excellent sources of naturally occurring glycosaminoglycan (GAG) mimetics that demonstrate therapeutic activities, such as antiviral/microbial infection, anticoagulant, anticancer, and anti-inflammation activities. Many viruses use the heparan sulfate (HS) GAG on the surface of host cells as co-receptors for attachment and initiating cell entry. Therefore, virion-HS interactions have been targeted to develop broad-spectrum antiviral therapeutics. Here we report the potential anti-monkeypox virus (MPXV) activities of eight defined marine sulfated glycans, three fucosylated chondroitin sulfates, and three sulfated fucans extracted from the sea cucumber species Isostichopus badionotus, Holothuria floridana, and Pentacta pygmaea, and the sea urchin Lytechinus variegatus, as well as two chemically desulfated derivatives. The inhibitions of these marine sulfated glycans on MPXV A29 and A35 protein-heparin interactions were evaluated using surface plasmon resonance (SPR). These results demonstrated that the viral surface proteins of MPXV A29 and A35 bound to heparin, which is a highly sulfated HS, and sulfated glycans from sea cucumbers showed strong inhibition of MPXV A29 and A35 interactions. The study of molecular interactions between viral proteins and host cell GAGs is important in developing therapeutics for the prevention and treatment of MPXV.

Selective 2-desulfation of tetrasaccharide-repeating sulfated fucans during oligosaccharide production by mild acid hydrolysis

Sulfated fucans (SFs) from echinoderms, such as sea cucumbers and sea urchins, present linear and regular sulfation patterns within defined oligosaccharide building blocks. The high molecular weights of these polymers pose a problem in advanced structure-activity relationship studies for which derived oligosaccharides are more appropriate tools for investigation. However, enzymes capable of specifically depolymerizing SFs, fucanases, are not very common. Scarce abundance and unknown catalytic activities are additional barriers to exploiting fucanases. Oligosaccharide production by controlled chemical reactions such as mild acid hydrolysis then becomes a convenient strategy. As a consequence, physicochemical studies are necessary to understand the structural modifications caused on SFs by this chemical hydrolysis. Hence, in this work, we subjected three tetrasaccharide-repeating SFs from sea cucumbers, Isostichopus badionotus (IbSF), Holothuria floridana (HfSF), and Lytechinus variegatus (LvSF) to mild acid hydrolysis for oligosaccharide production. Interestingly, selective 2-desulfation reaction was observed in all three SFs. Through our study, we indicate that selective 2-desulfation is a common and expected phenomenon in oligosaccharide production by mild acid hydrolysis of SFs, including those composed of tetrasaccharide-repeating units.

Structural requirements of Holothuria floridana fucosylated chondroitin sulfate oligosaccharides in anti-SARS-CoV-2 and anticoagulant activities

Fucosylated chondroitin sulfate (FucCS) is a unique glycosaminoglycan found primarily in sea cucumbers. This marine sulfated glycan is composed of a chondroitin sulfate backbone decorated with fucosyl branches attached to the glucuronic acid. FucCS exhibits potential biological actions including inhibition of blood clotting and severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection. These biological effects have been attributed to certain structural features, including molecular weight (MW), and/or those related to fucosylation, such as degrees of fucosyl branches, sulfation patterns and contents. In a previous work, we were able to generate oligosaccharides of the FucCS from Pentacta pygmaea (PpFucCS) with reduced anticoagulant effect but still retaining significant anti-SARS-CoV-2 activity against the delta strain. In this work, we extended our study to the FucCS extracted from the species Holothuria floridana (HfFucCS). The oligosaccharides were prepared by free-radical depolymerization of the HfFucCS via copper-based Fenton reaction. One-dimensional 1H nuclear magnetic resonance spectra were employed in structural analysis. Activated partial thromboplastin time and assays using protease (factors Xa and IIa) and serine protease inhibitors (antithrombin, and heparin cofactor II) in the presence of the sulfated carbohydrates were used to monitor anticoagulation. Anti-SARS-CoV-2 effects were measured using the concentration-response inhibitory curves of HEK-293T-human angiotensin-converting enzyme-2 cells infected with a baculovirus pseudotyped SARS-CoV-2 wild-type and delta variant spike (S)-proteins. Furthermore, the cytotoxicity of native HfFucCS and its oligosaccharides was also assessed. Like for PpFucCS, we were able to generate a HfFucCS oligosaccharide fraction devoid of high anticoagulant effect but still retaining considerable anti-SARS-CoV-2 actions against both variants. However, compared to the oligosaccharide fraction derived from PpFucCS, the average MW of the shortest active HfFucCS oligosaccharide fraction was significantly lower. This finding suggests that the specific structural feature in HfFucCS, the branching 3,4-di-sulfated fucoses together with the backbone 4,6-di-sulfated N-acetylgalactosamines, is relevant for the anti-SARS-CoV-2 activity of FucCS molecules.

Inhibition of SARS-CoV-2 wild-type (Wuhan-Hu-1) and Delta (B.1.617.2) strains by marine sulfated glycans

The Coronavirus disease pandemic has steered the global therapeutic research efforts toward the discovery of potential anti-severe acute respiratory syndrome coronavirus (SARS-CoV-2) molecules. The role of the viral spike glycoprotein (S-protein) has been clearly established in SARS-CoV-2 infection through its capacity to bind to the host cell surface heparan sulfate proteoglycan (HSPG) and angiotensin-converting enzyme-2. The antiviral strategies targeting these 2 virus receptors are currently under intense investigation. However, the rapid evolution of the SARS-CoV-2 genome has resulted in numerous mutations in the S-protein posing a significant challenge for the design of S-protein-targeted inhibitors. As an example, the 2 key mutations in the S-protein receptor-binding domain (RBD), L452R, and T478K in the SARS-CoV-2 Delta variant (B.1.617.2) confer tighter binding to the host epithelial cells. Marine sulfated glycans (MSGs) demonstrate excellent inhibitory activity against SARS-CoV-2 via competitive disruption of the S-protein RBD-HSPG interactions and thus have the potential to be developed into effective prophylactic and therapeutic molecules. In this study, 7 different MSGs were evaluated for their anti-SARS-CoV-2 activity in a virus entry assay utilizing a SARS-CoV-2 pseudovirus coated with S-protein of the wild-type (Wuhan-Hu-1) or the Delta (B.1.617.2) strain. Although all tested MSGs showed strong inhibitory activity against both strains, no correlations between MSG structural features and virus inhibition could be drawn. Nevertheless, the current study provides evidence for the maintenance of inhibitory activity of MSGs against evolving SARS-CoV-2 strains.

A Fucan Sulfate with Pentasaccharide Repeating Units from the Sea Cucumber Holothuriafloridana and Its Anticoagulant Activity

A fucan sulfate (HfFS) was isolated from the sea cucumber Holothuriafloridana after proteolysis-alkaline treatment and purified with anion-exchange chromatography. The molecular weight (Mw) of HfFS was determined to be 443.4 kDa, and the sulfate content of HfFS was 30.4%. The structural analysis of the peroxidative depolymerized product (dHfFS-1) showed that the primary structure of HfFS was mainly composed of a distinct pentasaccharide repeating unit -[l-Fuc_2S4S-α(1,3)-l-Fuc-α(1,3)-Fuc-α(1,3)-l-Fuc_2S-α(1,3)-l-Fuc_2S-α(1,3)-]_n-. Then, the “bottom-up” strategy was employed to confirm the structure of HfFS, and a series of fucooligosaccharides (disaccharides, trisaccharides, and tetrasaccharides) were purified from the mild acid-hydrolyzed HfFS. The structures identified through 1D/2D NMR spectra showed that these fucooligosaccharides could be derivates from the pentasaccharide units, while the irregular sulfate substituent also exists in the units. Anticoagulant activity assays of native HfFS and its depolymerized products (dHf-1~dHf-6) in vitro suggested that HfFS exhibits potent APTT-prolonging activity and the potencies decreased with the reduction in molecular weights, and HfFS fragments (dHf-4~dHf-6) with Mw less than 11.5 kDa showed no significant anticoagulant effect. Overall, our study enriched the knowledge about the structural diversity of FSs in different sea cucumber species and their biological activities.

Physicochemical Characterization of Fucoidans from Sargassum henslowianum C.Agardh and Their Antithrombotic Activity In Vitro

Sargassum fucoidan is a kind of sulfated heteropolysaccharide with a variety of biological activities. The aim of this study was to investigate the extraction, purification, physicochemical characterization and in vitro antithrombotic activity of fucoidan from Sargassum henslowianum C.Agardh. Hot-water-assisted ultrasound was used to extract fucoidan (F). Fucoidan was purified by DEAE cellulose 52 (F1), Vc-H2O2 (FD1) and Superdex 75 gel (FDS1). The physical and chemical properties of fucoidans were analyzed by chemical composition, monosaccharide composition, average molecular weight (Mw) and FTIR. The sulfate contents of F, F1, FD1 and FDS1 were 11.45%, 16.35% and 17.52%, 9.66%, respectively; the Mw was 5.677 × 105, 4.393 × 105, 2.176 × 104 and 6.166 × 103, respectively. The results of monosaccharide composition showed that the four fucoidans contained l-fucose, d-galactose, l-mannose, d-xylose, l-rhamnose and d-glucose, but the mass fraction ratio was different. The results of FTIR showed that fucoidan contained characteristic peaks of sugar and sulfate. In vitro, F1, FD1 and FDS1 could alleviate HUVEC damage induced by adrenaline (Adr). F1, FD1 and FDS1 decreased vWF and TF and increased the ratio of t-PA/PAI-1 in Adr-induced HUVEC.

Oligosaccharide mapping analysis by HILIC-ESI-HCD-MS/MS for structural elucidation of fucoidan from sea cucumber Holothuria floridana

The elucidation of precise structure of fucoidan is essential for understanding their structure-function relationship and promoting the development of marine drugs. In this work, we firstly reported the oligosaccharide mapping of fucoidan from Holothuria floridana using a combination of hydrothermal depolymerization, hydrophilic interaction liquid chromatography (HILIC) coupled with electrospray mass spectrometry (ESI-FTMS) and high energy collision-induced dissociation (HCD-MS/MS) and 2D NMR analysis. With careful selection of fully deprotonated molecular ions of fucoidan oligosaccharides and their NaBD₄ reduced alditols, HILIC-ESI-HCD-MS/MS provided structurally relevant glycosidic product ions with no sulfate loss for definitive assignment of sequence and sulfation pattern of all the oligosaccharides and their isomers from dp2 to dp7 from hydrothermal depolymerization. The oligosaccharide mapping clarified the structure of fucoidan with various oligosaccharide domains with 2,4-di-O-sulfated and 2-O sulfated fucose residues.

Recent advances in marine algae oligosaccharides: structure, analysis, and potential prebiotic activities

Marine algae contain abundant polysaccharides that support a range of health-promoting activities; however, the high molecular weight, high viscosity, and low solubility of marine algae polysaccharides (MAPs) limit their application in food, agriculture and medicine. Thus, as the degradation products of MAPs, marine algae oligosaccharides (MAOs) have drawn increasing attention. Most MAOs are non-digestible by digestive enzyme in the human gastrointestinal tract, but are fermented by bacteria in the gut and converted into short-chain fatty acids (SCFAs). MAOs can selectively enhance the activities of some populations of beneficial bacteria and stimulate a series of prebiotic effects, such as anti-oxidant, anti-diabetic, anti-tumour. However, the exact structures of MAOs and their prebiotic activities are, to a large extent, unexplored. This review summarizes recent advances in the sources, categories, and structure analysis methods of MAOs, emphasizing their effects on gut microbiota and its metabolite SCFAs as well as the resulting range of probiotic activities.

Health effects of dietary sulfated polysaccharides from seafoods and their interaction with gut microbiota

Various dietary sulfated polysaccharides (SPs) have been isolated from seafoods, including edible seaweeds and marine animals, and their health effects such as antiobesity and anti-inflammatory activities have attracted remarkable interest. Sulfate groups have been shown to play important roles in the bioactivities of these polysaccharides. Recent in vitro and in vivo studies have suggested that the biological effects of dietary SPs are associated with the modulation of the gut microbiota. Dietary SPs could regulate the gut microbiota structure and, accordingly, affect the production of bioactive microbial metabolites. Because of their differential chemical structures, dietary SPs may specifically affect the growth of certain gut microbiota and associated metabolite production, which may contribute to variable health effects. This review summarizes the latest findings on the types and structural characteristics of SPs, the effects of different processing techniques on the structural characteristics and health effects of SPs, and the current understanding of the role of gut microbiota in the health effects of SPs. These findings might help in better understanding the mechanism of the health effects of SPs and provide a scientific basis for their application as functional food.

Structural Characterization and Heparanase Inhibitory Activity of Fucosylated Glycosaminoglycan from Holothuria floridana

Unique fucosylated glycosaminoglycans (FG) have attracted increasing attention for various bioactivities. However, the precise structures of FGs usually vary in a species-specific manner. In this study, HfFG was isolated from Holothuria floridana and purified by anion exchange chromatography with the yield of ~0.9%. HfFG was composed of GlcA, GalNAc and Fuc, its molecular weight was 47.3 kDa, and the -OSO3-/-COO- molar ratio was 3.756. HfFG was depolymerized by a partial deacetylation-deaminative cleavage method to obtain the low-molecular-weight HfFG (dHfFG). Three oligosaccharide fragments (Fr-1, Fr-2, Fr-3) with different molecular weights were isolated from the dHfFG, and their structures were revealed by 1D and 2D NMR spectroscopy. HfFG should be composed of repeating trisaccharide units -{(L-FucS-α1,3-)d-GlcA-β1,3-d-GalNAc4S6S-β1,4-}-, in which sulfated fucose (FucS) includes Fuc2S4S, Fuc3S4S and Fuc4S residues linked to O-3 of GlcA in a ratio of 45:35:20. Furthermore, the heparanase inhibitory activities of native HfFG and oligosaccharide fragments (Fr-1, Fr-2, Fr-3) were evaluated. The native HfFG and its oligosaccharides exhibited heparanase inhibitory activities, and the activities increased with the increase of molecular weight. Additionally, structural characteristics such as sulfation patterns, the terminal structure of oligosaccharides and the presence of fucosyl branches may be important factors affecting heparanase inhibiting activity.

(Semi)-Synthetic Fucosylated Chondroitin Sulfate Oligo- and Polysaccharides

Fucosylated chondroitin sulfate (fCS) is a glycosaminoglycan (GAG) polysaccharide with a unique structure, displaying a backbone composed of alternating N-acetyl-d-galactosamine (GalNAc) and d-glucuronic acid (GlcA) units on which l-fucose (Fuc) branches are installed. fCS shows several potential biomedical applications, with the anticoagulant activity standing as the most promising and widely investigated one. Natural fCS polysaccharides extracted from marine organisms (Echinoidea, Holothuroidea) present some advantages over a largely employed antithrombotic drug such as heparin, but some adverse effects as well as a frequently found structural heterogeneity hamper its development as a new drug. To circumvent these drawbacks, several efforts have been made in the last decade to obtain synthetic and semi-synthetic fCS oligosaccharides and low molecular weight polysaccharides. In this Review we have for the first time collected these reports together, dividing them in two topics: (i) total syntheses of fCS oligosaccharides and (ii) semi-synthetic approaches to fCS oligosaccharides and low molecular weight polysaccharides as well as glycoclusters displaying multiple copies of fCS species.