Modulating the degree of fucosylation of fucosylated chondroitin sulfate enhances heparin cofactor II-dependent thrombin inhibition

Diversity, mechanism and structure-activity relationships of marine anticoagulant-active polysaccharides: A review

Thrombosis is a major complication of cardiovascular disease that can lead to fatal myocardial infarction, acute ischemic stroke and venous thromboembolism, posing a significant threat to human health and even life. Recent research showed that polysaccharides from marine organisms, including marine plants and marine animals, exhibit excellent anticoagulant activity. However, different marine anticoagulant-active polysaccharides (MAPs) exhibit significant differences in both the structure and anticoagulant activity. This review systematically summarizes the diversity and structure of MAPs from the last 30 years. We compared the anticoagulant activity and drug development potential of MAPs from different organisms including red algae, green algae, brown algae, marine fish, sea urchins and sea cucumbers, etc., and analyzed the structure-activity relationships of some MAPs with specific structures. In addition, we also discuss the current challenges and future perspectives of MAPs for the development of novel anticoagulant drugs. This review not only offers a comprehensive understanding of the diversity of marine anticoagulant polysaccharides but also provides valuable reference and guidance for the development of novel anticoagulant drugs in the future.

Heparan-6-O-endosulfatase 2, a cancer-related proteoglycan enzyme, is effectively inhibited by a specific sea cucumber fucosylated glycosaminoglycan

Heparan-6-O-endosulfatase 2 (Sulf-2) is a proteoglycan enzyme that modifies sulfation of heparan sulfate proteoglycans. Dysregulation of Sulf-2 is associated with various pathological conditions, including cancer, which makes Sulf-2 a potential therapeutic target. Despite the key pathophysiological roles of Sulf-2, inhibitors remain insufficiently developed. In previous work, a fucosylated chondroitin sulfate from the sea cucumber Holothuria floridana (HfFucCS) exhibited potent Sulf-2 inhibition. This study investigates the structural basis of HfFucCS-mediated Sulf-2 inhibition, examines the binding profile of HfFucCS to Sulf-2, and explores the mode of inhibition. Additionally, a structurally diverse library of sulfated poly/oligosaccharides, including common glycosaminoglycans and unique marine sulfated glycans, was screened for Sulf-2 inhibition. Results from a high-throughput arylsulfatase assay and specific 6-O-desulfation assay have proved that HfFucCS is the most potent among the tested sulfated glycans, likely due to the presence of the unique 3,4-disulfated fucose structural motif. HfFucCS demonstrated non-competitive inhibition, and inhibitory analysis of its low-molecular-weight fragments suggests a minimum length of ~7.5 kDa for effective inhibition. Surface plasmon resonance analyses revealed that Sulf-2 binds to surface heparin with high affinity (KD of 0.817 nM). HfFucCS and its derivatives effectively disrupt this interaction. Results from mass spectrometry-hydroxyl radical protein footprinting and repulsive scaling replica exchange molecular dynamics indicate similarities in the binding of heparin and HfFucCS oligosaccharides to both the catalytic and hydrophilic domains of Sulf-2. These findings reveal the unique inhibitory properties of a structurally distinct marine glycosaminoglycan, supporting its further investigation as a selective and effective inhibitor for Sulf-2-associated cancer events.

Depolymerization of oyster glycosaminoglycans for the enhancement of α-glucosidase inhibition and its application in hypoglycemic studies

Glycosaminoglycans are a class of naturally occurring macromolecular heteropolysaccharides with α-glucosidase inhibitory effects, which play an essential role in regulating postprandial hyperglycemia. However, the significant molecular weight hinders their inhibitory activity. In this study, oyster glycosaminoglycans were used for purification and depolymerization studies to obtain oyster glycosaminoglycan oligosaccharides (OGAG-Oli) and to study their inhibitory activity against α-glucosidase in vitro and hypoglycemic effect on hyperglycemic zebrafish in vivo. The results showed that the OGAG-Oli with optimal α-glucosidase inhibition obtained by the β-elimination mechanism of chondroitinase ABC had a molecular weight of about 2400 Da with five disaccharide repeating units, and their inhibitory effect on α-glucosidase was significantly enhanced with an IC50 value of 0.12 mg/mL, which was related to the strong binding capacity with α-glucosidase as evidenced by molecular docking. FT-IR and NMR results showed that the conformation of OGAG-Oli was predominantly in the α-configuration, which indicated that its inhibitory effect on α-glucosidase mainly depended on the α-glucosidic bond therein. The enzymatic depolymerization process of glycosaminoglycans was optimized, and the process conditions were determined as phosphate buffer solution pH 8.0, reaction time 3 h, reaction temperature 30 °C, chondroitin enzyme ABC activity 0.5 mU. The hypoglycemic ability of OGAG-Oli was evaluated in diabetic zebrafish, and the results showed that OGAG-Oli at a high-dose (0.12 mg/g, bw/d) could extremely significantly reduce fasting blood glucose in zebrafish, with an effect close to that of acarbose (p > 0.05), and exceptionally significantly (p < 0.01) reduced the elevation of TC, TG, and LDL-C caused by prolonged hyperglycemia, and extremely significantly (p < 0.01) increased the HDL-C level. This study showed that the structurally modified oyster glycosaminoglycans had intense α-glucosidase inhibitory activity, and exhibited biological activity of reducing glucose uptake and consequently improving body weight and lipid metabolism in diabetic zebrafish. As a bioactive ingredient of natural origin, this study provides a theoretical basis for the development and utilization of glycosaminoglycans with hypoglycemic effects in foods and drugs.

Fucosylated chondroitin sulfate, an intriguing polysaccharide from sea cucumber: past, present, and future

Fucosylated chondroitin sulfate (FCS) is a unique polysaccharide, first described nearly four decades ago, and found exclusively in sea cucumbers. It is a component of the extracellular matrix, possibly associated with peculiar properties of the invertebrate tissue. The carbohydrate features a chondroitin sulfate core with branches of sulfated α-Fuc linked to position 3 of the β-GlcA. FCSs from different species of sea cucumbers share a similar chondroitin sulfate core but the structure of the sulfated α-Fuc branches varies significantly. The predominant pattern consists of a single unit of sulfated α-Fuc, though some species exhibit branches with multiple α-Fuc units. This comprehensive review focuses on four major aspects of FCS. Firstly, we describe the initial approaches to elucidate the structure of FCS using classical methods of carbohydrate chemistry. Secondly, we highlight the impact of two-dimensional NMR methods in consolidating and revealing further details about the structure of FCS. These studies were conducted by various researchers across different countries and involving multiple species of sea cucumbers. Thirdly, we summarize the biological activities reported for FCS. Our survey identified 104 publications involving FCS from 42 species of sea cucumbers, reporting 10 types of biological activities. Most studies focused on anticoagulant and antithrombotic activities. Finally, we discuss future perspectives for studies related to FCS. These studies aim to clarify the evolutionary advantage for sea cucumbers in developing such a peculiar fucosylated glycosaminoglycan. Additionally, there is a need to identify the enzymes and genes involved in the metabolism of this unique carbohydrate.

Anti-enterovirus 71 activity of native fucosylated chondroitin sulfates and their derivatives

Enterovirus 71 (EV71) is recognized as a major causative agent of hand, foot, and mouth disease (HFMD), posing a significant global public health concern due to its widespread impact and resulting in a major public health issue worldwide. Despite its prevalence, current clinical therapy lacks effective antiviral agents. Fucosylated chondroitin sulfates (FCS) derived from sea cucumber exhibits a range of biological activities including potent antiviral effects. This study provides compelling evidence of the potent antiviral efficacy of FCS against EV71. To further elucidate the impact of structural variations on the anti-EV71 activity, native FCSs with diverse sulfation patterns and a varity of FCS derivatives were prepared and analyzed. Notably, this study presents the detailed structural characterization of FCSs from the sea cucumbers Holothuria scabra Jaege and Holothuria fuscopunctata. Analysis of the structure-activity relationships revealed that molecular weight, sulfated fucose branches, and sulfation pattern were all crucial factors contributing to the potent inhibitory effects of FCS against EV71. Interestingly, molecular weight emerged as the most significant structural determinant of the antiviral potency. These findings suggest the promising potential of utilizing FCS as an innovative EV71 entry inhibitor for the treatment of HFMD.

Immunological effect of fucosylated chondroitin sulfate and its oligomers from Holothuria fuscogilva on RAW 264.7 cells

Fucosylated chondroitin sulfate was obtained from the sea cucumber Holothuria fuscogilva (FCShf). The structure was elucidated by NMR and HILIC-FTMS analysis. FCShf contained a chondroitin core chain [→3)-β-D-GalNAc-(1 → 4)-β-D-GlcA-(1→]_n, where the sulfation positions were the O-4 or O-6 of the GalNAc residues. The ratio of sulfated and non-sulfated GalNAc at O-6 was 1:2, while the ratio of GalNAc at O-4 was 1:1. 2,4-disulfated-fucose (Fuc2,4S), 4-sulfated-fucose (Fuc4S) and 3,4-disulfated-fucose (Fuc3,4S) were attached to the O-3 of GlcA with a molar ratio of 1.00: 0.62: 1.32. The FCShf could significantly promote the proliferative rate, NO production and neutral red uptake of RAW 264.7 cells within the concentration range of 10-300 μg/mL. Compared with the fucosylation and deacetylation degrees, the molecular weight of FCShf had markedly influence on the activation of RAW 264.7 cells. A decrease in molecular weight dramatically improved the immunoregulatory activities. Furthermore, FCShf activated RAW 264.7 cells through TLR-2/4-NF-κB pathway.

The glycosidic bond cleavage and desulfation investigation of fucosylated glycosaminoglycan during mild acid hydrolysis through structural analysis of the resulting oligosaccharides

Mild acid hydrolysis is a common method to study the chemical structure of fucosylated glycosaminoglycan (FG). It was generally considered that the fucose branches α-L-FucS-(1, of FG could be hydrolyzed selectively in mild acid. This report focused on the selectivity of glycosidic bond cleavage and extensive desulfation characteristics of the backbone during mild acid hydrolysis. The hydrolyzed product of native SvFG (dfSvFG) was prepared by mild acid hydrolysis in 0.1 M H₂SO₄ at 100 °C for 2 h. A series of oligosaccharides were purified by GPC and SAX-HPLC from dfSvFG, then they were analyzed by HPGPC, 1D/2D NMR and ESI-Q-TOF-MS. The precise structure of these oligosaccharides was elucidated to be trisaccharides, tetrasaccharides and pentasaccharides, indicating SvFG branches hydrolyzed basically and its' backbone composed of repeating β-D-GlcA-(1,3)-D-GalNAc and β-D-GalNAc-(1,4)-D-GlcA unit. The prevalent presence of the GlcA residues at the non-reducing terminal of these oligosaccharides, suggesting the glycosidic bond of β-D-GalNAc-(1,4)-D-GlcA was more susceptible to acid than that of β-D-GlcA-(1,3)-D-GalNAc during mild acid hydrolysis. Moreover, the sulfate ester groups in GalNAc_4S6S unit could also be hydrolyzed by acid, and it at position C-4 was more susceptible to hydrolysis than that at C-6. This extensive degradation and desulfation of the backbone should be taken into consideration when mild acid hydrolysis was used in elucidating the exact structure or structure-activity relationship of native FG.

Structural and kinetic analyses of holothurian sulfated glycans suggest potential treatment for SARS-CoV-2 infection

Certain sulfated glycans, including those from marine sources, can show potential effects against SARS-CoV-2. Here, a new fucosylated chondroitin sulfate (FucCS) from the sea cucumber Pentacta pygmaea (PpFucCS) (MW ∼10-60 kDa) was isolated and structurally characterized by NMR. PpFucCS is composed of {→3)-β-GalNAcX-(1→4)-β-GlcA-[(3→1)Y]-(1→}, where X = 4S (80%), 6S (10%) or nonsulfated (10%), Y = α-Fuc2,4S (40%), α-Fuc2,4S-(1→4)-α-Fuc (30%), or α-Fuc4S (30%), and S = SO3-. The anti-SARS-CoV-2 activity of PpFucCS and those of the FucCS and sulfated fucan isolated from Isostichopus badionotus (IbFucCS and IbSF) were compared with that of heparin. IC50 values demonstrated the activity of the three holothurian sulfated glycans to be ∼12 times more efficient than heparin, with no cytotoxic effects. The dissociation constant (KD) values obtained by surface plasmon resonance of the wildtype SARS-CoV-2 spike (S)-protein receptor-binding domain (RBD) and N501Y mutant RBD in interactions with the heparin-immobilized sensor chip were 94 and 1.8 × 103 nM, respectively. Competitive surface plasmon resonance inhibition analysis of PpFucCS, IbFucCS, and IbSF against heparin binding to wildtype S-protein showed IC50 values (in the nanomolar range) 6, 25, and 6 times more efficient than heparin, respectively. Data from computational simulations suggest an influence of the sulfation patterns of the Fuc units on hydrogen bonding with GlcA and that conformational change of some of the oligosaccharide structures occurs upon S-protein RBD binding. Compared with heparin, negligible anticoagulant action was observed for IbSF. Our results suggest that IbSF may represent a promising molecule for future investigations against SARS-CoV-2.

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.

Characterization of the Hydrolysis Kinetics of Fucosylated Glycosaminoglycan in Mild Acid and Structures of the Resulting Oligosaccharides

: Mild acid hydrolysis is a common method for the structure analysis of fucosylated glycosaminoglycan (FG). In this work, the effects of acid hydrolysis on the structure of FG from S. variegatus (SvFG) and the reaction characteristic were systemically studied. The degree of defucosylation (DF) and molecular weights (Mw) of partial fucosylated glycosaminoglycans (pFs) were monitored by 1H NMR and size-exclusion chromatography, respectively. The kinetic plots of DF, degree of desulfation (DS) from fucose branches, and degree of hydrolysis (DH) of the backbone are exponentially increased with time, indicating that acid hydrolysis of SvFG followed a first-order kinetics. The kinetic rate constants kDF, kDS, and kDH were determined to be 0.0223 h-1, 0.0041 h-1, and 0.0005 h-1, respectively. The structure of the released sulfated fucose branches (FucS) from SvFG and HfFG (FG from H. fuscopunctata) was characterized by 1D/2D NMR spectroscopy, suggesting the presence of six types of fucose: α/β Fuc2S4S, Fuc3S4S, Fuc3S, Fuc4S, Fuc2S, and Fuc. The Fuc3S4S was more susceptible to acid than Fuc2S4S, and that the sulfate ester in position of O-2 and O-3 than in O-4 of fucose. The structure characteristic of pF18 indicated the cleavage of backbone glycosidic bonds. The APTT prolonged activity reduced with the decrease of the DF and Mw of the pFs, and became insignificant when its DF was 87% with Mw of 3.5 kDa.

A Study for the Access to a Semi-synthetic Regioisomer of Natural Fucosylated Chondroitin Sulfate with Fucosyl Branches on N-acetyl-Galactosamine Units

Fucosylated chondroitin sulfate (fCS) is a glycosaminoglycan found up to now exclusively in the body wall of sea cucumbers. It shows several interesting activities, with the anticoagulant and antithrombotic as the most attractive ones. Its different mechanism of action on the blood coagulation cascade with respect to heparin and the retention of its activity by oral administration make fCS a very promising anticoagulant drug candidate for heparin replacement. Nonetheless, its typically heterogeneous structure, the detection of some adverse effects and the preference for new drugs not sourced from animal tissues, explain how mandatory is to open an access to safer and less heterogeneous non-natural fCS species. Here we contribute to this aim by investigating a suitable chemical strategy to obtain a regioisomer of the natural fCS polysaccharide, with sulfated l-fucosyl branches placed at position O-6 of N-acetyl-d-galactosamine (GalNAc) units instead of O-3 of d-glucuronic acid (GlcA) ones, as in natural fCSs. This strategy is based on the structural modification of a microbial sourced chondroitin polysaccharide by regioselective insertion of fucosyl branches and sulfate groups on its polymeric structure. A preliminary in vitro evaluation of the anticoagulant activity of three of such semi-synthetic fCS analogues is also reported.

Structural Features and Digestive Behavior of Fucosylated Chondroitin Sulfate from Sea Cucumbers Stichopus japonicus

Fucosylated chondroitin sulfate from sea cucumber Stichopus japonicus (FCS_SJ) has been demonstrated with various biological activities; however, its precise structure is still controversial, and digestive behavior remains poorly understood. FCS_SJ was purified, and its detailed structure was elucidated mainly based on the NMR spectroscopic methods. Its main chain was characterized as →4)-β-d-GlcA-(1 → 3)-β-d-GalNAc-(1→ with GalNAc4S6S:GalNAc4S in a ratio of 1.5:1, and three types of sulfated fucosyl branches attaching C-3 of GlcA, namely, Fucp2S4S, Fucp3S4S, and Fucp4S, were found in a ratio of 2:1.5:1. The digestibility of FCS_SJ was investigated in vitro, and the unchanged molecular weight and reducing sugar content indicated that FCS_SJ was not broken down under salivary and gastrointestinal digestion. Furthermore, FCS_SJ showed a significant inhibitory impact on pancreatic lipase dose-dependently but not on α-amylase, indicating that the inhibition of pancreatic lipase by FCS_SJ might be a pathway for its hypolipidemic effect. These findings propose a fucosylated chondroitin sulfate and provide insight into the mechanism of its physiological effects in the digestion system.

Precise Structure and Anticoagulant Activity of Fucosylated Glycosaminoglycan from Apostichopus japonicus: Analysis of Its Depolymerized Fragments

Apostichopus japonicus is one of the most economically important species in sea cucumber aquaculture in China. Fucosylated glycosaminoglycan from A. japonicus (AjFG) has shown multiple pharmacological activities. However, results from studies on the structure of AjFG are still controversial. In this study, the deaminative depolymerization method that is glycosidic bond-selective was used to prepare the depolymerized products from AjFG (dAjFG), and then a series of purified oligosaccharide fragments such as tri-, hexa-, nona-, and dodecasaccharides were obtained from dAjFG by gel permeation chromatography. The 1D/2D NMR and ESI-MS spectrometry analyses showed that these oligosaccharides had the structural formula of l-FucS-α1,3-d-GlcA-β1,3-{d-GalNAc_4S6S-β1,4-[l-FucS-α1,3-]d-GlcA-β1,3-}_n-d-anTal-diol_4S6S (n = 0, 1, 2, 3; FucS represents Fuc_2S4S, Fuc_3S4S, or Fuc_4S). Thus, the unambiguous structure of native AjFG can be rationally deduced: it had the backbone of {-4-d-GlcA-β1,3-d-GalNAc_4S6S-β1-}_n, which is similar to chondroitin sulfate E, and each d-GlcA residue in the backbone was branched with a l-FucS monosaccharide at O-3. Bioactivity assays confirmed that dAjFG and nonasaccharides and dodecasaccharides from AjFG had potent anticoagulant activity by intrinsic FXase inhibition while avoiding side effects such as FXII activation and platelet aggregation.