Purification, structural characterization and anticoagulant activities of four sulfated polysaccharides from sea cucumber Holothuria fuscopunctata

A polysaccharide from Periplaneta americana promotes macrophage M2 polarization, exhibiting anti-inflammatory and wound-healing activities

A miscellaneous polysaccharide, PAP55-3-1, with a molecular weight of 23.03 kDa, was isolated from Periplaneta americana through extraction with dilute alkali solution, ethanol precipitation, and column chromatography purification. Structural analysis shows that PAP55-3-1 is mainly composed of five monosaccharides: galactosamine hydrochloride, glucosamine hydrochloride, galactose, glucose and mannose. Its main glycosidic bonds are: Manp-(1→, Galp-(1→, →3)-Galp-(1→, →3,6)-Manp-(1→, →2,6)-Manp-(1→, →6)-Manp-(1→, →4)-Galp-(1→, →6-Glcp-(1→, →6)-Galp-(1→, →2)-Manp-(1 →, →3,4)-Glcp-(1→, →3,6)-Galp-(1→. In vitro experiments demonstrated that PAP55-3-1 can effectively inhibit reactive oxygen species (ROS) and O2- production following H2O2-induction. After H2O2-induction, HIF-1α (hypoxia-inducible factor) was translocated in mitochondria PAP55-3-1 increased localization of HIF-1α was located on mitochondria to maintain the stability of mitochondrial function stability, thereby effectively inhibiting H2O2-induced mitochondrial oxidative damage. Additionally, PAP55-3-1 inhibited the M1 polarization of macrophages stimulated by H2O2 and promoted the phenotype polarization of macrophages from M1 to M2, displaying anti-inflammatory and pro-repair properties. In vivo experimental results indicated that PAP55-3-1 promoted wound healing in mice. Immunohistochemical experiments revealed a reduction in CD68 expression and increase in CD206 expression in both positive and the high-dose polysaccharide group control group. This further demonstrated that PAP55-3-1 promotes the phenotype polarization of macrophages from M1 to M2, exerting anti-inflammatory and wound-healing activities.

A comprehensive review of sulfated fucan from sea cucumber: Antecedent and prospect

Sulfated fucan from sea cucumber is mainly consists of L-fucose and sulfate groups. Recent studies have confirmed that the structure of sulfated fucan mainly consists of repeating units, typically tetrasaccharides. However, there is growing evidence indicating the presence of irregular domains with heterogeneous units that have not been extensively explored. Moreover, as a key contributor to the nutritional benefits of sea cucumbers, sulfated fucan demonstrates a range of biological activities, such as anti-inflammatory, anticancer, hypolipidemic, anti-hyperglycemic, antioxidant, and anticoagulant properties. These biological activities are profoundly influenced by the structural features of sulfated fucan including molecular weight and distribution patterns of sulfate groups. The latest research indicates that sulfated fucan is dispersed in the extracellular matrix of the body wall of sea cucumbers. This article aimed to review the research progress on the in-situ distribution, structures, structural elucidation strategies, functions, and structure-activity relationships of sulfated fucan, especially in the last decade. It also provided insights into the major challenges and potential solutions in the research and development of sulfated fucan. Moreover, the fucanase and carbohydrate binding modules are anticipated to play pivotal roles in advancing this field.

Structure and pharmacokinetics/pharmacodynamics of the anticoagulant tetradecasaccharide oHG-14 as an intrinsic tenase inhibitor

The intrinsic tenase complex (iXase) is an attractive antithrombotic target to treat or prevent pathological thrombosis with negligible bleeding risk. Fucosylated glycosaminoglycan (FG) is a promising anticoagulant by inhibiting iXase. A depolymerized FG (dHG-5) as an anticoagulant has been approved for clinical trials. Given that dHG-5 is a multi-component drug candidate consisting of a homologous series of oligosaccharides, it is difficult to predict a clear pharmacokinetics. Here, as a major oligosaccharide component, the tetradecasaccharide (oHG-14) was purified from dHG-5 and its structure was defined as L-Fuc3S4S-α(1,3)-L-Δ4,5GlcA-α(1,3)-{D-GalNAc4S6S-β(1,4)-[L-Fuc3S4S-α(1,]3)-D-GlcA-β(1,3)-}3-D-GalNAc4S6S-β(1,4)-[L-Fuc3S4S-α(1,]3)-D-GlcA-ol. oHG-14 showed potent iXase inhibitory activity in vitro and antithrombotic effect in vivo comparable to dHG-5. After single subcutaneous administration of oHG-14 at 8, 14.4 and 32.4 mg/kg to rats, the absolute bioavailability was 71.6 %-80.9 % determined by the validated bioanalytical methods. The maximum concentration (Cmax) was 3.73, 8.07, and 11.95 μg/mL, respectively, and the time reaching Cmax (Tmax) was about 1 h. oHG-14 was mainly excreted by kidney as the parent compound with the elimination kinetics of first-order linear model. Anticoagulant activity of oHG-14 was positively correlated with its concentration in rat plasma. The pharmacokinetics/pharmacodynamics (PK/PD) of oHG-14 is similar to that of dHG-5. This study could provide supportive data for the clinical trial of dHG-5 and further development of pure oligosaccharide as an antithrombotic drug candidate.

Purification and Structural Analyses of Sulfated Polysaccharides from Low-Value Sea Cucumber Stichopus naso and Anticoagulant Activities of Its Oligosaccharides

Three polysaccharides (SnNG, SnFS and SnFG) were purified from the body wall of Stichopus naso. The physicochemical properties, including monosaccharide composition, molecular weight, sulfate content, and optical rotation, were analyzed, confirming that SnFS and SnFG are sulfated polysaccharides commonly found in sea cucumbers. The highly regular structure {3)-L-Fuc2S-(α1,}n of SnFS was determined via a detailed NMR analysis of its oxidative degradation product. By employing β-elimination depolymerization of SnFG, tri-, penta-, octa-, hendeca-, tetradeca-, and heptadeca-saccharides were obtained from the low-molecular-weight product. Their well-defined structures confirmed that SnFG possessed the backbone of {D-GalNAc4S6S-β(1,4)-D-GlcA}, and each GlcA residue was branched with Fuc2S4S. SnFS and SnFG are both structurally the simplest version of natural fucan sulfate and fucosylated glycosaminoglycan, facilitating the application of low-value sea cucumbers S. naso. Bioactivity assays showed that SnFG and its derived oligosaccharides exhibited potent anticoagulation and intrinsic factor Xase (iXase) inhibition. Moreover, a comparative analysis with the series of oligosaccharides solely branched with Fuc3S4S showed that in oligosaccharides with lower degrees of polymerization, such as octasaccharides, Fuc2S4S led to a greater increase in APTT prolongation and iXase inhibition. As the degree of polymerization increases, the influence from the sulfation pattern diminishes, until it is overshadowed by the effects of molecular weight.

Structural clarification of mannoglucan GSBP-2 from Ganoderma sinense and its effects on triple-negative breast cancer migration and invasion

Ganoderma sinense, known as Lingzhi in China, is a medicinal fungus with anti-tumor properties. Herein, crude polysaccharides (GSB) extracted from G. sinense fruiting bodies were used to selectively inhibit triple-negative breast cancer (TNBC) cells. GSBP-2 was purified from GSB, with a molecular weight of 11.5 kDa and a composition of α-l-Fucp-(1→, β-d-Glcp-(1→, β-d-GlcpA-(1→, →3)-β-d-Glcp-(1→, →3)-β-d-GlcpA-(1→, →4)-α-d-Galp-(1→,→6)-β-d-Manp-(1→, and →3,6)-β-d-Glcp-(1→ at a ratio of 1.0:6.3:1.7:5.5:1.5:4.3:8.0:7.9. The anti-MDA-MB-231 cell activity of GSBP-2 was determined by methyl thiazolyl tetrazolium, colony formation, scratch wound healing, and transwell migration assays. The results showed that GSBP-2 could selectively inhibit the proliferation, migration, and invasion of MDA-MB-231 cells through the regulation of genes targeting epithelial-mesenchymal transition (i.e., Snail1, ZEB1, VIM, CDH1, CDH2, and MMP9) in the MDA-MB-231 cells. Furthermore, Western blotting results indicated that GSBP-2 could restrict epithelial-mesenchymal transition by increasing E-cadherin and decreasing N-cadherin expression through the PI3K/Akt pathway. GSBP-2 also suppressed the angiogenesis of human umbilical vein endothelial cells. In conclusion, GSBP-2 could inhibit the proliferation, migration, and invasion of MDA-MB-231 cells and showed significant anti-angiogenic ability. These findings indicate that GSBP-2 is a promising therapeutic adjuvant for TNBC.

Structural characterization and immunomodulatory activity of a polysaccharide from Dioscotea opposita

The purified polysaccharides fraction, DOP-2, was prepared from Dioscorea opposita Thunb (D. opposita). This study combined in vitro and in vivo experiments to comprehensively investigate the index changes in RAW264.7 cells and immunocompromised mice under DOP-2 intervention, aiming to elucidate the potential mechanisms of immunomodulatory effects of DOP-2. DOP-2 (10 ∼ 500 μg/mL) significantly elevated the levels of NO, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) factors secreted by RAW264.7 cells, and restored the body weight of immunosuppressed mice and improve the degree of injury to the immune organ index, resulting in significant immunomodulatory effects. Notably, DOP-2 promoted the production of short-chain fatty acids (SCFAs) in immunosuppressed mice and modulated the composition of their gut microflora. These findings highlight the potential benefits of DOP-2 therapy in improving immune function and gut health, and will provide a theoretical basis for the application of D. opposita polysaccharides as an immunomodulatory adjuvant.

The therapeutic effects of marine sulfated polysaccharides on diabetic nephropathy

Marine sulfated polysaccharide (MSP) is a natural high molecular polysaccharide containing sulfate groups, which widely exists in various marine organisms. The sources determine structural variabilities of MSPs which have high security and wide biological activities, such as anticoagulation, antitumor, antivirus, immune regulation, regulation of glucose and lipid metabolism, antioxidant, etc. Due to the structural similarities between MSP and endogenous heparan sulfate, a majority of studies have shown that MSP can be used to treat diabetic nephropathy (DN) in vivo and in vitro. In this paper, we reviewed the anti-DN activities, the dominant mechanisms and structure-activity relationship of MSPs in order to provide the overall scene of MSPs as a modality of treating DN.

Structural characterization of a distinct fucan sulfate from Pattalus mollis through an oligosaccharide mapping approach

The elucidation of the precise structure of fucan sulfate is essential for understanding the structure-activity relationship and promoting potential biomedical applications. In this work, the structure of a distinct fucan sulfate fraction V (PmFS in Ref 15 and FSV in Ref 16 → PFV) from Pattalus mollis was investigated using an oligosaccharide mapping approach. Six size-homogeneous fractions were purified from the mild acid hydrolyzed PFV and identified as fucitols, disaccharides and trisaccharides by 1D/2D NMR and MS analysis. Significantly, the sulfation pattern, glycosidic linkages, and sequences of all the oligosaccharides were unambiguously identified. The common 2-desulfation of the reducing end residue of the oligosaccharides was observed. Overall, the backbone of PFV was composed of L-Fuc2S (major) and L-Fuc3S (minor) linked by α1,4 glycosidic bonds. Importantly, the branches contain both monosaccharide and disaccharide linked to the backbone by α1,3 glycosidic linkages. Thus, the tentative structure of natural PFV was shown to be {-(R-α1,3)-L-Fuc2S-α1,4-(L-Fuc2S/3S-α1,4)x-}n, where R is L-Fuc(2S)4S-α1,3/4-L-Fuc4S(0S)- or L-Fuc(2S)4S-. Our results provide insight into the heterogeneous structure of the fucan sulfate found in sea cucumbers. Additionally, PFV and its fractions showed strong anticoagulant and anti-iXase activities, which may be related to the distinct structure of PFV.

Sulfated polysaccharides in sea cucumbers and their biological properties: A review

Sea cucumbers contain a wide range of biomolecules, including sulfated polysaccharides (SPs), with immense therapeutic and nutraceutical potential. SPs in sea cucumbers are mainly fucosylated chondroitin sulfate (FCS) and fucan sulfate (FS) which exhibit a series of pharmacological effects, including anticoagulant activity, in several biological systems. FCS is a structurally distinct glycosaminoglycan in the sea cucumber body wall, and its biological properties mainly depend on the degree of sulfation, position of sulfate group, molecular weight, and distribution of branches along the backbone. So far, FCS and FS have been recognized for their antithrombotic, anti-inflammatory, anticancer, antidiabetic, anti-hyperlipidemic, anti-obesity, and antioxidant potential. However, the functions of these SPs are mainly dependent on the species, origins, harvesting season, and extraction methods applied. This review focuses on the SPs of sea cucumbers and how their structural diversities affect various biological activities. In addition, the mechanism of actions of SPs, chemical structures, factors affecting their bioactivities, and their extraction methods are also discussed.

Structural Characterization and Anticoagulant Activities of a Keratan Sulfate-like Polysaccharide from the Sea Cucumber Holothuria fuscopunctata

A sulfated polysaccharide (AG) was extracted and isolated from the sea cucumber H. fuscopunctata, consisting of GlcNAc, GalNAc, Gal, Fuc and lacking any uronic acid residues. Importantly, several chemical depolymerization methods were used to elucidate the structure of the AG through a bottom-up strategy. A highly sulfated galactose (oAG-1) and two disaccharides labeled with 2,5-anhydro-D-mannose (oAG-2, oAG-3) were obtained from the deaminative depolymerized product along with the structures of the disaccharide derivatives (oAG-4~oAG-6) identified from the free radical depolymerized product, suggesting that the repeating building blocks in a natural AG should comprise the disaccharide β-D-GalS-1,4-D-GlcNAc6S. The possible disaccharide side chains (bAG-1) were obtained with mild acid hydrolysis. Thus, a natural AG may consist of a keratan sulfate-like (KS-like) glycosaminoglycan with diverse modifications, including the sulfation types of the Gal residue and the possible disaccharide branches α-D-GalNAc4S6S-1,2-α/β-L-Fuc3S linked to the KS-like chain. Additionally, the anticoagulant activities of the AG and its depolymerized products (dAG1-9) were evaluated in vitro using normal human plasma. The AG could prolong activated partial thromboplastin time (APTT) in a dose-dependent manner, and the activity potency was positively related to the chain length. The AG and dAG1-dAG3 could prolong thrombin time (TT), while they had little effect on prothrombin time (PT). The results indicate that the AG could inhibit the intrinsic and common coagulation pathways.

Branch distribution pattern and anticoagulant activity of a fucosylated chondroitin sulfate from Phyllophorella kohkutiensis

Fucosylated chondroitin sulfate (FCS) extracted from Phyllophorella kohkutiensis (PkFCS) is composed of d-GalNAc, d-GlcA, l-Fuc and -SO42-. According to the defined structures revealed by NMR spectra of the branches released by mild acid hydrolysis and oligosaccharides generated by β-eliminative depolymerization, the backbone of PkFCS is CS-E, and the branch types attached to C-3 of d-GlcA include l-Fuc2S4S, l-Fuc3S4S, l-Fuc4S, and the disaccharide α-d-GalNAc-1,2-α-l-Fuc3S4S with the ratio of 43:13:22:22. Notably, novel heptasaccharide and hendecasaccharide were identified that are branched with continuous distribution of the disaccharide. The structural sequences of the oligosaccharides indicate that three unique structural motifs are present in the entire PkFCS polymer, including a motif branched with randomly distributed different sulfated l-Fuc units, a motif containing regular l-Fuc2S4S branches and a motif enriched in α-d-GalNAc-1,2-α-l-Fuc3S4S. This is the first report about the distribution pattern of diverse branches in natural FCS. Natural PkFCS exhibited potent anticoagulant activity on APTT prolonging and anti-iXase activity. Regarding the structurally defined oligosaccharides with sulfated fucosyl side chains, octasaccharide (Pk4b) is the minimum fragment responsible for its anticoagulant activity correlated with anti-iXase. However, further glycosyl modification with a non-sulfated d-GalNAc at the C-2 position of l-Fuc3S4S could significantly decrease the anticoagulant and anti-iXase activity.

Oligomer-guided recognition of two fucan sulfate from Bohadschia argus and inhibition of P-selectin binding to its ligand

Fucan sulfate (FS) from sea cucumber shows intriguing structure and extensive activities. Here, three homogeneous FS (BaFSI - III) were obtained from Bohadschia argus, followed with physicochemical properties analyses including monosaccharide composition, molecular weight, and sulfate content. BaFSI was proposed to carry a unique distribution pattern of sulfate groups as a novel sequence composed of domain A and domain B that formed by different Fuc_S residues, markedly differing from FS reported before, according to the analyses of 12 oligosaccharides and a representative residual saccharide chain. BaFSII possessed a highly regular structure {4-L-Fuc_3S-α1,}_n according to its peroxide depolymerized product. BaFSIII was confirmed as a FS mixture bearing similar structural characteristics with BaFSI and BaFSII by means of mild acid hydrolysis and oligosaccharide analysis. Bioactivity assays showed that BaFSI and BaFSII could potently inhibit P-selectin binding to PSGL-1 and HL-60 cells. Structure-activity relationship analysis showed that molecular weight and sulfation pattern were the essential factors for the potent inhibition. Meanwhile, an acid hydrolysate of BaFSII with a molecular weight about 15 kDa exhibited a comparable inhibition with the native BaFSII. Given the potent activity and highly regular structure of BaFSII, it shows great potential for development as a P-selectin inhibitor.

Structural characterization and antioxidant activity of processed polysaccharides PCP-F1 from Polygonatum cyrtonema Hua

Introduction

Polygonatum cyrtonema Hua. (PC) is a traditional Chinese herb with a history of use in both food and medicine. For clinical use, processed PC pieces are most commonly used, while present research has focused on crude PC polysaccharides (PCPs).

Methods

In this study, a new polysaccharide, PCP-F1, with a molecular weight of 37.46 kDa, was separated from four-time processed PCPs by column chromatography and evaluated by antioxidant activity. It was composed of glucose, mannose, galactose, rhamnose, and galacturonic acid with a molar ratio of 3.5: 2.5: 1.3: 1.8: 0.8.

Results and Discussion

The methylation analysis and two-dimensional NMR measurement revealed that the configuration of PCP-F1 contained nine residues in the primary structural unit by the chain of →3)-α-D-Glcp, →2)-α-D-Glcp (6→, →1)-ꞵ-D-Glcp (2→, →2)-α-D-GalAp (3,4→, →1) -ꞵ-D-Manp (3→, →2)-α-D-Glcp (3→, branched for →3)-α-D-Glcp, →2)-ꞵ-D-Galp (4→, →1)-ꞵ-D-Glcp (2→, →2,4)-α-D-Manp (6→, →3)-α-L-Rhap (4→. Radical scavenging assays indicated that PCP-F1 could scavenge radicals with a high scavenging rate, suggesting PCP-F1 possesses good antioxidant activity. The study confirms the importance of processed PC and offers the potential for exploiting it as a functional food.

Chemical Modification of Polysaccharides: A Review of Synthetic Approaches, Biological Activity and the Structure-Activity Relationship

Natural polysaccharides are macromolecular substances with great potential owing to their wide biological activity and low toxicity. However, not all polysaccharides have significant pharmacodynamic activity; hence, appropriate chemical modification methods can be selected according to the unique structural characteristics of polysaccharides to assist in enhancing and promoting the presentation of their biological activities. This review summarizes research progress on modified polysaccharides, including common chemical modification methods, the change in biological activity following modification, and the factors affecting the biological activity of chemically modified polysaccharides. At the same time, the difficulties and challenges associated with the structural modification of natural polysaccharides are also outlined in this review. Thus, research on polysaccharide structure modification is critical for improving the development and utilization of sugar products.

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.

Sulfated polysaccharides as multi target molecules to fight COVID 19 and comorbidities

The majority of research to combat SARS-CoV-2 infection exploits the adaptive immune system, but innate immunity, the first line of defense against pathogenic microbes, is equally important in understanding and controlling infectious diseases. Various cellular mechanisms provide physiochemical barriers to microbe infection in mucosal membranes and epithelia, with extracellular polysaccharides, particularly sulfated polysaccharides, being among the most widespread and potent extracellular and secreted molecules blocking and deactivating bacteria, fungi, and viruses. New research reveals that a range of polysaccharides effectively inhibits COV-2 infection of mammalian cells in culture. This review provides an overview of sulfated polysaccharides nomenclature, its significance as immunomodulators, antioxidants, antitumors, anticoagulants, antibacterial, and as potent antivirals. It summarizes current research on various interactions of sulfated polysaccharide with a range of viruses, including SARS-CoV-2, and their application for potential treatments for COVID-19. These molecules interact with biochemical signaling in immune cell responses, by actions in oxidative reactions, cytokine signaling, receptor binding, and through antiviral and antibacterial toxicity. These properties provide the potential for the development of novel therapeutic treatments for SARS-CoV-2 and other infectious diseases from modified polysaccharides.

Critical Quality Control Methods for a Novel Anticoagulant Candidate LFG-Na by HPSEC-MALLS-RID and Bioactivity Assays

A low molecular weight fucosylated glycosaminoglycan sodium (LFG-Na) is a novel anticoagulant candidate from the sea cucumber Holothuria fuscopunctata that selectively inhibits intrinsic tenase (iXase). The molecular weight, molecular weight distribution and bioactivities are the critical quality attributes of LFG-Na. The determination of these quality attributes of such an oligosaccharides mixture drug is challenging but critical for the quality control process to ensure its safety and efficacy in clinical use. Herein, the molecular weight and molecular weight distribution of LFG-Na were successfully determined using high performance size exclusion chromatography coupled with multi angle laser light scattering and refractive index detector (HPSEC-MALLS-RID). Comparing to the conventional method, HPSEC-MALLS-RID based on the refractive index increment (dn/dc) did not require the reference substances to establish the calibration curve. The acceptance criteria of LFG-Na were established, the weight-average molecular weight (Mw) should be 4000 to 6000 Da, the polydispersity (Mw/Mn) < 1.40, and the fraction with molecular weights of 1500 to 8000 Da should be no less than 80% of the total. HPSEC-MALLS-RID was also utilized for the determination of the starting material native fucosylated glycosaminoglycan (NFG) to choose a better manufacturing process. Furthermore, APTT assay was selected and the potency of anti-iXase, referring to the parallel line assay (PLA) method, was established to clarify the consistency of its biological activities. The results suggest that HPSEC-MALLS-RID and bioactivity assays are critical quality control methods for multi-component glycosaminoglycan LFG-Na. The methods also provide a feasible strategy to control the quality of other polysaccharide medicines.

Fucose-Rich Sulfated Polysaccharides from Two Vietnamese Sea Cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera: Structures and Anticoagulant Activity

Fucosylated chondroitin sulfates (FCSs) FCS-BA and FCS-HS, as well as fucan sulfates (FSs) FS-BA-AT and FS-HS-AT were isolated from the sea cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera, respectively. Purification of the polysaccharides was carried out by anion-exchange chromatography on DEAE-Sephacel column. Structural characterization of polysaccharides was performed in terms of monosaccharide and sulfate content, as well as using a series of non-destructive NMR spectroscopic methods. Both FCSs were shown to contain a chondroitin core [→3)-β-d-GalNAc-(1→4)-β-d-GlcA-(1→]_n bearing sulfated fucosyl branches at O-3 of every GlcA residue in the chain. These fucosyl residues were different in pattern of sulfation: FCS-BA contained Fuc2S4S, Fuc3S4S and Fuc4S at a ratio of 1:8:2, while FCS-HS contained these residues at a ratio of 2:2:1. Polysaccharides differed also in content of GalNAc4S6S and GalNAc4S units, the ratios being 14:1 for FCS-BA and 4:1 for FCS-HS. Both FCSs demonstrated significant anticoagulant activity in clotting time assay and potentiated inhibition of thrombin, but not of factor Xa. FS-BA-AT was shown to be a regular linear polymer of 4-linked α-L-fucopyranose 3-sulfate, the structure being confirmed by NMR spectra of desulfated polysaccharide. In spite of considerable sulfate content, FS-BA-AT was practically devoid of anticoagulant activity. FS-HS-AT cannot be purified completely from contamination of some FCS. Its structure was tentatively represented as a mixture of chains identical with FS-BA-AT and other chains built up of randomly sulfated alternating 4- and 3-linked α-L-fucopyranose residues.

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.

Structure Elucidation of Fucan Sulfate from Sea Cucumber Holothuria fuscopunctata through a Bottom-Up Strategy and the Antioxidant Activity Analysis

Fucan sulfate I (FSI) from the sea cucumber Holothuria fuscopunctata was purified and its structure was clarified based on a bottom-up strategy. The unambiguous structures of a series of oligosaccharides including disaccharides, trisaccharides, and tetrasaccharides, which were released from mild acid hydrolysis of FSI, were identified by one-dimensional (1D)/two-dimensional (2D) nuclear magnetic resonance (NMR) and mass spectrometry (MS) analysis. All the glycosidic bonds in these oligosaccharides were presented as α1,3 linkages confirmed by correlated signals from their ¹H-¹H ROESY and ¹H-¹³C HMBC spectra. The structural sequence of these oligosaccharides formed by Fuc_2S4S, Fuc_2S, and non-sulfated ones (Fuc_0S), along with the general structural information of FSI, indicated that the structure of FSI could be elucidated as: [-L-Fuc_2S4S-α1,3-L-Fuc_(2S)-α1,3-L-Fuc_2S-α1,3-L-Fuc_0S-α1,3-1-]_n. Moreover, the L-Fuc_0S-α1,3-L-Fuc_2S4S linkage in FSI was susceptible to be cleaved by mild acid hydrolysis. The antioxidant activity assays in vitro showed that FSI and the depolymerized product (dFSI') had potent activities for superoxide radical scavenging activity with IC₅₀ of 65.71 and 83.72 μg/mL, respectively, while there was no scavenging effect on DPPH, hydroxyl and ABTS radicals.

Holothurian fucosylated chondroitin sulfates and their potential benefits for human health: Structures and biological activities

Fucosylated chondroitin sulfates (FCS) are a sulfated polysaccharide exclusively existing in the body wall of sea cucumber. FCS possesses a mammalian chondroitin sulfate like backbone, namely repeating disaccharides units composed of GlcA and GalNAc, with fucosyl branches linked to GlcA and/or GalNAc residues. It is found that FCS can prevent unhealthy dietary pattern-induced metabolic syndromes, including insulin resistance and β-cell function improvement, anti-inflammation, anti-hyperlipidemia, and anti-adipogenesis. Further studies show that those activities of FCS might be achieved through positively modulating gut microbiota composition. Besides, FCS also show therapeutic efficacy in cancer, HIV infection, and side effects of cyclophosphamide. Furthermore, bioactivities of FCS are closely affected by their molecular weights, sulfation pattern of the fucosyl branches, and chain conformations. This review summarizes the recent 20 years studies to provide references for the future studies and applications of FCS in functional foods or drugs.

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.

Marine Sulfated Polysaccharides: Preventive and Therapeutic Effects on Metabolic Syndrome: A Review

Metabolic syndrome is the pathological basis of cardiovascular and cerebrovascular diseases and type 2 diabetes. With the prevalence of modern lifestyles, the incidence of metabolic syndrome has risen rapidly. In recent years, marine sulfate polysaccharides (MSPs) have shown positive effects in the prevention and treatment of metabolic syndrome, and they mainly come from seaweeds and marine animals. MSPs are rich in sulfate and have stronger biological activity compared with terrestrial polysaccharides. MSPs can alleviate metabolic syndrome by regulating glucose metabolism and lipid metabolism. In addition, MSPs prevent and treat metabolic syndrome by interacting with gut microbiota. MSPs can be degraded by gut microbes to produce metabolites such as short chain fatty acids (SCFAs) and free sulfate and affect the composition of gut microbiota. The difference between MSPs and other polysaccharides lies in the sulfation pattern and sulfate content, therefore, which is very important for anti-metabolic syndrome activity of MSPs. This review summarizes the latest findings on effects of MSPs on metabolic syndrome, mechanisms of MSPs in treatment/prevention of metabolic syndrome, interactions between MSPs and gut microbiota, and the role of sulfate group and sulfation pattern in MSPs activity. However, more clinical trials are needed to confirm the potential preventive and therapeutic effects on human body. It may be a better choice to develop new functional foods containing MSPs for dietary intervention in metabolic syndrome.

Structural characterization of oligosaccharides from free radical depolymerized fucosylated glycosaminoglycan and suggested mechanism of depolymerization

Free radical depolymerization is a common method in structural analysis of polysaccharides, the major challenge is the analysis of the cleavage site and characterization of newly formed ends in this reaction. Here, a fucosylated glycosaminoglycan from H. fuscopunctata (HfFG) was depolymerized by H₂O₂ and a series of oligosaccharides were purified and their structures were elucidated. For non-reducing ends of the trisaccharides were intact GalNAc_4S6S, the cleavage site should mainly be the β(1,3) linkages between GlcA and GalNAc in the backbone of FG. Meanwhile, the reducing ends of the disaccharides and trisaccharides were almost dicarboxylic acid derivatives of GlcA, possibly arising from oxidative breaking of the CC bond of GlcA at the reducing ends. In addition, glycosidic linkages in D-GalNAc-β(1,4)-D-GlcA and L-FucS-α(1,3)-D-GlcA located at the reducing end could be cleaved, and the released GalNAc_4S6S were oxidized to N-acetylgalactosaminic acid.

Extraction, structural characterization, and antioxidant and immunomodulatory activities of a polysaccharide from Notarchus leachii freeri eggs

The crude polysaccharides (NLCEP) were extracted from Notarchus leachii freeri eggs strings by the saltextractionmethod. The extraction conditions were optimized using the single-factorexperimentmethod and response surface method (RSM). The results showed that the maximum extraction yield of NLCEP was obtained under the following conditions: NaCl solution concentration of 2.96 %, raw material to liquid ratio of 1: 40 g/mL, extraction time of 2 h and extraction temperature of 69 °C. A new novel pure polysaccharide fraction named as NLCEPs-1 was fractionated from NLCEP by using DEAE-Cellulose 52 and Sephadex G-100. Its structure and immunomodulatory and antioxidant activities were analyzed. The results exhibited that the molecular weight of NLCEPs-1 was 31.4 kDa and it was composed of rhamnose, glucose, galactose, xylose and arabinose in the molar percentage of 11.128: 63.770: 5.439: 6.585: 13.077. The backbone of NLCEPs-1 was mainly consisted of → )4-α-d-Glcp (1→, →6)-α-d-Glcp (1→, →1)-β-d-Galp and β-d-Galp-(1→. NLCEPs-1 exhibited the strong antioxidant activity in scavenging ability of various free radicals and immunomodulatory activity by the enhancement of the pinocytic capacity, nitric oxide (NO) and cytokines.

Five distinct fucan sulfates from sea cucumber Pattalus mollis: Purification, structural characterization and anticoagulant activities

Fucan sulfates from echinoderm possess characteristic structures and various biological activities. Herein, comprehensive methods including enzymolysis, ion-exchange chromatography and size exclusion chromatography lead to the purification of five fucan sulfates (FSI, FSII, FSIII, FSIV, FSV) from the sea cucumber Pattalus mollis. Chemical composition analysis showed that they were all composed of l-fucose. Their sulfate content was determined by a conductimetric method. The molecular weight (Mw) of FSI, FSII, FSIII, FSIV and FSV were measured as 238.3 kDa, 81.0 kDa, 82.0 kDa, 23.2 kDa and 6.12 kDa, respectively. Detailed NMR spectroscopic analysis revealed that the structural sequence of FSI and FSII was →3)-l-Fuc_S-α(1→, where Fuc_S were Fuc_2S4S (10%), Fuc_2S (44%), Fuc_0S (10%), Fuc_4S (36%), that of FSIII was →4)-l-Fuc_2S-(α1 → 4)-l-Fuc_2S-(α1 → 4)-l-Fuc_0S/3S-(α1→, where Fuc_0S and Fuc_3S were in equal molar, and that FSIV was →4)-l-Fuc_2S3S-(α1 → 4)-l-Fuc_2S3S-(α1 → 4)-l-Fuc_2S-(α1→4)-l-Fuc_2S-(α1 → 4)-l-Fuc_2S-(α1 → 4)-l-Fuc_2S-(α1 → . This is the first report that such a diversity of fucan sulfates were obtained from the same sea cucumber species. Biological activity showed that FSI, FSII, FSIII and FSIV exhibited potent anticoagulant by prolonging the APTT. Among them, FSII, FSIII and FSIV showed the similar potency, while FSI owned the strongest. Structure-activity relationships analysis showed that molecular weight and sulfation degree should be the crucial factors for the activity.