Structures and Anticoagulant Activities of the Partially Mild Acidic Hydrolysis Products of the Fucosylated Chondroitin Sulfate from Sea CucumberPearsonothuria graeffei

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.

Fucosylated Chondroitin Sulfate 9-18 Oligomers Exhibit Molecular Size-Independent Antithrombotic Activity while Circulating in the Blood

Fucosylated chondroitin sulfate (FCS) oligosaccharides extracted from sea cucumber and depolymerized exhibit potent anticoagulant activity. Knowledge of the antithrombotic activity of different size oligosaccharides and their fucose (Fuc) branch sulfation pattern should promote their development for clinical applications. We prepared highly purified FCS trisaccharide repeating units from hexasaccharide (6-mer) to octadecasaccharide (18-mer), including those with 2,4-disulfated and 3,4-disulfated Fuc branches. All 10 oligosaccharides were identified by their nuclear magnetic resonance structures and ESI-FTMS spectroscopy. In vitro anticoagulant activities and surface plasmon resonance binding tests indicated those of larger molecular sizes and 2,4-disulfated Fuc branches showed stronger anticoagulant effects with respect to anti-FXase activity, as well as stronger binding to FIXa among various clotting proteins. However, both types of FCS 9-mer to 18-mer exhibited molecular size-independent potent antithrombotic activity in vivo at the same dose. In addition, both types of the FCS 6-mer exhibited favorable antithrombotic activity in vivo, although they showed weak anticoagulant activity in vitro. Combining absorption and metabolism studies, we conclude that FCS 9-18 oligomers could remain in the circulation to interact with various clotting proteins to prevent thrombus formation, and appreciable quantities of these oligomers could be excreted through the kidneys. All FCS 9-18 oligomers also resulted in no bleeding, hypotension, or platelet aggregation risk during blood circulation. Thus, FCS 9-18 oligomers with 2,4-disulfated or 3,4-disulfated Fuc branches exhibit potent and safe antithrombotic activity needed for clinical applications.

Synthesis of structurally defined chondroitin sulfate: Paving the way to the structure-activity relationship studies

Chondroitin sulfate (CS) is one of the major and widespread glycosaminoglycans, a family of structurally complex, linear, anionic hetero-co-polysaccharides. CS plays a vital role in various normal physiological and pathological processes, thus, showing varieties of biological activities, such as anti-oxidation, anti-atherosclerosis, anti-thrombosis, and insignificant immunogenicity. However, the heterogeneity of the naturally occurring CS potentially leads to function unspecific and limits further structure-activity relationship studies. Therefore, the synthesis of CS with well-defined and uniform chain lengths is of major interest for the development of reliable drugs. In this review, we examine the remarkable progress that has been made in the chemical, enzymatic and chemoenzymatic synthesis of CS and its derivatives, providing a broad spectrum of options to access CS of well controlled chain lengths.

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.

Bottom-up analysis using liquid chromatography-Fourier transform mass spectrometry to characterize fucosylated chondroitin sulfates from sea cucumbers

Fucosylated chondroitin sulfates (FCSs) from sea cucumbers have repetitive structures that exhibit minor structural differences based on the organism from which they are recovered. A detailed characterization of FCSs and their derivatives is important to establish their structure-activity relationship in the development of new anticoagulant drugs. In the current study, online hydrophilic interaction chromatography-Fourier transform mass spectrometry (FTMS) was applied to analyze the FCS oligosaccharides generated by selective degradation from four species of sea cucumbers, Isostichopus badionotus, Pearsonothuria graeffei, Holothuria mexicana and Acaudina molpadioides. These depolymerized FCS fragments were quantified and compared using the glycomics software package, GlycReSoft. The quantified fragments mainly had trisaccharide-repeating compositions and showed significant differences in fucosylation (including its sulfation) among different species of sea cucumbers. Detailed analysis of FTMS ion peaks and top-down nuclear magnetic resonance spectroscopy of native FCS polysaccharides verified the accuracy of this method. Thus, a new structural model for FCS chains from these different sea cucumbers was defined. This bottom-up approach provides rich detailed structural analysis and provides quantitative information with high accuracy and reproducibility and should be suitable for the quality control in FCSs as well as their oligosaccharides.

Highly purified fucosylated chondroitin sulfate oligomers with selective intrinsic factor Xase complex inhibition

Fucosylated chondroitin sulfate (FCS) oligosaccharides of specific molecular weight have shown potent anticoagulant activities with selectivity towards intrinsic factor Xase complex. However, the preparation of FCS oligosaccharides by traditional methods requires multiple purification steps consuming large amounts of time and significant resources. The current study focuses on developing a method for the rapid preparation of FCS oligomers from sea cucumber Pearsonothuria graeffei having 6-18 saccharide residues. The key steps controlling molecular weight (Mw) and purity of these FCS oligomers were evaluated. Structural analysis showed the resulting FCS oligomers were primarily l-Fuc3,4diS-α1,3-d-GlcA-β1,3-(d-GalNAc4,6diS-β1,4-[l-Fuc3,4diS-α1,3-]d-GlcA-β1,3-)_nd-anTal-ol4,6diS (n = 1˜5) accompanied by partial de-fucosylation and/or de-sulfation. In vitro and in vivo experiments demonstrate that these FCS oligomers selectively inhibit intrinsic factor Xase complex and exhibit remarkable antithrombotic activity without hemorrhagic and hypotension side effects. This method is suitable for large-scale preparation of FCS oligosaccharides as clinical anticoagulants.

Molecular size is important for the safety and selective inhibition of intrinsic factor Xase for fucosylated chondroitin sulfate

Fucosylated chondroitin sulfate from sea cucumber Isostichopus badionotus (FCS-Ib) showed potent anticoagulant activities without selectivity. The present study focused on developing safe FCS-Ib oligomers showing selective inhibition of intrinsic factor Xase (anti-FXase) prepared through partial N-deacetylation-deaminative cleavage. The N-deacetylation degree was regulated by reaction time, controlling the resulting oligomer distribution. Structure analysis confirmed the selectivity of degradation, and 12 high purity fractions with trisaccharide-repeating units were separated. In vitro anticoagulant assays indicated a decrease in molecular weight (Mw) dramatically reduced activated partial thromboplastin time (APTT), thrombin time (TT), AT-dependent anti-FIIa and anti-FXa activities, while the oligomers retained potent anti-FXase activity until they fell below 3kDa. Meanwhile, human FXII activation and platelet aggregation were markedly reduced with decreasing Mw and were moderate when under 12.0kDa. Thus, fragments of 3-12.0kDa should be safe and effective as selective inhibitors of intrinsic tenase complex for application as clinical anticoagulants.