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Peroxidative depolymerization is often used to elucidate the structure and structure-activity relationship of fucosylated glycosaminoglycan (FG), while the selectivity of bond cleavage and structural characteristics of the resulting fragments remain to be confirmed. Here, the FG from Stichopus variegatus (SvFG) was depolymerized by H 2 O 2 , and a series of yielded mono- and oligo-saccharides were purified. Almost all the non-reducing ends of oligosaccharides were d -GalNAc 4S6S , suggesting that GlcA-β1,3-GalNAc 4S6S linkage was preferentially cleaved. The model reactions showed the glycosidic bond of uronate was more susceptible than those of N -acetyl hexosamine and fucose, which should be due to bond energy of the anomeric C H. The reducing ends of oligosaccharides include C4–C6 saccharic acid and GalNAc or GalNAcA, which should be derived from the oxidation of the reducing end. A hexasaccharide with tartaric acid exhibited increased anti-iXase activity, suggesting the oxidation of reducing end did not impair the anti-iXase activity of FG-derived oligosaccharides. [Display omitted] [ABSTRACT FROM AUTHOR]

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 H 2 O 2 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 C C 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. • Structures of oligosaccharides from free radical depolymerized HfFG were determined. • The preferential cleavage site in FG during depolymerization was identified. • Oligosaccharides with dicarboxylic acid as the reducing end were found. • The possible mechanism of free radical depolymerization of FG was proposed. [ABSTRACT FROM AUTHOR]

Glycosaminoglycan HnFG was extracted from sea cucumber Holothuria nobilis. Its chemical structure was characterized by analyzing the physicochemical properties, oligosaccharides from its mild acid hydrolysates and depolymerized products. The disaccharide d -GalNAc 4S6S -α1,2- l -Fuc 3S -ol found in its mild acid hydrolysates provided a clue for the presence of a unique disaccharide-branch in HnFG. Furthermore, it was confirmed by a series of oligosaccharides from the low-molecular weight HnFG prepared by β-eliminative depolymerization. Combining with the analysis of its peroxide depolymerized products, the precise structure of HnFG was determined: A chondroitin sulfate E (CS-E)-like backbone branched with sulfated monofucoses (~67%) and disaccharides d -GalNAc S -α1,2- l -Fuc 3S (~33%) at O-3 position of each GlcUA. This is the first report on the novel branches in glycosaminoglycan. Biologically, the native and depolymerized HnFG showed potent activities in prolonging the activated partial thrombin time (APTT) and inhibiting intrinsic coagulation Xase (iXase), whereas the oligosaccharides (degree of polymerization ≤6) had no obvious effects. • A glycosaminoglycan HnFG were isolated from sea cucumber Holothuria nobilis. • Structures of fifteen oligomers from hydrolysates and depolymerized HnFG were clarified. • HnFG was partially branched with unique disaccharide GalNAc S -α1,2-Fuc 3S. • Anticoagulant and anti-iXase activities of (d)HnFG and oligomers were discussed. [ABSTRACT FROM AUTHOR]

• A novel FG (AmFG) were extracted from sea cucumber Acaudina molpadioides. • The structures of eight oligosaccharides from depolymerized AmFG were determined. • AmFG branched with unusual disaccharide GalNAc-α1,2-Fuc, besides monosaccharides. • The anticoagulant and anti-iXase activities of AmFG and oligomers were discussed. A fucosylated glycosaminoglycan (AmFG) was extracted from the sea cucumber Acaudina molpadioides. And a series of oligosaccharides were purified from the size-homogeneous fractions, which were prepared from the β-eliminative depolymerized AmFG. According to "bottom-up" strategy, the precise structure of AmFG was elucidated by analyzing the structures of these purified oligosaccharides, combining with NMR analysis of its free-radical depolymerized product. It contained a CS-E-like backbone, and each GlcUA was branched with a mono- or di-sulfated fucose (Fuc) at O -3. Intriguingly, besides two types of monosaccharide branches, Fuc 2S4S (60 %) and Fuc 4S (25 %), that were common in FG, AmFG also contained an unusual disaccharide branch GalNAc-α1,2-Fuc 3S4S (15 %); this is the first report of such a structure in a glycosaminoglycan. Biological assays indicated that native AmFG and its oligosaccharides had potent anticoagulant and intrinsic tenase (iXase) inhibitory activities in a chain length-dependent manner. For these oligosaccharides, octasaccharide was the minimum structural fragment for potent anti-iXase activity, and the disaccharide branch might enhance this activity. [ABSTRACT FROM AUTHOR]