•Fucoidan reduces systematic inflammation and attenuates MetS in HFD-fed mice.•Fucoidan increases Akkermansia population in the gut microbiota of mice with MetS.•Fucoidan ameliorates MetS in association with a robust modulation of gut microbiota.Emerging evidence shows that dietary fucoidan contribute to the prevention and treatment of diverse diseases. Here, using a mouse model, we first demonstrate a similar beneficial effect of two fucoidans from Laminaria japonica and Ascophyllum nodosum on diet-induced metabolic syndrome (MetS). Both fucoidans were found to significantly reduce body weight, fasting blood glucose, hepatic steatosis and systematic inflammation. To decipher the mechanism behind this therapeutic effect, the gut microbiota was analyzed as fucoidan is poorly absorbed after oral administration. Interestingly, we found that benign microbes which conferred benefits upon host wellbeing including Akkermansia muciniphila and short-chain fatty acid-producers such as Alloprevotella, Blautia and Bacteroides were highly enriched by fucoidans. Collectively, our study illustrates a novel application of fucoidan as an anti-MetS functional food and, from a gut microbiota perspective, sheds new insight into the mechanism by which unabsorbed polysaccharide exerts a system therapeutic effect.

The protecting-group-free synthesis of versatile glycopolymers accelerated by microwave irradiation in an emulsion system is presented herein. Copper-catalyzed azide–alkyne cycloaddition (CuAAC) was employed to prepare a wide range of glycosylated hydrophilic monomers, and a series of glycopolymers were fabricated via ring-opening metathesis polymerization (ROMP). Our data revealed that phase transfer catalysis (PTC) in an emulsion system was more superior to that of homogeneous solvents (organic and aqueous solvents). Grubbs 2nd, Grubbs 3rd, and Hoveyda–Grubbs 2nd (H–G 2nd) catalysts were systematically screened from room temperature to 75 °C, of which the H–G 2nd catalyst exhibited more compatibility with microwave irradiation in emulsion polymerization. The efficiency of polymerization was significantly enhanced under microwave irradiation that was completed in less than 5 min for homopolymerization and within 15 min for multi-block polymerization. Six glycopolymers were successfully synthesized under optimum conditions. In addition, the surface plasmon resonance (SPR) analysis indicated that the mannose-functionalized multi-block glycopolymers (p-Glu-b-Man and p-Glu-b-Man-b-Fuc) exhibited dramatic improvements in their binding affinities to concanavalin A (ConA) as compared to the homoglycopolymer (p-Man). The robust approach developed in this study offers the efficient fabrication of versatile glycopolymers for potential biological and medical applications.

•Oral administration of carrageenan induces colitis in the colon of C57BL/6J mice.•The effect of carrageenan on the gut microbiota was studied using high-throughput sequencing.•Carrageenan-induced colitis is associated with decreased population of Akkermansia muciniphila.Carrageenan as a food additive has been used for years. However, controversy exists regarding to the safety of carrageenan and accumulating evidence indicates that it could induce colitis in experimental models. Here, to provide more information on this issue and solve the debate, we studied and compared in detail the toxic effects of different isomers of carrageenan (κ-, ι-, and λ-) on the colon of C57BL/6J mice. Interestingly, all isomers of carrageenan were found to induce colitis with a comparable activity. Given that carrageenan is unabsorbed after oral administration, and also in light of the fact that gut microbiota plays a pivotal role in the pathogenesis of colitis, we further investigated the effect of carrageenan on gut microbiota using high-throughput sequencing. Intriguingly, carrageenan-induced colitis was observed to be robustly correlated with changes in the composition of gut microbiota. Specifically, all carrageenans significantly decreased the abundance of a potent anti-inflammatory bacterium, Akkermansia muciniphila, in the gut, which is highly relevant for understanding the toxic effect of carrageenan. Altogether, our results corroborate previous studies demonstrating harmful gastrointestinal effect of carrageenan and, from a gut microbiota perspective, shed new light into the mechanism by which carrageenan induces colitis in experimental animals.

•FCSs structures from two sea cucumbers were characterized.•Anticoagulant and anti-thrombotic activity were compared in vitro and in vivo.•FCSs had similar activity with different sulfation patterns.•Sulfation patterns might not affect anti-thrombotic activity as much as molecular weight.Fucosylated chondroitin sulfate (FCS), a glycosaminoglycan extracted from the body wall of sea cucumber, is a promising antithrombotic agent. The chemical structures of FCSc isolated from sea cucumber Cucumaria frondosa and its depolymerized fragment (dFCSc) were characterized for the first time. Additionally, anticoagulant and antithrombotic activities were evaluated in vitro and in vivo. The results demonstrated that dFCSc exhibited better antithrombotic-hemorrhagic ratio than native FCSc on the electrical induced arterial thrombosis model in rats. Compared to FCSt obtained from Thelenota ananas, FCSc possessed different sulfation patterns but similar antithrombotic effects. Therefore, sulfation pattern of FCS might not affect anticoagulation and antithrombosis as much as molecular weight may. Our results proposed a new point of view to understand the structure-activity relationship of FCS as alternative agents.

•Polyguluronate sulfate (PGS) effectively inhibits HBV replication in HepG2.2.15 cells.•PGS inhibited the expression and secretion of HBsAg and HBeAg with low cytotoxicity.•PGS can bind and enter into HepG2.2.15 cells to interfere with HBV transcription.•PGS can enhance the production and secretion of interferon β in HepG2.2.15 cells.•PGS may upregulate NF-κB and Raf/MEK/ERK pathways to enhance the interferon system.Polyguluronate sulfate (PGS) is a low molecular-weight sulfated derivative, which has a structure of 2,3-O-disulfated-1,4-poly-l-guluronic acid (PG) with about 1.5 sulfate per sugar residue. Herein, our results showed that PGS effectively inhibited the expression and secretion of HBsAg and HBeAg in HepG2.2.15 cells. PGS could bind and enter into HepG2.2.15 cells to interfere with HBV transcription rather than blocking HBV DNA replication. Moreover, PGS also enhanced the production and secretion of interferon beta (IFN-β) in HepG2.2.15 cells. Cellular NF-κB and Raf/MEK/ERK signaling pathways were also involved in the anti-HBV actions of PGS. Thus, PGS may inhibit HBV replication through upregulating the NF-κB and Raf/MEK/ERK pathways to enhance the interferon system. In summary, PGS merits further investigation as a novel anti-HBV agent aimed at modulating the host innate immune system in the future.

•A novel and natural low anticoagulant heparin (LAH) was isolated and purified.•Low molecular weight derivatives of LAH were prepared and characterized.•Relationship between structure and anti-BACE-1 activities of samples was elucidated.•Hexa- to dodecasaccharides were promised to be administrated as BACE-1 inhibitors.•LAH-derived oligosaccharides were promised to be excellent leads for treatment of AD.Heparin (HP) is a promising agent for anti-Alzheimer’s disease (AD), but its anticoagulant activity limits its applications. So a low anticoagulant heparin (LAH) with anti-AD effect is needed. A novel LAH and heparan sulfate (HS) were purified from crude porcine intestinal heparin. Their structures were characterized by nuclear magnetic resonance and liquid chromatography-mass spectrometry. LAH had a relatively high degree of sulfation, but lower than that of HP. 3-O-Sulfated-containing glucosamine residues further confirmed the low anticoagulant activity of LAH. Sixteen oligosaccharides of LAH and HS were prepared and assigned. Evaluation of anti-BACE-1 activities suggested that their potencies were positively correlated with degree of sulfation and polymerization of oligosaccharides. Besides, LAH-derived hexa- to dodecasaccharides was promised to be administrated in vitro as BACE-1 inhibitors. This study presented ideal BACE-1 inhibitors, LAH-derived oligosaccharides, with virtually no anticoagulant activities, which were promised to be excellent leads for treatment of AD.

Recently, fucoidan has been proposed as a potential prebiotic agent for functional food and pharmaceutical development. However, while previous studies illustrated favorable modulations of gut microbiota by fucoidan, changes in the overall microbial structure remain elusive. In the present study, modulations of gut microbiota by different fucoidans were studied using high throughput sequencing and bioinformatics analysis. We found that at the expense of opportunistic pathogenic bacteria such as Peptococcus, the abundance of beneficial bacteria including Lactobacillus and Ruminococcaceae was significantly increased in response to fucoidan treatment. Besides, by maintaining a more balanced composition of gut microbiota, dietary fucoidan also significantly reduced the antigen load and the inflammatory response in the host as evidenced by the decreased serum lipopolysaccharide-binding protein levels. Collectively, our results indicate that fucoidan can be used as a gut microbiota modulator for health promotion and treatment of intestinal dysbiosis.

•We made and characterized LMG and SLMG derivatives from alginate polysaccharides.•Both LMG and SLMG improved TC, TG, and inhibited HMGCR activities in HepG2 cells.•SLMG up-regulated LDLR through activation of SREBP-2.•SLMG induced phosphorylations of AMPK, HMGCR, and ACC.•The activated AMPK affected SREBP-1 and CYP7A1.Low molecular weight and sulfated low molecular weight guluronate (LMG and SLMG) were prepared and hypolipidemic effects were studied in a human hepatocellular carcinoma HepG2 cell line. Both compounds decreased total cholesterol (TC) and triglycerides (TG) and inhibited 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) activity in HepG2 cells. In general, SLMG had greater effects than LMG. Activation of sterol regulatory element-binding protein 2 (SREBP-2), low density lipoprotein receptor (LDLR), AMP-activated protein kinase (AMPK), and AMPK's downstream targets were evidenced by increased phosphorylation of AMPK, HMGCR, and acetyl-CoA-carboxylase (ACC), which decreased HMGRC and ACC activity. We further demonstrated that activated AMPK was linked to down-regulated SREBP-1 and up-regulated cholesterol 7α-hydroxylase (CYP7A1).

A fucoidan from the brown alga Hizikia fusiforme was extracted with hot water and fractionated by anion-exchange chromatography. The main fraction YF5 was depolymerized by partial acid hydrolysis and further purified by gel filtration chromatograph. The sequences of oligosaccharides generated were then determined by ES-CID-MS/MS, which gave directly information on the structural heterogeneity of fucoidan from H. fusiforme. It was shown that YF5 had a backbone of a repeating disaccharide unit of [→4GlcAβ1,2Manα1→], in good agreement with previous report by NMR and methylation analysis. In the product-ion spectra, the unique 0.2A type fragmentation was important to establish the presence of a 2-linked Man in the backbone structure. In addition, abundant novel heterogeneous branched structural fragments were also detected and characterized: Fuc1,3Fuc, Fuc1,3Gal, Fuc1,4GlcA, Gal1,4Gal, Gal1,4GlcA and GlcA1,4GlcA. The sulfation mainly occurred at C2 or C4 of the fucose residue and C2, C4 or C6 of the galactose residue.Highlights► A heterogeneous fucoidan was isolated and purified from brown alga Hizikia fusiforme. ► The sequence of oligosaccharides prepared by partial acid hydrolysis of fucoidan was determined by ES-CID-MS/MS. ► A repeating disaccharide unit of [→4GlcAβ1,2Manα1→] was the backbone structure of the fucoidan.

A charge and size uniform polysaccharide GW2M was extracted with cold water from red alga Gloiopeltis furcata and purified by strong anion ion-exchange and gel permeation chromatography. Its chemical structure was identified by methylation, 1H–1H COSY, 1H–13C HMQC and 1H–13C HMBC techniques. The experimental data showed that GW2M was composed of galactose (40.3%), 3,6-anhydro-galactose (34.1%) and sulfate (24.8%) with an average molecular mass of 20.6 kDa. The results proved GW2M was a linear repeating sequence of alternating (1 → 3)-linked 6-O-sulfated-β-d-galactose (G6S) and (1 → 4)-linked 3,6-anhydro-α-l-galactose (A) which made it to be an ideal 6-O-sulfated-agarose. The sequences of serial oligosaccharides prepared by mild acid and reductive acid hydrolysis from GW2M were confirmed using electrospray collision induced dissociation tandem mass spectrometry (ES-CID-MS/MS) technique.Highlights► A natural ideal 6-O-sulfated agarose, GW2M, was prepared from a red alga Gloiopeltis furcata. ► GW2M is composed of a linear repeating unit of alternating (1 → 3)-linked 6-O-sulfated-β-d-galactose and (1 → 4)-linked 3,6-anhydro-α-l-galactose. ► Odd-numbered and even-numbered oligosaccharides from GW2M were prepared by mild and reductive acid hydrolysis, respectively.

Two polysaccharides CCC and CCH were extracted from red algae Chondracanthus chamissoi by cold water and hot water, respectively. Characterization of the structure by chemical and spectroscopic methods showed that CCC was a hybrid carrageenan composed of κ-carrageenan (35%) and ι-carrageenan (43%) along with its precursor μ-carrageenan (22%) and CCH was an ideal κ-carrageenan. Oligosaccharides from CCH and CCC were prepared and their structural sequences determined by ES-CID-MS/MS gave further insight into the structural characteristics of hybrid carrageenans from C. chamissoi. Some hybrid oligosaccharides, e.g., κ–κ, κ–μ and κ–ι, were obtained with mild acid hydrolysis of CCC. Then, a regular even-numbered oligosaccharides generated with reductive acid hydrolysis of CCH confirmed it an ideal κ-carrageenan.Highlights► The precise structure of carrageenans from Chondracanthus chamissoi was elucidated. ► A series of hybrid carrageenan-derived oligosaccharides, e.g., κ–κ, κ–μ and κ–ι, were obtained by mild acid hydrolysis. ► A series of even-numbered κ-carrageenan-derived oligosaccharides were obtained by reductive acid hydrolysis.

The red alga, Furcellaria lumbricalis from the coast of the Prince Edward Island (PEI) in Atlantic Canada, was extracted with hot water and fractionated with 0.125 M KCl to obtain a carrageenan-like polysaccharide. The polysaccharide was further purified on ion-exchange and gel-permeation chromatography to yield a fraction (FB1) of uniform size and charge, with an average molecular weight of 428 kD. Oligosaccharides generated with acid hydrolysis of FB1 were sequenced using the electrospray ionisation collision induced dissociation tandem mass spectrometry (ES-CID-MS/MS) technique. On the basis of chemical and spectroscopic analysis, FB1 was characterised to be composed of 1,4-linked 3,6-anhydro-galactose (40%), 1,3-linked 4-sulphated-galactose (30%), 1,3-linked galactose (20%), 1,4-linked galactose (8%) and 1,4-linked 3-O-methyl-galactose (2%), which makes it be a novel sulphated galactan hybrid. The β-secretase (BACE) inhibition and immunomodulation activities of FB1-derived oligosaccharides were evaluated in vitro.

The amino groups of aminofluorescein were covalently linked to the carboxyl groups of glycosaminoglycans (GAGs; heparin, heparan sulfate, and the chondroitin sulfates A, B, C, D and E) using 1-ethyl-3-(1,3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide as the catalytic reagents, and fluorescently labeled GAGs were obtained separately. The fluorescently labeled GAGs were transferred onto nitrocellulose-coated glass chips with a manual microarrayer. The retention rate of GAGs on the nitrocellulose membrane after washing was calculated, and their interactions with monoclonal anti-chondroitin sulfate antibody (clone number CS-56) were further studied. The experimental results showed that the retention rates were apparently different between the GAGs and of the order chondroitin sulfate E (51.7%) > chondroitin sulfate A (19.5%) > heparan sulfate (16.4%) > heparin (14.1%) > chondroitin sulfate B (12.3%) > chondroitin sulfate D (10.8%) > chondroitin sulfate C (10.7%). The interaction of GAGs with CS-56 was scientifically compared according to their retention rates on nitrocellulose-carbohydrate chips, and after quantitative calculation, the binding ability of the GAGs to CS-56 is of the order chondroitin sulfate C > D > A > E; furthermore, chondroitin sulfate B, heparin, and heparan sulfate did not show any interaction with CS-56.

Negative-ion electrospray tandem mass spectrometry (ES-MS/MS) with collision-induced dissociation (CID) is attempted for sequence determination of alginate oligosaccharides, derived from polyanionic alginic acid, polymannuronate, and polyguluronate by partial depolymerization using either alginate lyase or mild acid hydrolysis. Sixteen homo- and hetero-oligomeric fragments were obtained after fractionation by gel-filtration and strong anion exchange high performance liquid chromatography. The product-ion spectra of these alginate oligosaccharides were dominated by intense B-, C-, Y-, and Z-type ions together with 0,2A- and 2,5A-ions of lower intensities. Internal mannuronate residues (M) produce weak but specific decarboxylated Zint-ions (Zint − 44 Da; int: denotes internal), which can be used for distinction of M and a guluronate residue (G) at an internal position. A reducing terminal M or G, although neither gives rise to a specific ion, can be identified by differences in the intensity ratio of fragment ions of the reducing terminal residue [2,5Ared]/[0,4Ared] (red: denotes reducing terminal).

Oral preparations of chondroitin sulfate (CS) have long been used as anti-osteoarthritis (anti-OA) drugs. However, little is known about the degradation of CS by human gut microbiota. In the present study, degradation profiles of CSA (the main constituent of CS drugs) by the human gut microbiota from six healthy subjects were investigated. Each individual’s microbiota had differing degradation activities, but ΔUA-GalNAc4S was the end product in all cases. To elucidate the mechanisms underlying this phenomenon, different CSA-degrading bacteria were isolated from each individual’s microbiota and tested for CSA degradation. In addition to Bacteroides thetaiotaomicron J1, Bacteroides thetaiotaomicron 82 and Bacteroides ovatus E3, a new CSA-degrading bacterium, Clostridium hathewayi R4, was isolated and characterized. Interestingly, at least two different CSA-degrading species were identified from each individual’s gut microbiota. Predictably, these functional bacteria also had differing degradation rates, but still generated the same end product, ΔUA-GalNAc4S. In addition, the human fecal isolates produced different degradation profiles for CSC, CSD, and CSE, suggesting that CS could be readily metabolized to varying extents by diverse microbial consortiums, which may help to explain the poor bioavailability and unequal efficacy of CS among individuals in OA treatment.

The inhibition of α-glucosidase is an effective therapeutic approach for type 2 diabetes mellitus that involves decreasing postprandial hyperglycemia. In the present study, the α-glucosidase and α-amylase inhibitory effects of 11 fucoidans extracted from different brown seaweeds were evaluated. Although no significant α-amylase inhibition was observed, fucoidan from Fucus vesiculosus (FvF) showed the highest α-glucosidase inhibitory activity, with an IC50 value of 67.9 μg/mL. In addition, FvF at a concentration of 200 μg/mL displayed very mild cytotoxicity to IEC-6 cells as indicated by the MTT assay. An in vivo study indicated that FvF decreased the fasting blood glucose and hemoglobin A1c (HbA1c) levels of db/db mice, with minimal effect on their weight. Therefore, our present in vitro and in vivo studies demonstrated that FvF could be a promising α-glucosidase inhibitor for the treatment of type 2 diabetes mellitus.

Chondroitin sulfate (CS) as a dietary supplement and a symptomatic slow acting (SYSA) drug has been used for years. Recently, CS has been demonstrated to be readily degraded and fermented in vitro by specific human gut microbes, hinting that dietary CS may pose a potential effect on gut microbiota composition in vivo. However, until now, little information is available on modulations of gut microbiota by CS. In the present study, modulations of gut microbiota in Kunming mice by CS and its oligosaccharide (CSO) were investigated by high-throughput sequencing. As evidenced by Heatmap and principal component analysis (PCA), the female microbiota were more vulnerable than the male microbiota to CS and CSO treatment. Besides, it is of interest to found that CS and CSO had differing effects on the abundance of Bacteroidales S24-7, Bacteroides, Helicobacter, Odoribacter, Prevotellaceae and Lactobacillus in male mice versus female mice. Collectively, we demonstrated a sex-dependent effect on gut microbiota of CS and CSO. In addition, since gut microbiota exerts a major effect on host physiology, our study highlighted that certain beneficial effects of CS may be associated with modulations of gut microbiota, which merits further investigation.

Lectins are used extensively as research tools to detect and target specific oligosaccharide sequences. Ricinus communis agglutinin I (RCA120) recognizes non-reducing terminal β-d-galactose (Galβ) and its specificities of interactions with neutral and sialylated oligosaccharides have been well documented. Here we use carbohydrate arrays of sulfated Galβ-containing oligosaccharide probes, prepared from marine-derived galactans, to investigate their interactions with RCA120. Our results showed that RCA120 binding to Galβ1–4 was enhanced by 2-O- or 6-O-sulfation but abolished by 4-O-sulfation. The results were corroborated with competition experiments. Erythrina cristagalli lectin is also a Galβ-binding protein but it cannot accommodate any sulfation on Galβ.Highlights► Carbohydrate arrays were used to investigate RCA120 interaction with galactose. ► Sulfated galactose-containing probes were prepared from marine-derived galactans. ► RCA120 binding to galactose was enhanced by 2-O- or 6-O-sulfation. ► RCA120 binding to galactose was abolished by 4-O-sulfation. ► Erythrina cristagalli lectin cannot accommodate any sulfation on terminal galactose.