Systematic synthesis of sulfated oligofucosides and their effect on breast cancer MCF-7 cells

Synthesis and Characterization of Regioselectively Functionalized Mono-Sulfated and -Phosphorylated Anionic Poly-Amido-Saccharides

Polysaccharides are abundant in nature and employed in various biomedical applications ranging from scaffolds for tissue engineering to carriers for drug delivery systems. However, drawbacks such as tedious isolation protocols, contamination, batch-to-batch consistency, and lack of compositional control with regards to stereo- and regioselectivity impede the development and utility of polysaccharides, and thus mimetics are highly sought after. We report a synthetic strategy to regioselectively functionalize poly-amido-saccharides with sulfate or phosphate groups using post-polymerization modification reactions. Orthogonally protected β-lactam monomers, synthesized from D-glucal, undergo anionic ring-opening polymerization to yield polymers with degrees of polymerization of 12, 25, and 50. Regioselective deprotection followed by functionalization and global deprotection affords the sulfated and phosphorylated poly-amido-saccharides. The resulting anionic polymers are water soluble and non-cytotoxic and adopt helical conformations. This new methodology provides access to otherwise inaccessible functional polysaccharide mimetics for biomedical applications.

Synthesis of low-molecular weight fucoidan derivatives and their binding abilities to SARS-CoV-2 spike proteins

Fucoidan derivatives 10-13, whose basic sugar chains are composed of repeating α(1,4)-linked l-fucopyranosyl residues with different sulfation patterns, were designed and systematically synthesized. A structure-activity relationship (SAR) study examined competitive inhibition by thirteen fucoidan derivatives against heparin binding to the SARS-CoV-2 spike (S) protein. The results showed for the first time that 10 exhibited the highest inhibitory activity of the fucoidan derivatives used. The inhibitory activity of 10 was much higher than that of fondaparinux, the reported ligand of SARS-CoV-2 S protein. Furthermore, 10 exhibited inhibitory activities against the binding of heparin with several mutant SARS-CoV-2 S proteins, but was found to not inhibit factor Xa (FXa) activity that could otherwise lead to undesirable anticoagulant activity.

Progress and challenges in the synthesis of sequence controlled polysaccharides

The sequence, length and substitution of a polysaccharide influence its physical and biological properties. Thus, sequence controlled polysaccharides are important targets to establish structure-properties correlations. Polymerization techniques and enzymatic methods have been optimized to obtain samples with well-defined substitution patterns and narrow molecular weight distribution. Chemical synthesis has granted access to polysaccharides with full control over the length. Here, we review the progress towards the synthesis of well-defined polysaccharides. For each class of polysaccharides, we discuss the available synthetic approaches and their current limitations.

Design, synthesis, and biomedical applications of synthetic sulphated polysaccharides

This review summarizes the synthetic methods to sulphated polysaccharides, describes their compositional and structural diversity in regards to activity, and showcases their biomedical applications.

Phycochemical Constituents and Biological Activities of Fucus spp

Seaweeds are known to be a good supply of key nutrients including carbohydrates, protein, minerals, polyunsaturated lipids, as well as several other health-promoting compounds capable of acting on a wide spectrum of disorders and/or diseases. While these marine macroalgae are deeply rooted in the East Asian culture and dietary habits, their major application in Western countries has been in the phycocolloid industry. This scenario has however been gradually changing, since seaweed consumption is becoming more common worldwide. Among the numerous edible seaweeds, members of the genus Fucus have a high nutritional value and are considered good sources of dietary fibers and minerals, especially iodine. Additionally, their wealth of bioactive compounds such as fucoidan, phlorotannins, fucoxanthin and others make them strong candidates for multiple therapeutic applications (e.g., antioxidant, anti-inflammatory, anti-tumor, anti-obesity, anti-coagulant, anti-diabetes and others). This review presents an overview of the nutritional and phytochemical composition of Fucus spp., and their claimed biological activities, as well as the beneficial effects associated to their consumption. Furthermore, the use of Fucus seaweeds and/or their components as functional ingredients for formulation of novel and enhanced foods is also discussed.

Novel hemagglutinin-binding sulfated oligofucosides and their effect on influenza virus infection

Among a series of chemically synthesized fucoidan derivatives (1-9), 5 was found for the first time to bind to influenza virus hemagglutinins (HAs) and inhibit hemagglutination activity. In addition, a designed C3-symmetric tripodal ligand 10, synthesized with three sulfated oligofucoside moieties of 5, exhibited much greater hemagglutination inhibition activity than 5. A plaque assay using MDCK cells demonstrated that 10 effectively inhibited influenza virus infection.

Synthesis of Fucoidan-Mimetic Glycopolymers with Well-Defined Sulfation Patterns via Emulsion Ring-Opening Metathesis Polymerization

The approach developed here offers distinct and well-defined glycopolymers for deciphering the biological roles of natural bioactive polysaccharides. Fucose monomers were chemically synthesized and decorated with specific sulfation patterns including unsulfate, monosulfate, disulfate, and trisulfate groups. The six fucoidan-mimetic glycopolymers (18-23) were successfully fabricated through microwave-assisted ring-opening metathesis polymerization (ROMP) in an emulsion system. The molecular weight (M_w), polydispersity index (PDI), and multiple functional groups were fully characterized by SEC-MALLS-RI and NMR spectroscopy. Three glycopolymers (19, 21, 23) associated with 2-O-sulfation exhibited better inhibitory effects on the H1N1 virus, while glycopolymers (19, 20) with monosulfate groups were more effective against the H3N2 virus. These findings would promote the development of novel anti-influenza A virus (IAV) drugs based on natural fucoidans.

Mapping the Reactivity and Selectivity of 2-Azidofucosyl Donors for the Assembly of N-Acetylfucosamine-Containing Bacterial Oligosaccharides

The synthesis of complex oligosaccharides is often hindered by a lack of knowledge on the reactivity and selectivity of their constituent building blocks. We investigated the reactivity and selectivity of 2-azidofucosyl (FucN₃) donors, valuable synthons in the synthesis of 2-acetamido-2-deoxyfucose (FucNAc) containing oligosaccharides. Six FucN₃ donors, bearing benzyl, benzoyl, or tert-butyldimethylsilyl protecting groups at the C3-O and C4-O positions, were synthesized, and their reactivity was assessed in a series of glycosylations using acceptors of varying nucleophilicity and size. It was found that more reactive nucleophiles and electron-withdrawing benzoyl groups on the donor favor the formation of β-glycosides, while poorly reactive nucleophiles and electron-donating protecting groups on the donor favor α-glycosidic bond formation. Low-temperature NMR activation studies of Bn- and Bz-protected donors revealed the formation of covalent FucN₃ triflates and oxosulfonium triflates. From these results, a mechanistic explanation is offered in which more reactive acceptors preferentially react via an S_N2-like pathway, while less reactive acceptors react via an S_N1-like pathway. The knowledge obtained in this reactivity study was then applied in the construction of α-FucN₃ linkages relevant to bacterial saccharides. Finally, a modular synthesis of the Staphylococcus aureus type 5 capsular polysaccharide repeating unit, a trisaccharide consisting of two FucNAc units, is described.

Systematic synthesis of low-molecular weight fucoidan derivatives and their effect on cancer cells

Low-molecular weight fucoidan derivatives with different sulfation patterns were designed, systematically synthesized, and evaluated for their anti-cancer activities against MCF-7 and HeLa cells.

Characterization, antioxidant and cytotoxic activity of sulfated derivatives of a water-insoluble polysaccharides from Dictyophora indusiata

The present study described the characterization and biological properties of water‑soluble sulfated polysaccharides prepared from water‑insoluble polysaccharide (DIP), which were extracted from Dictyophora indusiata. The sulfation of DIP was performed using the chlorosulfonic acid‑pyridine method. The water solubilities of the sulfated derivatives were measured at room temperature according to the Chinese Pharmacopoeia. The scavenging activity of hydroxyl radicals and 1,1‑diphenyl‑2‑picrylhydrazyl (DPPH) as determined, together with the reduction ability of the sulfated polysaccharides. The cytotoxic and antiproliferative effects of DIP and the sulfated derivatives on MCF‑7 and B16 cells were then determined using an MTT assay. The substitution degrees of the sulfated polysaccharides were 0.584 (S1‑DIP), 0.989 (S2‑DIP) and 1.549 (S3‑DIP) according to barium chloride‑gelatin nephelometry. Infrared spectroscopy and 13C‑nuclear magnetic resonance indicated that the substitution of S‑DIP occurred mainly at the C‑6 position, followed by the C‑4 and C‑2 positions. A significant increase was noted in the antioxidant activity of the sulfated derivatives compared with that of DIP. In addition, the S‑DIPs exhibited a more marked reducing capacity and clearing activity of hydroxyl radicals and DPPH. This indicated that the antioxidant capacity of the polysaccharides was significantly higher following sulfation. Furthermore, in in vitro cell investigations, DIP exhibited no inhibitory effects on the growth of the B16 or MCF‑7 tumor cells. However, the sulfated derivatives exerted marked inhibitory effects on these cell lines. Sulfate modification may therefore contribute to an improvement in water solubility and in the antioxidant and antitumor activities of natural DIP.