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.

Protection of pancreatic beta cells against high glucose-induced toxicity by astaxanthin-s-allyl cysteine diester: alteration of oxidative stress and apoptotic-related protein expression

Purpose: High glucose (HG)-induced oxidative stress is associated with apoptosis in pancreatic β-cells. The protective effect of astaxanthin-s-allyl cysteine diester (AST-SAC) against HG-induced oxidative stress in pancreatic β-cells (βTC-tet cell line) in in vitro was studied.Materials and Methods: βTC-tet cell line was exposed to HG in the presence and absence of AST-SAC. Various parameters such as cell viability, reactive oxygen species generation, mitochondrial membrane potential, DNA fragmentation and expression of proteins involved in apoptosis [p53, B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X (Bax), cytochrome c and caspase 3] were studied.Results: Pre-treatment of βTC-tet cells with AST-SAC (4, 8 and 12 μg/ml) in the presence of HG (25 mM) protected the viability of the cells in a dose-dependent manner. AST-SAC treatment mitigated the oxidative stress thereby preventing the mitochondrial dysfunction, DNA damage and apoptosis in βTC-tet cells against HG toxicity. Treatment with AST-SAC prevented the increased expression of p53 under HG conditions. Further, AST-SAC treatment maintained the level of pro-apoptotic (Bax, cleaved caspase-3 and cytochrome c) and anti-apoptotic (Bcl-2) proteins to that of the control level under HG exposed conditions in βTC-tet cells.Conclusion: Altogether, AST-SAC alleviated HG-induced oxidative damage and apoptosis in pancreatic β-cells by enhancing the antioxidant status and altering apoptotic-related protein expression.

Comparative Bioactivities of Chemically Modified Fucoidan and λ-Carrageenan toward Cells Encapsulated in Covalently Cross-Linked Hydrogels

The sulfated marine polysaccharides, fucoidan and λ-carrageenan, are known to possess anti-inflammatory, immunomodulatory, and cellular protective properties. Although they hold considerable promise for tissue engineering constructs, their covalent cross-linking in hydrogels and comparative bioactivities to cells are absent from the literature. Thus, fucoidan and λ-carrageenan were modified with methacrylate groups and were covalently cross-linked with the synthetic polymer poly(vinyl alcohol)-methacrylate (PVA-MA) to form 20 wt % biosynthetic hydrogels. Identical degrees of methacrylation were confirmed by 1H NMR, and covalent conjugation was determined by using a colorimetric 1,9-dimethyl-methylene blue (DMMB) assay. Pancreatic beta cells were encapsulated in the hydrogels, followed by culturing in the 3D environment for a prolonged period of 32 days and evaluation of the cellular functionality by live/dead, adenosine 5'-triphosphate (ATP) level, and insulin secretion. The results confirmed that fucoidan and λ-carrageenan exhibited ∼12% methacrylate substitution, which generated hydrogels with stable conjugation of the polysaccharides with PVA-MA. The cells encapsulated in the PVA-fucoidan hydrogels demonstrated consistently high ATP levels over the culture period. Furthermore, only cells in the PVA-fucoidan hydrogels retained glucose responsiveness, demonstrating comparatively higher insulin secretion in response to glucose. In contrast, cells in the PVA-λ-carrageenan and the PVA control hydrogels lost all glucose responsiveness. The present work confirms the superior effects of chemically modified fucoidan over λ-carrageenan on pancreatic beta cell survival and function in covalently cross-linked hydrogels, thereby illustrating the importance of differential polysaccharide structural features on their biological effects.

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.

Northern Sea Cucumber (Cucumaria frondosa): A Potential Candidate for Functional Food, Nutraceutical, and Pharmaceutical Sector

Sea cucumber (Cucumaria frondosa) is the most abundant and widely distributed species in the cold waters of North Atlantic Ocean. C. frondosa contains a wide range of bioactive compounds, mainly collagen, cerebrosides, glycosaminoglycan, chondroitin sulfate, saponins, phenols, and mucopolysaccharides, which demonstrate unique biological and pharmacological properties. In particular, the body wall of this marine invertebrate is the major edible part and contains most of the active constituents, mainly polysaccharides and collagen, which exhibit numerous biological activities, including anticancer, anti-hypertensive, anti-angiogenic, anti-inflammatory, antidiabetic, anti-coagulation, antimicrobial, antioxidation, and anti- osteoclastogenic properties. In particular, triterpene glycosides (frondoside A and other) are the most researched group of compounds due to their potential anticancer activity. This review summarizes the latest information on C. frondosa, mainly geographical distribution, landings specific to Canadian coastlines, processing, commercial products, trade market, bioactive compounds, and potential health benefits in the context of functional foods and nutraceuticals.