THE ANTICOAGULANT ACTIVITY AND STRUCTURAL CHARACTERIZATION OF FRACTIONATED AND PURIFIED GLYCOSAMINOGLYCANS FROM VENERID CLAM MERETRIX CASTA (CHEMNITZ)

Bioactivity of polysaccharides derived from bivalves

Bivalves have high diversity, widely distributed in various aquatic environments, including saltwater, brackish water and freshwater. Bivalves are known to rich in polysaccharides and have wide applications in functional foods, pharmaceuticals, and industrial research. Despite many relevant reports are available, the information is poorly organized. Therefore, in this study, we conducted a comprehensive scientific review on the potential bioactivity of polysaccharides derived from bivalves. In general, the polysaccharides derived from bivalves possess various bioactive properties, including anticancer, antioxidant, anticoagulant and immunomodulatory activities. The bioactivity of these biomolecules highly depends on the bivalve species, extraction methods, purification methods, dosages, etc. The information in this study can provide an overview of the bioactivities of bivalve polysaccharides. This is very useful to be used as a guide for identifying the health benefits of polysaccharides derived from different bivalve species.

Novel Antiretroviral Structures from Marine Organisms

In spite of significant advancements and success in antiretroviral therapies directed against HIV infection, there is no cure for HIV, which scan persist in a human body in its latent form and become reactivated under favorable conditions. Therefore, novel antiretroviral drugs with different modes of actions are still a major focus for researchers. In particular, novel lead structures are being sought from natural sources. So far, a number of compounds from marine organisms have been identified as promising therapeutics for HIV infection. Therefore, in this paper, we provide an overview of marine natural products that were first identified in the period between 2013 and 2018 that could be potentially used, or further optimized, as novel antiretroviral agents. This pipeline includes the systematization of antiretroviral activities for several categories of marine structures including chitosan and its derivatives, sulfated polysaccharides, lectins, bromotyrosine derivatives, peptides, alkaloids, diterpenes, phlorotannins, and xanthones as well as adjuvants to the HAART therapy such as fish oil. We critically discuss the structures and activities of the most promising new marine anti-HIV compounds.

Abundance of saccharides and scarcity of glycosaminoglycans in the soft tissue of clam, Meretrix meretrix (Linnaeus)

We investigated presence and distribution of glycosaminoglycans (GAGs) in Meretrix meretrix soft tissue by determining GAG composition in the different parts, namely, mantle edge, foot, gill, adductor muscle, and viscera. The occurrence of glycan ingredients was examined by histochemistry, whereas GAG and general polysaccharide contents in clam tissue were qualified through extraction and determination. Tissue sections stained with alcian blue or periodic acid-Schiff demonstrated the general existence of saccharides and trifling generation of GAGs in clam tissues. GAGs coexisting with glycogens appeared to be primarily produced in the mantle and foot tissues in mucus form by visualization. The GAG content of the polysaccharide extract ranged from 16.8 to 75.8 mg in 10 g of 5 dried tissue materials in comparison with total carbohydrate level in the range of 500-1760 mg, thereby indicating that GAGs were not the major components of polysaccharide extracts. GAG composition only accounted for approximately 4% of total glycan components, which consist of the determinations of amino sugar and uronic acid. The soft tissues of clam contained abundant saccharide compounds but sparse amounts of GAGs. The results will benefit the subsequent development of products made from the polysaccharide components of M. meretrix.

Structural and Immunological Activity Characterization of a Polysaccharide Isolated from Meretrix meretrix Linnaeus

Polysaccharides from marine clams perform various biological activities, whereas information on structure is scarce. Here, a water-soluble polysaccharide MMPX-B2 was isolated from Meretrix meretrix Linnaeus. The proposed structure was deduced through characterization and its immunological activity was investigated. MMPX-B2 consisted of d-glucose and d-galctose residues at a molar ratio of 3.51:1.00. The average molecular weight of MMPX-B2 was 510 kDa. This polysaccharide possessed a main chain of (1→4)-linked-α-d-glucopyranosyl residues, partially substituted at the C-6 position by a few terminal β-d-galactose residues or branched chains consisting of (1→3)-linked β-d-galactose residues. Preliminary immunological tests in vitro showed that MMPX-B2 could stimulate the murine macrophages to release various cytokines, and the structure-activity relationship was then established. The present study demonstrated the potential immunological activity of MMPX-B2, and provided references for studying the active ingredients in M. meretrix.

Isolation of low-molecular-weight heparin/heparan sulfate from marine sources

The glycosaminoglycan (heparin and heparan sulfate) are polyanionic sulfated polysaccharides mostly recognized for its anticoagulant activity. In many countries, low-molecular-weight heparins have replaced the unfractionated heparin, owing to its high bioavailability, half-life, and less adverse effect. The low-molecular-weight heparins differ in mode of preparation (chemical or enzymatic synthesis and chromatography fractionations) and as a consequence in molecular weight distribution, chemical structure, and pharmacological activities. Bovine and porcine body parts are at present used for manufacturing of commercial heparins, and the appearance of mad cow disease and Creutzfeldt-Jakob disease in humans has limited the use of bovine heparin. Consequently, marine organisms come across the new resource for the production of low-molecular-weight heparin and heparan sulfate. The importance of this chapter suggests that the low-molecular-weight heparin and heparan sulfate from marine species could be alternative sources for commercial heparin.