Structure–function relationships of immunostimulatory polysaccharides: A review

Among the three main divisions of marine macroalgae (Chlorophyta, Phaeophyta and Rhodophyta), marine green algae are valuable sources of structurally diverse bioactive compounds and remain largely unexploited in nutraceutical and pharmaceutical areas. Recently, a great deal of interest has been developed to isolate novel sulfated polysaccharides (SPs) from marine green algae because of their numerous health beneficial effects. Green seaweeds are known to synthesize large quantities of SPs and are well established sources of these particularly interesting molecules such as ulvans from Ulva and Enteromorpha, sulfated rhamnans from Monostroma, sulfated arabinogalactans from Codium, sulfated galacotans from Caulerpa, and some special sulfated mannans from different species. These SPs exhibit many beneficial biological activities such as anticoagulant, antiviral, antioxidative, antitumor, immunomodulating, antihyperlipidemic and antihepatotoxic activities. Therefore, marine algae derived SPs have great potential for further development as healthy food and medical products. The present review focuses on SPs derived from marine green algae and presents an overview of the recent progress of determinations of their structural types and biological activities, especially their potential health benefits.

Overview on Biological Activities and Molecular Characteristics of Sulfated Polysaccharides from Marine Green Algae in Recent Years

The interest in functional food, both freshwater and marine algal products with their possible promotional health effects, increases also in regions where algae are considered as rather exotic food. Increased attention about algae as an abundant source of many nutrients and dietary fiber from the nutrition point of view, as well as from the scientific approaches to explore new nutraceuticals and pharmaceuticals, is based on the presence of many bioactive compounds including polysaccharides extracted from algal matter. Diverse chemical composition of dietary fiber polysaccharides is responsible for their different physicochemical properties, such as their ability to be fermented by the human colonic microbiota resulted in health benefit effects. Fundamental seaweed polysaccharides are presented by alginates, agars, carrageenans, ulvanes, and fucoidans, which are widely used in the food and pharmaceutical industry and also in other branches of industry. Moreover, freshwater algae and seaweed polysaccharides have emerged as an important source of bioactive natural compounds which are responsible for their possible physiological effects. Especially, sulfate polysaccharides exhibit immunomodulatory, antitumor, antithrombotic, anticoagulant, anti-mutagenic, anti-inflammatory, antimicrobial, and antiviral activities including anti-HIV infection, herpes, and hepatitis viruses. Generally, biological activity of sulfate polysaccharides is related to their different composition and mainly to the extent of the sulfation of their molecules. Significant attention has been recently focused on the use of both freshwater algae and seaweed for developing functional food by reason of a great variety of nutrients that are essential for human health.

Health Benefits of Algal Polysaccharides in Human Nutrition

Antioxidant and anticoagulant activity of sulfated polysaccharide from Gracilaria debilis (Forsskal).

Energy- and cost-efficient salt-assisted synthesis of nitrogen-doped porous carbon matrix decorated with nickel nanoparticles for superior electromagnetic wave absorption

Biomass-derived heterogeneous RGO/Ni/C composite with hollow structure for high-efficiency electromagnetic wave absorption

Polysaccharide from the green alga Monostroma angicava was extracted with boiling water and was purified by ion-exchange and size-exclusion column chromatography. The radioprotective effect of the polysaccharide was investigated in mice. The results show that polysaccharide from M. angicava has a different chemical composition to other Chlorophyta having a high rhamnose – containing sulfated polysaccharide. The sulfate ester content was estimated to be 21.8%. When the polysaccharide was applied to BALB/c mice following whole-body X-ray irradiation the counts of leukocytes, thrombocytes and erythrocytes recovered more rapidly in the polysaccharide treated mice after irradiation. In the irradiated mice, the polysaccharide significantly increased the spleen index, natural killer cytostatic activity and the transformation response of splenic lymphocytes. The present observations suggest that polysaccharide from M. angicava led to leukocytogensis and hematopoetic activation in mice after irradiation and that the biological response might be caused by immune activation.

Chemical characterization and radioprotective effect of polysaccharide from Monostroma angicava (Chlorophyta)

Over the years, selenium has caught the attention on its merits, high electronic conductivity, high melting point, and high energy capacity. Nevertheless, the enormous volumetric expansion and shuttle effects of polyselenides simultaneously hinder selenium application. We report a three-dimensional hierarchical structure composed of porous carbon layers derived from the metal-organic framework with Ni(OH)2 nanosheet shell as selenium host. The 3D hierarchical structure looks like slices of toast stacked on top of each other and decorated with Ni(OH)2 nanosheets. The toast improves the electronic conductivity of selenium and serves as a shelter to provide sufficient free space for volume change. The Ni(OH)2 nanosheet shell act as a functional protective barrier to restrain the shuttle effects and achieve a shorter ion transport path. Consequently, the Li–Se batteries deliver remarkable cyclic performance over 2500 cycles at 3 C with 0.018% capacity decay due to the unique structure. In addition, the electrode also performs well in Na–Se batteries. 

Rational design of 3D hierarchical MOFs-derived hollow porous Carbon/Ni(OH)2 nanosheet for long-cycle Li/Na–Se batteries

Existing self-supervised sequential recommendations face the problem of noisy interactions and sparse sequence data, and train models based only on item prediction losses, so they usually fail to learn an appropriate sequential representation. We propose long and short-term interest contrastive learning under filter-enhanced sequential recommendation (FLSCSR). Specifically, a filtering algorithm is used on the user’s interaction sequences to attenuate the noisy information in the sequence data. Two independent encoders are used to model the user’s long-term and short-term interests separately on the filter-based enhanced interaction sequences. Then user-specific gating mechanisms are constructed to capture the long-term and short-term interests tailored to the user’s personalized preferences, which are incorporated into the attention network to achieve better learning of interest representations in sequence recommendations. In addition, representation alignment learning goals are proposed to minimize the discrepancy between long-term and short-term interest representations in personalized global contexts and local sequence representations. Experiments were conducted on three public and industrial datasets, where the FLSCSR model could obtain superior performance compared to the benchmark model: AUC improves by 0.76%-2.02%, GAUC improves by 0.55%-1.01%, MRR improves by 1.19%-2.09%, and NDCG@2 improves by 1.07%-2.26%. 

/pdf/long-and-short-term-interest-contrastive-learning-under-2mrryw6z.pdf

Long and short-term interest contrastive learning under filter-enhanced sequential recommendation

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Biomass-derived heterogeneous RGO/Ni/C composite with hollow structure for high-efficiency electromagnetic wave absorption

Chemical characterization and radioprotective effect of polysaccharide from Monostroma angicava (Chlorophyta)

Rational design of 3D hierarchical MOFs-derived hollow porous Carbon/Ni(OH)2 nanosheet for long-cycle Li/Na–Se batteries

Long and short-term interest contrastive learning under filter-enhanced sequential recommendation