Carrageenan from Solieria chordalis (Gigartinales): Structural analysis and immunological activities of the low molecular weight fractions

Structural and biofunctional diversity of sulfated polysaccharides from the genus Codium (Bryopsidales, Chlorophyta): A review

It is believed that polysaccharides will become a focal point for future production of food, pharmaceuticals, and materials due to their ubiquitous and renewable nature, as well as their exceptional properties that have been extensively validated in the fields of nutrition, healthcare, and materials. Sulfated polysaccharides derived from seaweed sources have attracted considerable attention owing to their distinctive structures and properties. The genus Codium, represented by the species C. fragile, holds significance as a vital economic green seaweed and serves as a traditional Chinese medicinal herb. To date, the cell walls of the genus Codium have been found to contain at least four types of sulfated polysaccharides, specifically pyruvylated β-d-galactan sulfates, sulfated arabinogalactans, sulfated β-l-arabinans, and sulfated β-d-mannans. These sulfated polysaccharides exhibit diverse biofunctions, including anticoagulant, immune-enhancing, anticancer, antioxidant activities, and drug-carrying capacity. This review explores the structural and biofunctional diversity of sulfated polysaccharides derived from the genus Codium. Additionally, in addressing the impending challenges within the industrialization of these polysaccharides, encompassing concerns regarding scale-up production and quality control, we outline potential strategies to address these challenges from the perspectives of raw materials, extraction processes, purification technologies, and methods for quality control.

Studying the Relationship between the Antiviral Activity and the Structure of ἰ-Carrageenan Using Ultrasonication

ἰ-carrageenan is a linear macroalgal polysaccharide that is well known for its antiviral bioactivity. Although it is considered a candidate for antiviral therapeutics, its application is highly limited due to its low solubility and high viscosity, which lower its adsorption efficiency. With the aim of deriving an active ἰ-carrageenan fragment with an improved adsorption capacity, we studied the effects of ultrasonication on structural changes in ἰ-carrageenan with respect to changes in its bioactivity against herpesviruses. An FTIR analysis revealed that ultrasonication increased the hydrophilicity of ἰ-carrageenan without changing its functional groups, and a rheological analysis demonstrated that it gradually decreased the strength of the polysaccharide gel, which completely lost its gel structure and formed small nanoparticles after 30 min of ultrasonication. Concomitantly with these physicochemical changes, a plaque assay revealed that longer ultrasonication increased the antiviral activity of ἰ-carrageenan against two herpesviruses, namely, HSV-1 and VZV. Finally, we separated the 30-min ultrasonicated ἰ-carrageenan into four fractions and found that fractions with a lower molecular weight were significantly less active against both herpesviruses than those with a higher molecular weight. Our findings show that ultrasonication induces physicochemical changes in ἰ-carrageenan that increase its antiviral bioactivity.

A new chlorobenzoate derivative from the red alga Solieria sp

A new chlorobenzoate derivative, solieriate (1), together with six known compounds (2-7), were isolated from the red alga Solieria sp. The structures of 1-7 were determined by comprehensive spectroscopic methods and X-ray diffraction analysis. Compound 1 is the first example of halogenated derivative isolated from this genus. In addition, 1 exhibited moderate antibacterial activity on A. baumannii with MIC value of 64 μg/ml.

The Use of FTIR Spectroscopy as a Tool for the Seasonal Variation Analysis and for the Quality Control of Polysaccharides from Seaweeds

Macroalgae are a potentially novel source of nutrition and biologically active molecules. Proliferative species such as Eucheuma denticulatum, Solieria chordalis (red algae) and Sargassum muticum (brown alga) constitute a huge biomass that can be exploited. In this study, we focus on the extraction of polysaccharides from these three macroalgae species and the characterization of cell wall polysaccharides such as carrageenans, fucoidans and alginates by Fourier Transform Infrared spectroscopy with Attenuated Reflectance Module (FTIR-ATR). The comparison of purified extracts with commercial solutions of fucoidans, alginates or carrageenans shows a strong similarity between the spectra. It demonstrates that the methods of extraction that have been used are also suitable purifying technics. Moreover, it validates infrared spectroscopy as a quick, simple and non-destructive method for the accurate analysis of polysaccharides. The FTIR technique applied to samples collected at different periods of the year allowed us to highlight differences in the composition of fucoidans, alginates and carrageenans. Different classes corresponding to the season can be distinguished by statistical multidimensionnal analysis (Principal Component Analysis) showing that the structure of algal polysaccharides, related to bioactivity, depends on the period of harvest. FTIR results showed that S. chordalis and E. denticulatum possess a dominant type of carrageenan called iota-carrageenan. This type of carrageenan is in the majority when the alga is at maturity in its development cycle. During its growth phase, iota-carrageenan precursors can be detected by FTIR spectra, enabling a better control of the extraction and an application of these compounds in various economic sectors. When the alga E. denticulatum is in its juvenile stage, we found traces of kappa-carrageenan and nu-carrageenan polysaccharides in some extracts.

Bioactive polysaccharides from lotus as potent food supplements: a review of their preparation, structures, biological features and application prospects

Lotus is a famous plant of the food and medicine continuum for millennia, which possesses unique nutritional and medicinal values. Polysaccharides are the main bioactive component of lotus and have been widely used as health nutritional supplements and therapeutic agents. However, the industrial production and application of lotus polysaccharides (LPs) are hindered by the lack of a deeper understanding of the structure-activity relationship (SAR), structural modification, applications, and safety of LPs. This review comprehensively comments on the extraction and purification methods and structural characteristics of LPs. The SARs, bioactivities, and mechanisms involved are further evaluated. The potential application and safety issues of LPs are discussed. This review provides valuable updated information and inspires deeper insights for the large scale development and application of LPs.

The Antitumor Potential of λ-Carrageenan Oligosaccharides on Gastric Carcinoma by Immunomodulation

Gastric carcinoma is a frequently detected malignancy worldwide, while its mainstream drugs usually result in some adverse reactions, including immunosuppression. λ-carrageenan oligosaccharides (COS) have attracted increasing attention as potential anticancer agents due to their ability to enhance immune function. Our current work assessed the antitumor mechanism of λ-COS using BGC-823 cells. Our findings indicated that λ-COS alone did not have a significant impact on BGC-823 cells in vitro; however, it was effective in inhibiting tumor growth in vivo. When THP-1 cells were pre-incubated with λ-COS and used to condition the medium, BGC-823 cells in vitro displayed a concentration-dependent induction of cell apoptosis, nuclear damage, and the collapse of mitochondrial transmembrane potential. These findings suggested that the antineoplastic effect of λ-COS was primarily due to its immunoenhancement property. Treatment with λ-COS was found to significantly enhance the phagocytic capability of macrophages, increase the secretion of TNF-α and IFN-γ, and improve the indexes of spleen and thymus in BALB/c mice. In addition, λ-COS was found to inhibit the growth of BGC-823-derived tumors in vitro by activating the Par-4 signaling pathway, which may be stimulated by the combination of TNF-α and IFN-γ. When used in combination with 5-FU, λ-COS demonstrated enhanced anti-gastric carcinoma activity and improved the immunosuppression induced by 5-FU alone. These findings suggested that λ-COS could be used as an immune-modulating agent for chemotherapy.

κ-Selenocarrageenan Oligosaccharides Prepared by Deep-Sea Enzyme Alleviate Inflammatory Responses and Modulate Gut Microbiota in Ulcerative Colitis Mice

κ-Selenocarrageenan (KSC) is an organic selenium (Se) polysaccharide. There has been no report of an enzyme that can degrade κ-selenocarrageenan to κ-selenocarrageenan oligosaccharides (KSCOs). This study explored an enzyme, κ-selenocarrageenase (SeCar), from deep-sea bacteria and produced heterologously in Escherichia coli, which degraded KSC to KSCOs. Chemical and spectroscopic analyses demonstrated that purified KSCOs in hydrolysates were composed mainly of selenium-galactobiose. Organic selenium foods through dietary supplementation could help regulate inflammatory bowel diseases (IBD). This study discussed the effects of KSCOs on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) in C57BL/6 mice. The results showed that KSCOs alleviated the symptoms of UC and suppressed colonic inflammation by reducing the activity of myeloperoxidase (MPO) and regulating the unbalanced secretion of inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10). Furthermore, KSCOs treatment regulated the composition of gut microbiota, enriched the genera Bifidobacterium, Lachnospiraceae_NK4A136_group and Ruminococcus and inhibited Dubosiella, Turicibacter and Romboutsia. These findings proved that KSCOs obtained by enzymatic degradation could be utilized to prevent or treat UC.

Beneficial effects of seaweed-derived dietary fiber: Highlights of the sulfated polysaccharides

Seaweeds and their derivatives are important bioresources of natural bioactive compounds. Nutritional studies indicate that dietary fibers derived from seaweeds have great beneficial potentials in human health and can be developed as functional food. Moreover, sulfated polysaccharides are more likely to be the main bioactive components which are widely distributed in various species of seaweeds including Phaeophyceae, Rhodophyceae and Chlorophyceae. The catabolism by gut microbiota of the seaweeds-derived dietary fibers (DFs) may be one of the pivotal pathways of their physiological functions. Therefore, in this review, we summarized the latest results of the physiological characteristics of seaweed-derived dietary fiber and highlighted the roles of sulfated polysaccharides in the potential regulatory mechanisms against disorders. Meanwhile, the effects of different types of seaweed-derived dietary fiber on gut microbiota were discussed. The analysis of the structure-function correlations and gut microbiota related mechanisms and will contribute to further better applications in food and biotherapeutics.

NMR spectroscopy for structural elucidation of sulfated polysaccharides from red seaweeds

Some sulfated polysaccharides from red seaweeds are used as hydrocolloids. In addition, it is well known that there are sulfated galactans (carrageenans and agarans) and sulfated mannans, with remarkable biological properties, as antiviral, antitumoral, immunomodulating, antiangiogenic, antioxidant, anticoagulant, and antithrombotic activities, and so on. Knowledge of the detailed structure of the active compound is essential and difficult to acquire. The substitution patterns of the polymer chain, as degree of sulfation and position of sulfate groups, as well as other substituents of the backbone, determine their biological behavior. NMR spectroscopy is a powerful and versatile tool for structural determination. It can be used for elucidation of structures of polysaccharides from new algal sources with novel substitutions or to detect the already known structures from different algal sources, and it could even help to monitor the quality of the active compound on a productive scale. In this review, the available information about NMR spectroscopy of sulfated polysaccharides from red seaweeds is revised and rationalized, to help other researchers working in different fields to study their structures. In addition, considerations about the effects of different structural features, as well as some recording conditions on the chemical shifts of the signals are analyzed.

Structure–immunomodulatory activity relationships of dietary polysaccharides

Polysaccharides are usually composed of more than ten monosaccharide units, which are connected by linear or branched glycosidic bonds. The immunomodulatory effect of natural polysaccharides is one of the most important bioactive function. In this review, molecular weight, monosaccharide (including galactose, mannose, rhamnogalacturonan-I arabinogalactan and uronic acid), functional groups (namely sulfate, selenium, and acetyl groups), types of glycoside bond connection (including β-1,3-D-glucosyl, α-1,4-D-glucosyl, β-1,4-D-glucosyl, α-1,6-D-glucosyl, β-1,4-D-mannosyl, and β-1,4-D-Xylopyranosyl), conformation and the branching degrees are systematically identified as their contribution to the immunostimulatory activity of polysaccharides. At present, studies on the structure-activity relationships of polysaccharides are limited due to their low purity and high heterogeneity. However, it is an important step in providing useful guidance for dietary supplements with polysaccharides. The chemical structures and the process of immune responses induced are necessary to be discussed. Polysaccharides may bind with the cell surface receptors to modulate immune responses. This review mainly discusses the structure-activity relationship of dietary polysaccharides.

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Structure - activity relationships of polysaccharides with immune-enhancing effect are proposed.

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Polysaccharides with the higher molecular weight are helpful to improve immunity.

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Higer galactose, mannose, rhamnogalacturonan-I, arabinogalacta,n and uronic acid contents have immunoregulation.

Hepatic antioxidant activity, immunomodulation, and pro-anti-inflammatory cytokines manipulation of κ-carrageenan (κ-CGN) in cobia, Rachycentron canadum against Lactococcus garvieae

The effects of dietary k-Carrageenan (k-CGN) at 10, 20, and 30 g kg^-1 on growth rate, hemato-biochemical indices, innate-adaptive parameters and modification of pro- and/or anti-inflammatory cytokines and chemokines pathway in cobia, Rachycentron canadum against Lactococcus garvieae is reported. The weight gain (WG) increased substantially (P < 0.05) in all k-CGN treated groups; the specific growth rate (SGR) was significant in healthy uninfected normal (HuN) and L. garvieae challenged (LaC) groups fed with 20 g kg^-1k-CGN diet on 45 and 60 days. The white blood cell (WBC) counts, total protein (TP) level, total anti-oxidant (T-AOC), catalase (CAT), and glutathione (GSH) activities increased significantly when fed with 20 g and 30 g kg^-1k-CG diets on 45th and 60th day. The immunological parameters such as phagocytic (PC) index and the activity of phagocytic (PC), respiratory burst (RB), superoxide dismutase (SOD), alternate complement pathway (ACH₅₀), and lysozyme (LZM) were significantly enhanced with all k-CG diets in 45 and 60 days of treatment. No cumulative mortality (CM) in HuN group fed by control or any k-CGN diets. CM was 5% in LaC group fed with 20 g kg^-1k-CGN diet whereas in LaC groups fed with 10 g and 30 g kg^-1k-CGN diets the CM was 10%. The interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNFα) pro-inflammatory cytokines mRNA transcripts were one-fold high (P < 0.05) in both HuN and LaC group fed all k-CGN enriched diets on 45 and 60 days. Similarly, IL-18 and TLR2 mRNA was one-fold high expression in both groups fed the 20 g and 30 g kg^-1k-CGN enriched diets on 45 or 60 days. Interferon gamma (IFNγ) and interferon regulatory factor 3/7 (IRF3/IRF7) mRNA transcripts did not change with any diet. IL-6, IL-10, and IL-11 mRNA were one-fold high expressions in both groups fed the 20 g and 30 g kg^-1k-CGN enriched diets on 45 and 60 days. However, the expression of CC1, CC3, and CCR9 pro-inflammatory chemokines mRNA did not vary with any control or k-CGN enriched diets. The results indicate that diet enriched with k-CGN at 20 g kg^-1 significantly influences the growth, antioxidant and innate-adaptive immune performance, and pro-anti-inflammatory cytokines and chemokines regulation in cobia against L. garvieae.

Seaweed polysaccharides: Emerging extraction technologies, chemical modifications and bioactive properties

Nowadays, consumers are increasingly aware of the relationship between diet and health, showing a greater preference of products from natural origin. In the last decade, seaweeds have outlined as one of the natural sources with more potential to obtain bioactive carbohydrates. Numerous seaweed polysaccharides have aroused the interest of the scientific community, due to their biological activities and their high potential on biomedical, functional food and technological applications. To obtain polysaccharides from seaweeds, it is necessary to find methodologies that improve both yield and quality and that they are profitable. Nowadays, environmentally friendly extraction technologies are a viable alternative to conventional methods for obtaining these products, providing several advantages like reduced number of solvents, energy and time. On the other hand, chemical modification of their structure is a useful approach to improve their solubility and biological properties, and thus enhance the extent of their potential applications since some uses of polysaccharides are still limited. The present review aimed to compile current information about the most relevant seaweed polysaccharides, available extraction and modification methods, as well as a summary of their biological activities, to evaluate knowledge gaps and future trends for the industrial applications of these compounds.Key teaching pointsStructure and biological functions of main seaweed polysaccharides.Emerging extraction methods for sulfate polysaccharides.Chemical modification of seaweeds polysaccharides.Potential industrial applications of seaweed polysaccharides.Biological activities, knowledge gaps and future trends of seaweed polysaccharides.

Structural characterization and immunomodulatory activity of a heterogalactan from Panax ginseng flowers

A neutral polysaccharide fraction (WGFPN) was isolated from Panax ginseng flowers. Monosaccharide composition and HPSEC-MALLS-RI (high-performance size exclusion chromatography coupled with multi-angle laser light scattering detector and refractive index detector) analyses showed WGFPN was a heterogalactan with a molecular weight of 11.0 kDa. Methylation, 1D/2D NMR (nuclear magnetic resonance) spectra and enzymatic hydrolysis methods were used to characterize the structure of WGFPN. It possessed a less branched (1 → 4)-β-D-galactan and a significantly branched (1 → 6)-β-D-galactan. The side chains of (1 → 6)-β-D-galactan were branched with α-L-1,5-Araf and t-α-L-Araf residues at O-3. Trace amount of 1,4-linked Glcp, terminal Galp, terminal Glcp and terminal Manp residues might attached to the 1,6-linked galactan through O-3 or 1,4-linked galactan through O-6 as side chains. WGFPN could activate RAW264.7 macrophages through increasing macrophage phagocytosis, releasing NO and secreting TNF-α, IL-6, IFN-γ and IL-1β in vitro. Moreover, WGFPN could enhance the immunity of cyclophosphamide (CTX)-induced immunosuppressed mice in vivo. Hence, WGFPN might be a potential natural immunomodulatory agent.

Anti-Herpes simplex virus (HSV-1) activity and antioxidant capacity of carrageenan-rich enzymatic extracts from Solieria filiformis (Gigartinales, Rhodophyta)

Solieria filiformis has been reported to have molecules with various biological activities. In this study we used environmentally friendly extraction methods, such as enzyme-assisted extraction (EAE), as a first step to obtain bioactive compounds from this species. Five combinations of protease (PRO) and carbohydrase (AMG) were utilized (1:0, 0:1, 2:1, 1:1, 1:2 PRO:AMG) to obtain Water Soluble Enzymatic Hydrolysates (WSEHs). Extraction yields, biochemical and structural characterization, as well as in vitro activity against Herpes simplex virus type 1 (HSV-1) and antioxidant capacities were determined. All PRO:AMG combinations significantly improved yields. EAE yielded heterogeneous extracts rich in iota-carrageenan and phenols, as confirmed by FTIR spectra. The highest antiherpetic activity (EC₅₀ 4.5 ± 0.4 μg mL^-1) was found in the WSEHs obtained under 2:1 PRO:AMG. At this combination high antioxidant capacity was also obtained for ABTS (2,2'-Azino-Bis-3-ethylbenzoThiazoline-6-Sulfonic acid) radical scavenging activity and Ferric Reducing Antioxidant Power (FRAP). These could probably play a synergistic role associated to the strong antiviral activity obtained. These results suggest that 2:1 PRO:AMG could be effective in promoting the hydrolytic breakdown of high MW polysaccharides, contributing to the improvement of WSEHs bioactivity. Although Solieria filiformis WSEHs showed promising results, further research, including separation and purification techniques are needed.

Insight into anti-oxidative carbohydrate polymers from medicinal plants: Structure-activity relationships, mechanism of actions and interactions with bovine serum albumin

Recently, research associated with natural anti-oxidants leads to the chemical characterization of many compounds possessing strong anti-oxidant activity. Among these anti-oxidants, naturally occurring carbohydrate polymers containing pectic arabinogalactans esterified with phenolic acids in monomeric and dimeric forms are noteworthy. The presence of highly branched arabinogalactan type II side chains and sugar linked phenolic acid residues have been resolved as important parameters. The anti-oxidant activity of these compounds depend on their ability to convert free radicals into stable by-products and themselves oxidized to more stable and less reactive resonance stabilized radicals. Moreover, these carbohydrate polymers form water soluble stable complexes with protein. Such findings support their applications in a diversity of fields including food industry and pharmacy. This review highlights experimental evidences supporting that the carbohydrate polymers containing phenolic polysaccharides may become promising drug candidate for the prevention of aging and age related diseases.

Structure, antioxidant and immunomodulatory activity of a polysaccharide extracted from Sacha inchi seeds

In this study, a novel water-soluble polysaccharide (PVLP-1) was extracted and purified from Sacha inchi (Plukenetia volubilis L.) seeds and the structure, antioxidant and immunomodulatory activity of PVLP-1 were investigated. PVLP-1 (144 kDa) consisted of glucose (69.76%), mannose (14.86%), arabinose (10.53%), galactose (2.42%), ribose (1.23%), rhamnose (0.27%) and xylose (0.93%). PVLP-1 displayed characteristic polysaccharide bands in Fourier transform NMR spectra and infrared. The primary structure of PVLP-1 was a heteropolysaccharide with a backbone of (1 → 6)-linked glucose, sidechains of (1 → 4)-linked mannose, (1 → 4)-linked glucose and (1 → 3, 6)-linked mannose and a residue unit of →1)-linked arabinose as revealed the methylation analysis. PVLP-1 possessed good water-holding capacity (WHC), oil-holding capacity (OHC) and antioxidant capacities. Besides, PVLP-1 induced the proliferation of RAW264.7 cell and enhanced the expression of inflammatory cytokines IL-6, TNF-alpha(TNF-α) and IL-1 beta (IL-1β). The present study indicated that PVLP-1 possessed immune-enhancing bioactivities and could be functional food or adjuvant drug to improve biological immunity of immunodeficiency diseases and hypoimmunity.

Plant-Derived Nutraceuticals and Immune System Modulation: An Evidence-Based Overview

Immunomodulators are agents able to affect the immune system, by boosting the immune defences to improve the body reaction against infectious or exogenous injuries, or suppressing the abnormal immune response occurring in immune disorders. Moreover, immunoadjuvants can support immune system acting on nonimmune targets, thus improving the immune response. The modulation of inflammatory pathways and microbiome can also contribute to control the immune function. Some plant-based nutraceuticals have been studied as possible immunomodulating agents due to their multiple and pleiotropic effects. Being usually more tolerable than pharmacological treatments, their adjuvant contribution is approached as a desirable nutraceutical strategy. In the present review, the up to date knowledge about the immunomodulating properties of polysaccharides, fatty acids and labdane diterpenes have been analyzed, in order to give scientific basic and clinical evidence to support their practical use. Since promising evidence in preclinical studies, limited and sometimes confusing results have been highlighted in clinical trials, likely due to low methodological quality and lacking standardization. More investigations of high quality and specificity are required to describe in depth the usefulness of these plant-derived nutraceuticals in the immune system modulation, for health promoting and disease preventing purposes.

Solieritide A, a new polyketide from the red alga Solieria sp

A new polyketide, solieritide A (1), along with six known ones (2-7), had been isolated from the red alga Solieria sp. The structures of these compounds were elucidated by spectroscopic analysis. The absolute configuration of 1 was determined by the method of X-ray diffraction. Compound 1 was a rare polyketide bearing benzopyrone ring fused with γ-butyrolactone. Compounds 2-7 were isolated from the red algae of genus Solieria for the first time. The antibacterial activities of 1-7 were also discussed.

Biopolymer K-carrageenan wrapped ZnO nanoparticles as drug delivery vehicles for anti MRSA therapy

Kappa-Carrageenan wrapped ZnO nanoparticles (KC-ZnO NPs) was synthesized, physico-chemically characterized and evaluated their biocompatibility and antimicrobial therapy against MRSA. XRD showed the highly crystalline and hexagonal phase structure of ZnO NPs. FETEM confirmed the spherical and hexagonal shaped particle with the mean size of 97.03 ± 9.05 nm. The synthesized KC-ZnO NPs exhibited significant antibacterial activity against MRSA. The biofilm growth of MRSA was greatly inhibited at 100 μg/ml as observed through live and dead cell assay. KC-ZnO NPs have shown invitro anti-inflammatory activity (82%) at 500 μg/ml. KC-ZnO NPs was non-toxic to NIH3T3 mouse embryonic fibroblasts cell lines. Further, no apoptotic and necrotic mediated death in NIH3T3 mouse embryonic fibroblasts cells were noticed by flow cytometric analysis. KC-ZnO NPs have good biocompatibility as recorded by the least hemolysis percentage (<3%) up to 100 μg/ml, which is much lesser than the acceptable limit. In addition, ecosafety analysis has shown that KC-ZnO NPs and kappa karrageenan (0-500 μg/ml) caused no mortality of A. salina after 48 h. However, bare zinc acetate has shown 35% mortality of A. salina after 48 h. The results conclude that KC-ZnO NPs could be a novel antibacterial therapy for the treatment of MRSA associated infectious.

Natural Polysaccharide Nanomaterials: An Overview of Their Immunological Properties

Natural occurring polymers, or biopolymers, represent a huge part of our planet biomass. They are formed by long chains of monomers of the same type or a combination of different ones. Polysaccharides are biopolymers characterized by complex secondary structures performing several roles in plants, animals, and microorganisms. Because of their versatility and biodegradability, some of them are extensively used for packaging, food, pharmaceutical, and biomedical industries as sustainable and renewable materials. In the recent years, their manipulation at the nanometric scale enormously increased the range of potential applications, boosting an interdisciplinary research attempt to exploit all the potential advantages of nanostructured polysaccharides. Biomedical investigation mainly focused on nano-objects aimed at drug delivery, tissue repair, and vaccine adjuvants. The achievement of all these applications requires the deep knowledge of polysaccharide nanomaterials' interactions with the immune system, which orchestrates the biological response to any foreign substance entering the body. In the present manuscript we focused on natural polysaccharides of high commercial importance, namely, starch, cellulose, chitin, and its deacetylated form chitosan, as well as the seaweed-derived carrageenan and alginate. We reviewed the available information on their biocompatibility, highlighting the importance of their physicochemical feature at the nanoscale for the modulation of the immune system.

Pyruvate Substitutions on Glycoconjugates

Glycoconjugates are the most diverse biomolecules of life. Mostly located at the cell surface, they translate into cell-specific "barcodes" and offer a vast repertoire of functions, including support of cellular physiology, lifestyle, and pathogenicity. Functions can be fine-tuned by non-carbohydrate modifications on the constituting monosaccharides. Among these modifications is pyruvylation, which is present either in enol or ketal form. The most commonly best-understood example of pyruvylation is enol-pyruvylation of N-acetylglucosamine, which occurs at an early stage in the biosynthesis of the bacterial cell wall component peptidoglycan. Ketal-pyruvylation, in contrast, is present in diverse classes of glycoconjugates, from bacteria to algae to yeast-but not in humans. Mild purification strategies preventing the loss of the acid-labile ketal-pyruvyl group have led to a collection of elucidated pyruvylated glycan structures. However, knowledge of involved pyruvyltransferases creating a ring structure on various monosaccharides is scarce, mainly due to the lack of knowledge of fingerprint motifs of these enzymes and the unavailability of genome sequences of the organisms undergoing pyruvylation. This review compiles the current information on the widespread but under-investigated ketal-pyruvylation of monosaccharides, starting with different classes of pyruvylated glycoconjugates and associated functions, leading to pyruvyltransferases, their specificity and sequence space, and insight into pyruvate analytics.

Vaccine Adjuvants Derived from Marine Organisms

Vaccine adjuvants help to enhance the immunogenicity of weak antigens. The adjuvant effect of certain substances was noted long ago (the 40s of the last century), and since then a large number of adjuvants belonging to different groups of chemicals have been studied. This review presents research data on the nonspecific action of substances originated from marine organisms, their derivatives and complexes, united by the name 'adjuvants'. There are covered the mechanisms of their action, safety, as well as the practical use of adjuvants derived from marine hydrobionts in medical immunology and veterinary medicine to create modern vaccines that should be non-toxic and efficient. The present review is intended to briefly describe some important achievements in the use of marine resources to solve this important problem.

Structural Characterization and Immunomodulatory Activity of a Polysaccharide from Eurycoma longifolia

A polysaccharide, Ali-1, was isolated from the roots of Eurycoma longifolia, a popular traditional medicinal herb in Malaysia. The structure of Ali-1 was characterized by monosaccharide, methylation, and NMR data analyses. The average molecular weight of Ali-1 is 14.3 ku, and it is composed of arabinose (14.31%), xylose (57.69%), galacturonic acid (13.03%), and glucuronic acid (14.86%). The main chain comprises (1→4)-linked xylose residues. It has branch points in the main chain; (1→2,4)-linked xylose residues, 1,2-linked glucuronic acid residues, and 1,2-linked arabinose residues form the branches, and the branches are terminated with T-linked galacturonic acid residues and T-linked arabinose residues. Ali-1 significantly improves the pinocytic and phagocytic abilities of RAW264.7 cells and facilitates cytokine secretion according to an immunostimulation assay. These results demonstrate that Ali-1 has potential as a functional supplement for people with compromised immune systems.

Caulerpa Cupressoides Var. Flabellata

Green seaweeds are rich sources of sulfated polysaccharides (SPs) with potential biomedical and nutraceutical applications. The aim of this work was to evaluate the immunostimulatory activity of SPs from the seaweed, Caulerpa cupressoides var. flabellata on murine RAW 264.7 macrophages. SPs were evaluated for their ability to modify cell viability and to stimulate the production of inflammatory mediators, such as nitric oxide (NO), intracellular reactive oxygen species (ROS), and cytokines. Additionally, their effect on inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) gene expression was investigated. The results showed that SPs were not cytotoxic and were able to increase in the production of NO, ROS and the cytokines, tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). It was also observed that treatment with SPs increased iNOS and COX-2 gene expression. Together, these results indicate that C. cupressoides var. flabellata SPs have strong immunostimulatory activity, with potential biomedical applications.

Purification, structural analysis and mechanism of murine macrophage cell activation by sulfated polysaccharides from Cystoseira indica

Sulfated polysaccharides were isolated and purified from the water extract of Cystoseira indica using DEAE Sepharose Fast Flow column to evaluate their structure and macrophage stimulating capacity. Crude and fractionated polysaccharides, CIF1 and CIF2, were mostly composed of neutral sugars (73.1%-78.6%) with relatively lower amounts of acidic sugars (1.3%-9.0%) and sulfate esters (6.9%-9.7%). The polymer chains of polysaccharides were mainly built of different levels of glucose (2.1%-30.8%), fucose (17.2%-24.4%), mannose (17.8%-20.6%) and galactose (16.7%-17.3%). The weight average molecular weight (Mw) of polysaccharides varied between 573.1 × 103 g/mol to 1146.6 × 103 g/mol. The CIF2 polysaccharide, as the most immunostimulating polysaccharide, remarkably induced the release of nitric oxide and inflammatory cytokines including TNF-α, IL-1β, IL-6 and IL-10 from RAW264.7 murine macrophage cells through NF-κB and PAMKs transduction signaling pathways via cell surface TLR4. The interconnections of sugars in CIF2 polysaccharide were complex with (1→3)-fucopyranose, (1→2,3,4)-glucopyranose, (→1)-galactopyranose, (→1)-xylopyranose, (1→2)-rhamnopyranose and (1→2,3)-mannopyranose units being the most predominant residues.

Characterization of sulfated polysaccharide from Laurencia obtusa and its apoptotic, gastroprotective and antioxidant activities

This study was designed to characterize the physico-chemical properties of the sulfated polysaccharide (SP) isolated from the red alga Laurencia obtusa and to evaluate its apoptotic, gastroprotective and antioxidant activities. The different macromolecular characteristics of SP were determined by size exclusion chromatography combined with multi-angle laser light-scattering detection (SEC-MALLS), Fourier transform infrared spectroscopy (FTIR) analysis and nuclear magnetic resonance spectroscopy (¹H NMR and ¹³C NMR). The native molecular weight of the extracted polysaccharide is high (≥336,900 g·mol^-1). It showed high amounts of sulfated groups (28.2%) and low levels of proteins. It was found to be a potent inducer of apoptosis on acute monocytic leukaemia THP-1cell lines with EC₅₀ value of 53 μg·mL^-1. Furthermore, a significant gastroprotective effect (p < 0.01) was also observed with a gastric ulcer inhibition of 63.44%, 78.42% and 82.15% at the doses 25, 50 and 100 mg·kg^-1, respectively. In addition, SP significantly increased glutathione levels (GSH) and decreased the concentration of thiobarbituric acid-reactive substances (TBARS) in EtOH/HCl-damaged gastric mucosa in rats; it also exhibited an important antioxidant activity in vitro. Therefore, SP, derived from the red alga Laurencia obtusa, may have a potential therapeutic effect against acute myeloid leukaemia and a beneficial potential as gastroprotective and antioxidant natural product.

Evaluation of cytotoxicity and antimicrobial activity of an injectable bone substitute of carrageenan and nano hydroxyapatite

A successful post-surgical implant is associated with accelerated recovery periods, involving the efficient regeneration of lost or non-viable tissue and a reduction in microbial growth. Alternatively, the long-term success of an implant is guided by the selection of an engineered biomimetic material that is biocompatible, non-biodegradable, and stable at the site of implantation, without invoking any non-essential or undesirable biological responses. The potential for developing an injectable bone substitute (IBS) was investigated here. In particular, carrageenan (CG) and nano-hydroxyapatite (nHA) injectable composites were fabricated by chemical cross-linking, and the in vitro behavior of mammalian cells and bacteria on the IBS surface structures were evaluated. Formulations consisting of 1%, 1.5%, and 2.5% CG and 60% nHA by weight were then evaluated for their interactions with human osteoblasts (or bone forming cells). MTS viability testing indicated that osteoblast adhesion and viability on the IBS were excellent and uniform among various formulation types. Bacteria assays were also performed to assess antimicrobial functions on the CG/nHA composite against both Gram-negative and Gram-positive strains. A higher CG content, as found in some samples, correlated with improved Pseudomonas aeruginosa growth inhibition, although other bacteria strains appeared unaffected by the IBS. In summary, this study highlights CG/nHA composites as innovative biomaterials that should be further studied for reduced bacteria activity and promoted osteoblast responses which was achieved without using pharmaceutical drugs. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2984-2993, 2018.

Oligosaccharides Derived from Red Seaweed: Production, Properties, and Potential Health and Cosmetic Applications

Because of their potential use as functional ingredients in human nutrition, oligosaccharides derived from natural sources are receiving paramount consideration. Red seaweed, a proven rich source of agar and carrageenan, is one of the most abundantly present sources of such oligosaccharides. Agaro-oligosaccharides (AOS) and carrageenan-oligosaccharides (COS) are produced from agar and carrageenan, respectively, through chemical and enzymatic hydrolyses. Enzymatic hydrolysis of agar and carrageenan into oligosaccharides is preferred in industrial production because of certain problems associated with chemical hydrolysis, including the release of high amounts of monosaccharides and undesirable toxic products, such as furfural. AOS and COS possess many biological activities, including prebiotic, immuno-modulatory, anti-oxidant, and anti-tumor activities. These activities are related to their chemical structure, molecular weight, degree of polymerization, and the flexibility of the glycosidic linkages. Therefore, the structure–function relationship and the mechanisms occurring during the specific biological applications of AOS and COS are discussed herein. Moreover, the chromatographic separation, purification, and characterization of AOS and COS are also part of this review. This piece of writing strives to create a new perspective on the potential applications of AOS and COS in the functional food and pharmaceutical industry.

The Sulfated Polysaccharides of Brown Algae and Products of Their Enzymatic Transformation as Potential Vaccine Adjuvants

The review is devoted to critical analysis of literature data, deal with effects and mechanisms of action of sulfated polysaccharides (PSs) – fucoidans from brown algae and products of their enzymatic transformation as potential adjuvants for enhancement of anti-infective and antitumor immune response. Numerous experimental data indicate that sulfated PSs demonstrate properties of vaccine adjuvants. Application perspectiveness of fucoidans as vaccine adjuvants is defined by their high biocompatibility, low-toxicity, safety and good tolerance by macroorganism, and also mechanisms of their immunomodulatory action. In particular, fucoidans are agonists of receptors of innate immunity and strong inducers of cellular and humoral immune response. At presenting the data of structural - functional interrelations, attention focused to the defining role of degree of sulfation, uronic acids and polyphenols contents, and also molecular mass in actions of fucoidans to innate and adaptive immunity cells. Insufficiency of literary data on studying of correlation of structure – physicochemical characteristics with adjuvanticities of the sulfated PSs, and also the problem of standardization of their active fractions are noted. Special attention is paid to the analysis of immunomodulatory and adjuvant activity of fucoidan oligosaccharides. Presented here results of experimental trial indicate that, despite the difficulties due to preparation of highly purified structurally characterized fractions and complex structure of fucoidans, these substances can be used as safe and effective adjuvants in vaccines against various pathogens including viruses, and also in antitumor vaccines.

A novel ion-activated in situ gelling ophthalmic delivery system based on κ-carrageenan for acyclovir

The aim of this study was to prepare and evaluate ion-activated in situ gel ophthalmic drug delivery system based on κ-carrageenan (KC), using acyclovir as a model drug, hydroxypropyl methylcellulose (HPMC) as the viscosity agent and hydroxypropyl-β-cyclodextrin (HP-β-CD) as the penetration enhancer. The two ternary phase diagrams exhibited the effect of K⁺ and Ca²⁺ on the sol-to-gel transition, which turned out that KC was more sensitive to K⁺. The optimal ophthalmic matrix (prepared from KC and HPMC) was optimized with in vitro drug release test. The apparent permeability coefficient of acyclovir under 2% HP-β-CD was found to have dramatically increased (2.16-ploid) than that of conventional eye drops (p < .05). The ion-activated in situ gel based on KC significantly delayed drug release and its bioavailability could be improved in comparison with the conventional eye drops. Hence, it has the potential to be a novel kind of ocular drug delivery system.

Structure and immunomodulatory activity of a sulfated agarose with pyruvate and xylose substitutes from Polysiphonia senticulosa Harvey

A charged and size uniform polysaccharide PS2 was prepared from red seaweed Polysiphonia senticulosa Harvey. Based on nuclear magnetic resonance (NMR), fourier transform infrared (FTIR) spectroscopy, and electrospray ionization collision-induced-dissociation mass spectrometry (ESI-CID-MSⁿ) analysis, PS2 was determined to be a novel 6-O-sulfated agarose which was mainly composed of a repeating unit of alternating (1→3)-linked 6-sulfated-β-d-galactose and (1→4)-linked 3,6-anhydro-α-l-galactose in association with small amount of pyruvate substituted on galactose residues and xylose (Xyl) branched at C2 position of 3,6-anhydro-galactose. The immunomodulatory activity of PS2 was evaluated on RAW264.7 cells, and the results showed PS2 could increase nitric oxide (NO) production and enhanced the phagocytic activity of macrophages. Moreover, PS2 could significantly promote proliferation of T lymphocyte and potentiated the nature kill cell (NK) activity. These findings suggest that PS2 could be potentially developed as a novel valuable immunomodulator.

Looking Beyond the Terrestrial: The Potential of Seaweed Derived Bioactives to Treat Non-Communicable Diseases

Seaweeds are a large and diverse group of marine organisms that are commonly found in the maritime regions of the world. They are an excellent source of biologically active secondary metabolites and have been shown to exhibit a wide range of therapeutic properties, including anti-cancer, anti-oxidant, anti-inflammatory and anti-diabetic activities. Several Asian cultures have a strong tradition of using different varieties of seaweed extensively in cooking as well as in herbal medicines preparations. As such, seaweeds have been used to treat a wide variety of health conditions such as cancer, digestive problems, and renal disorders. Today, increasing numbers of people are adopting a "westernised lifestyle" characterised by low levels of physical exercise and excessive calorific and saturated fat intake. This has led to an increase in numbers of chronic Non-communicable diseases (NCDs) such as cancer, cardiovascular disease, and diabetes mellitus, being reported. Recently, NCDs have replaced communicable infectious diseases as the number one cause of human mortality. Current medical treatments for NCDs rely mainly on drugs that have been obtained from the terrestrial regions of the world, with the oceans and seas remaining largely an untapped reservoir for exploration. This review focuses on the potential of using seaweed derived bioactives including polysaccharides, antioxidants and fatty acids, amongst others, to treat chronic NCDs such as cancer, cardiovascular disease and diabetes mellitus.