Structure and anticoagulant activity of sulfated galactans. Isolation of a unique sulfated galactan from the red algae Botryocladia occidentalis and comparison of its anticoagulant action with that of sulfated galactans from invertebrates

Structure and rheology of the polysaccharides from Schizymenia dubyi: Isolation of an unusual glucurono-carrageenan

The system of polysaccharides from Schizymenia dubyi (Nemastomatales) was investigated. It contains a mixture of hybrid dl galactans (SH-S) and carrageenan-like polysaccharides, which were separated by means of precipitation with KCl at high concentrations. The structural features of the carrageenan-like fraction (SH-I) were investigated by methylation analysis, desulfation, uronic acid reduction, and NMR spectroscopy. It was concluded that the structure has the typical alternance α-(1 → 3), β-(1 → 4) of d-galactose units, with most of the 3-linked units sulfated in O-2 (and some in O-4), and most of the 4-linked units sulfated in O-3, and substituted in O-2 by single stubs of β-d-glucuronic acid (partly sulfated in each of the three available positions). This substituent has been only seldom found in red seaweed galactans. Rheological studies of 5 % and 10 % w/v SH, SH-S and SH-I aqueous systems, either without ions, or in KCl or CaCl2 solution gave thickening behaviors. Their random coil conformations justify the pseudoplastic behavior observed in the viscosity versus shear rate curves. As SH-S and SH-I are both contained in SH, an interpenetrating network could form in SH between the glucurono-carrageenan and the agaran, as inferred from the mechanical spectra recorded in water, especially with potassium ion.

Antidiabetic potentials of crude and purified sulphated polysaccharides isolated from Gracilaria gracilis, a seaweed from South Africa

Over 90 % of all cases of diabetes that have been diagnosed are type 2 diabetes (T2D), a disease exacerbated by an increase in sedentary behaviour, bad eating habits, and obesity. This study investigated the antidiabetic properties of Gracilaria gracilis, using in vitro and ex vivo experimental models. The sulphated polysaccharides (SPs) from crude extracts of the seaweed powder was prepared via hot (100°C) and cold (25°C) aqueous extraction procedures before purification via an anion exchange chromatographic technique. Both the crude and purified extracts were characterised by Fourier-transform infrared spectroscopy (FT-IR), LC-MS analysis, and Nuclear Magnetic Resonance (NMR) spectroscopy. The crude cold-aqueous and purified hot-aqueous SPs from G. gracilis had the strongest α-glucosidase inhibitory effect with IC50 value of 0.15 and 0.07 mg/ml, respectively. The purified cold-aqueous SP was the most potent inhibitor of α-glucosidase with an IC50 value of 0.17 mg/ml. The crude and purified SP-rich extracts inhibited pancreatic lipase (hot aqueous SP = 0.03 mg/ml) activity and effectively stimulated glucose uptake in yeast cells. Moreover, they showed significantly (p < 0.05) better intestinal glucose absorption inhibitory properties at the highest concentration (1 mg/ml) and displayed significantly (p < 0.05) better muscle glucose uptake compared to the commercial antidiabetic drug, metformin, at the same concentration. Overall, the current findings indicate that G. gracilis SPs may inhibit carbohydrate-hydrolysing enzymes, limit the release of simple sugars from the gut whilst effectively stimulating the use of glucose by peripheral tissue thus may be suitable to develop antidiabetic food supplements after further animal and clinical trials.

Ulvans are not equal - Linkage and substitution patterns in ulvan polysaccharides differ with Ulva morphology

Ulva are hardy green seaweeds that contain the sulfated polysaccharide ulvan and grow in two distinct morphologies: foliose and tubular. The authors hypothesise that ulvan from tubular species are more structurally complex than ulvans from foliose species. Herein, using standardised methods, the glycosyl linkage positions and sulfate ester substitutions of constituent monosaccharides of ulvan isolated from foliose (U. lacinulata and U. stenophylloides) and tubular (U. prolifera and U. ralfsii) species of Ulva were investigated. Comparison of native ulvans with 80 and 100 °C desulfated counterparts indicated that 4-linked rhamnose is predominantly 3-O-sulfated in all four ulvans. Ulvans from the foliose species predominantly contained →3,4)-Rhap-(1→, →4)-GlcAp-(1→ and →4)-IdoAp-(1→, collectively accounting for 67 to 81 mol% of the total linkages. In contrast, these same linkages in ulvans from the tubular species only collectively accounted for 29 to 36 mol%. Instead, ulvan from tubular species contained a combination of →2,3,4)-Rhap-(1→, terminal Rhap-(1→, →4)-GlcAp-(1→, →4)-Xylp-(1→, and/or →4)-Galp-(1→ in high proportions; some of the latter three residues were also likely O-2 sulfated. The results presented here suggest that ulvan from foliose species are predominantly unbranched polysaccharides composed of repeat disaccharides while ulvans from tubular species contain a greater diversity of branch and sulfate substitution locations.

Structural characterization of a Chlorella heteropolysaccharide by analyzing its depolymerized product and finding an inducer of human dendritic cell maturation

Chlorella polysaccharides have been gaining increasing attention because of their high yield from dried Chlorella powder and their remarkable immunomodulatory activity. In this study, the major polysaccharide fraction, CPP-3a, in Chlorella pyrenoidosa, was isolated, and its detailed structure was investigated by analyzing the low-molecular-weight product prepared via free radical depolymerization. The results indicated that CPP-3a with a molecular weight of 195.2 kDa was formed by →2)-α-L-Araf-(1→, →2)-α-D-Rhap-(1→, →5)-α-L-Araf-(1→, →3)-β-D-Glcp-(1→, →4)-α-D-Glcp-(1→, →4)-α-D-GlcpA-(1→, →2,3)-α-D-Manp-(1→, →3,4)-α-D-Manp-(1→, →3,4)-β-D-Galp-(1→, →3,6)-β-D-Galp-(1→, and →2,3,6)-α-D-Galp-(1→ residues, branched at C2, C3, C4, or C6 of α/β-D-Galp and α-D-Manp, and terminated by α/β-L-Araf, α-L-Arap, α-D-Galp, and β-D-Glcp. Biological assays showed that CPP-3a significantly altered the dendritic morphology of immature dendritic cells (DCs). Enhanced CD80, CD86, and MHC I expression on the cell surface and decreased phagocytic ability indicated that CPP-3a could induce the maturation of DCs. Furthermore, CPP-3a-stimulated DCs not only stimulated the proliferation of allogeneic naïve CD4+ T cells and the secretion of IFN-γ, but also directly stimulated the activation and proliferation of CD8+ T cells through cross-antigen presentation. These findings indicate that CPP-3a can promote human DC maturation and T-cell stimulation and may be a novel DC maturation inducer with potential developmental value in DC immunotherapy.

Marine Compounds and Age-Related Diseases: The Path from Pre-Clinical Research to Approved Drugs for the Treatment of Cardiovascular Diseases and Diabetes

Ageing represents a main risk factor for several pathologies. Among them, cardiovascular diseases (CVD) and type 2 diabetes mellitus (T2DM) are predominant in the elderly population and often require prolonged use of multiple drugs due to their chronic nature and the high proportion of co-morbidities. Hence, research is constantly looking for novel, effective molecules to treat CVD and T2DM with minimal side effects. Marine active compounds, holding a great diversity of chemical structures and biological properties, represent interesting therapeutic candidates to treat these age-related diseases. This review summarizes the current state of research on marine compounds for the treatment of CVD and T2DM, from pre-clinical studies to clinical investigations and approved drugs, highlighting the potential of marine compounds in the development of new therapies, together with the limitations in translating pre-clinical results into human application.

Hydrocolloid-based nutraceutical delivery systems: Potential of κ-carrageenan hydrogel beads for sustained release of curcumin

This study investigates the potential of κ-carrageenan hydrogel beads as a delivery system for curcumin, a bioactive compound with various health benefits. Hydrogel beads were prepared using the extrusion technique with a hypodermic needle. The encapsulation efficiency of curcumin in the κ-carrageenan hydrogel beads was found to be 74.61 ± 3.2 %. FTIR spectroscopy analysis revealed shifts in absorption peaks, indicating possible hydrogen bonding and/or ionic interactions between the polymer and salt. An increase in the melting point of curcumin, by 25 °C, in curcumin- κ-carrageenan beads suggests the heat protection offered by the carrageenan chains to curcumin molecules. The in vitro release of curcumin from the beads suggests a sustained and pH-dependent release nature. The release kinetics follow the first order and the Korsmeyer-Peppas model. The outcome offers value-added delivery systems of bioactive compounds toward developing novel food and pharmaceutical applications.

Nuclear magnetic resonance-based structural elucidation of novel marine glycans and derived oligosaccharides

Marine glycans of defined structures are unique representatives among all kinds of structurally complex glycans endowed with important biological actions. Besides their unique biological properties, these marine sugars also enable advanced structure-activity relationship (SAR) studies given their distinct and defined structures. However, the natural high molecular weights (MWs) of these marine polysaccharides, sometimes even bigger than 100 kDa, pose a problem in many biophysical and analytical studies. Hence, the preparation of low MW oligosaccharides becomes a strategy to overcome the problem. Regardless of the polymeric or oligomeric lengths of these molecules, structural elucidation is mandatory for SAR studies. For this, nuclear magnetic resonance (NMR) spectroscopy plays a pivotal role. Here, we revisit the NMR-based structural elucidation of a series of marine sulfated poly/oligosaccharides discovered in our laboratory within the last 2 years. This set of structures includes the α-glucan extracted from the bivalve Marcia hiantina; the two sulfated galactans extracted from the red alga Botryocladia occidentalis; the fucosylated chondroitin sulfate isolated from the sea cucumber Pentacta pygmaea; the oligosaccharides produced from the fucosylated chondroitin sulfates from this sea cucumber species and from another species, Holothuria floridana; and the sulfated fucan from this later species. Specific 1H and 13C chemical shifts, generated by various 1D and 2D homonuclear and heteronuclear NMR spectra, are exploited as the primary source of information in the structural elucidation of these marine glycans.

Structure and Binding Properties to Blood Co-Factors of the Least Sulfated Galactan Found in the Cell Wall of the Red Alga Botryocladia occidentalis

Three different populations of sulfated polysaccharides can be found in the cell wall of the red alga Botryocladia occidentalis. In a previous work, the structures of the two more sulfated polysaccharides were revised. In this work, NMR-based structural analysis was performed on the least sulfated polysaccharide and its chemically modified derivatives. Results have revealed the presence of both 4-linked α- and 3-linked β-galactose units having the following chemical features: more than half of the total galactose units are not sulfated, the α-units occur primarily as 3,6-anhydrogalactose units either 2-O-methylated or 2-O-sulfated, and the β-galactose units can be 4-O-sulfated or 2,4-O-disulfated. SPR-based results indicated weaker binding of the least sulfated galactan to thrombin, factor Xa, and antithrombin, but stronger binding to heparin cofactor II than unfractionated heparin. This report together with our previous publication completes the structural characterization of the three polysaccharides found in the cell wall of the red alga B. occidentalis and correlates the impact of their composing chemical groups with the levels of interaction with the blood co-factors.

Chemically modified galactans of Grateloupia indica: From production to in vitro antiviral activity

Herpes simplex viruses (HSVs) have an affinity for heparan sulfate proteoglycans on cell surfaces, which is a determinant for virus entry. Herein, several sulfated galactans that mimic the active domain of the entry receptor were employed to prevent HSV infection. They were produced from Grateloupia indica using chlorosulfonic acid-pyridine (ClSO3H.Py)/N,N-dimethylformamide reagent (fraction G-402), SO3.Py/DMF reagent (G-403), or by aqueous extraction (G-401). These galactans contained varied molecular masses (33-55 kDa), and sulfate contents (12-20 %), and have different antiviral activities. Especially, the galactan (G-402) generated by using ClSO3H.Py/DMF, a novel reagent, exhibited the highest level of antiviral activity (EC50 = 0.36 μg/mL) compared to G-403 (EC50 = 15.6 μg/mL) and G-401 (EC50 = 17.9 μg/mL). This most active sulfated galactan possessed a linear chain containing β-(1 → 3)- and α-(1 → 4)-linked Galp units with sulfate group at the O-2/4/6 and O-2/3/6 positions, respectively. The HSV-1 and HSV-2 strains were specifically inhibited by this novel 33 ± 15 kDa galactan, which also blocked the virus from entering the host cell. These results highlight the significant potential of this sulfated galactan for antiviral research and drug development. Additionally, the reagent used for the effective conversion of galactan hydroxy groups to sulfate during extraction may also be useful for the chemical transformation of other natural products.

Structure, anti-SARS-CoV-2, and anticoagulant effects of two sulfated galactans from the red alga Botryocladia occidentalis

The structure of the sulfated galactan from the red alga Botryocladia occidentalis (BoSG) was originally proposed as a simple repeating disaccharide of alternating 4-linked α-galactopyranose (Galp) and 3-linked β-Galp units with variable sulfation pattern. Abundance was estimated only for the α-Galp units: one-third of 2,3-disulfation and one-third of 2-monosulfation. Here, we isolated again the same BoSG fractions from the anion-exchange chromatography, obtaining the same NMR profile of the first report. More careful NMR analysis led us to revise the structure. A more complex sulfation pattern was noted along with the occurrence of 4-linked α-3,6-anhydro-Galp (AnGalp) units. Interestingly, the more sulfated BoSG fraction showed slightly reduced in vitro anti-SARS-CoV-2 activities against both wild-type and delta variants, and significantly reduced anticoagulant activity. The BoSG fractions showed no cytotoxic effects. The reduction in both bioactivities is attributed to the presence of the AnGalp unit. Docking scores from computational simulations using BoSG disaccharide constructs on wild-type and delta S-proteins, and binding analysis through competitive SPR assays using blood (co)-factors (antithrombin, heparin cofactor II and thrombin) and four S-proteins (wild-type, delta, gamma, and omicron) strongly support the conclusion about the deleterious impact of the AnGalp unit.

Seaweed polysaccharides treatment alleviates injury of inflammatory responses and gut barrier in LPS-induced mice

Gastrointestinal (GI) disease is a common digestive tract disease effects health of millions of human globally each year, thus the role of intestinal microflora had been emphasized. Seaweed polysaccharides featured a wide range of pharmacological activities, such as antioxidant activity and pharmacological action, but whether they can alleviate the dysbiosis of gut microbial ecology caused by lipopolysaccharide (LPS) exposure has not been well conducted. In this study, we investigated the effects of different concentration of seaweed polysaccharides on LPS-induced intestinal disorder by using microscope and 16S rRNA high-throughput sequencing. Histopathological results indicated that the intestinal structure in the LPS-induced group was damaged. Furthermore, LPS exposure not only reduced the intestinal microbial diversity in mice but also induced momentous transformation in its composition, including a significantly increased in some pathogenic bacteria (Helicobacter, Citrobacter and Mucispirillum) and decreased in several beneficial bacteria (Firmicutes, Lactobacillus, Akkermansia and Parabacteroides). Nonetheless, seaweed polysaccharide administration could recover the gut microbial dysbiosis and the loss of gut microbial diversity induced by LPS exposure. In summary, seaweed polysaccharides were effective against LPS-induced intestinal damage in mice via the modulation of intestinal microecology.

Antiviral activity of marine sulfated glycans against pathogenic human coronaviruses

Great interest exists towards the discovery and development of broad-spectrum antivirals. This occurs due to the frequent emergence of new viruses which can also eventually lead to pandemics. A reasonable and efficient strategy to develop new broad-spectrum antivirals relies on targeting a common molecular player of various viruses. Heparan sulfate is a sulfated glycosaminoglycan present on the surface of cells which plays a key role as co-receptor in many virus infections. In previous work, marine sulfated glycans (MSGs) were identified as having antiviral activities. Their mechanism of action relies primarily on competitive inhibition of virion binding to heparan sulfate, preventing virus attachment to the cell surface prior to entry. In the current work we used pseudotyped lentivirus particles to investigate in a comparative fashion the inhibitory properties of five structurally defined MSGs against SARS-CoV-1, SARS-CoV-2, MERS-CoV, and influenza A virus (IAV). MSGs include the disaccharide-repeating sulfated galactan from the red alga Botryocladia occidentalis, the tetrasaccharide-repeating sulfated fucans from the sea urchin Lytechinus variegatus and from the sea cucumber Isostichopus badionotus, and the two marine fucosylated chondroitin sulfates from the sea cucumbers I. badionotus and Pentacta pygmaea. Results indicate specificity of action against SARS-CoV-1 and SARS-CoV-2. Curiously, the MSGs showed decreased inhibitory potencies against MERS-CoV and negligible action against IAV. Among the five MSGs, the two sulfated fucans here studied deserve further attention since they have the lowest anticoagulant effects but still present potent and selective antiviral properties.

Partial characterization and anticoagulant activity of sulfated galactan from the green seaweed Halimeda opuntia

The number of deaths associated with cardiovascular diseases (CVD) increases every year, leading to an intense search for new compounds that may be employed as anticoagulants. One of the classes of bioprospected molecules comprises sulfated polysaccharides (SP) from seaweed, as heparin displays many adverse effects associated with its use. The present study aimed to characterize and evaluate the anticoagulant potential of SP extracted from the green algae Halimeda opuntia. Four PS-rich fractions, F23, F44, F60 and F75, were obtained by proteolytic digestion in papain followed by ethanol precipitation. The presence of SP was confirmed by agarose gel electrophoresis, revealing different populations in each fraction. The F44 fraction is noteworthy compared to the other fractions, presenting a 5% yield compared to the initial algae weight and anticoagulant activity revealed by the activated partial thromboplastin time (APTT) assay (intrinsic/common coagulation pathway). Surprisingly, F44 purification (SP peak P1F44) resulted in prothrombin time (PT) activity (extrinsic coagulation pathway) at a 160 µg/mL, in addition to enhanced APTT activity. The P1F44 anticoagulant activity mechanism was shown to be dependent on two coagulations factors, IIa and Xa, more potent via IIa. Future assessments will be performed to assess this fraction in the medical clinic.

Anti-SARS-CoV-2 and anticoagulant properties of Pentacta pygmaea fucosylated chondroitin sulfate depend on high molecular weight structures

Fucosylated chondroitin sulfate (FucCS) is a unique marine glycosaminoglycan that exhibits diverse biological functions, including antiviral and anticoagulant activity. In previous work, the FucCS derived from Pentacta pygmaea (PpFucCS) showed moderate anticoagulant effect but high inhibitory activity against the Wuhan strain of severe acute respiratory syndrome coronavirus (SARS-CoV-2). In this study, we perform free-radical depolymerization of PpFucCS by the copper-based Fenton method to generate low molecular weight (MW) oligosaccharides. PpFucCS oligosaccharides were structurally analyzed by 1H nuclear magnetic resonance spectroscopy and were used to conduct structure-activity relationship studies regarding their effects against SARS-CoV-2 and clotting. Anticoagulant properties were measured by activated partial thromboplastin time, protease (factors Xa and IIa) inhibition by serine protease inhibitors (antithrombin [AT] and heparin cofactor II [HCII]), and competitive surface plasmon resonance (SPR) assay using AT, HCII, and IIa. Anti-SARS-CoV-2 properties were measured by the concentration-response inhibitory curves of HEK-293T-human angiotensin-converting enzyme-2 cells infected with a baculovirus pseudotyped SARS-CoV-2 Delta variant spike (S)-protein and competitive SPR assays using multiple S-proteins (Wuhan, N501Y [Alpha], K417T/E484K/N501Y [Gamma], L542R [Delta], and Omicron [BA.2 subvariant]). Cytotoxicity of native PpFucCS and oligosaccharides was also assessed. The PpFucCS-derived oligosaccharide fraction of the highest MW showed great anti-SARS-CoV-2 Delta activity and reduced anticoagulant properties. Results have indicated no cytotoxicity and MW dependency on both anti-SARS-CoV-2 and anticoagulant effects of PpFucCS, as both actions were reduced accordingly to the MW decrease of PpFucCS. Our results demonstrate that the high-MW structures of PpFucCS is a key structural element to achieve the maximal anti-SARS-CoV-2 and anticoagulant effects.

Structural requirements of Holothuria floridana fucosylated chondroitin sulfate oligosaccharides in anti-SARS-CoV-2 and anticoagulant activities

Fucosylated chondroitin sulfate (FucCS) is a unique glycosaminoglycan found primarily in sea cucumbers. This marine sulfated glycan is composed of a chondroitin sulfate backbone decorated with fucosyl branches attached to the glucuronic acid. FucCS exhibits potential biological actions including inhibition of blood clotting and severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection. These biological effects have been attributed to certain structural features, including molecular weight (MW), and/or those related to fucosylation, such as degrees of fucosyl branches, sulfation patterns and contents. In a previous work, we were able to generate oligosaccharides of the FucCS from Pentacta pygmaea (PpFucCS) with reduced anticoagulant effect but still retaining significant anti-SARS-CoV-2 activity against the delta strain. In this work, we extended our study to the FucCS extracted from the species Holothuria floridana (HfFucCS). The oligosaccharides were prepared by free-radical depolymerization of the HfFucCS via copper-based Fenton reaction. One-dimensional 1H nuclear magnetic resonance spectra were employed in structural analysis. Activated partial thromboplastin time and assays using protease (factors Xa and IIa) and serine protease inhibitors (antithrombin, and heparin cofactor II) in the presence of the sulfated carbohydrates were used to monitor anticoagulation. Anti-SARS-CoV-2 effects were measured using the concentration-response inhibitory curves of HEK-293T-human angiotensin-converting enzyme-2 cells infected with a baculovirus pseudotyped SARS-CoV-2 wild-type and delta variant spike (S)-proteins. Furthermore, the cytotoxicity of native HfFucCS and its oligosaccharides was also assessed. Like for PpFucCS, we were able to generate a HfFucCS oligosaccharide fraction devoid of high anticoagulant effect but still retaining considerable anti-SARS-CoV-2 actions against both variants. However, compared to the oligosaccharide fraction derived from PpFucCS, the average MW of the shortest active HfFucCS oligosaccharide fraction was significantly lower. This finding suggests that the specific structural feature in HfFucCS, the branching 3,4-di-sulfated fucoses together with the backbone 4,6-di-sulfated N-acetylgalactosamines, is relevant for the anti-SARS-CoV-2 activity of FucCS molecules.

Sulfated Galactans from Gracilaria fisheri with Supplementation of Octanoyl Promote Wound Healing Activity In Vitro and In Vivo

Sulfated galactans (SG) isolated from Gracilaria fisheri is partially degraded (DSG), and subsequentially supplemented with octanoyl (DSGO) and sulfate (DSGS) groups. The molecular weights of DSG, DSGO, and DSGS are 7.87, 152.79, and 97.07 kDa, respectively. The modification is confirmed using FTIR and NMR, while in vitro wound healing activity is assessed using scratched wound fibroblasts. The results reveal that DSGO exhibits highest percentage of wound closure in scratched fibroblast L929 cells. Furthermore, DSGO is able to promote proliferation and accelerate migration of scratched fibroblasts, which correspond to the regulation of proteins and mRNA (Ki67, p-FAK, vimentin, and E-cadherin) determined by Western blotting and qPCR analysis. The superior wound healing activity of DSGO is also confirmed in excision wound of rats. The results demonstrate that DSGO significantly enhances the percentage of wound closure, re-epithelialization, and collagen arrangement, increases α-smoth muscle actin (α-SMA) and vimentin expression, and decreases that of tumor necrosis factor-α (TNF-α) at the wound site. The results suggest that degraded SG supplemented with medium-chain fatty acids of octanoyl group may pass through the membrane, subsequently activating the mediators associated with proliferation and migration of fibroblasts, which can potentially lead to the promotion of wound healing activity.

Sulfated galactofucan from seaweed Padina tetrastromatica attenuates proteolytic enzyme dipeptidyl-peptidase-4: a potential anti-hyperglycemic lead

Dipeptidyl-peptidase-4 is a multifunctional ectoenzyme, which is implicated with hyperglycemic pathophysiology. Therefore, dipeptidyl-peptidase-4 inhibitors could be used as an attractive therapeutic strategy in blood-glucose homeostasis to attenuate the pathophysiologies of diabetes. A sulfated galactofucan characterized as [→1)-O-4-sulfonato-α-fucopyranosyl-(2→1)-O-2-sulfonato-α-fucopyranose-(3→] along with a branch of [→1)-6-O-methyl-β-galactopyranosyl-(4→] unit at the C-4 position of O-2-sulfonato-α-fucopyranose, isolated from the seaweed Padina tetrastromatica, exhibited prospective attenuation property against dipeptidyl-peptidase-4 (IC50 0.25 mg mL-1). The studied sulfated galactofucan exhibited potential inhibitory properties against carbolytic enzymes α-amylase (IC50 0.98 mg mL-1) and α-glucosidase (IC50 0.87 mg mL-1) in comparison with the standard antidiabetic agent acarbose, along with radical scavenging activities. The seaweed-originated galactofucan could be developed as a promising natural therapeutic lead against hyperglycemic disorder.

Inhibition of SARS-CoV-2 wild-type (Wuhan-Hu-1) and Delta (B.1.617.2) strains by marine sulfated glycans

The Coronavirus disease pandemic has steered the global therapeutic research efforts toward the discovery of potential anti-severe acute respiratory syndrome coronavirus (SARS-CoV-2) molecules. The role of the viral spike glycoprotein (S-protein) has been clearly established in SARS-CoV-2 infection through its capacity to bind to the host cell surface heparan sulfate proteoglycan (HSPG) and angiotensin-converting enzyme-2. The antiviral strategies targeting these 2 virus receptors are currently under intense investigation. However, the rapid evolution of the SARS-CoV-2 genome has resulted in numerous mutations in the S-protein posing a significant challenge for the design of S-protein-targeted inhibitors. As an example, the 2 key mutations in the S-protein receptor-binding domain (RBD), L452R, and T478K in the SARS-CoV-2 Delta variant (B.1.617.2) confer tighter binding to the host epithelial cells. Marine sulfated glycans (MSGs) demonstrate excellent inhibitory activity against SARS-CoV-2 via competitive disruption of the S-protein RBD-HSPG interactions and thus have the potential to be developed into effective prophylactic and therapeutic molecules. In this study, 7 different MSGs were evaluated for their anti-SARS-CoV-2 activity in a virus entry assay utilizing a SARS-CoV-2 pseudovirus coated with S-protein of the wild-type (Wuhan-Hu-1) or the Delta (B.1.617.2) strain. Although all tested MSGs showed strong inhibitory activity against both strains, no correlations between MSG structural features and virus inhibition could be drawn. Nevertheless, the current study provides evidence for the maintenance of inhibitory activity of MSGs against evolving SARS-CoV-2 strains.

Biological properties and potential of compounds extracted from red seaweeds

Macroalgae have been recently used for different applications in the food, cosmetic and pharmaceutical industry since they do not compete for land and freshwater against other resources. Moreover, they have been highlighted as a potential source of bioactive compounds. Red algae (Rhodophyta) are the largest group of seaweeds, including around 6000 different species, thus it can be hypothesized that they are a potential source of bioactive compounds. Sulfated polysaccharides, mainly agar and carrageenans, are the most relevant and exploited compounds of red algae. Other potential molecules are essential fatty acids, phycobiliproteins, vitamins, minerals, and other secondary metabolites. All these compounds have been demonstrated to exert several biological activities, among which antioxidant, anti-inflammatory, antitumor, and antimicrobial properties can be highlighted. Nevertheless, these properties need to be further tested on in vivo experiments and go in-depth in the study of the mechanism of action of the specific molecules and the understanding of the structure-activity relation. At last, the extraction technologies are essential for the correct isolation of the molecules, in a cost-effective way, to facilitate the scale-up of the processes and their further application by the industry. This manuscript is aimed at describing the fundamental composition of red algae and their most studied biological properties to pave the way to the utilization of this underused resource.

Increased Sulfation in Gracilaria fisheri Sulfated Galactans Enhances Antioxidant and Antiurolithiatic Activities and Protects HK-2 Cell Death Induced by Sodium Oxalate

Urolithiasis is a common urological disease characterized by the presence of a stone anywhere along the urinary tract. The major component of such stones is calcium oxalate, and reactive oxygen species act as an essential mediator of calcium oxalate crystallization. Previous studies have demonstrated the antioxidant and antiurolithiatic activities of sulfated polysaccharides. In this study, native sulfated galactans (N-SGs) with a molecular weight of 217.4 kDa from Gracilaria fisheri were modified to obtain lower molecular weight SG (L-SG) and also subjected to sulfation SG (S-SG). The in vitro antioxidant and antiurolithiatic activities of the modified substances and their ability to protect against sodium oxalate-induced renal tubular (HK-2) cell death were investigated. The results revealed that S-SG showed more pronounced antioxidant activities (DPPH and O₂^- scavenging activities) than those of other compounds. S-SG exhibited the highest antiurolithiatic activity in terms of nucleation and aggregation, as well as crystal morphology and size. Moreover, S-SG showed improved cell survival and increased anti-apoptotic BCL-2 protein in HK-2 cells treated with sodium oxalate. Our findings highlight the potential application of S-SG in the functional food and pharmaceutical industries.

Fractionation of sulfated galactan from the red alga Botryocladia occidentalis separates its anticoagulant and anti-SARS-CoV-2 properties

Sulfation pattern and molecular weight (MW) play a key role in the biological actions of sulfated glycans. Besides anticoagulant effects, certain sulfated glycans can also exhibit anti-SARS-CoV-2 properties. To develop a more selective antiviral carbohydrate, an efficient strategy to separate these two actions is required. In this work, low MW fractions derived from the red alga Botryocladia occidentalis sulfated galactan (BoSG) were generated, structurally characterized, and tested for activity against SARS-CoV-2 and blood coagulation. The lowest MW fraction was found to be primarily composed of octasaccharides of monosulfated monosaccharides. Unlike heparin or native BoSG, we found that hydrolyzed BoSG products had weak anticoagulant activities as seen by aPTT and inhibitory assays using purified cofactors. In contrast, lower MW BoSG-derivatives retained anti-SARS-CoV-2 activity using SARS-CoV-2 spike (S)-protein pseudotyped lentivirus vector in HEK-293T-hACE2 cells monitored by GFP. Surface plasmon resonance confirmed that longer chains are necessary for BoSG to interact with coagulation cofactors but is not required for interactions with certain S-protein variants. We observed distinct affinities of BoSG derivatives for the S-proteins of different SARS-CoV-2 strains, including WT, N501Y (Alpha), K417T/E484K/N501Y (Gamma), and L542R (Delta) mutants, and stronger affinity for the N501Y-containing variants. Docking of the four possible monosulfated BoSG disaccharides in interactions with the N501Y mutant S-protein predicted potential binding poses of the BoSG constructs and favorable binding in close proximity to the 501Y residue. Our results demonstrate that depolymerization and fractionation of BoSG are an effective strategy to segregate its anticoagulant property from its anti-SARS-CoV-2 action.

An Overview of Potential Seaweed-Derived Bioactive Compounds for Pharmaceutical Applications

Nowadays, seaweeds are widely involved in biotechnological applications. Due to the variety of bioactive compounds in their composition, species of phylum Ochrophyta, class Phaeophyceae, phylum Rhodophyta and Chlorophyta are valuable for the food, cosmetic, pharmaceutical and nutraceutical industries. Seaweeds have been consumed as whole food since ancient times and used to treat several diseases, even though the mechanisms of action were unknown. During the last decades, research has demonstrated that those unique compounds express beneficial properties for human health. Each compound has peculiar properties (e.g., antioxidant, antimicrobial, antiviral activities, etc.) that can be exploited to enhance human health. Seaweed’s extracted polysaccharides are already involved in the pharmaceutical industry, with the aim of replacing synthetic compounds with components of natural origin. This review aims at a better understanding of the recent uses of algae in drug development, with the scope of replacing synthetic compounds and the multiple biotechnological applications that make up seaweed’s potential in industrial companies. Further research is needed to better understand the mechanisms of action of seaweed’s compounds and to embrace the use of seaweeds in pharmaceutical companies and other applications, with the final scope being to produce sustainable and healthier products.

OUP accepted manuscript

Ammonia-oxidising archaea (AOA) are environmentally important microorganisms involved in the biogeochemical cycling of nitrogen. Routine cultivation of AOA is exclusively performed in liquid cultures and reports on their growth on solid medium are scarce. The ability to grow AOA on solid medium would be beneficial for not only the purification of enrichment cultures but also for developing genetic tools. The aim of this study was to develop a reliable method for growing individual colonies from AOA cultures on solid medium. Three phylogenetically distinct AOA strains were tested: ‘Candidatus Nitrosocosmicus franklandus C13’, Nitrososphaera viennensis EN76 and ‘Candidatus Nitrosotalea sinensis Nd2’. Of the gelling agents tested, agar and Bacto-agar severely inhibited growth of all three strains. In contrast, both ‘Ca. N. franklandus C13’ and N. viennensis EN76 tolerated Phytagel™ while the acidophilic ‘Ca. N. sinensis Nd2’ was completely inhibited. Based on these observations, we developed a Liquid-Solid (LS) method that involves immobilising cells in Phytagel™ and overlaying with liquid medium. This approach resulted in the development of visible distinct colonies from ‘Ca. N. franklandus C13’ and N. viennensis EN76 cultures and lays the groundwork for the genetic manipulation of this group of microorganisms.

Structural characterization and protective effects of polysaccharide from Gracilaria lemaneiformis on LPS-induced injury in IEC-6 cells

This study was aimed to characterize Gracilaria lemaneiformis polysaccharides and evaluate their protective effects on Lipopolysaccharide-induced injury in IEC-6 cells. The G. lemaneiformis polysaccharide was degraded by UV/H₂O₂ treatment and purified to three fractions named GLP-1.0 M, GLP-1.4 M and GLP-1.6 M. The purified fractions were mainly composed of galactose, glucose and xylose. The structural analysis showed that GLP-1.6 M was a typical sulfated red alga polysaccharide containing the linear backbone of β-(1 → 3)- and α-(1 → 4)-linked galactosyl residues, anhydro-galactose units. In the Lipopolysaccharide-induced IEC-6 cells model, GLP-1.6 M exerted the strongest in vitro anti-inflammatory activity by inhibiting the release and expressions of tumor necrosis factor-α, interleukin-6 and interleukin-1β by 89.93%, 67.82% and 38.06%, respectively. Meanwhile, GLP-1.6 M enhanced the intestinal barrier function via up-regulating the expressions of tight junctions and mucin. Therefore, the purified polysaccharide from G. lemaneiformis could be a promising candidate for maintaining intestinal health in the food and pharmaceutical industries.

Cognition of polysaccharides from confusion to clarity: when the next "omic" will come?

With the accelerated pace of modern life, people are facing more and more health pressure. The study of polysaccharides seemed a good choice as a potential treasure trove. Polysaccharides, one of the four basic substances (proteins, nucleic acids, lipids and carbohydrates) that constitute life activities, are obviously an underrated macromolecular substance with great potential. Compared with protein and nucleic acid, the research of polysaccharides is still in the primary stage. The relationship between structure and function of polysaccharides is not clear. In this review, we highlighted the main methods of extraction, purification and structure identification of polysaccharides; summarized their biological activities including immunoregulation, hypoglycemic, anti-tumor, anti-virus, anti-coagulation, and so on. Particularly, the relationship between their structures and activities was described. In addition, the applications of polysaccharides in health food, medicine and cosmetics were also reviewed. This review can help polysaccharide researchers quickly understand the whole process of polysaccharides research, and also provide a reference for the comprehensive utilization of polysaccharides. We need to standardize the research of polysaccharides to make the experimental data more universal, and take it as important references in the review process. Glycomic may appear as the next "omic" after genomic and proteomic in the future. This review provides support for the advancement of glycomics.

Structural and kinetic analyses of holothurian sulfated glycans suggest potential treatment for SARS-CoV-2 infection

Certain sulfated glycans, including those from marine sources, can show potential effects against SARS-CoV-2. Here, a new fucosylated chondroitin sulfate (FucCS) from the sea cucumber Pentacta pygmaea (PpFucCS) (MW ∼10-60 kDa) was isolated and structurally characterized by NMR. PpFucCS is composed of {→3)-β-GalNAcX-(1→4)-β-GlcA-[(3→1)Y]-(1→}, where X = 4S (80%), 6S (10%) or nonsulfated (10%), Y = α-Fuc2,4S (40%), α-Fuc2,4S-(1→4)-α-Fuc (30%), or α-Fuc4S (30%), and S = SO3-. The anti-SARS-CoV-2 activity of PpFucCS and those of the FucCS and sulfated fucan isolated from Isostichopus badionotus (IbFucCS and IbSF) were compared with that of heparin. IC50 values demonstrated the activity of the three holothurian sulfated glycans to be ∼12 times more efficient than heparin, with no cytotoxic effects. The dissociation constant (KD) values obtained by surface plasmon resonance of the wildtype SARS-CoV-2 spike (S)-protein receptor-binding domain (RBD) and N501Y mutant RBD in interactions with the heparin-immobilized sensor chip were 94 and 1.8 × 103 nM, respectively. Competitive surface plasmon resonance inhibition analysis of PpFucCS, IbFucCS, and IbSF against heparin binding to wildtype S-protein showed IC50 values (in the nanomolar range) 6, 25, and 6 times more efficient than heparin, respectively. Data from computational simulations suggest an influence of the sulfation patterns of the Fuc units on hydrogen bonding with GlcA and that conformational change of some of the oligosaccharide structures occurs upon S-protein RBD binding. Compared with heparin, negligible anticoagulant action was observed for IbSF. Our results suggest that IbSF may represent a promising molecule for future investigations against SARS-CoV-2.

Red Algal Sulfated Galactan Binds and Protects Neural Cells from HIV-1 gp120 and Tat

The potential neuroprotective capacity of four different sulfated glycans: Botryocladia occidentalis-derived sulfated galactan (BoSG) (MW > 100 kDa), Lytechinus variegatus-derived sulfated fucan (LvSF) (MW~90 kDa), high-molecular weight dextran sulfate (DxS) (MW 100 kDa), and unfractionated heparin (UFH) (MW~15 kDa), was assessed in response to the HIV-1 proteins, R5-tropic glycoprotein 120 (gp120) and/or trans-activator of transcription (Tat), using primary murine neurons co-cultured with mixed glia. Compared to control-treated cells in which HIV-1 proteins alone or combined were neurotoxic, BoSG was, among the four tested sulfated glycans, the only one capable of showing significant concentration-dependent neuroprotection against Tat and/or gp120, alone or combined. Surface plasmon resonance-based data indicate that BoSG can bind both HIV-1 proteins at nM concentrations with preference for Tat (7.5 × 10⁻⁸ M) over gp120 (3.2 × 10⁻⁷ M) as compared to UFH, which bound gp120 (8.7 × 10⁻⁷ M) over Tat (5.7 × 10⁻⁶ M). Overall, these data support the notion that sulfated glycan extracted from the red alga B. occidentalis, BoSG, can exert neuroprotection against HIV-1 Tat and gp120, potentially via direct molecular interactions.

Antimicrobial Properties of Actively Purified Secondary Metabolites Isolated from Different Marine Organisms

BACKGROUND

The treatment of infection caused by pathogenic bacteria becomes one of the serious concerns globally. The failure in the treatment was found due to the exhibition of multiple resistance mechanisms against the antimicrobial agents. The emergence of resistant bacterial species has also been observed due to prolong treatment using conventional antibiotics. To combat these problems, several alternative strategies have been employed using biological and chemically synthesized compounds as antibacterial agents. Marine organisms are considered as one of the potential sources for the isolation of bioactive compounds due to the easily available, cost-effective, and eco-friendly.

METHODS

The online search methodology was adapted for the collection of information related to the antimicrobial properties of marine-derived compounds. These compound has been isolated and purified by different purification techniques, and their structure also characterized. Furthermore, the antibacterial activities have been reported by using broth microdilution as well as disc diffusion assays.

RESULTS

The present review paper describes the antimicrobial effect of diverse secondary metabolites which are isolated and purified from the different marine organisms. The structural elucidation of each secondary metabolite has also been done in the present paper, which will help for the in silico designing of the novel and potent antimicrobial compounds.

CONCLUSION

A thorough literature search has been made and summarizes the list of antimicrobial compounds that are isolated from both prokaryotic and eukaryotic marine organisms. The information obtained from the present paper will be helpful for the application of marine compounds as antimicrobial agents against different antibiotic-resistant human pathogenic bacteria.

Antiviral activities of four marine sulfated glycans against adenovirus and human cytomegalovirus

Broad-spectrum antivirals are more needed than ever to provide treatment options for novel emerging viruses and for viruses that lack therapeutic options or have developed resistance. A large number of viruses rely on charge-dependent non-specific interactions with heparan sulfate (HS), a highly sulfated glycosaminoglycan (GAG), for attachment to cell surfaces to initiate cell entry. As such, inhibitors targeting virion-HS interactions have potential to have broad-spectrum antiviral activity. Previous research has explored organic and inorganic small molecules, peptides, and GAG mimetics to disrupt virion-HS interactions. Here we report antiviral activities against both enveloped (the herpesvirus human cytomegalovirus) and non-enveloped (adenovirus) DNA viruses for four defined marine sulfated glycans: a sulfated galactan from the red alga Botryocladia occidentalis; a sulfated fucan from the sea urchin Lytechinus variegatus, and a sulfated fucan and a fucosylated chondroitin sulfate from the sea cucumber Isostichopus badionotus. As evidenced by gene expression, time of addition, and treatment/removal assays, all four novel glycans inhibited viral attachment and entry, most likely through interactions with virions. The sulfated fucans, which both lack anticoagulant activity, had similar antiviral profiles, suggesting that their activities are not only due to sulfation content or negative charge density but also due to other physicochemical factors such as the potential conformational shapes of these carbohydrates in solution and upon interaction with virion proteins. The structural and chemical properties of these marine sulfated glycans provide unique opportunities to explore relationships between glycan structure and their antiviral activities.

Functional foods and bioactive ingredients harnessed from the ocean: current status and future perspectives

With an increase in life expectancy and decrease of quality-of-life couple with the high prevalence of diseases, diet is expected to play a key function in sustaining human health. Nutritionists, food technologists and medical experts are working in synergy to cater for the increasing demand of food with associated therapeutic benefits, commonly known as functional food, that may improve well-being and reduce the risk of diseases. Interestingly, the marine ecosystem, due to its abundant and phenomenal biodiversity of marine organisms, constitutes a vital source of a panoply of healthy foods supply for the thriving functional food industry. Marine organisms such as seaweeds, sea cucumbers, sponges, and mollusks amongst others are sources of thousands of biologically active metabolites with antioxidant, anti-parasitic, antiviral, anti-inflammatory and anticancer properties. Given the growing number of research and interest to probe into the therapeutic roles of marine products, this review was designed to provide a comprehensive summary of the therapeutic properties of marine organisms (macroalgae, sea cucumbers and fish among others) which are consumed worldwide, in addition to their potentials and as sources of functional ingredients for developing novel food and fostering wellness. The gap between research development and actual commercialization, and future prospects of marine-based products also summarized to some extent.

Protective effect against gastric mucosa injury of a sulfated agaran from Acanthophora spicifera

In this study, a polysaccharide from marine alga Acanthophora spicifera (PAs) was isolated and structurally characterized. Its protective potential against chemically-induced gastric mucosa injury was evaluated. The gel permeation chromatography experiments and spectroscopy spectrum showed that PAs is a sulfated polysaccharide with a high molecular mass (6.98 × 10⁵g/mol) and degree of sulfation of 1.23, exhibiting structural characteristic typical of an agar-type polysaccharide. Experimental results demonstrated that PAs reduced the hemorrhagic gastric injury, in a dose-dependent manner. Additionally, PAs reduced the intense gastric oxidative stress, measured by glutathione (GSH) and malondialdehyde (MDA) levels. PAs also prevented the reduction of mucus levels adhered to the gastric mucosa, promoted by the aggressive effect of ethanol. In summary, the sulfated polysaccharide from A. spicifera protected the gastric mucosa through the prevention of lipid peroxidation and enhanced the defense mechanisms of the gastric mucosa, suggesting as a promising functional food as gastroprotective agent.

Structure and Biological Activity Analysis of Fucoidan Isolated from Sargassum siliquosum

Fucoidans are heterologous polysaccharides commonly seen in brown macroalgae and are known for their biological activity including anticancer, antiangiogenic, immunomodulation, and antiviral properties. The brown macroalga Sargassum siliquosum was used for the extraction and analysis of fucoidan in this study. The S. siliquosum fucoidan was indicated as a galactofucoidan composed of sugars, uronate, and sulfate at a ratio of 12:1:4 and its purity was 85% based on the abovementioned three major components. Structural analysis by electrospray ionization collision-induced dissociation tandem mass spectroscopy revealed that the purified fucoidan consisted of a carbohydrate chain composed of (1→3)-linked or (1→4)-linked l-fucose residues, with sulfate groups at C-2 and C-4 positions. Galactose residues with (1→4)-linkages function as the branch points and they are located at the C-3 or C-4 position of fucose residues. Galactose residues are sulfated mainly at C-4 and C-6, while some sulfation can also be seen at C-2. The fucoidan purified from S. siliquosum demonstrated antioxidant, anti-inflammatory, and antilipogenic activities.

Polygalactan from bivalve Crassostrea madrasensis attenuates nuclear factor-κB activation and cytokine production in lipopolysaccharide-activated macrophage

A polygalactosamino-glucopyranosyl fucopyranose →4)-β-GlcAp{(3→1)-α-Fucp}-β-GalNAcp-(4,6-SO₃^-)-(1→ isolated from the bivalve Crassostrea madrasensis exhibited prospective anti-inflammatory activity against cyclooxygenase-2 and 5-lipoxygenase (IC₅₀ < 50 μg mL^-1) on lipopolysaccharide-induced macrophages. The polygalactan attenuated inducible nitric oxide synthase (IC₅₀ 65.7 μg mL^-1) in lipopolysaccharide-prompted inflammation leading to the reduction of pro-inflammatory cytokine nitric oxide (236.2 μg mL^-1 lysate), nuclear factor-κB, tumor necrosis factor-α, and interleukins (0.19-0.22 units mg^-1 protein at 100 μg mL^-1) by inhibiting cyclooxygenase-2. The polygalacatan suppressed the mRNA of nuclear factor-κB and cyclooxygenase-2 in lipopolysaccharide-induced macrophages. Western blot experiment revealed that the polygalactan attenuated the migration of nuclear factor-κB-p⁶⁵ to the nucleus from cytoplasm, and suppressed the phosphorylation of α-subunit of κB inhibitor. Greater selectivity index of sulfated polygalactan (3.93) towards inducible cyclooxygenase-2 as compared with the anti-inflammatory agent ibuprofen (1.11), and the potential to inhibit nuclear factor-κB cascade to generate chemokine production manifested its utilization in the development of functional food attenuating inflammation-related disorders.

Sulfated N-acetylglucosamino-glucuronopyranosyl-arabinopyranan from seafood Amphioctopus neglectus attenuates angiotensin-II prompted cardiac hypertrophy

Angiotensin converting enzyme (ACE) is a multifunctional enzyme involved in translation of angiotensin-I (Ang^I) to vasoconstrictor angiotensin-II (Ang^II). A sulfated N-acetylglucosamino-glucuronopyranosyl-arabinopyranan characterized as poly-[(2-methoxy-β-arabinopyranosyl)-(1 → 3)-(β-glucurono)-(1 → 4)-(2-acetamido-2-deoxy-3,6-di-O-sulfonato-β-glucopyranose)] was purified and reported first time from the edible portion of Amphioctopus neglectus and evaluated for various pharmacological properties. The polysaccharide exhibited potential ACE attenuation property (IC₅₀ 0.11 mg mL^-1), whereas molecular docking simulations displayed its efficient binding at the ACE active site with lesser inhibitory constant (K_i) of 17.36 nM and binding energy (-10.59 kcal mol^-1). The in-vitro analysis showed that the studied polysacharide attenuated Ang^II prompted cardiac hypertrophy at 50 μg mL^-1 in the cardiomyoblast cells, whereas 48% reduction in cellular surface area with extended viability could be correlated with anti-hypertrophic properties of the studied polysaccharide. The sulfated N-acetylglucosamino-glucuronopyranosyl-arabinopyranan purified from A. neglectus could function as a prospective functional lead against the pathophysiological conditions leading to hypertension.

Chemical structure, anti-inflammatory and antinociceptive activities of a sulfated polysaccharide from Gracilaria intermedia algae

The present work aimed at carrying out the isolation and biochemical characterization of a sulfated polysaccharide fraction (PLS) from the marine algae Gracilaria intermedia and investigating its anti-inflammatory and antinociceptive potential. PLS was obtained through enzymatic digestion with papain and analyzed by means of gel permeation chromatography and Nuclear Magnetic Resonance to ¹H and ¹³C. In order to evaluate the potential of anti-inflammatory action of PLS, we performed paw edema induced by carrageenan, dextran, compound 48/80, histamine and serotonin. In addition, we also measured the concentration of myeloperoxidase, cytokines, the count of inflammatory cells and performed tests of the nociception. The PLS isolated was of high purity and free of contaminants such as proteins, and had molecular weight of 410 kDa. The same macromolecule was able to decrease the paw edema induced by all inflammatory agents (P < 0.05), myeloperoxidase (MPO) activity, neutrophil migration and IL-1β levels. It also decreased acetic acid-induced writhing (P < 0.05) and formalin-induced paw licking time (P < 0.05), but no in hot plate test. In summary, the PLS decreased the inflammatory response by reducing neutrophil migration and modulating IL-1β production and antinociceptive effects by a peripheral mechanism dependent on the down-modulation of the inflammatory mediators.

Insights on chemical-biological correlations learned from investigations on the sulfated galactan from the marine alga Bothryocladia occidentalis

Marine organisms have been proven to be a valuable source of bioactive compounds. Among them, we highlight the sulfated galactans (SGs) from seaweeds, which besides being massively exploited as industrial thickening and gelling agents (agarans and carrageenans), have also shown promising pharmacological properties. Investigations on the non-agaran/-carrageenan SG from the red algae Bothryocladia occidentalis (SGBo) have demonstrated clear correlations between physical-chemical features and biological activities. SGBo is composed of 2,3-disulfated (~33%) or 2-sulfated (33%) α-D-galactose linked to non- or 2-sulfated β-D-galactose repetitive disaccharide units. The notable serpin-dependent/-independent anticoagulant activity of SGBo (~130 international units [IU]/mg) is higher than those of other SGs containing less 2,3-disulfated α-D-galactose units and their low-molecular-weight derivatives, and thus is directly correlated to its high molecular mass (>200 kDa) and sulfation pattern. Although SGBo has antithrombotic efficacy equivalent to heparin and decreased bleeding potential at low-doses, high-doses substantially increase thrombus formation in animal models. Such an odd dose-dependent dual antithrombotic/prothrombotic activity has been attributed to the ability of SGBo to activate factor XII. In addition to anticoagulant properties, SGBo also exerts antimalarial, antileishmanial and antiophidic activities, and, therefore, has a remarkable potential for the research and development of novel drugs.

Structural Features and Rheological Properties of a Sulfated Xylogalactan-Rich Fraction Isolated from Tunisian Red Seaweed Jania adhaerens

A novel sulfated xylogalactan-rich fraction (JSP for J. adhaerens Sulfated Polysaccharide) was extracted from the red Tunisian seaweed Jania adhaerens. JSP was purified using an alcoholic precipitation process and characterized by Attenuated Total Reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR), high-pressure size exclusion chromatography (HPSEC) with a multi-angle laser light scattering (MALLS), gas chromatography coupled to mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR, 1D and 2D). JSP was then evaluated regarding its physicochemical and rheological properties. Results showed that JSP was mainly composed of an agar-like xylogalactan sharing the general characteristics of corallinans. The structure of JSP was mainly composed of agaran disaccharidic repeating units (→3)-β-d-Galp-(1,4)-α-l-Galp-(1→)n and (→3)-β-d-Galp-(1,4)-3,6-α-l-AnGalp-(1→)n, mainly substituted on O-6 of (1,3)-β-d-Galp residues by β-xylosyl side chains, and less with sulfate or methoxy groups. (1,4)-α-l-Galp residues were also substituted by methoxy and/or sulfate groups in the O-2 and O-3 positions. Mass-average and number-average molecular masses (Mw) and (Mn), intrinsic viscosity ([η]) and hydrodynamic radius (Rh) for JSP were, respectively, 8.0 × 105 g/mol, 1.0 × 105 g/mol, 76 mL/g and 16.8 nm, showing a flexible random coil conformation in solution. The critical overlap concentration C* of JSP was evaluated at 7.5 g/L using the Williamson model. In the semi-diluted regime, JSP solutions displayed a shear-thinning behavior with a great viscoelasticity character influenced by temperature and monovalent salts. The flow characteristics of JSP were described by the Ostwald model.

Metabolites from Marine Microorganisms, Micro, and Macroalgae: Immense Scope for Pharmacology

Marine organisms produce a large array of natural products with relevance in drug discovery. These compounds have biological activities such as antioxidant, antibacterial, antitumor, antivirus, anticoagulant, anti-inflammatory, antihypertensive, antidiabetic, and so forth. Consequently, several of the metabolites have made it to the advanced stages of clinical trials, and a few of them are commercially available. In this review, novel information on natural products isolated from marine microorganisms, microalgae, and macroalgae are presented. Given due research impetus, these marine metabolites might emerge as a new wave of promising drugs.

Antithrombotics from the Sea: Polysaccharides and Beyond

Marine organisms exhibit some advantages as a renewable source of potential drugs, far beyond chemotherapics. Particularly, the number of marine natural products with antithrombotic activity has increased in the last few years, and reports show a wide diversity in scaffolds, beyond the polysaccharide framework. While there are several reviews highlighting the anticoagulant and antithrombotic activities of marine-derived sulfated polysaccharides, reports including other molecules are sparse. Therefore, the present paper provides an update of the recent progress in marine-derived sulfated polysaccharides and quotes other scaffolds that are being considered for investigation due to their antithrombotic effect.

Structural characterization and antioxidant activity of water-soluble polysaccharides from the Tunisian brown seaweed Cystoseira compressa

A fucoidan (CCF) and a sodium alginate (CCSA) were extracted and purified from the Tunisian brown seaweed Cystoseira compressa. CCF was a highly sulfated heterogalactofucan composed of α-(1→3), α-(1→4)-linked l-Fucp as main backbone which could be highly branched (31.84%) at O-3 and O-4 positions of α-(1→4)-l-Fucp and α-(1→3)-l-Fucp by terminal monosaccharides and side chains such as terminal α-l-Fucp, terminal β-d-Galp, β-d-Galp-(1→3)-α-l-Fucp and β-d-Galp-(1→4)-α-l-Fucp. The ratio of α-(1→3)/α-(1→4) linkages was estimated at 3.86:1. CCSA was characterized by HPAEC-PAD, GC/MS-EI, ATR-FTIR, and 1H-NMR. The M/G ratio was M/G = 0.77, indicating that CCSA respectively contained 44% and 56% of mannuronic and guluronic acids. The values of FGG, FMM, FGM (or FMG) blocks as well as the parameter η were estimated. The two polysaccharides exhibited effective antioxidant activities by ferrous ion chelation, ferric ion reduction and DPPH radical-scavenging, outlining their potentials as natural additives.

Antidiarrheal activity of a novel sulfated polysaccharide from the red seaweed Gracilaria cervicornis

ETHNOPHARMACOLOGICAL RELEVANCE

The use of marine seaweeds as a source of natural compounds with medicinal purposes is increasing in Western countries in the last decades, becoming an important alternative in the traditional medicine of many developing countries, where diarrhea still remains a severe public health problem, with high rates of mortality and morbidity. Sulfated polysaccharides (PLS) extracted from red seaweeds can exhibit therapeutic effects for the treatment of gastrointestinal disorders. Thus, the pharmacological properties of the PLS from Gracilaria cervicornis, an endemic seaweed found in the Brazilian northeast coast, was evaluated as an alternative natural medication for diarrhea.

AIM OF THE STUDY

This study aimed to evaluate the antidiarrheal activity of sulfated polysaccharides (PLS) extracted from the red seaweed G. cervicornis in Swiss mice pre-treated with castor oil or cholera toxin.

MATERIALS AND METHODS

The seaweed Gracilaria cervicornis was collected at Flecheiras beach (city of Trairí, State of Ceará, Brazil) and the PLS was obtained through enzymatic extraction and administered in mice (25-30 g) before diarrhea induction with castor oil or cholera toxin. For the evaluation of the total number of fecal output and diarrheal feces, the animals were placed in cages lined with adsorbent material. The evaluation of intestinal fluid accumulation (enteropooling) on castor oil-induced diarrhea in mice occurred by dissecting the small intestine and measuring its volume. The determination of Na⁺/K⁺-ATPase activity was measured in the small intestine supernatants by colorimetry, using commercial biochemistry kits. The gastrointestinal motility was evaluated utilizing an activated charcoal as a food tracer. The intestinal fluid secretion and chloride ion concentration were evaluated in intestinal closed loops in mice with cholera toxin-induced secretory diarrhea. The binding ability of PLS with GM1 and/or cholera toxin was evaluated by an Enzyme-Linked Immunosorbent Assay (ELISA).

RESULTS

The G. cervicornis PLS showed antidiarrheal effects in both acute and secretory diarrhea, reducing the total number of fecal output, diarrheic stools, intestinal fluid accumulation, and increasing small intestine Na⁺/K⁺-ATPase activity on castor oil-induced diarrhea. However, the PLS did not affect gastrointestinal motility, indicating that this compound has a different action mechanism than loperamide. In secretory diarrhea, the PLS decreased intestinal fluid secretion and small intestine chloride excretion, binding with GM1 and/or cholera toxin and blocking their attachment to the enterocyte cell surface.

CONCLUSIONS

In conclusion, PLS has a significant antidiarrheal effect in acute and secretory diarrhea. Further investigation is needed towards its use as a natural medicine to treat diarrhea.