A new sulfated beta-galactan from clams with anti-HIV activity

A comprehensive overview on the role of phytocompounds in human immunodeficiency virus treatment

Acquired immune deficiency syndrome (AIDS) is a worldwide epidemic caused by human immunodeficiency virus (HIV) infection. Newer medicines for eliminating the viral reservoir and eradicating the virus are urgently needed. Attempts to locate relatively safe and non-toxic medications from natural resources are ongoing now. Natural-product-based antiviral candidates have been exploited to a limited extent. However, antiviral research is inadequate to counteract for the resistant patterns. Plant-derived bioactive compounds hold promise as powerful pharmacophore scaffolds, which have shown anti-HIV potential. This review focuses on a consideration of the virus, various possible HIV-controlling methods and the recent progress in alternative natural compounds with anti-HIV activity, with a particular emphasis on recent results from natural sources of anti-HIV agents. Please cite this article as: Mandhata CP, Sahoo CR, Padhy RN. A comprehensive overview on the role of phytocompounds in human immunodeficiency virus treatment. J Integr Med. 2023; Epub ahead of print.

Structural characterization and biological activity of an α-glucan from the mollusk Marcia hiantina (Lamarck, 1818)

Marcia hiantina (Mollusca, Bivalvia) (Lamarck, 1818), is an edible clam mainly distributed along the tropical coastal regions. Recent researches have demonstrated that clams can possess compounds, including polysaccharides, with a wide range of biological actions including antioxidant, immunomodulatory and antitumor activities. Here an α-glucan was isolated from M. hiantina by hot water, purified by anion exchange chromatography, and its structure was characterized by a combination of multiple nuclear magnetic resonance (NMR) methods (1D 1H, 1H-1H COSY, 1H-1H TOCSY, 1H-1H NOESY, 1H-13C HSQC and 1H-13C HSQC-NOESY spectra), gas chromatography-mass spectrometry, and high performance size exclusion chromatography (HPSEC). The analysis from NMR, monosaccharide composition, methylation analyses and HPSEC combined with multi-angle light scattering (MALS) of M. hiantina-derived α-glycan confirmed a branched polysaccharide exclusively composed of glucose (Glc), mostly 4-linked in its backbone, branched occasionally at 6-positions, and having a molecular weight of ~ 570 kDa. The mollusk α-glucan was subjected to four cell-based assays: (i) viability of three cell lines (RAW264.7, HaCaT, and HT-29), (ii) activity on lipopolysaccharide (LPS)-induced prostaglandin production in RAW264.7 cells, (iii) inhibitory activities of in H2O2- and LPS-induced reactive oxygen species (ROS) production in HMC3 cells, and (iv) HaCaT cell proliferation. Results have indicated no cytotoxicity, potent inhibition of both H2O2- and LPS-induced ROS, and potent cell proliferative activity.

Chemical characterization and biological activities of ulvan extracted from Ulva fasciata (Chlorophyta)

Ulvan is a sulfated heteropolysaccharide present in the cell wall of Ulva species with a unique structure and biological potential used in various fields. Chemical characterization was carried out to determine the structure of ulvan from Ulva fasciata Delile collected from Eastern Harbor, Alexandria coast, Egypt. Ulva contains 31.5% carbohydrate with a total ulvan content of 43.66% of total carbohydrate (13.75 g/100 g DW) and sulfate content of 20.45% of ulvan. FTIR spectrum presented signals of the sulfate ester (C–O–S) and sulfate groups (S=O), typical for ulvan. GC–MS revealed that ulvan was mainly composed of rhamnose and fucose. 1H-NMR spectra of ulvan showed identical behavior of monosaccharides nature with peaks characteristic of sulfated polysaccharides at 3.2–5.3 ppm region. Scanning electron micrographs (SEM) demonstrated amorphous architecture, and the sulfated nature of polysaccharides was emphasized by EDX analysis. The extracted ulvan showed significant antimicrobial activity against human and fish pathogens as well as antifouling bacteria with minimum inhibitory concentrations (MIC) of 8 µg/mL. The extracted ulvan exhibited potent antioxidant activity with a scavenging effect of 84.93% for 2,2-diphenyl-1-picrylhydrazy free radical (DPPH). Moreover, it showed anti-arthritic properties for the first time with a maximum inhibition of 86.04% with IC50 of 43.21%, indicating their potential value for the health and food industry.

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.

Ecological and evolutionary diversification of sulphated polysaccharides in diverse photosynthetic lineages: A review

Sulphated polysaccharides (SPs) are carbohydrate macromolecules with sulphate esters that are found among marine algae, seagrasses, mangroves and some terrestrial plants. The sulphate concentration in the ocean (28 mM) since ancient time could have driven the production of SPs in marine algae. SPs have a gelatinous property that can protect marine algae against desiccation and salinity stress. Agar and carrageenan are red algal SPs that are widely used as gelling agents in the food and pharmaceutical industries. The information on the SPs from freshwater and land plants are limited. In this review, we reviewed the taxonomic distribution and composition of SPs in different photosynthetic lineages, and explored the association of SP production in these diversified photosynthetic organisms with evolution history and environmental stresses. We also reviewed the genes/proteins involved in SP biosynthesis. Insights into SP biosynthetic machinery may shed light on the evolution that accompanied adaptation to life on earth.

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.

Chemical composition, nutritive value and health benefits of edible clam Meretrix casta (Chemnitz) from West Coast of India

The present study was undertaken with a view to determine the nutraceutical value of the commonly consumed edible clam, Meretrix casta (Chemnitz), based on the identification of its organic chemical constituents particularly lipids and carbohydrates. Electrospray ionization tandem mass analysis of the bivalve indicated maltodextrins to be the major carbohydrate constituent. Triacylglycerols (TAGs) (0.88%, dry weight) were rich in C14:0, C16:0 to C18:0 (6-11%) saturated and monounsaturated palmitoleic (C16:1n9c; 11.76%) and oleic fatty acids (C18:1n9c; 14.53%). Though the clams contained PUFAs which are known to be beneficial in lowering the risk of cardiovascular diseases, they were devoid of docosahexaenoic acid (C22:6n3). Maltodextrins being less digestible than glucose beneficially affects the host by selectively stimulating the growth of gut microflora particularly Lactobacillus and Bifidobacteria. These microflora inhibit colonization of pathogens by producing butyrate. The profile of sterols (1.67%, dry wt.) showed it to be a complex mixture of C26, C27, C29 and C30. To our knowledge no reports are available in the literature on the identification of maltodextrins and of positional distribution of PUFA's at the sn2 position of TAGs in M. casta. The results of this study demonstrated the positive attributes of the bivalve for human consumption.

High-value compounds from the molluscs of marine and estuarine ecosystems as prospective functional food ingredients: An overview

Extensive biodiversity and availability of marine and estuarine molluscs, along with their their wide-range of utilities as food and nutraceutical resources developed keen attention of the food technologists and dieticians, particularly during the recent years. The current review comprehensively summarized the nutritional qualities, functional food attributes, and bioactive properties of these organisms. Among the phylum mollusca, Cephalopoda, Bivalvia, and Gastropoda were mostly reported for their nutraceutical applications and bioactive properties. The online search tools, like Scifinder/Science Direct/PubMed/Google Scholar/MarinLit database and marine natural product reports (1984-2019) were used to comprehend the information about the molluscs. More than 1334 secondary metabolites were reported from marine molluscs between the periods from 1984 to 2019. Among various classes of specialized metabolites, terpenes were occupied by 55% in gastropods, whereas sterols occupied 41% in bivalves. The marketed nutraceuticals, such as CadalminTM green mussel extract (Perna viridis) and Lyprinol® (Perna canaliculus) were endowed with potential anti-inflammatory activities, and were used against arthritis. Molluscan-derived therapeutics, for example, ziconotide was used as an analgesic, and elisidepsin was used in the treatment of cancer. Greater numbers of granted patents (30%) during 2016-2019 recognized the increasing importance of bioactive compounds from molluscs. Consumption of molluscs as daily diets could be helpful in the enhancement of immunity, and reduce the risk of several ailments. The present review comprehended the high value compounds and functional food ingredients from marine and estuarine molluscs.

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.

Chemical modifications of polysaccharides and their anti-tumor activities

With the rising trend of incidence of cancers, effective therapies are urgently needed to control human malignancies. However, the chemotherapy drugs currently on the market cause serious side effects. Polysaccharides belong to a class of biomacromolecules, which have drawn considerable research interest over the years as it possess anti-cancer activities or can increase the efficacy of conventional chemotherapy drugs with fewer side effects. The antitumor activity of many polysaccharides was significantly increased after modification. Based on these encouraging observations, a great deal of effort has been focused on discovering anti-cancer polysaccharides and modified derivatives for the development of effective therapeutics for various human cancers. This review highlights recent advances on the major chemical modification methods of polysaccharides, and discusses the effect of molecular modification on the physicochemical properties and anti-tumor activities of polysaccharides. Meanwhile, the underlying anti-tumor mechanisms of polysaccharide and its modified derivatives were also discussed.

Extraction techniques and potential health benefits of bioactive compounds from marine molluscs: a review

Marine molluscs and their bioactive compounds are of particular relevance to the growing pool of nutraceutical resources under global investigation.

Glycans with Antiviral Activity from Marine Organisms

There remains today a critical need for new antiviral agents, particularly in view of the alarming increase in drug resistance and associated issues. The marine environment has been a prolific contributor towards the identification of novel therapeutic agents in the recent few decades. Added to this, glycans (or carbohydrate- or sugar-based compounds) have in very recent decades made outstanding contributions to the development of novel therapeutics. This review brings together these significant facets of modern drug discovery by presenting the reported literature on glycans derived from marine organisms that possess antiviral activity.The glycans have been grouped together based on the marine organism they were isolated from, namely, (1) bacteria, (2) chromists, (3) plants and (4) animals. For chromists, glycans are further subsectioned into Ochrophyta (brown algae), Miozoa (according to www.algaebase.org ; also called Myzozoa according to WoRMS, www.marinespecies.org ) (dinoflagellates) and Bacillariophyta (diatoms). For plants, glycans are further subsectioned into Chlorophyta, Rhodophyta and Tracheophyta. Glycans isolated to date are reported as alginates, chitosan, extracellular polysaccharides, fucans (e.g. fucoidans), galactans (e.g. carrageenans), glycolipids, glycosaminoglycans, glycosides, glycosylated haemocyanin, laminarans, mannans, polysaccharides (not defined), rhamnans and xylomannans. Interestingly, many of the glycans displaying antiviral properties are sulfated.Reports indicate that marine-sourced glycans have exhibited antiviral activity against African swine fever virus, cytomegalovirus, dengue virus, Epstein-Barr virus, encephalomyocarditis virus, human immunodeficiency virus, hepatitis C virus, herpes simplex virus, human cytomegalovirus, human papilloma virus, human rhino virus, influenza virus, Japanese encephalitis virus, murine leukaemia virus, murine sarcoma virus, Newcastle disease virus, parainfluenza virus, respiratory syncytial virus, Semliki Forest virus, tobacco mosaic virus, vaccinia virus, varicella zoster virus, viral haemorrhagic septicaemia virus and vesicular stomatitis virus. Selected representative glycan structures are presented in Fig. 20.1.

Overview on the antiviral activities and mechanisms of marine polysaccharides from seaweeds

Marine polysaccharides are attracting increasing attention in medical and pharmaceutical development because of their important biological properties. The seaweed polysaccharides have now become a rich resource of potential antiviral drugs due to their antiviral activities against various viruses. The structural diversity and complexity of marine polysaccharides and their derivatives contribute to their antiviral activities in different phases of many different viral infection processes. This review mainly introduces the different types of seaweed polysaccharides and their derivatives with potent antiviral activities. Moreover, the antiviral mechanisms and medical applications of certain marine polysaccharides from seaweeds are also demonstrated.

Sulfated Glycans and Related Digestive Enzymes in the Zika Virus Infectivity: Potential Mechanisms of Virus-Host Interaction and Perspectives in Drug Discovery

As broadly reported, there is an ongoing Zika virus (ZIKV) outbreak in countries of Latin America. Recent findings have demonstrated that ZIKV causes severe defects on the neural development in fetuses in utero and newborns. Very little is known about the molecular mechanisms involved in the ZIKV infectivity. Potential therapeutic agents are also under investigation. In this report, the possible mechanisms of action played by glycosaminoglycans (GAGs) displayed at the surface proteoglycans of host cells, and likely in charge of interactions with surface proteins of the ZIKV, are highlighted. As is common for the most viruses, these sulfated glycans serve as receptors for virus attachment onto the host cells and consequential entry during infection. The applications of (1) exogenous sulfated glycans of different origins and chemical structures capable of competing with the virus attachment receptors (supposedly GAGs) and (2) GAG-degrading enzymes able to digest the virus attachment receptors on the cells may be therapeutically beneficial as anti-ZIKV. This communication attempts, therefore, to offer some guidance for the future research programs aimed to unveil the molecular mechanisms underlying the ZIKV infectivity and to develop therapeutics capable of decreasing the devastating consequences caused by ZIKV outbreak in the Americas.

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

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

Solomonseal polysaccharide and sulfated Codonopsis pilosula polysaccharide synergistically resist Newcastle disease virus

Five combinations of three ratios (PS₉-sPS₁, PS₇-sPS₃ and PS₆-sPS₄) were prepared with polysaccharide (PS) and sulfated polysaccharide (sPS). The antiviral activities of these compounds were subsequently compared in vitro using the MTT assay, observation of the virus structure and immunofluorescence. The results demonstrated that SP₉-sCP₁, CP₇-sCA₃, EP₇-sAP₃, CA₉-sEP₁ and EP₇-sCA₃ presented higher activities, and SP₉-sCP₁ displayed the highest virus inhibition rate and clearly killed the virus and inhibited viral antigen expression. In an in vivo test, 28-day-old chickens were challenged with Newcastle disease virus (NDV) and were administered the five drug combinations. On day 14 after the challenge, the morbidity, mortality and cure rate in each group were calculated. The results indicated that SP₉-sCP₁ presented the lowest morbidity and mortality and the highest cure rate. These results indicate that Solomonseal polysaccharide and sulfated Codonopsis pilosula polysaccharide synergistically resist NDV. Moreover, SP₉-sCP₁ had the highest efficacy and may be used as a new antiviral drug.

Sulfation of Aegle marmelos gum: synthesis, physico-chemical and functional characterization

The present investigation was aimed at optimizing the conditions for preparing sulfated derivative of gum obtained from partially ripe fruits of Aegle marmelos. Elemental analysis, FTIR-ATR and NMR studies confirmed successful sulfation. The ratio of chlorosulfonic acid to pyridine exerted maximum influence on the degree of substitution followed by reaction temperature and reaction time. The sulfated derivative showed higher swelling in both acidic and alkaline pH as compared to unmodified gum. It also possessed higher negative zeta potential, higher viscosity, work of shear, firmness, consistency, cohesiveness and index of viscosity as compared to both unmodified gum as well as sodium alginate. Sulfated derivative was superior to unmodified gum and sodium alginate in terms of antimicrobial and anticoagulant activity. The sulfated sample appears to be a potential substitute over the unmodified gum sample and sodium alginate for modulating physicochemical properties of food and drug release dosage forms.

Structure and antioxidant activity of polysaccharide POJ-U1a extracted by ultrasound from Ophiopogon japonicus

An ultrasonic technique was employed to extract polysaccharides from Ophiopogon japonicus. The ultrasonic extracted polysaccharides (POJ-U) were purified, and POJ-U1a (a homogeneous fraction) was obtained. The structural characteristics of POJ-U1a were investigated by infrared spectra, gas chromatography, high performance liquid chromatography, periodate oxidation, Smith degradation, methylation analysis, gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy. The results indicated that the relative molecular weight of POJ-U1a was 4.02×10(3)Da. POJ-U1a was an α-configuration polysaccharide with a highly branched structure, and consisted of pyranoside and funanside. The backbone of POJ-U1a consisted of 1,6-α-d-glucopyranose and 1,3,6-α-d-glucofuranose in the molar ratio of 7:3, while the branched chains were mainly composed of 1,3-α-d-glucopyranose and 1-α-d-glucopyranose in the molar ratio of 1:3. The branched structure of POJ-U1a was proved intuitively by AFM. Significant antioxidant activity of POJ-U1a has been proved as shown by its DPPH radical scavenging, hydrogen radical scavenging and superoxide anion scavenging activities, which indicated that POJ-U1a showed strong antioxidant activity.

Antiviral activity of natural products extracted from marine organisms

Many epidemics have broken out over the centuries. Hundreds and thousands of humans have died over a disease. Available treatments for infectious diseases have always been limited. Some infections are more deadly than the others, especially viral pathogens. These pathogens have continuously resisted all kinds of medical treatment, due to a need for new treatments to be developed. Drugs are present in nature and are also synthesized in vitro and they help in combating diseases and restoring health. Synthesizing drugs is a hard and time consuming task, which requires a lot of man power and financial aid. However, the natural compounds are just lying around on the earth, may it be land or water. Over a thousand novel compounds isolated from marine organisms are used as antiviral agents. Others are being pharmacologically tested. Today, over forty antiviral compounds are present in the pharmacological market. Some of these compounds are undergoing clinical and preclinical stages. Marine compounds are paving the way for a new trend in modern medicine.

Potential anti-HIV agents from marine resources: an overview

Human immunodeficiency virus (HIV) infection causes acquired immune deficiency syndrome (AIDS) and is a global public health issue. Anti-HIV therapy involving chemical drugs has improved the life quality of HIV/AIDS patients. However, emergence of HIV drug resistance, side effects and the necessity for long-term anti-HIV treatment are the main reasons for failure of anti-HIV therapy. Therefore, it is essential to isolate novel anti-HIV therapeutics from natural resources. Recently, a great deal of interest has been expressed regarding marine-derived anti-HIV agents such as phlorotannins, sulfated chitooligosaccharides, sulfated polysaccharides, lectins and bioactive peptides. This contribution presents an overview of anti-HIV therapeutics derived from marine resources and their potential application in HIV therapy.

Endangered medicinal species of the Indian Ocean: radical need for conservation

Life originated in the Oceans, which are also the most fertile source of chemically distinctive natural products that are mainly accumulated in living organisms. Several of these compounds show pharmacological activities, and are helpful for the invention and discovery of bioactive compounds, primarily for several fatal diseases. The Indian Ocean is home to several exotic species of flora and fauna. Several environmental and man-made factors are responsible for deterioration of several precious biodiversity areas of the Ocean. The author, while highlighting the medicinal importance of these organisms, underlines the need for comprehensive conservatory measures on the part of the international community to be taken in order to maintain the rich Oceanic biodiversity.

A unique 2-sulfated {beta}-galactan from the egg jelly of the sea urchin Glyptocidaris crenularis: conformation flexibility versus induction of the sperm acrosome reaction

Sulfated polysaccharides from the egg jelly of sea urchins act as species-specific inducers of the sperm acrosome reaction, which is a rare molecular mechanism of carbohydrate-induced signal-transduction event in animal cells. The sea urchin polysaccharides differ in monosaccharide composition (l-fucose or l-galactose), glycosylation, and sulfation sites, but they are always in the alpha-anomeric configuration. Herein, structural analysis of the polysaccharide from the sea urchin Glyptocidaris crenularis surprisingly revealed a unique sulfated beta-d-galactan composed by (3-beta-d-Galp-2(OSO(3))-1-->3-beta-d-Galp-1)(n) repeating units. Subsequently, we used the G. crenularis galactan to compare different 2-sulfated polysaccharides as inducers of the acrosome reaction using homologous and heterologous sperm. We also tested the effect of chemically over-sulfated galactans. Intriguingly, the anomeric configuration of the glycosidic linkage rather than the monosaccharide composition (galactose or fucose) is the preferential structural requirement for the effect of these polysaccharides on sea urchin fertilization. Nuclear magnetic resonance and molecular dynamics indicate that sulfated alpha-galactan or alpha-fucan have less dynamic structural behavior, exhibiting fewer conformational populations, with an almost exclusive conformational state with glycosidic dihedral angles Phi/Psi = -102 degrees /131 degrees . The preponderant conformer observed in the sulfated alpha-galactan or alpha-fucan is not observed among populations in the beta-form despite its more flexible structure in solution. Possibly, a proper spatial arrangement is required for interaction of the sea urchin-sulfated polysaccharides with the specific sperm receptor.

Structure, biology, evolution, and medical importance of sulfated fucans and galactans

Sulfated fucans and galactans are strongly anionic polysaccharides found in marine organisms. Their structures vary among species, but their major features are conserved among phyla. Sulfated fucans are found in marine brown algae and echinoderms, whereas sulfated galactans occur in red and green algae, marine angiosperms, tunicates (ascidians), and sea urchins. Polysaccharides with 3-linked, beta-galactose units are highly conserved in some taxonomic groups of marine organisms and show a strong tendency toward 4-sulfation in algae and marine angiosperms, and 2-sulfation in invertebrates. Marine algae mainly express sulfated polysaccharides with complex, heterogeneous structures, whereas marine invertebrates synthesize sulfated fucans and sulfated galactans with regular repetitive structures. These polysaccharides are structural components of the extracellular matrix. Sulfated fucans and galactans are involved in sea urchin fertilization acting as species-specific inducers of the sperm acrosome reaction. Because of this function the structural evolution of sulfated fucans could be a component in the speciation process. The algal and invertebrate polysaccharides are also potent anticoagulant agents of mammalian blood and represent a potential source of compounds for antithrombotic therapies.

Focus on antivirally active sulfated polysaccharides: from structure-activity analysis to clinical evaluation

In recent years, many compounds having potent antiviral activity in cell culture have been detected and some of these compounds are currently undergoing either preclinical or clinical evaluation. Among these antiviral substances, naturally occurring sulfated polysaccharides and those from synthetic origin are noteworthy. Recently, several controversies over the molecular structures of sulfated polysaccharides, viral glycoproteins, and cell-surface receptors have been resolved, and many aspects of their antiviral activity have been elucidated. It has become clear that the antiviral properties of sulfated polysaccharides are not only a simple function of their charge density and chain length but also their detailed structural features. The in vivo efficacy of these compounds mostly corresponds to their ability to inhibit the attachment of the virion to the host cell surface although in some cases virucidal activity plays an additional role. This review summarizes experimental evidence indicating that sulfated polysaccharides might become increasingly important in drug development for the prevention of sexually transmitted diseases in the near future.

A preponderantly 4-sulfated, 3-linked galactan from the green alga Codium isthmocladum

The green algae of the genus Codium have recently been demonstrated to be an important source of sulfated galactans from the marine environment. Here, a sulfated galactan was isolated from the species Codium isthmocladum and its structure was studied by a combination of chemical analyses and NMR spectroscopy. Two fractions (SG 1, approximately 14 kDa, and SG 2, approximately 20 kDa) were derived from this highly polydisperse and heterogeneous polysaccharide. Both exhibited similar structures in (1)H 1D NMR spectra. The structural features of SG 2 and its desulfated derivative were analyzed by COSY, TOCSY, DEPT-HSQC, HSQC, and HMBC. This sulfated galactan is composed preponderantly of 4-sulfated, 3-linked beta-D-galactopyranosyl units. In minor amounts, it is sulfated and glycosylated at C-6. Pyruvate groups are also found, forming five-membered cyclic ketals as 3,4-O-(1'carboxy)-ethylidene-beta-D-galactose residues. A comparison of sulfated galactans from different marine taxonomic groups revealed similar backbones of 3-beta-D-Galp-1.

Polysulfated sialic acid derivatives as anti-human immunodeficiency virus

We report the synthesis of a novel alkyl polysulfated sialic acid derivative denoted as NMSO3. NMSO3 exhibited potent inhibition against both laboratory and clinical human immunodeficiency virus type 1 (HIV-1). The anti-viral activity of this compound (1 uM) was compared to dextran sulfate (3 uM), and was found to be more potent against HIV-1IIIb than AZT (10 uM). The anti-coagulation time was more than 15-fold shorter than that of dextran sulfate. An in vivo anti-viral study of NMSO3 in NOD-SCID-PBL mice HIV model showed complete protection of the animals from virus challenge at the concentration of 10 mg/kg. This suggests that NMSO3 can be effective in the treatment of HIV-infected individuals.

Molecular mass and antitumor activities of sulfated derivatives of alpha-glucan from Poria cocos mycelia

Two kinds of water-insoluble (1-->3)-alpha-D-glucan samples, ab-PCM3-I and ac-PCM3-I, isolated from different Poria cocos mycelia were sulfated, to produce two series of water-soluble derivatives ab-PCM3-I-S1-S5 and ac-PCM3-I-S1-S5, respectively. The derivatives having different weight-average molecular mass (Mw) were produced by changing reaction temperature and time as well as molar ratios between chlorosulfonic acid and number of hydroxyl groups in the glucan. The degrees of substitution (DS) of the sulfated derivatives were analyzed by elemental analysis (EA) to be 0.39-0.67 for ab-PCM3-I-S and 0.73-0.96 for ac-PCM3-I-S, respectively. The Mw and the intrinsic viscosity ([eta]) of the samples ab-PCM3-I-S and the ac-PCM3-I-S were measured by size exclusion chromatography combined with laser light scattering (SEC-LLS) and viscometry in phosphate buffer solution (PBS) at 37 degrees C. The results indicated that their Mw ranged from 2.0 to 11.3 x 10(4) for the samples ab-PCM3-I-S, and 4.7 to 40.0 x 10(4) for the samples ac-PCM3-I-S. Moreover, the antitumor activities of the sulfated derivatives ab-PCM3-I-S and ac-PCM3-I-S against Sarcoma 180 tumor cell tested both in vitro and in vivo are significantly higher than those of the native alpha-D-glucans. Therefore, a moderate range of molecular mass from 2.0 x 10(4) to 40.0 x 10(4), relatively high chain stiffness and good water solubility of the sulfated derivatives are beneficial to the enhancement of their antitumor activities.

Antiviral Activities of Polysaccharides from Natural Sources

The ever increasing resistance of human pathogens to current anti-infective agents is a serious medical problem, leading to the need to develop novel antibiotic prototype molecules. In the case of viruses, the search for antiviral agents involves additional difficulties, particularly due to the nature of the infectious viral agents. Thus, many compounds that may cause the death of viruses are also very likely to injure the host cell that harbours them. Natural products are increasingly appreciated as leads for drug discovery and development. Screening studies have been carried out in order to find antiviral agents from natural sources, and the occurrence of antiviral activity in extracts of plants, marine organisms and fungi is frequent. The evidence indicates that there may be numerous potentially useful antiviral phytochemicals in nature, waiting to be evaluated and exploited. In addition, other plants, not previously utilized medicinally, may also reveal antivirals. Among natural antiviral agents, recent investigations have reconsidered the interest of phyto-polysaccharides, which act as potent inhibitors of different viruses. This chapter will illustrate a variety of antiviral polysaccharides from natural sources since 1990, with the aim of making this matter more accessible to drug development

In vitro and in vivo antiviral properties of sulfated galactomannans against yellow fever virus (BeH111 strain) and dengue 1 virus (Hawaii strain)

Two galactomannans, one extracted from seeds of Mimosa scabrella, having a mannose to galactose ratio of 1.1, and another with a 1.4 ratio from seeds of Leucaena leucocephala, were sulfated. The products from M. scabrella (BRS) and L. leucocephala (LLS) had a degree of sulfation of 0.62 and 0.50, and an average molecular weight of 620x10(3) and 574x10(3) gmol(-1), respectively. Their activities against yellow fever virus (YFV; BeH111 strain) and dengue 1 virus (DEN-1; Hawaii strain) were evaluated. This was carried out in young mice following intraperitoneal infection with YFV. At a dose of 49 mgkg(-1), BRS and LLS gave protection against death in 87.7 and 96.5% of the mice, respectively. When challenged with 37.5 LD50 of YFV, mice previously inoculated with BRS+virus or LLS+virus, showed 93.3 and 100% resistance, respectively, with neutralization titers similar to mice injected with 25 LD50 of formaldehyde-inactivated YFV. In vitro experiments with YFV and DEN-1 in C6/36 cell culture assays in 24-well microplates showed that concentrations that produced a 100-fold decrease in virus titer of YFV were 586 and 385 mgl(-1) for BRS and LLS, respectively. For DEN-1 they were 347 and 37 mgl(-1), respectively. Sulfated galactomannans, thus demonstrate in vitro and in vivo activity against flaviviruses.

Marine pharmacology in 1999: compounds with antibacterial, anticoagulant, antifungal, anthelmintic, anti-inflammatory, antiplatelet, antiprotozoal and antiviral activities affecting the cardiovascular, endocrine, immune and nervous systems, and other miscellaneous mechanisms of action

This review, a sequel to the 1998 review, classifies 63 peer-reviewed articles on the basis of the reported preclinical pharmacological properties of marine chemicals derived from a diverse group of marine animals, algae, fungi and bacteria. In all, 21 marine chemicals demonstrated anthelmintic, antibacterial, anticoagulant, antifungal, antimalarial, antiplatelet, antituberculosis or antiviral activities. An additional 23 compounds had significant effects on the cardiovascular, sympathomimetic or the nervous system, as well as possessed anti-inflammatory, immunosuppressant or fibrinolytic effects. Finally, 22 marine compounds were reported to act on a variety of molecular targets, and thus could potentially contribute to several pharmacological classes. Thus, during 1999 pharmacological research with marine chemicals continued to contribute potentially novel chemical leads in the ongoing global search for therapeutic agents for the treatment of multiple disease categories.

Effect of (1-->3)- and (1-->4)-linkages of fully sulfated polysaccharides on their anticoagulant activity

Chemically fully sulfated polysaccharides including xylan (-->4Xylbeta-(1-->4)Xylbeta1-->), amylose (-->4Glcalpha-(1-->4)Glcalpha1-->), cellulose (-->4Glcbeta-(1-->4)Glcbeta1-->), curdlan (-->3Glcbeta-(1-->3)Glcbeta1-->) and galactan (-->3Galbeta-(1-->3)Galbeta1-->), which have been isolated from Korean clam, were prepared, and their anticoagulant activity was investigated. The results strongly suggest that the activity might not be depending on anomeric configuration (alpha or beta) or monosaccharide species but on the glycosidic linkage, either (1-->3) or (1-->4). 1H NMR studies of these modified polysaccharides show that the neighboring sulfate groups at the C-2 and C-3 positions might have caused the conformational changes of each monosaccharide from 4C(1) to 1C(4). Furthermore, the effect of 6-sulfate residues on the anticoagulant activity was investigated using a specific desulfated reaction for the chemically fully sulfated polysaccharides. The 6-sulfate group is very important in determining anticoagulant activity of (1-->3)-linked polysaccharides, whereas the activity is not affected by presence or absence of the 6-sulfate group in (1-->4)-linked polysaccharides.

Virus-cell fusion inhibitory activity for the polysaccharides from various Korean edible clams

In order to find potent virus-cell fusion inhibitory components from Korean edible clams, thirteen prepared polysaccharides were introduced to syncytia formation inhibition assay, which is based on the interaction between the HIV-1 envelope protein gp120/41 and the cellular membrane protein CD4 of T lymphocytes. Among them, Meretrix petechialis showed a potent virus-cell fusion inhibitory activity. Fusion index (FI) and percent (%) fusion inhibition of the polysaccharide of this clam were 0.21 +/- 0.02, and 67.52 +/- 4.09 at 100 microg/ml, respectively. It exhibited almost equivalent virus-cell fusion inhibitory activity to that of dextran sulfate which was used as a standard control.

Isolation and NMR characterization of rosacelose, a novel sulfated polysaccharide from the sponge Mixylla rosacea

Rosacelose, a new anti-HIV polysaccharide composed of glucose and fucose sulfate, has been isolated from an aqueous extract of the marine sponge Mixylla rosacea. Extensive use of 1H and 13C multidimensional NMR spectroscopy, combined with chemical analysis were used to establish a linear polysaccharide structure composed mainly of 4,6-disulfated 3-O-glycosylated alpha-D-glucopyranosyl and 2,4-disulfated 3-O-glycosylated alpha-L-fucopyranosyl residues (in a 3:1 molar ratio).