Structural Characterization of Fucoidan from Laminaria hyperborea: Assessment of Coagulation and Inflammatory Properties and Their Structure–Function Relationship

Structural characterization and immunomodulating assessment of ultra-purified water extracted fucoidans from Saccharina latissima, Alaria esculenta and Laminaria hyperborea

Fucoidans, a group of high molecular weight polysaccharides derived mainly from brown algae, are characterized by their high fucose content, degree of sulfation (DS), and intra- and interspecific structural variation. Fucoidans are increasingly recognized due to various reported bioactivities, potentially beneficial for human health. To unlock their potential use within biomedical applications, a better understanding of their structure-functional relationship is needed. To achieve this, systematic bioactivity studies based on well-defined, pure fucoidans, and the establishment of standardized, satisfactory purification protocols are required. We performed a comprehensive compositional and structural characterization of crude and ultra-purified fucoidans from three kelps: Saccharina latissima (SL), Alaria esculenta (AE) and Laminaria hyperborea (LH). Further, the complement-inhibiting activity of the purified fucoidans was assessed in a human whole blood model. The purification process led to fucoidans with higher DS and fucose and lower concentrations of other monosaccharides. Fucoidans from SL and LH resembles homofucans, while AE is a heterofucan rich in galactose with comparably lower DS. Fucoidans from SL and LH showed complement-inhibiting activity in blood and blood plasma, while no inhibition was observed for AE under the same conditions. The results emphasize the importance of high DS and possibly fucose content for fucoidans' bioactive properties.

Refined linkage analysis of the sulphated marine polysaccharide fucoidan of Cladosiphon okamuranus with a focus on fucose

Methylation followed by depolymerization and gas chromatography (GC) is an effective methodology for the linkage analysis of polysaccharides, including fucoidan, a sulphated algal polysaccharide. However, this sample material demands attention to experimental details to prevent aberrations in the analytical result. The use of deficient bases for methylation, the presence of water, analyte degradation during hydrolysis, and coelution of the target analytes during gas chromatography create doubts about published results. We therefore investigated critical parameters of the method and carefully optimized the steps of the protocol to ensure the integrity of the results for the fucose monomers. Fucoidan from Cladosiphon okamuranus was used as reference sample to determine the glycosidic bonds, and sulphate positions in the monomer. Fucoidan in protonated form was methylated in a strictly water-free environment using lithium dimsyl as base and methyl iodide for methylation. The methylated polymer was isolated by solid phase extraction, which was crucial to recover also the highly sulfated fraction. Hydrolysis was conducted with trifluoroacetic acid. To separate all target analytes in GC-FID/MS, a stationary phase with high cyanopropyl content (HP-88) was required, as the commonly employed phenyl siloxane phases result in co-elution, which distorts the result severely.

Seaweed-derived fucoidans and rhamnan sulfates serve as potent anti-SARS-CoV-2 agents with potential for prophylaxis

Seaweeds represent a rich source of sulfated polysaccharides with similarity to heparan sulfate, a facilitator of myriad virus host cell attachment. For this reason, attention has been drawn to their antiviral activity, including the potential for anti-SARS-CoV-2 activity. We have identified and structurally characterized several fucoidan extracts, including those from different species of brown macroalga, and a rhamnan sulfate from a green macroalga species. A high molecular weight fucoidan extracted from Saccharina japonica (FSjRPI-27), and a rhamnan sulfate extracted from Monostroma nitidum (RSMn), showed potent competitive inhibition of spike glycoprotein receptor binding to a heparin-coated SPR chip. This inhibition was also observed in cell-based assays using hACE2 HEK-293 T cells infected by pseudotyped SARS-CoV-2 virus with IC50 values <1 μg/mL. Effectiveness was demonstrated in vivo using hACE2-transgenic mice. Intranasal administration of FSjRPI-27 showed protection when dosed 6 h prior to and at infection, and then every 2 days post-infection, with 100 % survival and no toxicity at 104 plaque-forming units per mouse vs. buffer control. At 5-fold higher virus dose, FSjRPI-27 reduced mortality and yielded reduced viral titers in bronchioalveolar fluid and lung homogenates vs. buffer control. These findings suggest the potential application of seaweed-based sulfated polysaccharides as promising anti-SARS-CoV-2 prophylactics.

Anti-respiratory syncytial virus and anti-herpes simplex virus activity of chemically engineered sulfated fucans from Cystoseira indica

Seaweed polysaccharides, particularly sulfated ones, exhibited potent antiviral activity against a wide variety of enveloped viruses, such as herpes simplex virus and respiratory viruses. Different mechanisms of action were suggested, which may range from preventing infection to intracellular antiviral activity, at different stages of the viral cycle. Herein, we generated two chemically engineered sulfated fucans (C303 and C304) from Cystoseira indica by an amalgamated extraction-sulfation procedure using chlorosulfonic acid-pyridine/N,N-dimethylformamide and sulfur trioxide-pyridine/N,N-dimethylformamide reagents, respectively. These compounds exhibited activity against HSV-1 and RSV with 50 % inhibitory concentration values in the range of 0.75-2.5 μg/mL and low cytotoxicity at concentrations up to 500 μg/mL. The antiviral activities of chemically sulfated fucans (C303 and C304) were higher than the water (C301) and CaCl2 extracted (C302) polysaccharides. Compound C303 had a (1,3)-linked fucan backbone and was branched. Sulfates were present at positions C-2, C-4, and C-2,4 of Fucp, and C-6 of Galp residues of this polymer. Compound C304 had a comparable structure but with more sulfates at C-4 of Fucp residue. Both C303 and C304 were potent antiviral candidates, acting in a dose-dependent manner on the adsorption and other intracellular stages of HSV-1 and RSV replication, in vitro.

Automated Synthesis of Algal Fucoidan Oligosaccharides

Fucoidan, a sulfated polysaccharide found in algae, plays a central role in marine carbon sequestration and exhibits a wide array of bioactivities. However, the molecular diversity and structural complexity of fucoidan hinder precise structure-function studies. To address this, we present an automated method for generating well-defined linear and branched α-fucan oligosaccharides. Our syntheses include oligosaccharides with up to 20 cis-glycosidic linkages, diverse branching patterns, and 11 sulfate monoesters. In this study, we demonstrate the utility of these oligosaccharides by (i) characterizing two endo-acting fucoidan glycoside hydrolases (GH107), (ii) utilizing them as standards for NMR studies to confirm suggested structures of algal fucoidans, and (iii) developing a fucoidan microarray. This microarray enabled the screening of the molecular specificity of four monoclonal antibodies (mAb) targeting fucoidan. It was found that mAb BAM4 has cross-reactivity to β-glucans, while mAb BAM2 has reactivity to fucoidans with 4-O-sulfate esters. Knowledge of the mAb BAM2 epitope specificity provided evidence that a globally abundant marine diatom, Thalassiosira weissflogii, synthesizes a fucoidan with structural homology to those found in brown algae. Automated glycan assembly provides access to fucoidan oligosaccharides. These oligosaccharides provide the basis for molecular level investigations into fucoidan's roles in medicine and carbon sequestration.

Sequential and enzyme-assisted extraction of algal bioproducts from Ecklonia maxima

Brown algae are gaining recognition as sources of bio-compounds with diverse properties and potential applications in the food, nutraceutical, and pharmaceutical industries. Compounds such as polyphenols, alginates and fucoidan possess multiple bioactivities, including antidiabetic, antioxidant, anticancer, anti-inflammatory, and antibacterial properties. Conventional extraction methods provide low yields, posing challenges for the industrial applications of biocompounds. However, innovations are rapidly emerging to address these challenges, and one such approach is enzyme-assisted extraction. Furthermore, extracting single compounds undervalues algal biomass as valuable compounds may remain in the waste. Therefore, the aim of our study was to develop a framework for the sequential and enzyme-assisted extraction of various bio-compounds using the same biomass in a biorefinery process. The Ecklonia maxima algal biomass was defatted, and polyphenols were extracted using solid-liquid extraction with aqueous ethanol. The remaining residue was treated with an enzyme combination (Cellic® Ctec 2 and Viscozyme L) to liberate carbohydrates into solution, where an alginate and fucoidan fraction were isolated. A second alginate fraction was harvested from the residue. The phenolic fraction yielded about 11% (dry weight of extract/dry weight of seaweed biomass), the alginate fraction 35% and the fucoidan fraction 18%. These were analysed using a variety of biochemical methods. Structural analyses, including FTIR, NMR and TGA, were performed to confirm the integrity of these compounds. This study demonstrated that a sequential extraction method for various algal bioproducts is possible, which can pave the way for a biorefinery approach. Furthermore, our study primarily employed environmentally and eco-friendly extraction technologies promoting an environmentally sustainable industrial approach. This approach enhances the feasibility and flexibility of biorefinery operations, contributing to the development of a circular bio-economy.

Investigating anti-inflammatory and apoptotic actions of fucoidan concentrating on computational and therapeutic applications

Fucoidan is linked to a variety of biological processes. Differences in algae species, extraction, seasons, and locations generate structural variability in fucoidan, affecting its bioactivities. Nothing is known about fucoidan from the brown alga Dictyota bartayresiana, its anti-inflammatory properties, or its inherent mechanism. This study aimed to investigate the anti-inflammatory properties of fucoidan isolated from D. bartayresiana against LPS-induced RAW 264.7 macrophages and to explore potential molecular pathways associated with this anti-inflammatory effects. Fucoidan was first isolated and purified from D. bartayresiana, and then, MTT assay was used to determine the effect of fucoidan on cell viability. Its effects on reactive oxygen species (ROS) formation and apoptosis were also studied using the ROS assay and acridine orange/ethidium bromide fluorescence labelling, respectively. Molecular docking and molecular dynamics simulation studies were performed on target proteins NF-κB and TNF-α to identify the route implicated in these inflammatory events. It was observed that fucoidan reduced LPS-induced inflammation in RAW 264.7 cells. Fucoidan also decreased the LPS-stimulated ROS surge and was found to induce apoptosis in the cells. Molecular docking and molecular dynamics simulation studies revealed that fucoidan's potent anti-inflammatory action was achieved by obstructing the NF-κB signalling pathway. These findings were particularly noteworthy and novel because fucoidan isolated from D. bartayresiana had not previously been shown to have anti-inflammatory properties in RAW 264.7 cells or to exert its activity by obstructing the NF-κB signalling pathway. Conclusively, these findings proposed fucoidan as a potential pharmaceutical drug for inflammation-related diseases.

Effect of Marine-Derived Saccharides on Human Skin Fibroblasts and Dermal Papilla Cells

The skin is the largest organ of the human body, composed of a diverse range of cell types, non-cellular components, and an extracellular matrix. With aging, molecules that are part of the extracellular matrix undergo qualitative and quantitative changes and the effects, such as a loss of skin firmness or wrinkles, can be visible. The changes caused by the aging process do not only affect the surface of the skin, but also extend to skin appendages such as hair follicles. In the present study, the ability of marine-derived saccharides, L-fucose and chondroitin sulphate disaccharide, to support skin and hair health and minimize the effects of intrinsic and extrinsic aging was investigated. The potential of the tested samples to prevent adverse changes in the skin and hair through stimulation of natural processes, cellular proliferation, and production of extracellular matrix components collagen, elastin, or glycosaminoglycans was investigated. The tested compounds, L-fucose and chondroitin sulphate disaccharide, supported skin and hair health, especially in terms of anti-aging effects. The obtained results indicate that both ingredients support and promote the proliferation of dermal fibroblasts and dermal papilla cells, provide cells with a supply of sulphated disaccharide GAG building blocks, increase ECM molecule production (collagen and elastin) by HDFa, and support the growth phase of the hair cycle (anagen).

Establishment of specific age-related macular degeneration relevant gene expression panels using porcine retinal pigment epithelium for assessing fucoidan bioactivity

PURPOSE

Age-related macular degeneration (AMD) is the leading cause of severe vision loss in industrialized nations. Important factors in pathogenesis are oxidative stress, inflammation, and, in the wet form of AMD, angiogenesis. Fucoidans, sulfated polysaccharides from brown algae, may have antioxidant, anti-inflammatory, and antiangiogenic effects. In this study, we established specific gene expression panels for inflammation, oxidative stress and angiogenesis in porcine retinal pigment epithelium (RPE), and investigated the effect of fucoidans on gene expression under different noxious agents.

METHODS

Primary porcine RPE cells cultured for at least 14 days were used. Using viability assays with tetrazolium bromide and real-time polymerase chain reaction of marker genes, positive controls were established for appropriate concentrations and exposure times of selected noxious agents (lipopolysaccharide (LPS), H₂O₂, CoCl₂). Three different AMD relevant gene panels specific for porcine RPE for inflammation, oxidative stress, and angiogenesis were established, and the influence of fucoidans (mainly Fucus vesiculosus; FV) on gene expression was investigated.

RESULTS

The following was shown by gene expression analyses: (1) Inflammation panel: Expression of 18 genes was affected under LPS (three days). Among them, LPS increased genes for interleukin 1 receptor 2, interleukin 8, cyclooxygenase-2 and vascular cell adhesion protein 1 expression which were diminished when FV was present. (2) Oxidative stress panel: Under stimulation of H₂O₂ (one day) and LPS (one day), expression of a total of 15 genes was affected. LPS induced increase in genes for superoxide dismutase-1, C-X-C motif chemokine 10, and CC chemokine ligand-5 expression was not detected when FV was present. (3) Angiogenesis panel: Under stimulation with CoCl₂ (three days) expression of six genes was affected, with the increase of genes for angiopoietin 2, vascular endothelial growth factor receptor-1, and follistatin being diminished when FV was present.

CONCLUSION

Three specific gene expression panels for porcine RPE that map genes for three of the major pathological factors of AMD, inflammation, oxidative stress, and angiogenesis, were established. Further, we demonstrated that fucoidans can reduce stress related gene activation in all of these three major pathogenic pathways. This study is another indication that fucoidans can act on different pathomechanisms of AMD simultaneously, which provides further evidence for fucoidans as a possible drug for treatment and prevention of AMD.

Fucoidan and topography modification improved in situ endothelialization on acellular synthetic vascular grafts

Thrombogenesis remains the primary failure of synthetic vascular grafts. Endothelial coverage is crucial to provide an antithrombogenic surface. However, most synthetic materials do not support cell adhesion, and transanastomotic endothelial migration is limited. Here, a surface modification strategy using fucoidan and topography was developed to enable fast in situ endothelialization of polyvinyl alcohol, which is not endothelial cell-adhesive. Among three different immobilization approaches compared, conjugation of aminated-fucoidan promoted endothelial monolayer formation while minimizing thrombogenicity in both in vitro platelet rich plasma testing and ex vivo non-human primate shunt assay. Screening of six topographical patterns showed that 2 μm gratings increased endothelial cell migration without inducing inflammation responses of endothelial cells. Mechanistic studies demonstrated that fucoidan could attract fibronectin, enabling integrin binding and focal adhesion formation and activating focal adhesion kinase (FAK) signaling, and 2 μm gratings further enhanced FAK-mediated cell migration. In a clinically relevant rabbit carotid artery end-to-side anastomosis model, 60% in situ endothelialization was observed throughout the entire lumen of 1.7 mm inner diameter modified grafts, compared to 0% of unmodified graft, and the four-week graft patency also increased. This work presents a promising strategy to stimulate in situ endothelialization on synthetic materials for improving long-term performance.

Comparative Analyses of Fucoidans from South African Brown Seaweeds That Inhibit Adhesion, Migration, and Long-Term Survival of Colorectal Cancer Cells

Human colorectal cancer (CRC) is a recurrent, deadly malignant tumour with a high incidence. The incidence of CRC is of increasing alarm in highly developed countries, as well as in middle to low-income countries, posing a significant global health challenge. Therefore, novel management and prevention strategies are vital in reducing the morbidity and mortality of CRC. Fucoidans from South African seaweeds were hot water extracted and structurally characterised using FTIR, NMR and TGA. The fucoidans were chemically characterised to analyse their composition. In addition, the anti-cancer properties of the fucoidans on human HCT116 colorectal cells were investigated. The effect of fucoidans on HCT116 cell viability was explored using the resazurin assay. Thereafter, the anti-colony formation potential of fucoidans was explored. The potency of fucoidans on the 2D and 3D migration of HCT116 cells was investigated by wound healing assay and spheroid migration assays, respectively. Lastly, the anti-cell adhesion potential of fucoidans on HCT116 cells was also investigated. Our study found that Ecklonia sp. Fucoidans had a higher carbohydrate content and lower sulphate content than Sargassum elegans and commercial Fucus vesiculosus fucoidans. The fucoidans prevented 2D and 3D migration of HCT116 colorectal cancer cells to 80% at a fucoidan concentration of 100 µg/mL. This concentration of fucoidans also significantly inhibited HCT116 cell adhesion by 40%. Moreover, some fucoidan extracts hindered long-term colony formation by HCT116 cancer cells. In summary, the characterised fucoidan extracts demonstrated promising anti-cancer activities in vitro, and this warrants their further analyses in pre-clinical and clinical studies.

Immunopotentiating Activity of Fucoidans and Relevance to Cancer Immunotherapy

Fucoidans, discovered in 1913, are fucose-rich sulfated polysaccharides extracted mainly from brown seaweed. These versatile and nontoxic marine-origin heteropolysaccharides have a wide range of favorable biological activities, including antitumor, immunomodulatory, antiviral, antithrombotic, anticoagulant, antithrombotic, antioxidant, and lipid-lowering activities. In the early 1980s, fucoidans were first recognized for their role in supporting the immune response and later, in the 1990s, their effects on immune potentiation began to emerge. In recent years, the understanding of the immunomodulatory effects of fucoidan has expanded significantly. The ability of fucoidan(s) to activate CTL-mediated cytotoxicity against cancer cells, strong antitumor property, and robust safety profile make fucoidans desirable for effective cancer immunotherapy. This review focusses on current progress and understanding of the immunopotentiation activity of various fucoidans, emphasizing their relevance to cancer immunotherapy. Here, we will discuss the action of fucoidans in different immune cells and review how fucoidans can be used as adjuvants in conjunction with immunotherapeutic products to improve cancer treatment and clinical outcome. Some key rationales for the possible combination of fucoidans with immunotherapy will be discussed. An update is provided on human clinical studies and available registered cancer clinical trials using fucoidans while highlighting future prospects and challenges.

Nano-Sized Fucoidan Interpolyelectrolyte Complexes: Recent Advances in Design and Prospects for Biomedical Applications

The marine polysaccharide fucoidan (FUC) is a promising polymer for pharmaceutical research and development of novel drug delivery systems with modified release and targeted delivery. The presence of a sulfate group in the polysaccharide makes FUC an excellent candidate for the formation of interpolyelectrolyte complexes (PECs) with various polycations. However, due to the structural diversity of FUC, the design of FUC-based nanoformulations is challenging. This review describes the main strategies for the use of FUC-based PECs to develop drug delivery systems with improved biopharmaceutical properties, including nanocarriers in the form of FUC-chitosan PECs for pH-sensitive oral delivery, targeted delivery systems, and polymeric nanoparticles for improved hydrophobic drug delivery (e.g., FUC-zein PECs, core-shell structures obtained by the layer-by-layer self-assembly method, and self-assembled hydrophobically modified FUC particles). The importance of a complex study of the FUC structure, and the formation process of PECs based on it for obtaining reproducible polymeric nanoformulations with the desired properties, is also discussed.

Interaction of High-Molecular Weight Fucoidan from Laminaria hyperborea with Natural Functions of the Retinal Pigment Epithelium

Fucoidans are polysaccharides and constituents of cell walls of brown algae such as Laminaria hyperborea (LH). They exhibit promising effects regarding age-related macular degeneration (AMD). However, the safety of this compound needs to be assured. The focus of this study lies on influences of an LH fucoidan on the retinal pigment epithelium (RPE). The high-molecular weight LH fucoidan Fuc1 was applied to primary porcine RPE cells, and a tetrazolium (MTT) cell viability assay was conducted. Further tests included a scratch assay to measure wound healing, Western blotting to measure expression of retinal pigment epithelium-specific 65 kDa protein (RPE65), as well as immunofluorescence to measure uptake of opsonized fluorescence beads into RPE cells. Lipopolysaccharide was used to proinflammatorily activate the RPE, and interleukin 6 (IL-6) and interleukin 8 (IL-8) secretion was measured. RPE/choroid cultures were used to assess vascular endothelial growth factor (VEGF) secretion. Real-time polymerase chain reaction (real-time PCR) was performed to detect the gene expression of 91 different genes in a specific porcine RPE gene array. Fuc1 slightly reduced wound healing, but did not influence cell viability, phagocytosis or RPE65 expression. Fuc1 lowered IL-6, IL-8 and VEGF secretion. Furthermore, Fuc1 did not change tested RPE genes. In conclusion, Fuc1 does not impair RPE cellular functions and shows antiangiogenic and anti-inflammatory activities, which indicates its safety and strengthens its suitability concerning ocular diseases.

Characterization and therapeutic effect of Sargassum coreanum fucoidan that inhibits lipopolysaccharide-induced inflammation in RAW 264.7 macrophages by blocking NF-κB signaling

Inflammation is a complex host-protective response against harmful stimuli involving macrophage activation that results in secretion of inflammatory mediators, like nitric oxide (NO), pro-inflammatory cytokines, and prostaglandin E2 (PGE2). In this study, we evaluated fucoidan isolated using Viscozyme-assisted enzymatic extraction of Sargassum coreanum extract against lipopolysaccharide (LPS)-stimulated inflammation in RAW 264.7 macrophages and zebrafish model. Among the fucoidan fractions isolated using ion exchange chromatography, SCVF5 showed the highest sulfate and fucose contents based on chemical composition and monosaccharide analysis. Fourier-transform infrared (FT-IR) spectroscopy confirmed the presence of sulfate esters by the stretching vibrations of the SO peak at 1240 cm-1. SCVF5 showed anti-inflammatory effects by inhibiting NO and PGE2 generation in LPS-stimulated RAW 264.7 macrophages by downregulating inducible NO synthase and cyclooxygenase-2 expression. Treatment with SCVF5 suppressed pro-inflammatory cytokine production, such as TNF-α, (IL)-1β, and IL-6 by modulating the nuclear factor-kappa B signaling cascade in LPS-induced RAW 264.7 cells. Furthermore, in vivo results showed that SCVF5 can potentially downregulate LPS-induced toxicity, cell death, and NO production in LPS-induced zebrafish model. Collectively, these results suggest that S. coreanum fucoidan has remarkable anti-inflammatory activity in vitro and in vivo and may have potential applications in the functional food, cosmetic, and pharmaceutical industries.

The Therapeutic Potential of Algal Nanoparticles: A Brief Review

Recently, the green synthesis of metallic nanoparticles (NPs) has received tremendous attention as a simple approach. The green pathway of biogenic synthesis of metallic NPs through microbes may provide a sustainable and environmentally friendly protocol. Green technology is the most innovative technology for various biological activities and lacks toxic effects. Reports have shown the algae-mediated synthesis of metal NPs. Algae are widely used for biosynthesis as they grow fast; they produce biomass on average ten times that of plants and are easily utilized experimentally. In the future, the production of metal NPs by different microalgae and their biological activity can be explored in diverse areas such as catalysis, medical diagnosis, and anti-biofilm applications.

Structures and functions of algal glycans shape their capacity to sequester carbon in the ocean

Algae synthesise structurally complex glycans to build a protective barrier, the extracellular matrix. One function of matrix glycans is to slow down microorganisms that try to enzymatically enter living algae and degrade and convert their organic carbon back to carbon dioxide. We propose that matrix glycans lock up carbon in the ocean by controlling degradation of organic carbon by bacteria and other microbes not only while algae are alive, but also after death. Data revised in this review shows accumulation of algal glycans in the ocean underscoring the challenge bacteria and other microbes face to breach the glycan barrier with carbohydrate active enzymes. Briefly we also update on methods required to certify the uncertain magnitude and unknown molecular causes of glycan-controlled carbon sequestration in a changing ocean.

Seaweeds in the Oncology Arena: Anti-Cancer Potential of Fucoidan as a Drug—A Review

Marine natural products are a discerning arena to search for the future generation of medications to treat a spectrum of ailments. Meanwhile, cancer is becoming more ubiquitous over the world, and the likelihood of dying from it is rising. Surgery, radiation, and chemotherapy are the mainstays of cancer treatment worldwide, but their extensive side effects limit their curative effect. The quest for low-toxicity marine drugs to prevent and treat cancer is one of the current research priorities of researchers. Fucoidan, an algal sulfated polysaccharide, is a potent therapeutic lead candidate against cancer, signifying that far more research is needed. Fucoidan is a versatile, nontoxic marine-origin heteropolysaccharide that has received much attention due to its beneficial biological properties and safety. Fucoidan has been demonstrated to exhibit a variety of conventional bioactivities, such as antiviral, antioxidant, and immune-modulatory characteristics, and anticancer activity against a wide range of malignancies has also recently been discovered. Fucoidan inhibits tumorigenesis by prompting cell cycle arrest and apoptosis, blocking metastasis and angiogenesis, and modulating physiological signaling molecules. This review compiles the molecular and cellular aspects, immunomodulatory and anticancer actions of fucoidan as a natural marine anticancer agent. Specific fucoidan and membranaceous polysaccharides from Ecklonia cava, Laminaria japonica, Fucus vesiculosus, Astragalus, Ascophyllum nodosum, Codium fragile serving as potential anticancer marine drugs are discussed in this review.

Fucoidan from Marine Macroalgae: Biological Actions and Applications in Regenerative Medicine, Drug Delivery Systems and Food Industry

The marine macroalgae produce a collection of bioactive polysaccharides, of which the sulfated heteropolysaccharide fucoidan produced by brown algae of the class Phaeophyceae has received worldwide attention because of its particular biological actions that confer nutritional and health benefits to humans and animals. The biological actions of fucoidan are determined by their structure and chemical composition, which are largely influenced by the geographical location, harvest season, extraction process, etc. This review discusses the structure, chemical composition and physicochemical properties of fucoidan. The biological action of fucoidan and its applications for human health, tissue engineering, regenerative medicine and drug delivery are also addressed. The industrial scenario and prospects of research depicted would give an insight into developing fucoidan as a commercially viable and sustainable bioactive material in the nutritional and pharmacological sectors.

Structural characteristics of sulfated polysaccharides from Sargassum horneri and immune-enhancing activity of polysaccharides combined with lactic acid bacteria

Sargassum horneri (SH), a marine brown alga, is known to contain a variety of bioactive ingredients and previous studies reported sulfated polysaccharides in SH as a potential candidate for a functional ingredient. However, immune-enhancing activity combined with Lactobacillus plantarum (LAB) is not yet studied. In the present study, we attempted to characterize sulfated polysaccharides (SHCPs) in SH by MALDI-TOF/TOF mass spectrometry and evaluate their immune-enhancing effect on macrophage cells. The main residue of SHCPs in SH is 2-sulfated 1,4-linked L-fucose and this epitope combined with LAB shows immune enhancement properties through cytokine production at the cellular level and increases the population of lymphocytes and myelomonocytes in the adult zebrafish kidney. These results indicate that SHCPs, along with LAB, have potent immune-enhancing activity and may be utilized as a potential immunomodulatory ingredient.

Sulfated Glucuronorhamnoxylan from Capsosiphon fulvescens Ameliorates Osteoporotic Bone Resorption via Inhibition of Osteoclastic Cell Differentiation and Function In Vitro and In Vivo

Excessive osteoclast differentiation and/or bone resorptive function causes a gradual loss of bone, leading to the pathogenesis of bone diseases such as osteoporosis (OP). In this study, a sulfated glucuronorhamnoxylan polysaccharide (designated SPS-CF) of the green alga Capsosiphon fulvescens was evaluated for anti-osteoporotic activity using osteoclastic cells differentiated from RAW264.7 macrophages by receptor activator of NF-κB ligand (RANKL) treatment and ovariectomized (OVX) female mice as a postmenopausal OP model. With negligible cytotoxicity, SPS-CF (50 μg/mL) significantly suppressed tartrate-resistant acid phosphatase (TRAP) activity, actin ring formation, and expression of matrix metalloproteinase 9 (MMP-9), cathepsin K, TRAF6, p-Pyk2, c-Cbl, c-Src, gelsolin, carbonic anhydrase II (CA II), and integrin β3, indicating that SPS-CF inhibits the differentiation and bone resorptive function of osteoclasts. Removal of sulfate groups from SPS-CF abolished its anti-osteoclastogenic activities, demonstrating that sulfate groups are critical for its activity. Oral administration of SPS-CF (400 mg/kg/day) to OVX mice significantly augmented the bone mineral density (BMD) and serum osteoprotegerin (OPG)/RANKL ratio. These results demonstrated that SPS-CF exerts significant anti-osteoporotic activity by dampening osteoclastogenesis and bone resorption via downregulation of TRAF6-c-Src-Pyk2-c-Cbl-gelsolin signaling and augmentation of serum OPG/RANKL ratios in OVX mice, suggesting that SPS-CF can be a novel anti-osteoporotic compound for treating postmenopausal OP.

Sulfated Galactofucans: An Outstanding Class of Fucoidans with Promising Bioactivities

Fucoidans encompass versatile and heterogeneous sulfated biopolysaccharides of marine origin, specifically brown algae and marine invertebrates. Their chemistry and bioactivities have been extensively investigated in the last few decades. The reported studies revealed diverse chemical skeletons in which l-fucose is the main sugar monomer. However, other sugars, i.e., galactose, mannose, etc., have been identified to be interspersed, forming several heteropolymers, including galactofucans/fucogalactans (G-fucoidans). Particularly, sulfated galactofucans are associated with rich chemistry contributing to more promising bioactivities than fucans and other marine polysaccharides. The previous reports in the last 20 years showed that G-fucoidans derived from Undaria pinnatifida were the most studied; 21 bioactivities were investigated, especially antitumor and antiviral activities, and unique biomedical applications compared to other marine polysaccharides were demonstrated. Hence, the current article specifically reviews the biogenic sources, chemistry, and outstanding bioactivities of G-fucoidans providing the opportunity to discover novel drug candidates.

Applications of algae to obtain healthier meat products: A critical review on nutrients, acceptability and quality

Meat constitutes one the main protein sources worldwide. However, ethical and health concerns have limited its consumption over the last years. To overcome this negative impact, new ingredients from natural sources are being applied to meat products to obtain healthier proteinaceous meat products. Algae is a good source of unsaturated fatty acids, proteins, essential amino acids, and vitamins, which can nutritionally enrich several foods. On this basis, algae have been applied to meat products as a functional ingredient to obtain healthier meat-based products. This paper mainly reviews the bioactive compounds in algae and their application in meat products. The bioactive ingredients present in algae can give meat products functional properties such as antioxidant, neuroprotective, antigenotoxic, resulting in healthier foods. At the same time, algae addition to foods can also contribute to delay microbial spoilage extending shelf-life. Additionally, other algae-based applications such as for packaging materials for meat products are being explored. However, consumers' acceptance for new products (particularly in Western countries), namely those containing algae, not only depends on their knowledge, but also on their eating habits. Therefore, it is necessary to further explore the nutritional properties of algae-containing meat products to overcome the gap between new meat products and traditional products, so that healthier algae-containing meat can occupy a significant place in the market.

Pericapsular fibrotic overgrowth mitigated in immunocompetent mice through microbead formulations based on sulfated or intermediate G alginates

Cell encapsulation in alginate microbeads is a promising approach to provide immune isolation in cell therapy without immunosuppression. However, the efficacy is hampered by pericapsular fibrotic overgrowth (PFO), causing encapsulated cells to lose function. Stability of the microbeads is important to maintain immune isolation in the long-term. Here, we report alginate microbeads with minimal PFO in immunocompetent C57BL/6JRj mice. Microbead formulations included either alginate with an intermediate (47 %) guluronate (G) content (IntG) or sulfated alginate (SA), gelled in Ca²⁺/Ba²⁺ or Sr²⁺. A screening panel of eleven microbead formulations were evaluated for PFO, yielding multiple promising microbeads. Two candidate formulations were evaluated for 112 days in vivo, exhibiting maintained stability and minimal PFO. Microbeads investigated in a human whole blood assay revealed low cytokine and complement responses, while SA microbeads activated coagulation. Protein deposition on microbeads explanted from mice investigated by confocal laser scanning microscopy (CLSM) showed minimal deposition of complement C3. Fibrinogen was positively associated with PFO, with a high deposition on microbeads of high G (68 %) alginate compared to IntG and SA microbeads. Overall, stable microbeads containing IntG or SA may serve in long-term therapeutic applications of cell encapsulation. STATEMENT OF SIGNIFICANCE: Alginate-based hydrogels in the format of micrometer size beads is a promising approach for the immunoisolation of cells in cell therapy. Clinical trials in type 1 diabetes have so far had limited success due to fibrotic responses that hinder the diffusion of nutrients and oxygen to the encapsulated cells, resulting in graft failure. In this study, minimal fibrotic response towards micrometer size alginate beads was achieved by chemical modification of alginate with sulfate groups. Also, the use of alginate with intermediate guluronic acid content resulted in minimally fibrotic microbeads. Fibrinogen deposition was revealed to be a good indicator of fibrosis. This study points to both new microsphere developments and novel insight in the mechanisms behind the fibrotic responses.

Bio-based and bio-inspired adhesives from animals and plants for biomedical applications

With the "many-headed" slime mold Physarum polycelphalum having been voted the unicellular organism of the year 2021 by the German Society of Protozoology, we are reminded that a large part of nature's huge variety of life forms is easily overlooked - both by the general public and researchers alike. Indeed, whereas several animals such as mussels or spiders have already inspired many scientists to create novel materials with glue-like properties, there is much more to discover in the flora and fauna. Here, we provide an overview of naturally occurring slimy substances with adhesive properties and categorize them in terms of the main chemical motifs that convey their stickiness, i.e., carbohydrate-, protein-, and glycoprotein-based biological glues. Furthermore, we highlight selected recent developments in the area of material design and functionalization that aim at making use of such biological compounds for novel applications in medicine - either by conjugating adhesive motifs found in nature to biological or synthetic macromolecules or by synthetically creating (multi-)functional materials, which combine adhesive properties with additional, problem-specific (and sometimes tunable) features.

Structural diversity of fucoidans and their radioprotective effect

Fucoidans are biologically active sulfated polysaccharides of brown algae. They have a great structural diversity and a wide spectrum of biological activity. This review is intended to outline what is currently known about the structures of fucoidans and their radioprotective effect. We classified fucoidans according to their composition and structure, examined the structure of fucoidans of individual representatives of algae, summarized the available data on changes in the yields and compositions of fucoidans during algae development, and focused on information about underexplored radioprotective effect of these polysaccharides. Based on the presented in the review data, it is possible to select algae, which are the sources of fucoidans of desired structures and to determine the best time to harvest them. The use of high purified polysaccharides with established structures increase the value of studies of their biological effects and the determination of the dependence "structure - biological effect".

Anti-Inflammatory Mechanisms of Fucoidans to Treat Inflammatory Diseases: A Review

Fucoidans are sulfated heteropolysaccharides found in the cell walls of brown seaweeds (Phaeophyceae) and in some marine invertebrates. Generally, fucoidans are composed of significant amounts of L-fucose and sulfate groups, and lesser amounts of arabinose, galactose, glucose, glucuronic acid, mannose, rhamnose, and xylose. In recent years, fucoidans isolated from brown seaweeds have gained considerable attention owing to their promising bioactive properties such as antioxidant, immunomodulatory, anti-inflammatory, antiobesity, antidiabetic, and anticancer properties. Inflammation is a complex immune response that protects the organs from infection and tissue injury. While controlled inflammatory responses are beneficial to the host, leading to the removal of immunostimulants from the host tissues and restoration of structural and physiological functions in the host tissues, chronic inflammatory responses are often associated with the pathogenesis of tumor development, arthritis, cardiovascular diseases, diabetes, obesity, and neurodegenerative diseases. In this review, the authors mainly discuss the studies since 2016 that have reported anti-inflammatory properties of fucoidans isolated from various brown seaweeds, and their potential as a novel functional material for the treatment of inflammatory diseases.

A Combination Approach in Inhibiting Type 2 Diabetes-Related Enzymes Using Ecklonia radiata Fucoidan and Acarbose

Although there are chemotherapeutic efforts in place for Type 2 diabetes mellitus (T2DM), there is a need for novel strategies (including natural products) to manage T2DM. Fucoidan, a sulphated polysaccharide was extracted from Ecklonia radiata. The integrity of the fucoidan was confirmed by structural analysis techniques such as FT-IR, NMR and TGA. In addition, the fucoidan was chemically characterised and tested for cell toxicity. The fucoidan was investigated with regards to its potential to inhibit α-amylase and α-glucosidase. The fucoidan was not cytotoxic and inhibited α-glucosidase (IC50 19 µg/mL) more strongly than the standard commercial drug acarbose (IC50 332 µg/mL). However, the fucoidan lacked potency against α-amylase. On the other hand, acarbose was a more potent inhibitor of α-amylase (IC50 of 109 µg/mL) than α-glucosidase. Due to side effects associated with the use of acarbose, a combination approach using acarbose and fucoidan was investigated. The combination showed synergistic inhibition (>70%) of α-glucosidase compared to when the drugs were used alone. The medicinal implication of this synergism is that a regimen with a reduced acarbose dose may be used, thus minimising side effects to the patient, while achieving the desired therapeutic effect for managing T2DM.

Fucoidan for cardiovascular application and the factors mediating its activities

Fucoidan is a sulfated polysaccharide with various bioactivities. The application of fucoidan in cancer treatment, wound healing, and food industry has been extensively studied. However, the therapeutic value of fucoidan in cardiovascular diseases has been less explored. Increasing number of investigations in the past years have demonstrated the effects of fucoidan on cardiovascular system. In this review, we will focus on the bioactivities related to cardiovascular applications, for example, the modulation functions of fucoidan on coagulation system, inflammation, and vascular cells. Factors mediating those activities will be discussed in detail. Current therapeutic strategies and future opportunities and challenges will be provided to inspire and guide further research.

Evaluation of the Effects of Fucoidans from Fucus Species and Laminaria hyperborea against Oxidative Stress and Iron-Dependent Cell Death

Fucoidans are algal polysaccharides that exhibit protective properties against oxidative stress. The aim of this study was to investigate different fucoidans from brown seaweeds for their ability to protect against iron-dependent oxidative stress (ferroptosis), a main hallmark of retinal and brain diseases, including hemorrhage. We investigated five new high-molecular weight fucoidan extracts from Fucus vesiculosus, F. serratus, and F. distichus subsp. evanescens, a previously published Laminaria hyperborean extract, and commercially available extracts from F. vesiculosus and Undaria pinnatifida. We induced oxidative stress by glutathione depletion (erastin) and H2O2 in four retinal and neuronal cell lines as well as primary cortical neurons. Only extracts from F. serratus, F. distichus subsp. evanescens, and Laminaria hyperborea were partially protective against erastin-induced cell death in ARPE-19 and OMM-1 cells, while none of the extracts showed beneficial effects in neuronal cells. Protective fucoidans also attenuated the decrease in protein levels of the antioxidant enzyme GPX4, a key regulator of ferroptosis. This comprehensive analysis demonstrates that the antioxidant abilities of fucoidans may be cell type-specific, besides depending on the algal species and extraction method. Future studies are needed to further characterize the health-benefiting effects of fucoidans and to determine the exact mechanism underlying their antioxidative abilities.

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

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

Ion-exchange purification and structural characterization of five sulfated fucoidans from brown algae

Fucoidans are a diverse class of sulfated polysaccharides integral to the cell wall of brown algae, and due to their various bioactivities, they are potential drugs. Standardized work with fucoidans is required for structure-function studies, but remains challenging since available fucoidan preparations are often contaminated with other algal compounds. Additionally, fucoidans are structurally diverse depending on species and season, urging the need for standardized purification protocols. Here, we use ion-exchange chromatography to purify different fucoidans and found a high structural diversity between fucoidans. Ion-exchange chromatography efficiently removes the polysaccharides alginate and laminarin and other contaminants such as proteins and phlorotannins across a broad range of fucoidans from major brown algal orders including Ectocarpales, Laminariales and Fucales. By monomer composition, linkage analysis and NMR characterization, we identified galacturonic acid, glucuronic acid and O-acetylation as new structural features of certain fucoidans and provided a novel structure of fucoidan from Durvillaea potatorum with α-1,3-linked fucose backbone and β-1,6 and β-1,3 galactose branches. This study emphasizes the use of standardized ion-exchange chromatography to obtain defined fucoidans for subsequent molecular studies.

Study of fucoidans as natural biomolecules for therapeutical applications in osteoarthritis

Osteoarthritis (OA) is the most prevalent articular chronic disease. Although, to date there is no cure for OA. Fucoidans, one of the main therapeutic components of brown algae, have emerged as promising molecules in OA treatment. However, the variability between fucoidans makes difficult the pursuit of the most suitable candidate to target specific pathological processes. By an in vitro experimental approach in chondrocytes and fibroblast-like synoviocytes, we observed that chemical composition of fucoidan, and specifically the phlorotannin content and the ratio sulfate:fucose, seems critically relevant for its biological activity. Nonetheless, other factors like concentration and molecular weight of the fucoidan may influence on its beneficial effects. Additionally, a cell-type dependent response was also detected. Thus, our results shed light on the potential use of fucoidans as natural molecules in the treatment of key pathological processes in the joint that favor the development of rheumatic disorders as OA.

Fucoidans as Potential Therapeutics for Age-Related Macular Degeneration-Current Evidence from In Vitro Research

Age-related macular degeneration (AMD) is the major reason for blindness in the industrialized world with limited treatment options. Important pathogenic pathways in AMD include oxidative stress and vascular endothelial growth factor (VEGF) secretion. Due to their bioactivities, fucoidans have recently been suggested as potential therapeutics. This review gives an overview of the recent developments in this field. Recent studies have characterized several fucoidans from different species, with different molecular characteristics and different extraction methods, in regard to their ability to reduce oxidative stress and inhibit VEGF in AMD-relevant in vitro systems. As shown in these studies, fucoidans exhibit a species dependency in their bioactivity. Additionally, molecular properties such as molecular weight and fucose content are important issues. Fucoidans from Saccharina latissima and Laminaria hyperborea were identified as the most promising candidates for further development. Further research is warranted to establish fucoidans as potential therapeutics for AMD.

A Comprehensive and Comparative Analysis of the Fucoidan Compositional Data Across the Phaeophyceae

In the current review, compositional data on fucoidans extracted from more than hundred different species were surveyed through the available literature. The analysis of crude extracts, purified extracts or carefully isolated fractions is included in tabular form, discriminating the seaweed source by its taxonomical order (and sometimes the family). This survey was able to encounter some similarities between the different species, as well as some differences. Fractions which were obtained through anion-exchange chromatography or cationic detergent precipitation showed the best separation patterns: the fractions with low charge correspond mostly to highly heterogeneous fucoidans, containing (besides fucose) other monosaccharides like xylose, galactose, mannose, rhamnose, and glucuronic acid, and contain low-sulfate/high uronic acid proportions, whereas those with higher total charge usually contain mainly fucose, accompanied with variable proportions of galactose, are highly sulfated and show almost no uronic acids. The latter fractions are usually the most biologically active. Fractions containing intermediate proportions of both polysaccharides appear at middle ionic strengths. This pattern is common for all the orders of brown seaweeds, and most differences appear from the seaweed source (habitat, season), and from the diverse extraction, purification, and analytitcal methods. The Dictyotales appear to be the most atypical order, as usually large proportions of mannose and uronic acids appear, and thus they obscure the differences between the fractions with different charge. Within the family Alariaceae (order Laminariales), the presence of sulfated galactofucans with high galactose content (almost equal to that of fucose) is especially noteworthy.

Fucoidan Characterization: Determination of Purity and Physicochemical and Chemical Properties

Fucoidans are marine sulfated biopolysaccharides that have heterogenous and complicated chemical structures. Various sugar monomers, glycosidic linkages, molecular masses, branching sites, and sulfate ester pattern and content are involved within their backbones. Additionally, sources, downstream processes, and geographical and seasonal factors show potential effects on fucoidan structural characteristics. These characteristics are documented to be highly related to fucoidan potential activities. Therefore, numerous chemical qualitative and quantitative determinations and structural elucidation methods are conducted to characterize fucoidans regarding their physicochemical and chemical features. Characterization of fucoidan polymers is considered a bottleneck for further biological and industrial applications. Consequently, the obtained results may be related to different activities, which could be improved afterward by further functional modifications. The current article highlights the different spectrometric and nonspectrometric methods applied for the characterization of native fucoidans, including degree of purity, sugar monomeric composition, sulfation pattern and content, molecular mass, and glycosidic linkages.

Verrucomicrobia use hundreds of enzymes to digest the algal polysaccharide fucoidan

Brown algae are important players in the global carbon cycle by fixing carbon dioxide into 1 Gt of biomass annually, yet the fate of fucoidan-their major cell wall polysaccharide-remains poorly understood. Microbial degradation of fucoidans is slower than that of other polysaccharides, suggesting that fucoidans are more recalcitrant and may sequester carbon in the ocean. This may be due to the complex, branched and highly sulfated structure of fucoidans, which also varies among species of brown algae. Here, we show that 'Lentimonas' sp. CC4, belonging to the Verrucomicrobia, acquired a remarkably complex machinery for the degradation of six different fucoidans. The strain accumulated 284 putative fucoidanases, including glycoside hydrolases, sulfatases and carbohydrate esterases, which are primarily located on a 0.89-megabase pair plasmid. Proteomics reveals that these enzymes assemble into substrate-specific pathways requiring about 100 enzymes per fucoidan from different species of brown algae. These enzymes depolymerize fucoidan into fucose, which is metabolized in a proteome-costly bacterial microcompartment that spatially constrains the metabolism of the toxic intermediate lactaldehyde. Marine metagenomes and microbial genomes show that Verrucomicrobia including 'Lentimonas' are abundant and highly specialized degraders of fucoidans and other complex polysaccharides. Overall, the complexity of the pathways underscores why fucoidans are probably recalcitrant and more slowly degraded, since only highly specialized organisms can effectively degrade them in the ocean.

Size distribution and chain conformation of six different fucoidans using size-exclusion chromatography with multiple detection

Fucoidans represent an intriguing class of fucose-containing sulfated polysaccharides. The biological activities of these polysaccharides are related to their compositional and structural parameters, whereby their degree of sulfation, as well as molecular weight (MW) distribution and chain conformation play important roles. Modern NMR and mass spectrometry techniques allow elucidating details of the glycan structure, but not the structure of the whole molecules in their native state. Accordingly, the knowledge about the latter of the fucoidans is currently still limited. Contrary to traditional MW determination by SEC with column calibration, SEC with triple detection provides not only the absolute Mw, but can also give information on additional molecule characteristics. In the present study, we used this method to compare six fucoidans extracted from Fucus vesiculosus (FV), F. serratus (FS), F. evanescens (FE), Dictyosiphon foeniculaceus (DF), Laminaria digitata (LD), and Saccharina latissima (SL) concerning their molar mass (Mw, Mn, Mp, dispersity) and size (rms radius, Rh) characteristics and distribution as well as their chain conformation in solution. The tested fucoidans displayed considerable structural diversity including large differences in their MW profiles and showed to be heterogeneously composed. Fuc-FV and Fuc-SL showed the broadest MW distributions, those from Fuc-FE and Fuc-DF the narrowest ones. Most of the fucoidan fractions (except for Fuc-DF) turned out to exist as expanded flexible chains in PBS solution. The conformation data suggest branched structures with partly long side chains. The knowledge obtained by this study is useful for further fractionation and structural characterization as well as the interpretation of the bioactivity differences between the various fucoidans.

Effects of Sulfated Fucans from Laminaria hyperborea Regarding VEGF Secretion, Cell Viability, and Oxidative Stress and Correlation with Molecular Weight

BACKGROUND

Sulfated fucans show interesting effects in the treatment of ocular diseases (e.g., age-related macular degeneration), depending on their chemical structure. Here, we compared three purified sulfated fucans from Laminaria hyperborea (LH) regarding cell viability, oxidative stress protection, and vascular endothelial growth factor (VEGF) secretion in ocular cells.

METHODS

High-molecular-weight sulfated fucan (Mw = 1548.6 kDa, Fuc1) was extracted with warm water and purified through ultrafiltration. Lower-molecular-weight samples (Mw = 499 kDa, Fuc2; 26.9 kDa, Fuc3) were obtained by mild acid hydrolysis of ultrapurified sulfated fucan and analyzed (SEC-MALS (Size-exclusion chromatography-Multi-Angle Light Scattering), ICP-MS, and GC). Concentrations between 1 and 100 µg/mL were tested. Cell viability was measured after 24 h (uveal melanoma cell line (OMM-1), retinal pigment epithelium (RPE) cell line ARPE-19, primary RPE cells) via MTT/MTS (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide/3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. Oxidative stress protection was determined after 24 h (OMM-1, ARPE-19). VEGF secretion was analyzed via ELISA after three days (ARPE-19, RPE).

RESULTS

Fuc2 and Fuc3 were antiproliferative for OMM-1, but not for ARPE. Fuc1 protected OMM-1. VEGF secretion was lowered with all fucans except Fuc3 in ARPE-19 and RPE. The results suggest a correlation between molecular weight and biological activity, with efficiency increasing with size.

CONCLUSION

The LH sulfated fucan Fuc1 showed promising results regarding VEGF inhibition and protection, encouraging further medical research.