A review about brown algal cell walls and fucose-containing sulfated polysaccharides: Cell wall context, biomedical properties and key research challenges

Fucoidan and its derivatives: From extraction to cutting-edge biomedical applications

Fucoidan, a sulfated polymeric carbohydrate isolated from various marine brown algae, has attracted the interest of biomedical scientists because of its unique structural features and extensive spectrum of biological activity. This review encompasses a comprehensive insight into fucoidan's extraction procedures, cross-linking strategies, chemical modifications, and biomedical applications. Advanced extraction methods, such as microwave-assisted and enzyme-assisted extraction, are emphasized to get high-quality fucoidan that has augmented bioactivity. Moreover, the production and role of fucoidan-based materials in drug delivery systems are investigated, with a focus on their potential for targeted therapies. The study also explores the strategies to improve fucoidan's bioavailability and mechanical properties via structural modifications, such as Sulfation, desulfation, methylation, benzoylation, sulfation, amination, acetylation and phosphorylation, and cross-linking with other polymers to form films, hydrogels, and nanocomposites. In addition, fucoidan's applications in drug delivery systems, tissue engineering, microneedles, and 3D bioprinting are discussed. By summarizing current research findings, this study seeks to comprehend the mechanisms underpinning fucoidan's therapeutic efficacy and its potential to develop robust biomaterials.

Fucoidan alginate and sulfated alginate microbeads induce distinct coagulation, inflammatory and fibrotic responses

This study investigates the host response to fucoidan alginate microbeads in comparison to sulfated alginate microbeads, which are relevant for immune protection in cell therapy. While sulfated alginate microbeads reduce fibrosis and inflammation, fucoidan, a kelp-derived polysaccharide rich in sulfate groups, has not been evaluated in this context. The study assesses surface reactivity to acute-phase proteins and cytokines using ex vivo human whole blood and plasma models. It also examines pericapsular overgrowth (PFO) in C57BL/6JRj mice, incorporating protein pattern mapping through LC-MS/MS proteomics. Fucoidan alginate microbeads activated complement and coagulation, while both fucoidan and sulfated alginate microbeads induced plasmin activity. Fucoidan alginate microbeads exhibited a distinct cytokine profile, characterized by high levels of MCP-1, IL-8, IFN-γ, and reduced levels of RANTES, Eotaxin, PDGF-BB, TGF-β isoforms, along with higher PFO. The balance between plasmin activity and coagulation emerged as a potential predictor of fibrosis resistance, favouring sulfated alginate microbeads. Explanted materials were enriched with both complement and coagulation activators (Complement C1q and C3, Factor 12, Kallikrein, HMW-kininogen) and inhibitors (C1-inhibitor, Factor H, Factor I). Fucoidan alginate microbeads predominantly enriched extracellular matrix factors (Fibrinogen, Collagen, TGF-β, Bmp), while sulfated alginate microbeads favoured ECM-degrading proteases (Metalloproteases and Cathepsins). This study reveals significant differences in host responses to fucoidan and sulfated alginate in microbeads. The plasmin activity to coagulation ratio is highlighted as a key indicator of fibrosis resistance. Additionally, the preferential enrichment of ECM-degrading proteases on the material surface post-implantation proved to be another crucial factor.

Steam explosion improved the physicochemical properties, hypoglycemic effects of polysaccharides from Clerodendranthus spicatus leaf via regulating IRS1/PI3K/AKT/GSK-3β signaling pathway in IR-HepG2 cells

Clerodendranthus spicatus (C. spicatus) leaf is a kind of functional tea and traditional Chinese folk medicine and it is famous for hypoglycemic value. The effects of steam explosion (SE) pretreatment on structural characteristics, α-glucosidase inhibition activity and hypoglycemic effects of C. spicatus leaf polysaccharides (CSP) were investigated. Two polysaccharides fractions from the untreated C. spicatus leaf (NTCSP-A) and SE treated C. spicatus leaf (SECSP-C) were obtained after the purification by DEAE Sepharose Fast Flow column chromatography. Results showed that SE pretreatment obviously increased the yields of CSP from 10.17 % to 13.43 % and decreased the molecular weight distribution. Monosaccharide composition analysis indicated that the main compositional modification by SE pretreatment was the increase in the proportion of mannose, glucuronic acid and arabinose. And SE pretreatment changed the inhibition type against α-glucosidase from competitive inhibition (NTCSP-A) to uncompetitive inhibition (SECSP-C). In addition, SE pretreatment increased the anti-diabetic activity on IR-HepG2 cells by increasing the glucose consumption and glycogen synthesis and regulating IRS1/PI3K/AKT/GSK-3β signaling pathway. This study indicated that SE technology modified the physiochemical properties and increased the hypoglycemic activity of CSP. It also provided helpful information on the application of SE in the efficient preparation and utilization of bioactive polysaccharides.

Renewable Energy from Beach-Cast Seaweed: Calorific Power Heating Studies with Macroalgae

Some stretches of the Brazilian coast are regularly subject to a natural process of macroalgae deposition. In urban beach areas, public institutions responsible for cleaning collect this biomass and dispose of it in landfills. When this biomass is exposed to the sun for a long time in the littoral area, a decomposition process begins and causes greenhouse gas emission into the atmosphere. Macroalgae biomass is a natural resource that could be used for renewable energy, contributing to meeting the growing demand for low environmental impacts of energy, indicating the possibility of participating in sustainable development. The objective of this research was to evaluate the energetic potential of macroalgae biomass deposited on the Maceió coast; specifically, the combustion capacity of aggregate biomass and pellet biofuel produced with macroalgae. The research, which analysed 13 species, proceeded using a calorimetric pump methodology to determine the power heating value and a mass spectrophotometer to determine the available energetic chemical elements. The result of 8.82 MJ/Kg was similar to the main biomass used in Brazil, the sugarcane bagasse, evaluated at 8.91 MJ/Kg. Aggregated macroalgae biomass in condensed pellets with energetic composites obtained a value of 4823 Kcal/Kg, 1.2% more than the average of terrestrial biomass pellets. Therefore, these results show possibilities to produce biofuel using thermal energy from marine macroalgae biomass.

Genomic analysis of Isoptericola halotolerans SM2308 reveals its potential involved in fucoidan degradation

Marine bacteria play important roles in the degradation and recycling of algal polysaccharides. However, the marine bacteria involved in fucoidan degradation and their degradation pathways remain poorly understood. Here, we report the complete genome sequence of Isoptericola halotolerans SM2308, isolated from a brown algal sample collected from an intertidal zone of the Yellow Sea in China. The genome of strain SM2308 consists of a single circular chromosome of 4,011,455 bp with a high GC content of 72.70 %. Strain SM2308 exhibited rapid growth on fucoidan as the sole carbon source, indicating its capacity to degrade fucoidan. Gene annotation and metabolic pathway analyses showed that strain SM2308 possesses a complete pathway for utilizing fucoidan, including the extracellular breakdown of polymeric fucoidan into smaller fucooligosaccharides/fucose by fucoidanases, the transmembrane transport of fucooligosaccharides/fucose into the cytoplasm by an ABC transporter, and the intracellular fucose catabolism via a non-phosphorylative pathway. This represents the first genome of an actinobacterium from the order Micrococcales with fucoidan-degrading ability. The genome of Isoptericola halotolerans SM2308 provides insights into the role of actinobacteria in the biogeochemical cycling of fucoidan in marine ecosystems.

Neuroprotective effect of apo-9'-fucoxanthinone against cerebral ischemia injury by targeting the PI3K/AKT/GSK-3β pathway

Neuronal loss in cerebral ischemia primarily results from the combined effects of inflammatory responses and programmed cell death. Currently, there is an urgent need for potent neuroprotectants targeting both inflammatory and apoptotic responses for the treatment of ischemic stroke. Marine natural products are a vital source of novel drug candidates. Apo-9'-fucoxanthinone (APO-9'), a degradation product of fucoxanthin derived from marine brown algae, is known for its substantial anti-inflammatory effects, yet its neuroprotective action has not been clearly defined. In this study, the neuroprotective effects of APO-9' in alleviating cerebral ischemia injury and the underlying mechanism were primarily explored with the aid of tandem mass tag-based quantitative proteomics. APO-9' was found to markedly decrease the levels of inflammation factors by suppressing the IKK/IκB/NF-κB pathway in lipopolysaccharide (LPS)-induced BV2 cells. It also attenuated apoptotic responses in both LPS-induced BV2 cells and oxygen-glucose deprivation/reoxygenation (OGD/R)-induced SH-SY5Y cells. These neuroprotective effects of APO-9' were linked to the activation of the PI3K/AKT pathway. Intraperitoneal injection of APO-9' in a MCAO mouse model showed significant cerebral protection against ischemia. The involvements of the IKK/IκB/NF-κB and PI3K/AKT/GSK-3β pathways were also confirmed in its alleviation of cerebral ischemia in vivo. This study established that APO-9' exerted neuroprotection against cerebral ischemia by inhibiting inflammatory and apoptotic cascades via the IKK/IκB/NF-κB and PI3K/AKT/GSK-3β signaling pathways.

Seaweed-derived laminarin and alginate as potential chemotherapeutical agents: An updated comprehensive review considering cancer treatment

Seaweed-derived bioactive substances such as polysaccharides have proven to be effective chemotherapeutic and chemopreventive agents. Laminarin and alginate antioxidant properties aid in the prevention of cancer through dynamic modulation of critical intracellular signaling pathways via apoptosis which produce low cytotoxicity and potential chemotherapeutic effects. Understanding the effects of laminarin and alginate on human cancer cells and their molecular roles in cell death pathways can help to develop a novel chemoprevention strategy. This review emphasizes the importance of apoptosis-modulating laminarin and alginate in a range of malignancies as well as their extraction, molecular structure, and weight. In addition, future nano-formulation enhancements for greater clinical efficacy are discussed. Laminarin and alginate are perfect ingredients because of their distinct physicochemical and biological characteristics and their use-based delivery systems in cancer. The effectiveness of laminarin and alginate against cancer and more preclinical and clinical trials will open up as new chemotherapeutic natural drugs which lead to established as potential cancer drugs.

Influence of a Very High-Molecular Weight Fucoidan from Laminaria hyperborea on Age-Related Macular Degeneration-Relevant Pathomechanisms in Ocular Cell Models

Fucoidans from Laminaria hyperborea (LH) can be antioxidative, antiangiogenic, and anti-inflammatory. In this study, a very high-molecular weight (3700 kDa) fucoidan from LH, FucBB04, was tested regarding its bioactivity in age-related macular degeneration (AMD) models in vitro. Primary retinal pigment epithelium (RPE) from pig eyes, human uveal melanoma cell line OMM-1, and RPE cell line ARPE-19 were used. Substituents of the extract were determined with chemical analysis. Cell viability was tested with tetrazolium assay (MTT), oxidative stress was induced by H2O2 or erastin, respectively. Secreted vascular endothelial growth factor A (VEGF-A) was assessed with ELISA. Retinal pigment epithelium 65 kDa protein (RPE65) and protectin (CD59) protein expression were tested in Western blot. Cell barrier was assessed by measuring trans-epithelial electrical resistance (TEER), phagocytic ability by a fluorescence assay. Gene expression and secretion of interleukin 6 (IL-6) and interleukin 8 (IL-8) were tested in real-time PCR and ELISA. FucBB04 displayed no oxidative stress protective effects. Its effect on VEGF was inconsistent, with VEGF secretion reduced in primary RPE, but not in ARPE-19. On the other hand, Lipopolysaccharide (LPS) and polyinosinic/polycytidylic acid (PIC)-induced IL-6 or IL-8 secretion was reduced by FucBB04, while complement inhibiting protein CD59 was not affected. In addition, FucBB04 did not influence the gene expression of IL-6 or IL-8. Visual cycle protein RPE65 expression, phagocytic ability, and barrier function were reduced by FucBB04. Very high-molecular weight fucoidan from LH shows bioactivities against AMD-related pathological pathways, but adverse effects on RPE function may limit its suitability as a therapeutic compound. Smaller high-molecular weight fucoidans are recommended for further research.

Synergistic Antiviral Activity of Xanthan Gum and Camostat Against Influenza Virus Infection

Influenza A virus (IAV) is a major cause of respiratory infections worldwide. Current preventive measures, though effective for decades, face limitations due to the continuous evolution of viral strains and challenges in targeting specific viral proteins. In this study, we conducted in vivo screenings to evaluate the antiviral properties of various promising polymers to overcome the limitations of current virus infection prevention strategies. Subsequently, we performed detailed physiological and pathological assessments over an extended infection period. In the animal experiments regarding weight loss, a key symptom of viral infection, the group treated with xanthan gum (XG) showed significant suppression of weight loss compared to the untreated group starting from 3 DPI. Throughout the experiment, the treated group maintained a body weight similar to that of the uninfected group. In the virus titration and lung tissue pathology analysis, the group treated with the test substance showed a significantly lower viral load and tissue pathology results closer to normal compared to the untreated group. Additionally, we conducted in vitro combination treatment experiments to evaluate the antiviral ability of XG in conjunction with camostat, a previously known TMPRSS2 inhibitor. The results demonstrated that in the combination-treated groups, XG and camostat exhibited significantly higher cell viability at lower concentrations compared to the single-treatment groups for influenza A H1N1, A H3N2, and B type. These results indicate that XG possesses potential capabilities in inhibiting respiratory viruses and may be utilized in conjunction with existing antiviral treatments.

Nutrient based classification of Phyllospora comosa biomasses using machine learning algorithms: Towards sustainable valorisation

Sustainable seaweed value chains necessitate accurate biomass biochemical characterisation that leads to product development, geographical authentications and quality and sustainability assurances. Underutilised yet abundantly available seaweed species require a thorough investigation of biochemical characteristics prior to their valorisation. Abundantly available Australian seaweed species lack such comprehensive investigations within the global seaweed industrial value chains. Aiming to bridge this gap, this study characterises Phyllospora comosa thallus segments (blades, stipes, and vesicles) and unsegmented samples collected from separate locations in Victoria, Australia using high throughput characterisation techniques and machine learning classification models. Carbohydrate (64-68 %), ash (27-31 %), potassium (31.01 - 65.01 mg/g), sodium (20.36 - 30.59 mg/g), calcium (15.10 - 18.40 mg/g), magnesium (7.71 - 11.81 mg/g) and iodine (1.57 - 2.74 mg/g) were the most abundant nutrients of the P. comosa biomasses, on a dry weight basis. Variations between segments showed that stipes were rich in carbohydrate, blades in glutamic acid, calcium, magnesium, and iodine and vesicles in potassium, suggesting differing valorisation paths. The "rpart" classification separated the collection sites based on cadmium: Bancoora < 84.9 x 10-6 mg/g (dw) ≤ Port Fairy with a 88 % accuracy and segments, initially based on glutamic acid : blades ≥ 10.61 mg/g (dw) or protein 45.25 mg/g (dw) > stipes and vesicles and then by potassium : vesicles ≥ 44.88 mg/g (dw) > stipes with a 100 % accuracy. These highly accurate characterisation and classification methods, when applied to larger sample sizes will assist in the diversification and expansions of authentic and sustainable Australian seaweed value chains.

Unlocking the Therapeutic Potential of Algae-Derived Compounds in Hematological Malignancies

Algae are a rich source of bioactive compounds that have a wide range of beneficial effects on human health and can show significant potential in the treatment of hematological malignancies such as leukemia, lymphoma, and multiple myeloma. These diseases often pose a therapeutic challenge despite recent advances in treatment (e.g., the use of immunomodulatory drugs, proteasome inhibitors, CD38 monoclonal antibodies, stem cell transplant, and targeted therapy). A considerable number of patients experience relapses or resistance to the applied therapies. Algal compounds, alone or in combination with chemotherapy or other more advanced therapies, have exhibited antitumor and immunomodulatory effects in preclinical studies that may improve disease outcomes. These include the ability to induce apoptosis, inhibit tumor growth, and improve immune responses. However, most of these studies are conducted in vitro, often without in vivo validation or clinical trials. This paper summarizes the current evidence on the in vitro effects of algae extracts and isolated compounds on leukemia, lymphoma, and myeloma cell lines. In addition, we address the current advances in the application of algae-derived compounds as targeted drug carriers and their synergistic potential against hematologic malignancies.

Longitudinal growth of the Saccharina kelp embryo depends on actin filaments that control the formation of a corset-like structure composed of alginate

The initiation of embryogenesis in the kelp Saccharina latissima is accompanied by significant anisotropy in cell shape. Using monoclonal antibodies, we show that this anisotropy coincides with a spatio-temporal pattern of accumulation of alginates in the cell wall of the zygote and embryo. Alginates rich in guluronates as well as sulphated fucans show a homogeneous distribution in the embryo throughout Phase I of embryogenesis, but mannuronate alginates accumulate mainly on the sides of the zygote and embryo, disappearing as the embryo enlarges at the start of Phase II. This pattern depends on the presence of cortical actin filaments. In contrast, within the embryo lamina, the alginate composition of the walls newly formed by cytokinesis is not affected by the depolymerisation of actin filaments. Thus, in addition to revealing the existence of a mannuronate-rich alginate corset-like structure that may restrict the enlargement of the zygote and the embryo, thereby promoting the formation of the apico-basal growth axis, we demonstrate stage- and cytoskeleton-dependent differences in cell wall deposition in Saccharina embryos.

Crystal structures of Aspergillus oryzae exo-β-(1,3)-glucanase reveal insights into oligosaccharide binding, recognition, and hydrolysis

Exo-β-(1,3)-glucanases are promising enzymes for use in the biofuel industry as they hydrolyse sugars such as laminarin, a major constituent of the algal cell wall. This study reports structural and biochemical characterizations of Aspergillus oryzae exo-β-(1,3)-glucanase (AoBgl) belonging to the GH5 family. Purified AoBgl hydrolyses β-(1,3)-glycosidic linkages of the oligosaccharide laminaritriose and the polysaccharide laminarin effectively. We have determined three high-resolution structures of AoBgl: (a) the apo form at 1.75 Å, (b) the complexed form with bound cellobiose at 1.73 Å and (c) the glucose-bound form at 1.20 Å. The crystal structures, molecular dynamics simulation studies and site-directed mutagenesis reveal the mode of substrate binding and interactions at the active site. The results also indicate that AoBgl effectively hydrolyses trisaccharides and higher oligosaccharides. The findings from our structural and biochemical studies would aid in rational engineering efforts to generate superior AoBgl variants and similar GH5 enzymes for their industrial use.

Mechanisms of recalcitrant fucoidan breakdown in marine Planctomycetota

Marine brown algae produce the highly recalcitrant polysaccharide fucoidan, contributing to long-term oceanic carbon storage and climate regulation. Fucoidan is degraded by specialized heterotrophic bacteria, which promote ecosystem function and global carbon turnover using largely uncharacterized mechanisms. Here, we isolate and study two Planctomycetota strains from the microbiome associated with the alga Fucus spiralis, which grow efficiently on chemically diverse fucoidans. One of the strains appears to internalize the polymer, while the other strain degrades it extracellularly. Multi-omic approaches show that fucoidan breakdown is mediated by the expression of divergent polysaccharide utilization loci, and endo-fucanases of family GH168 are strongly upregulated during fucoidan digestion. Enzymatic assays and structural biology studies reveal how GH168 endo-fucanases degrade various fucoidan cores from brown algae, assisted by auxiliary hydrolytic enzymes. Overall, our results provide insights into fucoidan processing mechanisms in macroalgal-associated bacteria.

Cell walls, a comparative view of the composition of cell surfaces of plants, algae and microorganisms

While evolutionary studies indicate that the most ancient groups of organisms on Earth likely descended from a common wall-less ancestor, contemporary organisms lacking a carbohydrate-rich cell surface are exceedingly rare. By developing a cell wall to cover the plasma membrane, cells were able to withstand higher osmotic pressures, colonise new habitats and develop complex multicellular structures. This way, the cells of plants, algae and microorganisms are covered by a cell wall, which can generally be defined as a highly complex structure whose main framework is usually composed of carbohydrates. Rather than static structures, they are highly dynamic and serve a multitude of functions that modulate vital cellular processes, such as growth and interactions with neighbouring cells or the surrounding environment. Thus, despite its vital importance for many groups of life, it is striking that there are few comprehensive documents comparing the cell wall composition of these groups. Thus, the aim of this review was to compare the cell walls of plants with those of algae and microorganisms, paying particular attention to their polysaccharide components. It should be highlighted that, despite the important differences in composition, we have also found numerous common aspects and functionalities.

Production and ecological function of fucoidans from marine algae in a changing ocean

Fucoidans have multiple biological and biomedical functions, e.g., antibacterial, antiviral, immunomodulatory, inflammatory, and growth-promoting effects. Recent studies show that they also have essential ecological functions whereas our understanding in this field is very superficial. This study first reviewed the fucoidan content in algae and the highest content of 13.3 % in Undaria pinnatifida sporophyll and the lowest content of 0.1 % in Alaria angusta were found. Field investigation demonstrates that light, temperature, salinity, and nutrient can affect fucoidan production in algae; while more laboratory experiments need to be carried out to verify these conclusions. Brown algae can excrete 8-31 % of their net carbon fixation into seawater in the form of fucoidans. Fucoidans are highly recalcitrant to bacterial degradation, enabling the carbon within them to be stored for centuries. Therefore, fucoidans can play an essential role in carbon sequestration. Ocean afforestation with brown algae may be an effective approach to remove atmospheric CO2 since fucoidans have a high carbon content while seldom need any nitrogen or phosphorus. Fucoidan production in a warming and CO2 enriched ocean was also discussed. This study provides new insight into production and ecological functions of fucoidans, indicating their role in carbon sequestration and climate change alleviation.

Algal carbohydrates: Sources, biosynthetic pathway, production, and applications

Algae play a significant role in the global carbon cycle by utilizing photosynthesis to efficiently convert solar energy and atmospheric carbon dioxide into various chemical compounds, notably carbohydrates, pigments, lipids, and released oxygen, making them a unique sustainable cellular factory. Algae mostly consist of carbohydrates, which include a broad variety of structures that contribute to their distinct physical and chemical properties such as degree of polymerization, side chain, branching, degree of sulfation, hydrogen bond etc., these features play a crucial role in regulating many biological activity, nutritional and pharmaceutical properties. Algal carbohydrates have not received enough attention in spite of their distinctive structural traits linked to certain biological and physicochemical properties. Nevertheless, it is anticipated that there will be a significant increase in the near future due to increasing demand, sustainable source, biofuel generation and their bioactivity. This is facilitated by the abundance of easily accessible information on the structural data and distinctive characteristics of these biopolymers. This review delves into the different types of saccharides such as agar, alginate, fucoidan, carrageenan, ulvan, EPS and glucans synthesized by various macroalgal and microalgal systems, which include intracellular, extracellular and cell wall saccharides. Their structure, biosynthetic pathway, sources, production strategies and their applications in various field such as nutraceuticals, pharmaceuticals, biomedicine, food and feed, cosmetics, and bioenergy are also elaborately discussed. Algal polysaccharide has huge a scope for exploitation in future due to their application in food and pharmaceutical industry and it can become a huge source of capital and income.

Bacterial communities on giant kelp in the Magellan Strait: Geographical and intra-thallus patterns

The giant kelp Macrocystis pyrifera is categorized as a keystone species, forming highly productive forests that provide ecosystem services and host a remarkable marine biodiversity of macro and microorganisms. The association of microorganisms with the algae is close and can be functionally interdependent. The Magellan Strait, a natural marine passage between the Atlantic and Pacific oceans, harbours extensive giant kelp forests. However, information related to the diversity of bacterial communities in this region is still scarce. In this study, 16S rRNA gene metabarcoding was used to characterize the diversity and composition of bacterial communities associated with apical blades and sporophylls of M. pyrifera from different sites (Bahía Buzo, San Gregorio, and Buque Quemado). Additionally, data from satellites and reanalysis, as well as tide data, were used to characterize the environmental variability. The findings revealed discernible local variations in bacterial taxa across sampling sites, with consistent dominance of Proteobacteria, Verrucomicrobia, Bacteroidetes, and Planctomycetes. Furthermore, a distinctive bacterial community structure was identified between apical and sporophyll blades of M. pyrifera. This research marks the inaugural characterization of bacterial community diversity and composition associated with M. pyrifera in the remote and understudied sub-Antarctic region of the Magellan Strait.

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.

Host-Parasite interaction between brown algae and eukaryote biotrophic pathogens

Brown algae belong to the class Phaeophyceae which are mainly multicellular, photosynthetic organisms, however they evolved independently from terrestrial plants, green and red algae. In the past years marine aquaculture involving brown algae has gained enormous momentum. In both natural environments and aquaculture, brown algae are susceptible to infection by various prokaryotic and eukaryotic parasites. While our understanding of host-parasite interactions in brown algae is gaining recognition, our understanding of how brown algae react to biotic stress remains incomplete. The objective of this review is to address research gaps in the field by providing a summary of what is already known about the response of brown algae to abiotic and biotic stress. The biology of eukaryotic zoosporic pathogens Maullinia ectocarpii, Eurychasma dicksonii, Anisolpidium ectocarpii is also discussed, as those parasites have been used in laboratory experiments to study diseases of brown algae. These studies often relied on parasites-infecting Ectocarpus siliculosus which has become a brown algal model organism to study host-pathogen interactions. Stress response in brown algae involves processes similar to hypersensitivity response, oxidative stress response, and activation of peroxidases, but also the production of blue fluorescent metabolites and deposition of β-1,3-glucan in the cell wall. Cell wall modification, expression of several defence related proteins, and secondary metabolite production also hold a crucial role in brown algal defence mechanism. Understanding host-pathogen interactions and the associated mechanisms is vital to discover strategies to control pathogens in the growing aquaculture sector.

Candidate genes involved in biosynthesis and degradation of the main extracellular matrix polysaccharides of brown algae and their probable evolutionary history

BACKGROUND

Brown algae belong to the Stramenopiles phylum and are phylogenetically distant from plants and other multicellular organisms. This independent evolutionary history has shaped brown algae with numerous metabolic characteristics specific to this group, including the synthesis of peculiar polysaccharides contained in their extracellular matrix (ECM). Alginates and fucose-containing sulphated polysaccharides (FCSPs), the latter including fucans, are the main components of ECMs. However, the metabolic pathways of these polysaccharides remain poorly described due to a lack of genomic data.

RESULTS

An extensive genomic dataset has been recently released for brown algae and their close sister species, for which we previously performed an expert annotation of key genes involved in ECM-carbohydrate metabolisms. Here we provide a deeper analysis of this set of genes using comparative genomics, phylogenetics analyses, and protein modelling. Two key gene families involved in both the synthesis and degradation of alginate were suggested to have been acquired by the common ancestor of brown algae and their closest sister species Schizocladia ischiensis. Our analysis indicates that this assumption can be extended to additional metabolic steps, and thus to the whole alginate metabolic pathway. The pathway for the biosynthesis of fucans still remains biochemically unresolved and we also investigate putative fucosyltransferase genes that may harbour a fucan synthase activity in brown algae.

CONCLUSIONS

Our analysis is the first extensive survey of carbohydrate-related enzymes in brown algae, and provides a valuable resource for future research into the glycome and ECM of brown algae. The expansion of specific families related to alginate metabolism may have represented an important prerequisite for the evolution of developmental complexity in brown algae. Our analysis questions the possible occurrence of FCSPs outside brown algae, notably within their closest sister taxon and in other Stramenopiles such as diatoms. Filling this knowledge gap in the future will help determine the origin and evolutionary history of fucan synthesis in eukaryotes.

Characterization of Unfractionated Polysaccharides in Brown Seaweed by Methylation-GC-MS-Based Linkage Analysis

This study introduces a novel approach to analyze glycosidic linkages in unfractionated polysaccharides from alcohol-insoluble residues (AIRs) of five brown seaweed species. GC-MS analysis of partially methylated alditol acetates (PMAAs) enables monitoring and comparison of structural variations across different species, harvest years, and tissues with and without blanching treatments. The method detects a wide array of fucose linkages, highlighting the structural diversity in glycosidic linkages and sulfation position in fucose-containing sulfated polysaccharides. Additionally, this technique enhances cellulose quantitation, overcoming the limitations of traditional monosaccharide composition analysis that typically underestimates cellulose abundance due to incomplete hydrolysis of crystalline cellulose. The introduction of a weak methanolysis-sodium borodeuteride reduction pretreatment allows for the detection and quantitation of uronic acid linkages in alginates.

Application of MALDI-MS for characterization of fucoidan hydrolysates and screening of endo-fucoidanase activity

Brown macroalgae synthesize large amounts of fucoidans, sulfated fucose-containing polysaccharides, in the ocean. Fucoidans are of importance for their recently discovered contribution to marine carbon dioxide sequestration and due to their potential applications in biotechnology and biomedicine. However, fucoidans have high intra- and intermolecular diversity that challenges assignment of structure to biological function and the development of applications. Fucoidan-active enzymes may be used to simplify this diversity by producing defined oligosaccharides more applicable for structural refinement, characterization, and structure to function assignment for example via bioassays. In this study, we combined MALDI mass spectrometry with biocatalysis to show that the endo-fucoidanases P5AFcnA and Wv323 can produce defined oligosaccharide structures directly from unrefined macroalgal biomass. P5AFcnA released oligosaccharides from seven commercial fucoidan extracts in addition to unrefined biomass of three macroalgae species indicating a broadly applicable approach reproducible across 10 species. Both MALDI-TOF/TOF and AP-MALDI-Orbitrap systems were used, demonstrating that the approach is not instrument-specific and exploiting their combined high-throughput and high-resolution capabilities. Overall, the combination of MALDI-MS and endo-fucoidanase assays offers high-throughput evaluation of fucoidan samples and also enables extraction of defined oligosaccharides of known structure from unrefined seaweed biomass.

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.

Essential bioactive competence of laminarin (β-glucan)/ laminaran extracted from Padina tetrastromatica and Sargassum cinereum biomass

Marine algae-based drug discovery has recently received a lot of attention. This study was conducted to extract laminarin-enriched solvent extracts from Padina tetrastromatica and Sargassum cinereum and to evaluate their anticancer activity against the HeLa cell line in vitro (MTT assay). Furthermore, their toxicity was determined through a zebra fish model study. P. tetrastromatica and S. cinereum biomasses have a higher concentration of essential biomolecules such as carbohydrates, protein, and crude fiber, as well as essential minerals (Na, Mg, K, Ca, and Fe) and secondary metabolites. Methanol extracts, in particular, contain a higher concentration of vital phytochemicals than other solvent extracts. The laminarin quantification assay states that methanol extracts of P. tetrastromatica and S. cinereum are rich in laminarin, which is primarily confirmed by FTIR analysis. In an anticancer study, laminarin-MeE from P. tetrastromatica and S. cinereum at concentrations of 750 and 1000 μg mL-1 demonstrated 100% activity against HeLa cells. The Zebra fish model-based toxicity study revealed that the laminarin-enriched MeE of P. tetrastromatica and S. cinereum is non-toxic. These findings revealed that the laminarin-enriched MeE of P. tetrastromatica and S. cinereum has significant anticancer activity without causing toxicity.

Fucoidan from the cell wall of Silvetia siliquosa with immunomodulatory effect on RAW 264.7 cells

Silvetia siliquosa, the only species of the family Fucaceae in China, is used as a medicine food homology. Fucoidan from S. siliquosa was extracted by hot water twice thoroughly (13 % of total yield), and a purified fucoidan SSF with a molecular weight of 93 kD was obtained. Chemical composition analysis demonstrated that SSF was primarily composed of sulfate (21.68 wt%) and fucose (84 % of all neutral monosaccharides). IR, methylation analysis, NMR and ESI-MS results indicated SSF had the backbone of mainly (1 → 3)-α-L-fucopyranose and minor (1 → 4)-α-L-fucopyranose, with little 1,3 and 1,4 branched β-D-Xylp and β-D-Galp. The in vitro immunomodulatory test on RAW 264.7 cells showed that SSF could up-regulate the expression of immune related factors and proteins in a concentration-dependent manner, but the immunomodulatory effect disappeared from desulfated SSF. This research indicated that highly sulfated fucan possessed immunomodulatory effect and the importance of sulfate groups in the activity of SSF.

Direct Degradation of Fresh and Dried Macroalgae by Agarivorans albus B2Z047

Marine macroalgae are increasingly recognized for their significant biological and economic potential. The key to unlocking this potential lies in the efficient degradation of all carbohydrates from the macroalgae biomass. However, a variety of polysaccharides (alginate, cellulose, fucoidan, and laminarin), are difficult to degrade simultaneously in a short time. In this study, the brown alga Saccharina japonica was found to be rapidly and thoroughly degraded by the marine bacterium Agarivorans albus B2Z047. This strain harbors a broad spectrum of carbohydrate-active enzymes capable of degrading various polysaccharides, making it uniquely equipped to efficiently break down both fresh and dried kelp, achieving a hydrolysis rate of up to 52%. A transcriptomic analysis elucidated the presence of pivotal enzyme genes implicated in the degradation pathways of alginate, cellulose, fucoidan, and laminarin. This discovery highlights the bacterium's capability for the efficient and comprehensive conversion of kelp biomass, indicating its significant potential in biotechnological applications for macroalgae resource utilization.

Phenylboronic Acid-Functionalized Micelles Dual-Targeting Boronic Acid Transporter and Polysaccharides for siRNA Delivery into Brown Algae

Brown algae play essential roles ecologically, practically, and evolutionarily because they maintain coastal areas, capture carbon dioxide, and produce valuable chemicals such as therapeutic drugs. To unlock their full potential, understanding the unique molecular biology of brown algae is imperative. Genetic engineering tools that regulate homeostasis in brown algae are essential for determining their biological mechanisms in detail. However, few methodologies have been developed to control gene expression due to the robust structural barriers of brown algae. To address this issue, we designed peptide-based, small interfering RNA (siRNA)-loaded micelles decorated with phenylboronic acid (PBA) ligands. The PBA ligands facilitated the cellular uptake of the micelles into a model brown alga, Ectocarpus siliculosus (E. Siliculosus), through chemical interaction with polysaccharides in the cell wall and biological recognition by boronic acid transporters on the plasma membrane. The micelles, featuring "kill two birds with one stone" ligands, effectively induced gene silencing related to auxin biosynthesis. As a result, the growth of E. siliculosus was temporarily inhibited without persistent genome editing. This study demonstrated the potential for exploring the characteristics of brown algae through a simple yet effective approach and presented a feasible system for delivering siRNA in brown algae.

Optimization of Ultrasonic Extraction Parameters for the Recovery of Phenolic Compounds in Brown Seaweed: Comparison with Conventional Techniques

Seaweed, in particular, brown seaweed, has gained research interest in the past few years due to its distinctive phenolic profile that has a multitude of bioactive properties. In order to obtain the maximum extraction efficiency of brown seaweed phenolic compounds, Response Surface Methodology was utilized to optimize the ultrasound-assisted extraction (UAE) conditions such as the amplitude, time, solvent:solid ratio, and NaOH concentration. Under optimal conditions, UAE had a higher extraction efficiency of free and bound phenolic compounds compared to conventional extraction (stirred 16 h at 4 °C). This led to higher antioxidant activity in the seaweed extract obtained under UAE conditions. The profiling of phenolic compounds using LC-ESI-QTOF-MS/MS identified a total of 25 phenolics with more phenolics extracted from the free phenolic extraction compared to the bound phenolic extracts. Among them, peonidin 3-O-diglucodise-5-O-glucoside and hesperidin 5,7-O-diglucuronide are unique compounds that were identified in P. comosa, E. radiata and D. potatorum, which are not reported in plants. Overall, our findings provided optimal phenolic extraction from brown seaweed for research into employing brown seaweed as a functional food.

Enzymatically-derived oligo-carrageenans interact with α-Gal antibodies and Galectin-3

Carrageenans are linear sulfated galactans synthesized in the Gigartinales, Rhodophyceae species with a varied range of biological properties that are of value to the pharmaceutical and cosmetic sectors. It is unknown how the fine structure of carrageenans dictates their capacity to affect molecular and cellular responses important to wound healing, or the ability to mitigate oxidative, hemostatic and inflammatory processes. Here we use specific endo-carrageenases, from the marine bacterium Zobellia galactanivorans, to produce enzymatically defined neo-series oligosaccharides from carrageenans with 3,6-anhydro-D-galactose on the non-reducing end. Further enzymatic modification of the oligosaccharides was done by treating with the 3,6-anhydro-D-galactosidases from the same bacterium which hydrolyze non-reducing end 3,6-anhydro-D-galactose moieties from neo-carrageenan oligosaccharides. Using the enzymatically produced oligosaccharides, we demonstrate binding to natural human serum antibodies and a monoclonal anti-αGal Ab (m86). The significant interactions with the Galα(1,3)Gal reactive antibodies produced by humans makes them potential potent inducers of complement-dependent reactions and attractive for therapeutic applications. We also demonstrate modulation of the galectin selectivity for the Gal-3 Carbohydrate Recognition Domain (CRD) relative to Gal-1 which has implications to targeting specific biological pathways regulated by the galectins.

Carbohydrates and carbohydrate degradation gene abundance and transcription in Atlantic waters of the Arctic

Carbohydrates are chemically and structurally diverse, represent a substantial fraction of marine organic matter and are key substrates for heterotrophic microbes. Studies on carbohydrate utilisation by marine microbes have been centred on phytoplankton blooms in temperate regions, while far less is known from high-latitude waters and during later seasonal stages. Here, we combine glycan microarrays and analytical chromatography with metagenomics and metatranscriptomics to show the spatial heterogeneity in glycan distribution and potential carbohydrate utilisation by microbes in Atlantic waters of the Arctic. The composition and abundance of monomers and glycan structures in POM varied with location and depth. Complex fucose-containing sulfated polysaccharides, known to accumulate in the ocean, were consistently detected, while the more labile β-1,3-glucan exhibited a patchy distribution. Through 'omics analysis, we identify variations in the abundance and transcription of carbohydrate degradation-related genes across samples at the community and population level. The populations contributing the most to transcription were taxonomically related to those known as primary responders and key carbohydrate degraders in temperate ecosystems, such as NS4 Marine Group and Formosa. The unique transcription profiles for these populations suggest distinct substrate utilisation potentials, with predicted glycan targets corresponding to those structurally identified in POM from the same sampling sites. By combining cutting-edge technologies and protocols, we provide insights into the carbohydrate component of the carbon cycle in the Arctic during late summer and present a high-quality dataset that will be of great value for future comparative analyses.

Unraveling the bioactive interplay: seaweed polysaccharide, polyphenol and their gut modulation effect

Seaweed is rich in many unique bioactive compounds such as polyphenols and sulfated polysaccharides that are not found in terrestrial plant. The discovery of numerous biological activities from seaweed has made seaweed an attractive functional food source with the potential to be exploited for human health benefits. During food processing and digestion, cell wall polysaccharide and polyphenols commonly interact, and this may influence the nutritional properties of food. Interactions between cell wall polysaccharide and polyphenols in plant-based system has been extensively studied. However, similar interactions in seaweed have received little attention despite the vast disparity between the structural and chemical composition of plant and seaweed cell wall. This poses a challenge in extracting seaweed bioactive compounds with intact biological properties. This review aims to summarize the cell wall polysaccharide and polyphenols present in brown, red and green seaweed, and current knowledge on their potential interactions. Moreover, this review gives an overview of the gut modulation effect of seaweed polysaccharide and polyphenol.

Advances in oligosaccharides production from algal sources and potential applications

In recent years, algal-derived glycans and oligosaccharides have become increasingly important in health applications due to higher bioactivities than plant-derived oligosaccharides. The marine organisms have complex, and highly branched glycans and more reactive groups to elicit greater bioactivities. However, complex and large molecules have limited use in broad commercial applications due to dissolution limitations. In comparison to these, oligosaccharides show better solubility and retain their bioactivities, hence, offering better applications opportunity. Accordingly, efforts are being made to develop a cost-effective method for enzymatic extraction of oligosaccharides from algal polysaccharides and algal biomass. Yet detailed structural characterization of algal-derived glycans is required to produce and characterize the potential biomolecules for improved bioactivity and commercial applications. Some macroalgae and microalgae are being evaluated as in vivo biofactories for efficient clinical trials, which could be very helpful in understanding the therapeutic responses. This review discusses the recent advancements in the production of oligosaccharides from microalgae. It also discusses the bottlenecks of the oligosaccharides research, technological limitations, and probable solutions to these problems. Furthermore, it presents the emerging bioactivities of algal oligosaccharides and their promising potential for possible biotherapeutic application.

Naturally and Chemically Sulfated Polysaccharides in Drug Delivery Systems

Sulfated polysaccharides have always attracted much attention in food, cosmetic and pharmaceutical industries. These polysaccharides can be obtained from natural sources such as seaweeds (agarans, carrageenans, fucoidans, mannans and ulvans), or animal tissues (glucosaminoglycans). In the last few years, several neutral or cationic polysaccharides have been sulfated by chemical methods and anionic or amphoteric derivatives were obtained, respectively, for drug delivery and other biomedical applications. An important characteristic of sulfated polysaccharides in this field is that they can associate with cationic drugs generating polyelectrolyte-drug complexes, or with cationic polymers to form interpolyelectrolyte complexes, with hydrogel properties that expand even more their applications. The aims of this chapter are to present the structural characteristics of these polysaccharides, to describe the methods of sulfation applied and to review extensively and discuss developments in their use or their role in interpolyelectrolyte complexes in drug delivery platforms. A variety of pharmaceutical dosage forms which were developed and administered by multiple routes (oral, transdermal, ophthalmic, and pulmonary, among others) to treat diverse pathologies were considered. Different IPECs were formed employing these sulfated polysaccharides as the anionic component. The most widely investigated is κ-carrageenan. Chitosan is usually employed as a cationic polyelectrolyte, with a variety of sulfated polysaccharides, besides the applications of chemically sulfated chitosan. Although chemical sulfation is often carried out in neutral polysaccharides and, to a less extent, in cationic ones, examples of oversulfation of naturally sulfated fucoidan have been found which improve its drug binding capacity and biological properties.

The Cell Wall Characterization of Brown Alga Cladosiphon okamuranus during Growth

The present study provides new insights into the growth of the brown algal cell wall by showing that cell wall polysaccharides play an important role in the process of growth, considering the physicochemical characteristic of young and old Cladosiphon okamuranus. To determine its structural variation in detail, the cell wall was sequentially fractionated into five fractions: hot water (HW), ammonium oxalate, hemicellulose-I (HC-I), HC-II, and cellulose, and analyzed physicochemically. Results showed that almost 80% of the total recovery cell wall from both young and old thalli was HW, and HC-I contained mainly fucoidan composed of Fucose, Glucuronic acid, and sulfate in molar ratios of 1.0:0.3:0.6~0.7 and 1.0:0.3:0.2~0.3, respectively. Fucoidan in HW was a highly sulfated matrix polysaccharide abundance in young thalli, while fucoidan in HC-I was rich in old thalli and functions as hemicellulose in land plants, crosslinking with cellulose and strengthening the cell wall. We found that HW and HC-I were particularly involved in the growth and strength of old thalli appeared to be due to the deposition of HC-I and the reduction in water content during the growth process.

Anti-Melanogenesis and Anti-Photoaging Effects of the Sulfated Polysaccharides Isolated from the Brown Seaweed Padina boryana

Sulfated polysaccharides isolated from seaweeds are thought of as ideal ingredients in the pharmaceutical, nutraceutical, and cosmetics industries. Our previous study isolated and characterized sulfated polysaccharides from Padina boryana. The sulfated polysaccharides of Padina boryana (PBP) were extracted, and the antioxidant activity of PBP was evaluated. The results indicate that PBP possesses antioxidant effects and potential in the cosmetic industry. To further investigate the potential of PBP in cosmetics, the photoprotective and anti-melanogenesis effects of PBP were evaluated. The anti-melanogenesis test results display that PBP reduced the melanin content in the murine melanoma cells stimulated by alpha melanocyte-stimulating hormone from 203.7% to 183.64%, 144.63%, and 127.57% at concentrations of 25 μg/mL, 50 μg/mL, and 100 μg/mL, respectively. The anti-photodamage test results showed that PBP significantly protected skin cells against UVB-stimulated photodamage. PBP suppressed human epidermal keratinocyte (HaCaT cell) death by inhibiting apoptosis and reducing the level of intracellular reactive oxygen species. The intracellular reactive oxygen species level of HaCaT cells irradiated by UVB was reduced from 192.67% to 181.22%, 170.25%, and 160.48% by 25 μg/mL, 50 μg/mL, and 100 μg/mL PBP, respectively. In addition, PBP remarkably reduced UVB-induced human dermal fibroblast damage by suppressing oxidative damage, inhibiting collagen degradation, and attenuating inflammatory responses. These results indicate that PBP possesses photoprotective and anti-melanogenesis activities and suggest that PBP is a potential ingredient in the cosmetic industry.

Unveiling the Potential of Marine Biopolymers: Sources, Classification, and Diverse Food Applications

Environmental concerns regarding the usage of nonrenewable materials are driving up the demand for biodegradable marine biopolymers. Marine biopolymers are gaining increasing attention as sustainable alternatives in various industries, including the food sector. This review article aims to provide a comprehensive overview of marine biopolymers and their applications in the food industry. Marine sources are given attention as innovative resources for the production of sea-originated biopolymers, such as agar, alginate, chitin/chitosan, and carrageenan, which are safe, biodegradable, and are widely employed in a broad spectrum of industrial uses. This article begins by discussing the diverse source materials of marine biopolymers, which encompass biopolymers derived from seaweed and marine animals. It explores the unique characteristics and properties of these biopolymers, highlighting their potential for food applications. Furthermore, this review presents a classification of marine biopolymers, categorizing them based on their chemical composition and structural properties. This classification provides a framework for understanding the versatility and functionality of different marine biopolymers in food systems. This article also delves into the various food applications of marine biopolymers across different sectors, including meat, milk products, fruits, and vegetables. Thus, the motive of this review article is to offer a brief outline of (a) the source materials of marine biopolymers, which incorporates marine biopolymers derived from seaweed and marine animals, (b) a marine biopolymer classification, and (c) the various food applications in different food systems such as meat, milk products, fruits, and vegetables.

A Blend Consisting of Agaran from Seaweed Gracilaria birdiae and Chromium Picolinate Is a Better Antioxidant Agent than These Two Compounds Alone

A blend refers to the combination of two or more components to achieve properties that are superior to those found in the individual products used for their production. Gracilaria birdiae agaran (SPGb) and chromium picolinate (ChrPic) are both antioxidant agents. However, there is no documentation of blends that incorporate agarans and ChrPic. Hence, the objective of this study was to generate blends containing SPGb and ChrPic that exhibit enhanced antioxidant activity compared to SPGb or ChrPic alone. ChrPic was commercially acquired, while SPGb was extracted from the seaweed. Five blends (B1; B2; B3; B4; B5) were produced, and tests indicated B5 as the best antioxidant blend. B5 was not cytotoxic or genotoxic. H₂O₂ (0.6 mM) induced toxicity in fibroblasts (3T3), and this effect was abolished by B5 (0.05 mg·mL^-1); neither ChrPic nor SPGb showed this effect. The cells also showed no signs of toxicity when exposed to H₂O₂ after being incubated with B5 and ChrPic for 24 h. In another experiment, cells were incubated with H₂O₂ and later exposed to SPGb, ChrPic, or B5. Again, SPGb was not effective, while cells exposed to ChrPic and B5 reduced MTT by 100%. The data demonstrated that B5 has activity superior to SPGb and ChrPic and points to B5 as a product to be used in future in vivo tests to confirm its antioxidant action. It may also be indicated as a possible nutraceutical agent.

Polysaccharides from marine biological resources and their anticancer activity on breast cancer

In recent decades, natural products from marine organisms have been widely studied for the treatment of various breast cancers. Among them, polysaccharides have been favored by researchers because of their good effects and safety. In this review, polysaccharides from marine algae including macroalgae and microalgae, chitosan, microorganisms such as marine bacteria and fungi, and starfish are addressed. Their anticancer activities on different breast cancers and action mechanisms are discussed in detail. In general, polysaccharides from marine organisms are potential sources of low side-effect and high efficiency anticancer drugs for development. However, further research on animals and clinical research are needed.

A propitious role of marine sourced polysaccharides: Drug delivery and biomedical applications

Numerous compounds, with extensive applications in biomedical and biotechnological fields, are present in the oceans, which serve as a prime renewable source of natural substances, further promoting the development of novel medical systems and devices. Polysaccharides are present in the marine ecosystem in abundance, promoting minimal extraction costs, in addition to their solubility in extraction media, and an aqueous solvent, along with their interactions with biological compounds. Certain algae-derived polysaccharides include fucoidan, alginate, and carrageenan, while animal-derived polysaccharides comprise hyaluronan, chitosan and many others. Furthermore, these compounds can be modified to facilitate their processing into multiple shapes and sizes, as well as exhibit response dependence to external conditions like temperature and pH. All these properties have promoted the use of these biomaterials as raw materials for the development of drug delivery carrier systems (hydrogels, particles, capsules). The present review enlightens marine polysaccharides providing its sources, structures, biological properties, and its biomedical applications. In addition to this, their role as nanomaterials is also portrayed by the authors, along with the methods employed to develop them and associated biological and physicochemical properties designed to develop suitable drug delivery systems.

Structural characterization of a sulfated polysaccharide from Ishige okamurae and its effect on recovery from immunosuppression

A sulfated polysaccharide from the brown alga Ishige okamurae Yendo, designated IOY, was successfully isolated by anion-exchange and size-exclusion chromatography. Chemical and spectroscopic analyses demonstrated that IOY was a fucoidan, that consisted of →3)-α-l-Fucp-(1→, →4)-α-l-Fucp-(1→, →6)-β-d-Galp-(1 → and →3)-β-d-Galp-(1 → residues with sulfate groups at C-2/C-4 the of (1 → 3)-α-l-Fucp and C-6 the of (1 → 3)-β-d-Galp residues. IOY possessed a potent immunomodulatory effect in vitro as measured by lymphocyte proliferation assay. The immunomodulatory effect of IOY was further investigated in vivo using immunosuppressed mice induced by cyclophosphamide (CTX). The results showed that IOY significantly increased the spleen and thymus indexes and alleviated CTX-induced spleen and thymus damage. Furthermore, IOY had a significant effect on hematopoietic function recovery and promoted the secretion of interleukin-2 (IL-2) and tumor necrosis factor (TNF-α). Notably, IOY reversed CD4+ and CD8+ T cell reduction and improved immune response. These data indicated that IOY had vital in immunomodulatory function and could be used as drug or functional food to lessen chemotherapy-induced immunosuppression.

Water-Soluble Saccharina latissima Polysaccharides and Relation of Their Structural Characteristics with In Vitro Immunostimulatory and Hypocholesterolemic Activities

Brown macroalgae are an important source of polysaccharides, mainly fucose-containing sulphated polysaccharides (FCSPs), associated with several biological activities. However, the structural diversity and structure-function relationships for their bioactivities are still undisclosed. Thus, the aim of this work was to characterize the chemical structure of water-soluble Saccharina latissima polysaccharides and evaluate their immunostimulatory and hypocholesterolemic activities, helping to pinpoint a structure-activity relationship. Alginate, laminarans (F1, neutral glucose-rich polysaccharides), and two fractions (F2 and F3) of FCSPs (negatively charged) were studied. Whereas F2 is rich in uronic acids (45 mol%) and fucose (29 mol%), F3 is rich in fucose (59 mol%) and galactose (21 mol%). These two fractions of FCSPs showed immunostimulatory activity on B lymphocytes, which could be associated with the presence of sulphate groups. Only F2 exhibited a significant effect in reductions in in vitro cholesterol's bioaccessibility attributed to the sequestration of bile salts. Therefore, S. latissima FCSPs were shown to have potential as immunostimulatory and hypocholesterolemic functional ingredients, where their content in uronic acids and sulphation seem to be relevant for the bioactive and healthy properties.

Sulfated fuco-manno-glucuronogalactan alleviates pancreatic beta cell senescence via PI3K/AKT/FoxO1 pathway

Appearance of senescent beta cells in the pancreas leads to the onset of type 2 diabetes (T2D). The structural analysis of a sulfated fuco-manno-glucuronogalactan (SFGG) indicated SFGG had the backbones of interspersing 1, 3-linked β-D-GlcpA residues, 1, 4-linked α-D-Galp residues, and alternating 1, 2-linked α-D-Manp residues and 1, 4-linked β-D-GlcpA residues, sulfated at C6 of Man residues, C2/C3/C4 of Fuc residues and C3/C6 of Gal residues, and branched at C3 of Man residues. SFGG effectively alleviated senescence-related phenotypes in vitro and in vivo, including cell cycle, senescence-associated β-galactosidase, DNA damage and senescence-associated secretory phenotype (SASP) -associated cytokines and hall markers of senescence. SFGG also alleviated beta cell dysfunction in insulin synthesis and glucose-stimulated insulin secretion. Mechanistically, SFGG attenuated senescence and improved beta cell function via PI3K/AKT/FoxO1 signaling pathway. Therefore, SFGG could be used for beta cell senescence treatment and alleviation of the progression of T2D.

Extraction of high purity fucoidans from brown seaweeds using cellulases and alginate lyases

Fucoidans are fucose rich sulfated polysaccharides that are found in the cell wall of brown seaweeds and have been shown to have several beneficial bioactivities. In the present study, we report a new enzymatic extraction technique for the production of pure and intact fucoidans from the two brown seaweeds Saccharina latissima and Alaria esculenta. This new extraction protocol uses the commercial cellulase blend Cellic® CTec2 in combination with endo- and exo-acting thermophilic alginate lyases. The fucoidans obtained by this extraction technique are compared to traditionally extracted fucoidans in terms of chemical compositions and molecular weights and are shown to contain significantly higher amounts of fucose and sulfate, the main components of fucoidans, while cellulose, laminarin, and alginate contamination is low. Thus, by using this combination of enzymes, the extracted fucoidans do not undergo depolymerization during extraction and additional purification steps are not needed. The high purity fucoidans isolated by this new enzymatic extraction technique can be used to provide insight into the different fucoidan structures and biological activities.

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.

Antibacterial, Antifungal and Algicidal Activity of Phlorotannins, as Principal Biologically Active Components of Ten Species of Brown Algae

Marine seaweeds synthesize a plethora of bioactive metabolites, of which phlorotannins of brown algae currently attract special attention due to their high antibiotic and cytotoxic capacities. Here we measured the minimum inhibitory concentrations (MICs) of several semi-purified phlorotannin preparations of different origins and molecular composition using a set of model unicellular organisms, such as Escherichia coli, Saccharomyces cerevisiae, Chlamydomonas reinhardtii, etc. For the first time, MIC values were evaluated for phlorotannin-enriched extracts of brown algae of the orders Ectocarpales and Desmarestiales. Phlorotannin extracts of Desmarestia aculeata, Fucus vesiculosus, and Ectocarpus siliculosus showed the lowest MIC values against most of the treated organisms (4-25 μg/mL for bacteria and yeast). Analysis of the survival curves of E. coli showed that massive loss of cells started after 3-4 h of exposure. Microalgae were less susceptible to activity of phlorotannin extracts, with the highest MIC values (≥200 µg/mL) measured for Chlorella vulgaris cells. D. aculeata, E. siliculosus, and three fucalean algae accumulate considerable amounts (4-16% of dry weight) of phlorotannins with MIC values similar to those widely used antibiotics. As these species grow abundantly in polar and temperate seas and have considerable biomass, they may be regarded as promising sources of phlorotannins.

Fucoidan in Pharmaceutical Formulations: A Comprehensive Review for Smart Drug Delivery Systems

Fucoidan is a heterogeneous group of polysaccharides isolated from marine organisms, including brown algae and marine invertebrates. The physicochemical characteristics and potential bioactivities of fucoidan have attracted substantial interest in pharmaceutical industries in the past few decades. These polysaccharides are characterized by possessing sulfate ester groups that impart negatively charged surfaces, low/high molecular weight, and water solubility. In addition, various promising bioactivities have been reported, such as antitumor, immunomodulatory, and antiviral effects. Hence, the formulation of fucoidan has been investigated in the past few years in diverse pharmaceutical dosage forms to be able to reach their site of action effectively. Moreover, they can act as carriers for various drugs in value-added drug delivery systems. The current work highlights the attractive biopharmaceutical properties of fucoidan being formulated in oral, inhalable, topical, injectable, and other advanced formulations treating life-quality-affecting diseases. Therefore, the present work points out the current status of fucoidan pharmaceutical formulations for future research transferring their application from in vitro and in vivo studies to clinical application and market availability.

Bioactive Compounds from Brown Algae Alleviate Nonalcoholic Fatty Liver Disease: An Extensive Review

Nonalcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases. The increasing NAFLD incidences are associated with unhealthy lifestyles. Currently, there are no effective therapeutic options for NAFLD. Thus, there is a need to develop safe, efficient, and economic treatment options for NAFLD. Brown algae, which are edible, contain abundant bioactive compounds, including polysaccharides and phlorotannins. They have been shown to ameliorate insulin resistance, as well as hepatic steatosis, and all of these biological functions can potentially alleviate NAFLD. Accumulating reports have shown that increasing dietary consumption of brown algae reduces the risk for NAFLD development. In this review, we summarized the animal experiments and clinical proof of brown algae and their bioactive compounds for NAFLD treatment within the past decade. Our findings show possible avenues for further research into the pathophysiology of NAFLD and brown algae therapy.

Assembly and synthesis of the extracellular matrix in brown algae

In brown algae, the extracellular matrix (ECM) and its constitutive polymers play crucial roles in specialized functions, including algal growth and development. In this review we offer an integrative view of ECM construction in brown algae. We briefly report the chemical composition of its main constituents, and how these are interlinked in a structural model. We examine the ECM assembly at the tissue and cell level, with consideration on its structure in vivo and on the putative subcellular sites for the synthesis of its main constituents. We further discuss the biosynthetic pathways of two major polysaccharides, alginates and sulfated fucans, and the progress made beyond the candidate genes with the biochemical validation of encoded proteins. Key enzymes involved in the elongation of the glycan chains are still unknown and predictions have been made at the gene level. Here, we offer a re-examination of some glycosyltransferases and sulfotransferases from published genomes. Overall, our analysis suggests novel investigations to be performed at both the cellular and biochemical levels. First, to depict the location of polysaccharide structures in tissues. Secondly, to identify putative actors in the ECM synthesis to be functionally studied in the future.

Brown algal cell walls and development

Brown algae are complex multicellular eukaryotes whose cells possess a cell wall, which is an important structure that regulates cell size and shape. Alginate and fucose-containing sulfated polysaccharides (FCSPs) are two carbohydrate types that have major roles in influencing the mechanical properties of the cell wall (i.e. increasing or decreasing wall stiffness), which in turn regulate cell expansion, division, adhesion, and other processes; however, how brown algal cell wall structure regulates its mechanical properties, and how this relationship influences cellular growth and organismal development, is not well-understood. This chapter is focused on reviewing what we currently know about how the roles of alginates and FCSPs in brown algal developmental processes, as well as how they influence the structural and mechanical properties of cell walls. Additionally, we discuss how brown algal mutants may be leveraged to learn more about the underlying mechanisms that regulate cell wall structure, mechanics, and developmental processes, and finally we propose questions to guide future research with the use of emerging technologies.