Sulfated Polysaccharides in the Freshwater Green Macroalga Cladophora surera Not Linked to Salinity Adaptation

Study of phenolic-polysaccharide interactions in brown seaweed

Brown seaweed has a rich source of bioactives, notably antioxidative phenolic compounds and sulphated polysaccharides. Despite their importance, the interactions between these compounds and their resultant antioxidant activities have not been extensively studied. This research aims to investigate the interaction between seaweed-derived phenolics and polysaccharides in terms of their antioxidant activity, exploring their potential interactions through in silico molecular docking, and validating them using Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and differential scanning calorimetry (DSC). Reduced antioxidant activities were observed in the seaweed-derived phenolics and polysaccharides combination. The in silico molecular docking studies and experimental analyses revealed non-covalent interactions, mainly driven by hydrogen bonding between fucoidan and catechin or phloroglucinol. The resulting 'complex' formation varied in size and thermodynamic stability, suggesting structure-dependent interactions between fucoidan and phenolic compounds. This research helps to understand the marine phenolic-polysaccharide interaction, contributing to their effective application in the functional food and nutraceutical industries.

Inhibitory effects of algal polysaccharide extract from Cladophora spp. against herpes simplex virus infection

Herpes simplex virus (HSV) is a causative agent of fever blister, genital herpes, and neonatal herpes. Nowadays, edible algae are recognized as health food due to high nutrition content and their many active compounds that are beneficial to health. The purpose of this study is to investigate the inhibitory effects of algal polysaccharide extract from Cladophora spp. against herpes simplex virus type 1 and type 2 on Vero cells. In this study, the structure of polysaccharide extract is presented as S=O and C-O-S of the sulfate group, as identified by the FT-IR technique. The toxicity of algal polysaccharide extract on Vero cells was determined by MTT assay. The algal extract showed low toxicity on the cells, with 50% cytotoxic concentration (CC50) value greater than 5000 µg mL-1. The inhibition of HSV infection by the algal extract was then evaluated on Vero cells using plaque reduction assay. The 50% effective concentration (EC50) values of algal extract exhibited antiviral activity against HSV-1 upon treatment before, during, and after viral adsorption with and without removal of the extract were 70.31, 15.17, > 5000 and 9.78 µg mL-1, respectively. Additionally, the EC50 values of algal extract against HSV-2 upon treatment before, during and after viral adsorption with, and without removal of the extract were 5.85, 2.57, > 5000 and 26.96 µg mL-1, respectively. Moreover, the algal extract demonstrated direct inactivation of HSV-1 and HSV-2 virions as well as inhibitory effect against HSV replication. Accordingly, algal polysaccharide extract containing sulfated polysaccharides showed strong activity against HSV. Therefore, it is proved to be useful to apply Cladophora spp. polysaccharide extract as an anti-HSV agent.

The extracellular matrix of green algae

Green algae display a wide range of extracellular matrix (ECM) components that include various types of cell walls (CW), scales, crystalline glycoprotein coverings, hydrophobic compounds, and complex gels or mucilage. Recently, new information derived from genomic/transcriptomic screening, advanced biochemical analyses, immunocytochemical studies, and ecophysiology has significantly enhanced and refined our understanding of the green algal ECM. In the later diverging charophyte group of green algae, the CW and other ECM components provide insight into the evolution of plants and the ways the ECM modulates during environmental stress. Chlorophytes produce diverse ECM components, many of which have been exploited for various uses in medicine, food, and biofuel production. This review highlights major advances in ECM studies of green algae.

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.

Characterization and in vitro antibacterial activity of sulfated polysaccharides from freshwater alga Cladophora crispata

Barada River is characterized by an abundant growth of freshwater algae. Cladophora sp. algae have emerged as a new source of bioactive compounds. In this research Cladophora crispata was cultivated with the outdoor method, and algal sulfated polysaccharides (SPs) were extracted by an ultrasonic-assisted extraction method. After extraction, gel filtration was used to purify the crude SPs, SP compounds were determined and selected, and the effect of purified SPs as antibacterial agents was investigated. The purified extract gave two fractions (F1 and F2). The chemical components of both crude and purified SPs were then determined. The highest carbohydrate content (74.12%) and protein content (4.02%) was found in the crude extract, while the highest sulfate content (12.17%) was found in purified fraction F2, and the highest uronic acid content (18.46%) was found in purified fraction F1. Fourier transform infrared spectroscopy (FT-IR) was used to confirm that the crude extract and fractions consist of sugar, uronic acids, protein and sulfate groups. Both F1 and F2 consisted of rhamnose, galactose, xylose and ribose based on high performance liquid chromatography (HPLC) separation. Each fraction showed an inhibitory effect on Gram-positive and Gram-negative bacteria. F2 has the lowest minimum inhibitory concentration (MIC) value against Staphylococcus aureus , Bacillus anthracis , Enterobacter aerogenes and Pseudomonas aeruginosa , where its MIC values were 6, 13, 25 and 30 mg ml-1, respectively. Algae polysaccharides are of key interest due to their antibacterial properties, which has led to them being included in pharmaceutics and food applications.

Freshwater Macroalgae, Oedogonium, Grown in Wastewater Reduce Diet-Induced Metabolic Syndrome in Rats

Macroalgae produce compounds with industrial, pharmaceutical and nutritional applications. In this study, biomass from the freshwater macroalgal genus Oedogonium was grown in either treated municipal wastewater (M) or ash dam water from a coal-fired power station (D). The biomass was investigated for its metabolic responses in high-carbohydrate, high-fat diet-fed rats, a model of human metabolic syndrome. The Oedogonium biomass cultured in M contained higher amounts of K, Mg, omega-3 polyunsaturated fatty acids (PUFA), insoluble fibre and β-carotene, while biomass grown in D contained higher amounts of Al, Fe, V, Zn, Mn and As. Biomass from M further increased body weight and inflammation in the heart and colon in high-carbohydrate, high-fat diet-fed rats. In contrast, biomass from D prevented changes in metabolic, cardiovascular and liver parameters without changing tissue histology. We suggest that increased intake of metals and metalloids through macroalgal biomass from D may decrease abdominal fat deposition while polysaccharides, PUFA and carotenoids from M may improve blood glucose responses in an obesogenic diet. Thus, macroalgal biomass grown in different wastewater sources could be acceptable for feed or food applications. This biomass could even provide potential health benefits in diet-induced metabolic syndrome.

NMR spectroscopy for structural elucidation of sulfated polysaccharides from red seaweeds

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

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

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

Removal of metals from aqueous solutions using dried Cladophora parriaudii of varying biochemical composition

Macroalgal biosorption has shown promise for the removal of metal ions from wastewaters, whose presence can pose a threat to the aquatic environment. There is a wealth of literature published on macroalgal biosorption, the common thread being that the biosorbent material was collected from the field, under undefined conditions. These studies offer little insight into the impact of prior cultivation or biomass production practices upon the biosorbent material, its adsorptive physico-chemical properties and its subsequent capacity for metal removal. The present study sought to investigate the influence of changes in macroalgal cultivation, specifically nutrient regime, upon biomass properties and the resultant adsorption performance. The macroalga Cladophora parriaudii was cultivated under six different nutrient regimes; 2:1 and 12:1 N:P molar ratios, with nitrogen supplied either as ammonium (NH₄⁺), nitrate (NO₃^-), or urea (CO(NH₂)₂). These nutrient regimes were designed to produce biomass of varying biochemical and cell surface profiles. After cultivation, the biomass was rinsed, dried, biochemically analysed and then used for the removal of four individual metals from solution. Metal removal varied considerably between treatments and across initial metal concentrations, with removal values of 46-85%, 9-80%, 8-71%, and 49-94% achieved for Al, Cu, Mn, and Pb, respectively, with initial metal concentrations varying between 0 and 150 mg L^-1. The observed variation in metal removal can only be attributed to differences in biochemistry and cell surface properties of the biosorbent induced by nutrient regime, as all other variables were constant. This study demonstrates that prior cultivation conditions influence the biochemistry of a biosorbent material, namely macroalgae Cladophora parriaudii, which has an impact upon metal removal. This aspect should be given due consideration for future biosorption research and when reviewing already published literature.

Disentangling the role of extracellular polysaccharides in desiccation tolerance in lichen-forming microalgae. First evidence of sulfated polysaccharides and ancient sulfotransferase genes

Trebouxia sp. TR9 and Coccomyxa simplex are desiccation-tolerant microalgae with flexible cell walls, which undergo species-specific remodelling during dehydration-rehydration (D/R) due to their distinct ultrastructure and biochemical composition. Here, we tested the hypothesis that extracellular polysaccharides excreted by each microalga could be quantitatively and/or qualitatively modified by D/R. Extracellular polysaccharides were analysed by size exclusion and anion exchange chromatography, specific stains after gel electrophoresis and gas chromatography/mass spectrometry of trimethylsilyl derivatives (to determine their monosaccharide composition). The structure of a TR9-sulfated polymer was deduced from nuclear magnetic resonance (NMR) analyses. In addition, sugar-sulfotransferase encoding genes were identified in both microalgae, and their expression was measured by RT-qPCR. D/R did not alter the polydispersed profile of extracellular polysaccharides in either microalga but did induce quantitative changes in several peaks. Furthermore, medium-low-sized uronic acid-containing polysaccharides were almost completely substituted by higher molecular mass carbohydrates after D/R. Sulfated polysaccharide(s) were detected, for the first time, in the extracellular polymeric substances of both microalgae, but only increased significantly in TR9 after cyclic D/R, which induced a sugar-sulfotransferase gene and accumulated sulfated ß-D-galactofuranan(s). Biochemical remodelling of extracellular polysaccharides in aeroterrestrial desiccation-tolerant microalgae is species-specific and seems to play a role in the response to changes in environmental water availability.

Comparative genomics reveals differences in algal galactan biosynthesis and related pathways in early and late diverging red algae

Red algae are a major source of marine sulfated galactans. In this study, orthologs and inparalogs from seven red algae were analyzed and compared with the aim to discover differences in algal galactan biosynthesis and related pathways of these algae. Red algal orthologs for putative carbohydrate sulfotransferases were found to be prevalent in Porphyridium purpureum, Florideophytes and Bangiophytes, while red algal orthologs for putative chondroitin sulfate synthases, sulfurylases, and porphyranases /carrageenases were found exclusively in Florideophytes and Bangiophytes. The acquirement of these genes could have happened after the divergence from Cyanidiales red algae. Cyanidiales red algae were found to have more number and types of putative sulfate permeases, suggesting that these genes could have been acquired in adaptation to the environmental stresses and biogeochemistry of respective habitats. The findings of this study shed lights on the evolution of different homeostasis mechanisms by the early and late diverging red algal orders.

Diversity of Sulfated Polysaccharides From Cell Walls of Coenocytic Green Algae and Their Structural Relationships in View of Green Algal Evolution

Seaweeds biosynthesize sulfated polysaccharides as key components of their cell walls. These polysaccharides are potentially interesting as biologically active compounds. Green macroalgae of the class Ulvophyceae comprise sulfated polysaccharides with great structural differences regarding the monosaccharide constituents, linearity of their backbones, and presence of other acidic substituents in their structure, including uronic acid residues and pyruvic acid. These structures have been thoroughly studied in the Ulvales and Ulotrichales, but only more recently have they been investigated with some detail in ulvophytes with giant multinucleate (coenocytic) cells, including the siphonous Bryopsidales and Dasycladales, and the siphonocladous Cladophorales. An early classification of these structurally heterogeneous polysaccharides was based on the presence of uronic acid residues in these molecules. In agreement with this classification based on chemical structures, sulfated polysaccharides of the orders Bryopsidales and Cladophorales fall in the same group, in which this acidic component is absent, or only present in very low quantities. The cell walls of Dasycladales have been less studied, and it remains unclear if they comprise sulfated polysaccharides of both types. Although in the Bryopsidales and Cladophorales the most important sulfated polysaccharides are arabinans and galactans (or arabinogalactans), their major structures are very different. The Bryopsidales produce sulfated pyruvylated 3-linked β-d-galactans, in most cases, with ramifications on C6. For some species, linear sulfated pyranosic β-l-arabinans have been described. In the Cladophorales, also sulfated pyranosic β-l-arabinans have been found, but 4-linked and highly substituted with side chains. These differences are consistent with recent molecular phylogenetic analyses, which indicate that the Bryopsidales and Cladophorales are distantly related. In addition, some of the Bryopsidales also biosynthesize other sulfated polysaccharides, i.e., sulfated mannans and sulfated rhamnans. The presence of sulfate groups as a distinctive characteristic of these biopolymers has been related to their adaptation to the marine environment. However, it has been shown that some freshwater algae from the Cladophorales also produce sulfated polysaccharides. In this review, structures of sulfated polysaccharides from bryopsidalean, dasycladalean, and cladophoralean green algae studied until now are described and analyzed based on current phylogenetic understanding, with the aim of unveiling the important knowledge gaps that still exist.