Chlorella vulgaris α-L-arabino-α-L-rhamno-α,β-D-galactan structure and mechanisms of its anti-inflammatory and anti-remodelling effects

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

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

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

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

A sulfated exopolysaccharide derived from Chlorella sp. exhibiting in vitro anti-α-D-Glucosidase activity

There is a great scientific curiosity to discover all environments sheltering microalgae, especially those with exceptional characteristics from coldest to hottest ones, the purpose remains to explore the potential of the native microalgae flora and the research for new bioactive compounds. This study aimed to isolate a polysaccharide-producing microalga from an extreme ecosystem and to evaluate its capacity to inhibit the α-D-glucosidase enzyme. Chlorella strain is isolated from hypersaline Lake in the Algerian desert. The exopolysaccharide extraction was performed by the concentration of free-cell supernatant in a rotary evaporator. The infrared analysis showed a characteristic footprint of carbohydrates with particular functional groups, such as sulfate. Gas chromatography-mass spectrometry has revealed a hetero-exopolysaccharide composed of galactose 35.75%, glucose 21.13%, xylose 16.81%, fructose 6.96%, arabinose 5.10%, and glucuronic acid 2.68%. The evaluation of the anti-hyperglycemic activity demonstrated a significant α-D-glucosidase inhibition of 80.94 ± 0.01% at 10 mg mL-1 with IC50 equal to 4.31 ± 0.20 mg mL-1. This study opens a vast prospect to use exopolysaccharides as natural nutraceutical or food additive.

The great potential of polysaccharides from natural resources in the treatment of asthma: A review

Despite significant progress in diagnosis and treatment, asthma remains a serious public health challenge. The conventional therapeutic drugs for asthma often have side effects and unsatisfactory clinical efficacy. Therefore, it is very urgent to develop new drugs to overcome the shortcomings of conventional drugs. Natural polysaccharides provide enormous resources for the development of drugs or health products, and they are receiving a lot of attention from scientists around the world due to their safety, effective anti-inflammatory and immune regulatory properties. Increasing evidence shows that polysaccharides have favorable biological activities in the respiratory disease, including asthma. This review provides an overview of primary literature on the recent advances of polysaccharides from natural resources in the treatment of asthma. The mechanisms and practicability of polysaccharides, including polysaccharides from plants, fungus, bacteria, alga, animals and others are reviewed. Finally, the further research of polysaccharides in the treatment of asthma are discussed. This review can provide a basis for further study of polysaccharides in the treatment of asthma and provides guidance for the development and clinical application of novel asthma treatment drugs.

Structural properties of the extracellular biopolymer (β-D-xylo-α-D-mannan) produced by the green microalga Gloeocystis vesiculosa Nägeli

Many species of microalgae produce a relatively diverse range of metabolites that are interesting for biotechnological applications, and among them exopolysaccharides attract attention due to their structural complexity, biological activities, biodegradability or biocompatibility. An exopolysaccharide of high molecular weight (M_p) of 6.8 × 10⁵ g/mol was obtained by cultivation of the freshwater green coccal microalga Gloeocystis vesiculosa Nägeli 1849 (Chlorophyta). Chemical analyses revealed a dominance of Manp (63.4 wt%), Xylp and its 3-O-Me-derivative (22.4 wt%), and Glcp (11.5 wt%) residues. The results of the chemical and NMR analyses showed an alternating branched 1,2- and 1,3-linked α-D-Manp backbone terminated by a single β-D-Xylp and its 3-O-methyl derivative at O2 of the 1,3-linked α-D-Manp residues. The α-D-Glcp residues were found mainly as 1,4-linked and to a lesser extent as the terminal sugar, indicating partial contamination of β-D-xylo-α-D-mannan with amylose (∼10 wt%) in G. vesiculosa exopolysaccharide.

Soluble Extracellular Polymeric Substances Produced by Parachlorella kessleri and Chlorella vulgaris: Biochemical Characterization and Assessment of Their Cadmium and Lead Sorption Abilities

In the present study, the potential of lead and cadmium removal by the extracellular polymeric substances (EPS) produced from Parachlorella kessleri and Chlorella vulgaris were investigated. Carbohydrates were the dominant components of EPS from both analyzed species. The contents of reducing sugars, uronic acids, and amino acids were higher in EPS synthesized by C. vulgaris than in EPS from P. kessleri. The analysis of the monosaccharide composition showed the presence of rhamnose, mannose and galactose in the EPS obtained from both species. The ICP-OES (inductively coupled plasma optical emission spectrometry) analyses demonstrated that C. vulgaris EPS showed higher sorption capacity in comparison to P. kessleri EPS. The sorption capacity of C. vulgaris EPS increased with the increase in the amount of metal ions. P. kessleri EPS had a maximum sorption capacity in the presence of 100 mg/L of metal ions. The FTIR analysis demonstrated that the carboxyl, hydroxyl, and carbonyl groups of EPS play a key role in the interactions with metal ions. The present study showed C. vulgaris EPS can be used as a biosorbent in bioremediation processes due to its biochemical composition, the presence of significant amounts of negatively charged uronic acids, and higher sorption capacity.

Structural features of biologically active extracellular polysaccharide produced by green microalgae Dictyosphaerium chlorelloides

Ion-exchange chromatography of the biologically active extracellular biopolymer produced by D. chlorelloides yielded ten fractions differing in yield, protein content, monosaccharide composition and molecular weight distribution. Their sugar compositional analyses showed rhamnogalactans, substituted to different extent by mannose and glucose, as a dominant EPS component in all fractions (91 %) except one containing arabinogalactan (7 %). In highly branched rhamnogalactans the quantity of linear (1,3-; 1,4- and 1,6-linked) and branched β-D-galactose units (1,3,6-, 1,4,6- and 1,3,4,6-linked) was nearly equal. From various α-L-rhamnose linkages the 1,2,4-linkage was dominant. Data indicate a rhamnogalactan backbone of EPS, branched by terminal mannose and glucose units, and a lot of O-methylated derivatives of galactose residues (2-O-methyl, 2,3-O-dimethyl, 3-O-methyl and 6-O-methyl). In individual fractions their content and type varied. Detail study of the arabinogalactan showed that its backbone consists of 1,3-linked β-D-Galp units; some of them are branched through O-4 by 6-OMe-α-D-Galp- (1 → 2) -α-L-Araf side chain, other through O-6 by 3-OMe-β-D-Galp, 6-OMe-β-D-Galp, β-D-Galp and β-D-Galf.

Chlorella pyrenoidosa Polysaccharides as a Prebiotic to Modulate Gut Microbiota: Physicochemical Properties and Fermentation Characteristics In Vitro

This study was conducted to investigate the prebiotic potential of Chlorella pyrenoidosa polysaccharides to provide useful information for developing C. pyrenoidosa as a green healthy food. C. pyrenoidosa polysaccharides were prepared and their physicochemical characteristics were determined. The digestibility and fermentation characteristics of C. pyrenoidosa polysaccharides were evaluated using in vitro models. The results revealed that C. pyrenoidosa polysaccharides were composed of five non-starch polysaccharide fractions with monosaccharide compositions of Man, Rib, Rha, GlcA, Glc, Gal, Xyl and Ara. C. pyrenoidosa polysaccharides could not be degraded under saliva and the gastrointestinal conditions. However, the molecular weight and contents of residual carbohydrates and reducing sugars of C. pyrenoidosa polysaccharides were significantly reduced after fecal fermentation at a moderate speed. Notably, C. pyrenoidosa polysaccharides could remarkably modulate gut microbiota, including the promotion of beneficial bacteria, inhibition of growth of harmful bacteria, and reduction of the ratio of Firmicutes to Bacteroidetes. Intriguingly, C. pyrenoidosa polysaccharides can promote growth of Parabacteroides distasonis and increase short-chain fatty acid contents, thereby probably contributing to the promotion of intestinal health and prevention of diseases. Thus, these results suggested that C. pyrenoidosa polysaccharides had prebiotic functions with different fermentation characteristics compared with conventional prebiotics such as fructooligosaccharide, and they may be a new prebiotic for improving human health.

Gibberellic acids promote growth and exopolysaccharide production in Tetraselmis suecica under reciprocal nitrogen concentration: an assessment on antioxidant properties and nutrient removal efficacy of immobilized iron-magnetic nanoparticles

The present study was aimed to assess the effect of gibberellic acids to enhance the growth, biomass, pigment, and exopolysaccharides production in Tetraselmis suecica under reciprocal nitrogen concentrations. For this study, the seven types of experimental media (N-P, NL-P/2GA3, N0-P/2GA3, NL-P/4GA3, N0-P/4GA3, NL-P/6GA3, and N0-P/6GA3) were prepared with the addition of gibberellic acids under various nitrogen concentrations. The experiment lasted for 15 days and the cell density, biomass, chlorophyll 'a', and exopolysaccharides (EPS) concentration of T. suecica were estimated for every 3 days. Then the EPS was subjected to the analyses of chemical (carbohydrate, protein, sulfate, and uronic acid), and antioxidant activity. In addition, nutrient removal efficiency was evaluated using different concentration of EPS. The highest DPPH (2,2-diphenyl-1-picrylhydrazyl) (86.7 ± 0.95%) and hydroxyl radical activity (85.7 ± 2.48%) were observed at the EPS concentrations 2.5 and 1.2 mg/mL, respectively. The immobilized magnetic Fe₃O₄-EPS (ferric oxide-exopolysaccharides) nanoparticles (5.0 and 10.0 g/L) have efficiently removed the excessive phosphate (89.5 ± 1.65%) and nitrate (73.5 ± 1.72%) from the Litopenaeus vannamei cultured wastewater. Thus, the application of gibberellic acids combined with limited nitrogen concentration could produce higher EPS that could exhibit excellent antioxidant activity, and nutrient removal efficacy in the form of Fe₃O₄-EPS magnetic nanoparticles.