Isolation and structural characterization of sulfated polysaccharide from Spirulina platensis and its bioactive potential: In vitro antioxidant, antibacterial activity and Zebrafish growth and reproductive performance

Cyanobacterial and microalgae polymers: antiviral activity and applications

At the end of 2019, the world witnessed the beginning of the COVID-19 pandemic. As an aggressive viral infection, the entire world remained attentive to new discoveries about the SARS-CoV-2 virus and its effects in the human body. The search for new antivirals capable of preventing and/or controlling the infection became one of the main goals of research during this time. New biocompounds from marine sources, especially microalgae and cyanobacteria, with pharmacological benefits, such as anticoagulant, anti-inflammatory and antiviral attracted particular interest. Polysaccharides (PS) and extracellular polymeric substances (EPS), especially those containing sulfated groups in their structure, have potential antiviral activity against several types of viruses including HIV-1, herpes simplex virus type 1, and SARS-CoV-2. We review the main characteristics of PS and EPS with antiviral activity, the mechanisms of action, and the different extraction methodologies from microalgae and cyanobacteria biomass.

Extraction, structural characterization, and antioxidant activity of polysaccharides from three microalgae

Microalgal polysaccharides have received much attention due to their potential value in preventing and regulating oxidative damage. This study aims to reveal the mechanisms of regulating oxidative stress and the differences in the yield, structure, and effect of polysaccharides extracted from three microalgae: Golenkinia sp. polysaccharides (GPS), Chlorella sorokiniana polysaccharides (CPS), and Spirulina subsalsa polysaccharides (SPS). Using the same extraction method, GPS, CPS, and SPS were all heteropoly- saccharides composed of small molecular fraction: the monosaccharides mainly comprised galactose (Gal). Among the three, SPS had a higher proportion of small molecular fraction, and a higher proportion of Gal; thus it had the highest yield and antioxidant activity. GPS, CPS, and SPS all showed strong antioxidant activity in vitro, and showed strong ability to regulate oxidative stress, among which SPS was slightly higher. From the analysis of gene expression, the Nrf2-ARE signalling pathway was an important pathway for GPS, CPS, and SPS to regulate cellular oxidative stress. This study provides a theoretical foundation for further research on the utilization of microalgae polysaccharides and product development.

Challenges in Functional Food Products with the Incorporation of Some Microalgae

Much attention has been given to the use of microalgae to produce functional foods that have valuable bioactive chemicals, including essential amino acids, polyunsaturated fatty acids, vitamins, carotenoids, fiber, and minerals. Microalgal biomasses are increasingly being used to improve the nutritional values of foods because of their unique nutrient compositions that are beneficial to human health. Their protein content and amino acid composition are the most important components. The microalgal biomass used in the therapeutic supplement industry is dominated by bio-compounds like astaxanthin, β-carotene, polyunsaturated fatty acids like eicosapentaenoic acid and docosahexaenoic acid, and polysaccharides such as β-glucan. The popularity of microalgal supplements is growing because of the health benefits of their bioactive substances. Moreover, some microalgae, such as Dunaliella, Arthrospira (Spirulina), Chlorella, and Haematococcus, are commonly used microalgal species in functional food production. The incorporation of microalgal biomass leads not only to enhanced nutritional value but also to improved sensory quality of food products without altering their cooking or textural characteristics. Microalgae, because of their eco-friendly potential, have emerged as one of the most promising and novel sources of new functional foods. This study reviews some recent and relevant works, as well as the current challenges for future research, using different methods of chemical modification in foods with the addition of a few commercial algae to allow their use in nutritional and sensory areas. It can be concluded that the production of functional foods through the use of microalgae in foods has become an important issue.

Soluble non-starch polysaccharides in fish feed: implications for fish metabolism

Because of their unique glycosidic bond structure, non-starch polysaccharides (NSP) are difficult for the stomach to break down. NSP can be classified as insoluble NSP (iNSP, fiber, lignin, etc.) and soluble NSP (sNSP, oligosaccharides, β-glucan, pectin, fermentable fiber, inulin, plant-derived polysaccharides, etc.). sNSP is viscous, fermentable, and soluble. Gut microbiota may catabolize sNSP, which can then control fish lipid, glucose, and protein metabolism and impact development rates. This review examined the most recent studies on the impacts of various forms of sNSP on the nutritional metabolism of various fish in order to comprehend the effects of sNSP on fish. According to certain investigations, sNSP can enhance fish development, boost the activity of digestive enzymes, reduce blood sugar and cholesterol, enhance the colonization of good gut flora, and modify fish nutrition metabolism. In-depth research on the mechanism of action is also lacking in most studies on the effects of sNSP on fish metabolism. It is necessary to have a deeper comprehension of the underlying processes by which sNSP induce host metabolism. This is crucial to address the main issue of the sensible use of carbohydrates in fish feed.

The potential, challenges, and prospects of the genus Spirulina polysaccharides as future multipurpose biomacromolecules

Spirulina has been widely used worldwide as a food and medicinal ingredient for centuries. Polysaccharides are major bioactive constituents of Spirulina and are of interest because of their functional properties and unlimited application potential. However, the clinical translation and market industrialization of the polysaccharides from genus Spirulina (PGS) are retarded due to the lack of a further understanding of their isolation, bioactivities, structure-activity relationships (SARs), toxicity, and, most importantly, versatile applications. Herein, we provide an overview of the extraction, purification, and structural features of PGS; meanwhile, the advances in bioactivities, SARs, mechanisms of effects, and toxicity are discussed and summarized. Furthermore, the applications, potential developments, and future research directions are scrutinized and highlighted. This review may help fill the knowledge gap between theoretical insights and practical applications and guide future research and industrial application of PGS.

Development of antimicrobial gelatin-ulvan-beeswax composite films: Optimization of formulation using mixture design methodology

A new generation of antimicrobial film was developed by incorporation of ulvan extracted from Ulva intestinalis into gelatin from common carp scale and its water sensitivity was reduced with addition of beeswax. Optimum composition of gelatin (0-100%w/w), ulvan (0-100%w/w) and beeswax (0-10%w/w) for achieving composite films with minimum water solubility (S) and water vapor permeability (WVP) and maximum tensile strength (TS), elongation at break point (EAB) and antibacterial effect on E. coli (EC) were investigated using mixture design methodology. Both pure gelatin and ulvan films and their composites had relatively good mechanical and optical properties. Addition of ulvan to gelatin produced composite films with good antibacterial properties but water resistance of all the films was weak. Addition of beeswax up to ∼5 % improved the water resistance and mechanical properties of the films without jeopardizing their antibacterial properties. The final optimum formulation with a desirability of 0.709 was achieved as 52.18 % of gelatin, 40.83 % of ulvan and 6.97 % of beeswax resulting in a minimum possible S (40 %) and WVP (1.86 10^-10 g/ms Pa) and maximum possible TS (6.23 MPa) and EAB (89 %) with good EC (7.66 mm). Finally, good mechanical, thermal and microstructural properties of the optimum composite film was confirmed. Altogether, a combination of ulvan and beeswax can be a promising solution for development of gelatin films with both antimicrobial properties and lower water sensitivity.

Polysaccharides from Spirulina platensis: Extraction methods, structural features and bioactivities diversity

Spirulina platensis, a well-known blue-green microalga cultivated and consumed in China and United States, is traditionally used as a food supplement and medical ingredient. Increasing evidence has confirmed that the Spirulina platensis polysaccharides (SPPs) are vital and representative pharmacologically active biomacromolecules and exhibit multiple health-promoting activities both in vivo and in vitro, such as those of anti-cancer, anti-oxidant, immunomodulatory, hypolipidemic and hypoglycemic, anti-thrombotic, anti-viral, regulation of the gut microbiota properties and other biological activity. The purpose of this review aims to comprehensively and systematically outline the extraction and purification methods, structural features, biological activities, underlying mechanisms, and toxicities of SPPs to support their potential utilization value in pharmaceuticals fields and functional foods. The structural and activities relationship of SPPs is also discussed. Besides, new valuable insights for future research with SPPs have also been proposed in the important areas of structural characterization and pharmacological activities.

Anti-colon cancer effects of Spirulina polysaccharide and its mechanism based on 3D models

Spirulina polysaccharides (PSP) possess significant biological properties. However, it is still a lack of investigation on the anti-colorectal cancer effect and mechanism. In this study, PSP showed significant effects on LoVo cell spheroids with an IC₅₀ value of 0.1943 mg/mL. The analysis of transcriptomics and metabolomics indicated the impact of PSP on LoVo spheroid cells through involvement in the two pathways of "glycine, serine, and threonine metabolism" and "ABC transporters". And, the q-PCR data further verified the pointed mechanism of PSP on colon cancer (CC) by regulating the expression levels of relevant genes in the synthesis pathways of serine and glycine in tumor cells. Furthermore, the anti-colon cancer effects of PSP were verified via other human colon cancer cell lines HCT116 and HT29 spheroids (IC₅₀ = 0.0646 mg/mL and 0.2213 mg/mL, respectively), and three patient-derived organoids (PDOs) with IC₅₀ values ranging from 3.807 to 7.788 mg/mL. In addition, this study found that a mild concentration of PSP cannot enhance the anti-tumor effect of 5-Fu. And a significant inhibition was found of PSP in 5-Fu resistance organoids. These results illustrated that PSP could be a treatment or supplement for 5-Fu resistant colorectal cancer (CRC).

Food and drug industry applications of microalgae Spirulina platensis: A review

Spirulina platensis is a photosynthetic, blue-green, spiral- or bulb-shaped microalgae. Due to the presence of minerals, vitamins, pigments (carotenes, phycocyanin and chlorophyll) proteins (55%-70%), carbohydrates (15%-25%), and essential fatty acids (5%-8%), it has been used as a nutritional supplement for decades. NASA successfully employed it as a nutritional supplement for astronauts on space missions then its popularity was increased. The chemical composition of Spirulina, which is rich in vitamins, minerals, phenolics, vital fatty acids, amino acids, and pigments, can be beneficial to human health when incorporated into meals. The pharmacological effects include antibacterial, anticancer, metalloprotective, immune-stimulating, and antioxidant. It modulates immunological activities and possesses anti-inflammatory qualities by preventing mast cells from releasing histamine. Due to its high quantity of protein, carbohydrate, lipid, vital amino and fatty acids, dietary minerals and vitamins, Spirulina exerts the abovementioned benefits. In this review, up-to-date and possible biological aspects, patents applied on Spirulina and heights of confirmation are addressed, and the extent of current and future exploration is also explored.

The Analgesic and Anti-inflammatory Effects of Partially Purified Polysaccharide Fractions of Cell-free Medium and Biomass of Spirulina platensis PCST5

Background

Spirulina is a cyanobacteria species containing various bioactive compounds. Spirulina is a known source of nutrients in some traditional diets. Different activities have been reported for various extracts of S. platensis.

Objectives

In this study, the polysaccharide content of culture media and biomass extract of one species of Spirulina was partially purified, and its analgesic and anti-inflammatory effects were evaluated.

Methods

Spirulina platensis PCST5 was cultured in a sterile Zarouk medium at 27°C and 16/8h of light/ dark exposure cycle for 25 days. Then, the polysaccharide content of biomass and cell-free culture medium samples (BPSs and CFPSs, respectively) was partially purified. The analgesic and anti-inflammatory effects were evaluated using animal models.

Results

16S rRNA gene analysis confirmed that the organism was genetically similar to Spirulina platensis. The CFPSs (30 and 100 mg/kg) and BPSs (30 mg/kg) significantly reduced pain-related behaviors in rats. Similarly, all samples could significantly reduce carrageenan-induced paw inflammation volume compared with the control group. Our results suggest Spirulina's polysaccharide fractions (CFPSs and BPSs) had significant analgesic and anti-inflammatory effects.

Conclusions

Since Spirulina is a readily available source of bioactive compounds, finding such potent anti-inflammatory and anti-nociceptive compounds can provide promising leads for novel drug development.

Spirulina extract improves age-induced vascular dysfunction

CONTEXT

Vascular dysfunction is considered a hallmark of ageing that has been associated with altered vasomotor responses, in which nitric oxide (NO) and reactive oxygen species participate. The consumption of Spirulina extracts, with antioxidant properties, increased recently.

OBJECTIVE

This study investigates the effect of Spirulina aqueous extract (SAE) on the vascular function of the aorta from aged rats.

MATERIALS AND METHODS

Aortic segments from aged male Sprague-Dawley rats (20-22 months old) were exposed to SAE (0.1% w/v, for 3 h) to analyse: (i) the vasodilator response induced by acetylcholine (ACh), by the NO donor sodium nitroprusside (SNP), by the carbon monoxide releasing molecule (CORM) and by the K_ATP channel opener, cromakalim (CK); (ii) the vasoconstrictor response induced by KCl and noradrenaline (NA); (iii) the production of NO and superoxide anion, and (iv) the expression of the p-eNOS and HO-1 proteins.

RESULTS

Incubation with SAE increased the expression of p-eNOS (1.6-fold) and HO-1 (2.0-fold), enhanced NO release (1.4-fold in basal and 1.9-fold in ACh-stimulated conditions) while decreased the production of superoxide (0.7-fold). SAE also increased the sensitivity (measured as pEC₅₀) to ACh (control: -7.06 ± 0.11; SAE: -8.16 ± 0.21), SNP (control: -7.96 ± 0.16; SAE: -9.11 ± 0.14) and CK (control: -7.05 ± 0.39; SAE: -8.29 ± 0.53), and potentiated the response to KCl (1.3-fold) and to NA (1.7-fold).

CONCLUSION

The antioxidant properties of SAE improved the vasomotor responses of aorta from aged rats. These results may support the use of Spirulina as a protection against vascular dysfunction.

Antioxidant Efficacy of a Spirulina Liquid Extract on Oxidative Stress Status and Metabolic Disturbances in Subjects with Metabolic Syndrome

Lipid peroxidation is associated with the development of some pathologies, such as cardiovascular diseases. Reduction in oxidative stress by antioxidants, such as Arthrospira (formely Spirulina), helps improving this redox imbalance. The aim of the study was to evaluate the effect of the Arthrospira liquid extract “Spirulysat^®” on oxidative markers—in particular, oxidized LDL (oxLDL)/total LDL cholesterol—and isoprostanes and to investigate its impact on lipid and glucose metabolism in the metabolic syndrome subject. A controlled, randomised, double-blind design was conducted in 40 subjects aged 18 to 65 years with metabolic syndrome after a daily intake of Spirulysat^® or placebo for twelve weeks. Blood and urinary samples were collected at three visits (V1, V2, V3) in the two groups for parameters determination. Although the Spirulysat^® group showed a decrease at all visits of the oxLDL/total cholesterol ratio, there was no significant difference compared to the placebo (p = 0.36). The urinary isoprostanes concentration in the Spirulysat^® group was reduced (p = 0.014) at V3. Plasma triglycerides decreased at V3 (p = 0.003) and HDL-cholesterol increased (p = 0.031) at all visits with Spirulysat^®. In conclusion, Spirulysat^® did not change the oxidized LDL (oxLDL)/LDL ratio but decreased the urinary isoprostanes, plasma triglycerides and increased HDL cholesterol, suggesting a beneficial effect on metabolic syndrome.

Polysaccharide from Spirulina platensis Evokes Antitumor Activity in Gastric Cancer Cells via Modulation of Galectin-3 and Exhibited Cyto/DNA Protection: Structure-Function Study

Polysaccharides play significant role in the management of different cancer types including gastric cancer. Here, we report the effect of spirulina polysaccharide (Sp) on galectin-3 modulatory activity in gastric cancer cells (AGS). The isolated Sp possessed an average molecular weight of 1457 kDa and galactose (42%) as a major sugar consisting of (β1-4d) units with a galactoarabinorhamnoglycan backbone. The Sp inhibited the proliferation of AGS cells by 48% without affecting normal NIH/3T3 cells as compared to doxorubicin, a known anticancer drug. Also, Sp exhibited significant (p < 0.05) galectin-3 mediated hemeagglutination inhibition with MIC of 9.37 μg/mL compared to galactose (6.25 μg/mL), a sugar specific to galectin-3. Galactose showed the highest molecular interaction with galectin-3 in the in silico study. In addition, Sp exhibited the cytoprotection in RBCs, buccal cells, and DNA exposed to oxidants. These findings suggest that Sp offers a promising therapeutic tool in the management of gastric cancer.

Microalgae Polysaccharides: An Alternative Source for Food Production and Sustainable Agriculture

Carbohydrates or polysaccharides are the main products derived from photosynthesis and carbon fixation in the Calvin cycle. Compared to other sources, polysaccharides derived from microalgae are safe, biocompatible, biodegradable, stable, and versatile. These polymeric macromolecules present complex biochemical structures according to each microalgal species. In addition, they exhibit emulsifying properties and biological characteristics that include antioxidant, anti-inflammatory, antitumor, and antimicrobial activities. Some microalgal species have a naturally high concentration of carbohydrates. Other species can adapt their metabolism to produce more sugars from changes in temperature and light, carbon source, macro and micronutrient limitations (mainly nitrogen), and saline stress. In addition to growing in adverse conditions, microalgae can use industrial effluents as an alternative source of nutrients. Microalgal polysaccharides are predominantly composed of pentose and hexose monosaccharide subunits with many glycosidic bonds. Microalgae polysaccharides can be structural constituents of the cell wall, energy stores, or protective polysaccharides and cell interaction. The industrial use of microalgae polysaccharides is on the rise. These microorganisms present rheological and biological properties, making them a promising candidate for application in the food industry and agriculture. Thus, microalgae polysaccharides are promising sustainable alternatives for potential applications in several sectors, and the choice of producing microalgal species depends on the required functional activity. In this context, this review article aims to provide an overview of microalgae technology for polysaccharide production, emphasizing its potential in the food, animal feed, and agriculture sector.

Effect of Different Extraction Methods on Physicochemical Characteristics and Antioxidant Activity of C-Phycocyanin from Dry Biomass of Arthrospira platensis

The effect of four different extraction methods on physicochemical characteristics and functionalities of chloro-phycocyanin (CP) was investigated. Swelling (S-CP), freezing and thawing (4FT-CP), ultrasonication with freezing and thawing (4FT+U-CP), and the high-pressure cell disruption (HPCD-CP) process affected CP differently, thus resulting in different levels of solubility, DPPH scavenging activity, ABTS scavenging activity, and reducing power. Among the four CPs, HPCD-CP had the highest CP content (15.3%), purity (1.66 ± 0.16), and ∆E value but the lowest ∆b value. The ζ potential of HPCD-CP (−38.8 mV) was the highest, but the average particle size of 4FT+U-CP (719.1 nm) was the highest. UV-Vis absorption spectra and fluorescence spectra illustrated that high-pressure cell disruption-assisted extraction had more profound impacts on the microenvironment of tetrapyrrole chromophores, the environment of aromatic amino acids, and the phycocyanobilin of CP. Furthermore, HPCD-CP and 4FT-CP showed higher solubility and antioxidant activities than S-CP, especially 4FT+U-CP. The results obtained in this study demonstrate that HPCD technology could obtain a food-grade C-phycocyanin product with higher CP concentration, purity, solubility, and antioxidant activity.

Microalgal Proteins and Bioactives for Food, Feed, and Other Applications

Microalgae are a known source of proteins, prebiotics, lipids, small molecules, anti-oxidants and bioactives with health benefits that can be harnessed for the development of functional foods, feeds, cosmeceuticals and pharmaceuticals. This review collates information on the supply, processing costs, target markets and value of microalgae, as well as microalgal proteins, lipids, vitamins and minerals. It discusses the potential impact that microalgae could have on global food and feed supply and highlights gaps that exist with regards to the use of microalgal proteins and ingredients as foods and supplements.

Immunomodulatory effects of the polysaccharide from Sinonovacula constricta on RAW264.7 macrophage cells

This study aimed to evaluate the immunomodulatory effect of the polysaccharide from Sinonovacula constricta (SCP‐1‐1) in RAW264.7 cells. SCP‐1‐1 with a molecular weight of 440.0 kDa consisted of glucose and mannose. The immunomodulatory assay results showed that SCP‐1‐1 could significantly enhance phagocytic ability, NO production, and some cytokines (TNF‐α, IL‐6, and IL‐1β) secretion of RAW264.7 cell in a dose‐dependent manner. Western blot analysis results demonstrated that SCP‐1‐1 could regulate the expression levels of the key proteins in the signaling pathways of RAW264.7 cell and might associated with NF‐κβ and PI3K signaling pathway. These findings could contribute to elucidate the immunomodulatory activities of the polysaccharide from Sinonovacula constricta.

Application progress of bioactive compounds in microalgae on pharmaceutical and cosmetics

Microalgae is an autotrophic organism with fast growth, short reproduction cycle, and strong environmental adaptability. In recent years, microalgae and the bioactive ingredients extracted from microalgae are regarded as potential substitutes for raw materials in the pharmaceutical and the cosmetics industry. In this review, the characteristics and efficacy of the high-value components of microalgae are discussed in detail, along with the sources and extraction technologies of algae used to obtain high-value ingredients are reviewed. Moreover, the latest trends in biotherapy based on high-value algae extracts as materials are discussed. The excellent antioxidant properties of microalgae derivatives are regarded as an attractive replacement for safe and environmentally friendly cosmetics formulation and production. Through further studies, the mechanism of microalgae bioactive compounds can be understood better and reasonable clinical trials conducted can safely conclude the compliance of microalgae-derived drugs or cosmetics to be necessary standards to be marketed.

Structural characterization, and in vitro immunostimulatory and antitumor activity of an acid polysaccharide from Spirulina platensis

In this study, a novel heteropolysaccharide named SP90-1 with immunostimulatory and antitumor activity was purified and characterized from Spirulina platensis. SP90-1 has a molecular weight of 63.92 kDa and mainly consists of rhamnose (Rha), glucose (Glc), galactose (Gal) and glucuronic acid (GlcA), followed by the minor components Fuc and Xyl. The backbone of SP90-1 was determined to be →2)-α-d-Rhap-(1 → 2,3)-α-d-Rhap-(1 → 4)-β-d-Glcp-(1 → [3)-β-d-Rhap-(1→]₃, with branches at the O-3 of Rha, consisting of the side chains 4-Galp and 4-GlcpA. SP90-1 was found to significantly enhance phagocytic capacity, promote the secretion of nitric oxide (NO), interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) in RAW264.7 cells, and remarkably inhibit the growth of A549 lung cancer cells. These findings demonstrate that SP90-1 could potentially be further explored for immunomodulatory biomedical applications.

Separation, Purification, Structure Analysis, In Vitro Antioxidant Activity and circRNA-miRNA-mRNA Regulatory Network on PRV-Infected RAW264.7 Cells of a Polysaccharide Derived from Arthrospira platensis

To investigate the structure of Arthrospira platensis polysaccharide (PAP) (intracellular polysaccharide) and the antioxidant activity of the first component of PAP (PAP-1) on pseudorabies virus (PRV) -infected RAW264.7 cells. The PAP was separated and purified by the Cellulose DE-52 chromatography column and Sephacryl S-200 high-resolution gel column to obtain PAP-1. The antioxidant activity and regulation of PAP-1 on PRV-infected RAW264.7 cells of circRNA-miRNA-mRNA network were investigated by chemical kit, Q-PCR, and ce-RNA seq. The results indicated that the molecular weight (Mw) of PAP-1, which was mainly composed of glucose and eight other monosaccharides, was 1.48 × 106 Da. The main glycosidic bond structure of PAP-1 was →4)-α-D-Glcp-(1→. PAP-1 may be increased the antioxidant capacity by regulating the circRNA-miRNA-mRNA network in PRV-infected RAW264.7 cells. This study provided a scientific foundation for further exploring the antioxidant activity of PAP-1 based on its structure.

Isolation, Purification, Characterization, and Immunomodulatory Activity Analysis of α-Glucans from Spirulina platensis

Crude polysaccharides from Spirulina platensis (SP) were isolated by maceration with a hot alkali solution and further fractionated by DEAE-52 cellulose and Sephadex G-100 chromatography into two purified fractions PSP-1 and PSP-2. The monosaccharide composition analysis indicated that SP was mainly composed of rhamnose and glucose, while PSP-1 and PSP-2 were composed only of glucose. The composition analysis of PSP-1 and PSP-2 by HPLC, FT-IR, and NMR showed that PSP-1 and PSP-2 were branching dextran, and their structures were (1 → 4)-linked-α-D-Glcp as the main chain, and C-6 replaced the single α-D-Glcp as the linear structure of the branch chain. The glucans (SP/PSP-1/PSP-2) can significantly improve the phagocytic ability of macrophages, enhance iNOS activity, promote NO production, and increase IL-6 mRNA expression, so they may possess certain immunomodulatory activity.

Selenium-Containing Polysaccharides—Structural Diversity, Biosynthesis, Chemical Modifications and Biological Activity

Selenosugars are a group of sugar derivatives of great structural diversity (e.g., molar masses, selenium oxidation state, and selenium binding), obtained as a result of biosynthesis, chemical modification of natural compounds, or chemical synthesis. Seleno-monosaccharides and disaccharides are known to be non-toxic products of the natural metabolism of selenium compounds in mammals. In the case of the selenium-containing polysaccharides of natural origin, their formation is also postulated as a form of detoxification of excess selenium in microorganisms, mushroom, and plants. The valency of selenium in selenium-containing polysaccharides can be: 0 (encapsulated nano-selenium), IV (selenites of polysaccharides), or II (selenoglycosides or selenium built into the sugar ring to replace oxygen). The great interest in Se-polysaccharides results from the expected synergy between selenium and polysaccharides. Several plant- and mushroom-derived polysaccharides are potent macromolecules with antitumor, immunomodulatory, antioxidant, and other biological properties. Selenium, a trace element of fundamental importance to human health, has been shown to possess several analogous functions. The mechanism by which selenium exerts anticancer and immunomodulatory activity differs from that of polysaccharide fractions, but a similar pharmacological effect suggests a possible synergy of these two agents. Various functions of Se-polysaccharides have been explored, including antitumor, immune-enhancement, antioxidant, antidiabetic, anti-inflammatory, hepatoprotective, and neuroprotective activities. Due to being non-toxic or much less toxic than inorganic selenium compounds, Se-polysaccharides are potential dietary supplements that could be used, e.g., in chemoprevention.

Recent advances in the application of microalgae and its derivatives for preservation, quality improvement, and shelf-life extension of seafood

Seafood is a highly perishable food product due to microbiological, chemical, and enzymatic reactions, which are the principal causes of their rapid quality deterioration. Therefore, ever-increasing consumers' demand for high-quality seafood along with a negative perception of synthetic preservatives creates opportunities for natural preservatives such as microalgae extracts. They are potential alternatives to reduce microbial growth, increase oxidative stability, and protect the sensorial properties of seafood. Research has shown that the inclusion of microalgae extracts into the aquatic animal's diet could enhance their meat quality and increase production. This review focuses on the direct application of various microalgae extracts as seafood preservative, and their functional properties in seafood, such as antioxidant and antimicrobial activities. Besides, the potential nutritional application of microalgae extracts as an alternative in aqua-feed and their impact on seafood quality (indirect application) are also presented. The safety aspects and regulatory issues of products from microalgae are highlighted.

Beneficial Effects of Spirulina Aqueous Extract on Vasodilator Function of Arteries from Hypertensive Rats

Hypertension is a multifactorial disorder considered one of the major causes of premature death worldwide. This pathology is associated with vascular functional/structural alterations in which nitric oxide (NO) and oxygen reactive species participate. On the other hand, the use of microalgae extracts in the treatment of cardiovascular diseases is increasing. Based on the antioxidant and antihypertensive properties of Spirulina, this study aims to investigate the effect of an aqueous extract of Spirulina on the vasodilator function of the aorta from spontaneously hypertensive rats (SHR), analyzing the functional role of NO. For this, aortic segments from male SHR were divided into two groups, one control and the other exposed to an Spirulina aqueous extract (0.1% w/v, for 3 hours), to analyze (i) the production of NO, superoxide anion, and hydrogen peroxide; (ii) the vasodilator response induced by acetylcholine (ACh), by the NO donor and sodium nitroprusside (SNP), and by the KATP channel opener and pinacidil; and (iii) the expression of the p-Akt, p-eNOS, and HO-1 proteins. The results showed that the aqueous Spirulina extract (i) increased the production of NO, did not significantly modify that of superoxide, while decreased that of hydrogen peroxide; (ii) increased the vasodilatory responses induced by ACh, NPS, and pinacidil; and (iii) increased the expression of p-Akt and HO-1. These results suggest that incubation with the aqueous Spirulina extract improves the vascular function of arteries from SHR by increasing the release/bioavailability/function of NO. Increased KATP channel activation and expression of pAkt and HO-1 appear to be participating in these actions.

Effects of the polysaccharide SPS-3-1 purified from Spirulina on barrier integrity and proliferation of Caco-2 cells

Following ultrasonication combined with a hot water extraction, a new type of bioactive polysaccharide, SPS-3-1, was purified from Spirulina using ultrafiltration centrifugation and gel filtration chromatography. The structure of SPS-3-1 was determined with high performance gel permeation chromatography, gas chromatography, periodate oxidation, fourier transform infrared spectroscopy, nuclear magnetic resonance, and atomic force microscopy performance. SPS-3-1 is a homogeneous β-pyran polysaccharide with 1 → 2, 1 → 3, and 1 → 4 glycosyl bonds, mainly composed of d-ribose, l-rhamnose, l-arabinose, l-foucose, and d-glucose. The molar ratio of these components is 1:0.70:1.03:2.1:6.59. The molecular weight of SPS-3-1 is 623.02 kDa. SPS-3-1 has a linear filament structure with a width of 34.132 nm and a height of 819.169 pm. We found that SPS-3-1 significantly enhanced transepithelial electrical resistance, a tight junction integrity marker, in a Caco-2 intestinal cell monolayer model. Analysis of the effect of SPS-3-1 on cell proliferation showed that SPS-3-1 inhibited the in vitro growth of Caco-2 and HepG2 cells with an IC₅₀ of 566.67 μg/mL and 1078.95 μg/mL, respectively.

Fucoidan: Biological Activity in Liver Diseases

Fucoidan is a type of polysaccharide rich in sulfuric acid groups and is mainly found in brown algae. Due to its extensive biological activities, such as anticoagulant, antitumor, antithrombotic, antiviral, anti-oxidant and enhancing immune function, fucoidan has gradually become a research hotspot. Under the scientific guidance of modern medical theory, fucoidan and its mechanism in oxidative stress, carbohydrate and lipid metabolism, inflammatory response, tumor proliferation, and metastasis have become a new research direction and an important basis as an effective liver protection drug. In this paper, we discuss the important role of fucoidan in viral hepatitis, liver fibrosis, liver cancer, nonalcoholic fatty liver and liver injury induced by drugs and ischemia and briefly discuss its underlying mechanism. We supplement the theoretical basis for its clinical application and provide effective targets for the development of follow-up dominant drugs.

Studies on isolation, characterization of fucoidan from brown algae Turbinaria decurrens and evaluation of it's in vivo and in vitro anti-inflammatory activities

In the present study, the anti-nociception and anti-inflammatory activity of fucoidan isolated from T. decurrens on formalin induced paw-edema in mice model were investigated. The extracted fucoidan contain 54.86% of total sugar, 23.51% of sulfate and 3.4% of protein. The monosaccharide composition analysis revealed that fucoidan encompassed of fucose (59.3%), galactose (12.6%), mannose (9.6%), rhamnose (6.4%) and xylose (11.4%). Further, the structural characterization was done by UV-visible spectroscopy, X-ray diffraction, FT-IR and 1HNMR analysis. The fucoidan reduced the licking time thereby suggesting anti-nociceptive effect and decreased the size of paw swelling in the formalin induced inflammatory edema condition. The isolated fucoidan could significantly decreased the MDA and also increase the SOD, CAT, GPx, GST and GSH activity in paw edema tissue of formalin injected mice. Furthermore, fucoidan administration retained p65/NF-κB transcription factor in the cytosol thereby showing down regulation of the gene expression of pro-inflammatory mediators such as IL-1β, COX-2 and MMP-9 in fucoidan treated mice. The anti-inflammatory effect of fucoidan was attributed to its capacity on modulating the levels of enzymatic antioxidants, master regulator NF-κB and pro-inflammatory cytokines. The fucoidan has reduced LPS induced cytotoxicity in IC-21 macrophage at a dose depended on manner.

Spectroscopic and molecular docking studies on the interaction of phycocyanobilin with peptide moieties of C-phycocyanin

The binding of C-phycocyanin (CPC), a light harvesting pigment with phycocyanobilin (PCB), a chromophore is instrumental for the coloration and bioactivity. In this study, structure-mediated color changes of CPC from Spirulina platensis during various enzymatic hydrolysis was investigated based on UV-visible, circular dichroism, infra-red, fluorescence, mass spectrometry, and molecular docking. CPC was hydrolyzed using 7.09 U/mg protein of each enzyme at their optimal hydrolytic conditions for 3 h as follows: papain (pH 6.6, 60 °C), dispase (pH 6.6, 50 °C), and trypsin (pH 7.8, 37 °C). The degree of hydrolysis was in the order of papain (28.4%) > dispase (20.8%) > trypsin (7.3%). The sequence of color degradation rate and total color difference (ΔE) are dispase (82.9% and 40.37), papain (72.4% and 24.70), and trypsin (58.7% and 25.43). The hydrolyzed peptides were of diverse sequence length ranging from 8 to 9 residues (papain), 7-12 residues (dispase), and 9-63 residues (trypsin). Molecular docking studies showed that key amino acid residues in the peptides interacting with chromophore. Amino acid residues such as Arg86, Asp87, Tyr97, Asp152, Phe164, Ala167, and Val171 are crucial in hydrogen bonding interaction. These results indicate that the color properties of CPC might associate with chromopeptide sequences and their non-covalent interactions.