Comparative Lipidomics Study of Four Edible Red Seaweeds Based on RPLC-Q-TOF

Red seaweeds (Rhodophyta) are becoming increasingly important as a food and medicine source in blue biotechnology applications such as functional foods, feeds, and pharmaceuticals. Compared to fatty acid composition and sterols, the lipidome in red seaweeds is still in an early disclosure stage. In this study, the lipidomes of four red seaweeds (Gracilaria sjoestedtii, Gracilaria verrucosa, Gelidium amansii, and Chondrus ocellatus) collected from the coastal area in north China were characterized using reversed-phase liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (RPLC-Q-TOF). Hundreds of lipid molecular species including glycolipids, phospholipids, sphingolipids, glycerolipids, and betaine lipids were identified and quantified. Novel lipids with unique molecular structures such as glucuronosyldiacylglycerols (GlcADG), head-group acylated GlcADG (acGlcADG), and hexose-inositol-phosphoceramides (Hex-IPC) were discovered in red seaweeds for the first time, greatly expanding our knowledge on glycolipids and sphingolipids in seaweeds. Glycolipids were the dominant components (45.6-67.7% of total lipids) with a high proportion of polyunsaturated fatty acids (PUFA) including arachidonic acid (AA) and eicosapentaenoic acid (EPA), indicating the potential nutritional value of the four red seaweeds. The investigated red seaweeds showed a distinctive sphingolipid profile with the t18:1 being the predominant LCB in Cer (41.1-71.5%) and HexCer (91.3-97.9%) except for Gelidium amansii, which had the highest proportion of t18:0. Comparison of lipid profiles among the four red seaweeds revealed that AA- and EPA-glycolipids are good lipid markers for the differentiation of red seaweed samples. The AA proportion in glycolipids of Gracilaria genus was much higher than Gelidium genus and Chondrus genus. This study acquired comprehensive lipid profiles from four red seaweeds, revealing the uniqueness of natural biochemical fingerprints of red seaweeds and further promoting their utilization.

Desiccation Stress Tolerance in Porphyra and Pyropia Species: A Latitudinal Analysis along the Chilean Coast

One of the most important factors regulating the distribution and abundance of seaweeds is desiccation, triggered mainly by tidal changes and climatic variation. Porphyra and Pyropia species have evolved multiple strategies to tolerate desiccation stress; however, how these tolerance strategies differ in these species inhabiting different latitudes is still unknown. In this context, we analyzed, in situ, the physiological responses of these species (collected from 18° S to 41° S along the Chilean coast) to desiccation stress using biochemical and molecular analyses. The hyper-arid terrestrial climate of northern Chile, with high evaporation and lack of constant rain determines a very steep increase in desiccation stress in the upper intertidal during low tide for these species. Accordingly, the results showed that, in comparison with the southernmost populations, the Porphyra/Pyropia species from the north zone of Chile (18°-30° S) exhibited higher contents of lipoperoxide and carbonyls (1.6-1.9 fold) together with higher enzymatic activities, including ascorbate peroxidase, catalase, peroxiredoxin, and thioredoxin (2-3-fold). In addition, a substantial expression of cat, prx, and trx transcripts during desiccation was demonstrated, mainly in the northernmost populations. These results provide evidence of (i) significant activation of antioxidant enzymes and transcripts (principally cat and prx); (ii) participation of phenolic antioxidant compounds as a highly plastic physiological strategy to cope with desiccation; and (iii) the activation of the tolerance responses was affected by species latitudinal distribution. Thus, for the first time, this study integrated the biochemical and genetic responses of diverse Porphyra/Pyropia species to better understand their physiological dynamics of tolerance over a wide latitudinal range.

Seasonal Nutritional Profile of Gelidium corneum (Rhodophyta, Gelidiaceae) from the Center of Portugal

Gelidium corneum is a well-known agarophyte, harvested worldwide for its high agar quality. However, the species also exhibits an interesting nutritional profile, but with seasonal variations. Therefore, to evaluate the nutritional value of G. corneum, ash, crude protein, total lipids, and carbohydrates were analyzed at different times of the year. The heavy metals mercury, arsenic, lead, cadmium, and tin, as well as iodine were also measured. Finally, the seasonal antioxidant capacity of G. corneum extracts was evaluated. Our results indicate that the biomass is rich in protein (up to 16.25 ± 0.33%) and carbohydrates (up to 39.5 ± 3.29%), and low in lipids (up to 2.75 ± 0.28%), and especially in the summer, the AI, TI indexes, n-6/n-3 and h/H ratios (0.93, 0.6, 0.88 and 1.08, respectively) are very interesting. None of the contaminants exceeded the legally established limits, and the iodine values were adequate for a healthy diet. Finally, the antioxidant capacity is fair, with the DPPH ≤ 10.89 ± 1.46%, and ABTS ≤ 13.90 ± 1.54% inhibition, FRAP ≤ 0.91 ± 0.22 AAE.g⁻¹, and TPC ≤ 6.82 ± 0.26 GAE.g⁻¹. The results show that G. corneum is an attractive resource, with potential use as food or as a food supplement.

Polar Lipids Composition, Antioxidant and Anti-Inflammatory Activities of the Atlantic Red Seaweed Grateloupia turuturu

Grateloupia turuturu Yamada, 1941, is a red seaweed widely used for food in Japan and Korea which was recorded on the Atlantic Coast of Europe about twenty years ago. This seaweed presents eicosapentaenoic acid (EPA) and other polyunsaturated fatty acids (PUFAs) in its lipid fraction, a feature that sparked the interest on its potential applications. In seaweeds, PUFAs are mostly esterified to polar lipids, emerging as healthy phytochemicals. However, to date, these biomolecules are still unknown for G. turuturu. The present work aimed to identify the polar lipid profile of G. turuturu, using modern lipidomics approaches based on high performance liquid chromatography coupled to high resolution mass spectrometry (LC-MS) and gas chromatography coupled to mass spectrometry (GC-MS). The health benefits of polar lipids were identified by health lipid indices and the assessment of antioxidant and anti-inflammatory activities. The polar lipids profile identified from G. turuturu included 205 lipid species distributed over glycolipids, phospholipids, betaine lipids and phosphosphingolipids, which featured a high number of lipid species with EPA and PUFAs. The nutritional value of G. turuturu has been shown by its protein content, fatty acyl composition and health lipid indices, thus confirming G. turuturu as an alternative source of protein and lipids. Some of the lipid species assigned were associated to biological activity, as polar lipid extracts showed antioxidant activity evidenced by free radical scavenging potential for the 2,2'-azino-bis-3-ethyl benzothiazoline-6-sulfonic acid (ABTS^●+) radical (IC₅₀ ca. 130.4 μg mL^-1) and for the 2,2-diphenyl-1-picrylhydrazyl (DPPH^●) radical (IC₂₅ ca. 129.1 μg mL^-1) and anti-inflammatory activity by inhibition of the COX-2 enzyme (IC₅₀ ca. 33 µg mL^-1). Both antioxidant and anti-inflammatory activities were detected using a low concentration of extracts. This integrative approach contributes to increase the knowledge of G. turuturu as a species capable of providing nutrients and bioactive molecules with potential applications in the nutraceutical, pharmaceutical and cosmeceutical industries.

In Vitro Prebiotic and Anti-Colon Cancer Activities of Agar-Derived Sugars from Red Seaweeds

Numerous health benefits of diets containing red seaweeds or agar-derived sugar mixtures produced by enzymatic or acid hydrolysis of agar have been reported. However, among various agar-derived sugars, the key components that confer health-beneficial effects, such as prebiotic and anti-colon cancer activities, remain unclear. Here, we prepared various agar-derived sugars by multiple enzymatic reactions using an endo-type and an exo-type of β-agarase and a neoagarobiose hydrolase and tested their in vitro prebiotic and anti-colon cancer activities. Among various agar-derived sugars, agarotriose exhibited prebiotic activity that was verified based on the fermentability of agarotriose by probiotic bifidobacteria. Furthermore, we demonstrated the anti-colon cancer activity of 3,6-anhydro-l-galactose, which significantly inhibited the proliferation of human colon cancer cells and induced their apoptosis. Our results provide crucial information regarding the key compounds derived from red seaweeds that confer beneficial health effects, including prebiotic and anti-colon cancer activities, to the host.

Structural Diversity in Galactans From Red Seaweeds and Its Influence on Rheological Properties

Galactans are important components of many plant cell walls. Besides, they are the major polysaccharides in extracellular matrixes from different seaweeds, and other marine organisms, which have an acidic character due to the presence of sulfate groups in their structures. In particular, most of the red seaweeds biosynthesize sulfated galactans with very special linear backbones, constituted by alternating (1→3)-β-d-galactopyranose units (A-unit) and (1→4)-α-galactopyranose residues (B-unit). In the industrially significant seaweeds as source of hydrocolloids, B-units belong either to the d-series and they produce carrageenans (as in the order Gigartinales), or to the l-series, and they are sources of agarose and/or structurally related polymers (i.e., Gelidiales, Gracilariales). In both cases, the latter units appear as cyclized 3,6-anhydro-α-galactose in certain amounts, which can be increased by alkaline cyclization of α-galactose 6-sulfate units. Besides, it has been clearly shown that some red algae produce different amounts of both galactan structures, known as d/l-hybrids. It is not yet clear if they comprise both diasteromeric types of units in the same molecule, or if they are mixtures of carrageenans and agarans that are very difficult to separate. It has been reported that the biosynthesis of these galactans, showing that the nucleotide transport for d-galactopyranose units is UDP-d-Gal, while for l-galactose, it is GDP-l-Gal, so, there is a different pathway in the biosynthesis of agarans. However, at least in those seaweeds that produce carrageenans as major galactans, but also agarans, both synthetic pathways should coexist. Another interesting characteristic of these galactans is the important variation in the sulfation patterns, which modulate their physical behavior in aqueous solutions. Although the most common carrageenans are of the κ/ι- and λ-types (with A-units sulfated at the 4- and 2-positions, respectively) and usually in agarans, when sulfated, is at the 6-position, many other sulfate arrangements have been reported, greatly influencing the functional properties of the corresponding galactans. Other substituents can modify their structures, as methyl ethers, pyruvic acid ketals, acetates, and single stubs of xylose or other monosaccharides. It has been shown that structural heterogeneity at some extent is essential for the proper functional performance of red algal galactans.

The influence of environmental features in the content of mycosporine-like amino acids in red marine algae along the Brazilian coast

Mycosporine-like amino acids (MAA) are ultraviolet screen substances synthesized by marine algae. The physiological function of these substances is related to cellular protection against UV radiation and as a protective mechanism against oxidative stress. These substances can be found mainly in the ocean, among red seaweeds. Its concentration in organisms has been related to ultraviolet radiation and availability of inorganic nitrogen in the environment. We start our study of MAA content in different species to understand if environmental conditions influence the concentration of MAAs in red seaweeds. The Brazilian coast presents abiotic factors that interact to create different physical-chemical features in the environment. We collected 441 samples from 39 species of red seaweed easily found in the intertidal zone, in low tide, during the summer of 2015. The sampling encompassed a latitudinal gradient (3° S to 28°5' S) at 23 points along the coast. We quantified and identified the content of MAAs in species through the method of high performance liquid chromatography. We detected for the first time the occurrence of MAAs in certain species of red algae that have not been reported to contain MAAs before. We confirmed that some environmental factors influenced the content of MAAs. Enhanced MAA contents, for example, were found in environments with a basic pH, a high ultraviolet index, and high concentrations of phosphate and nitrate. Salinity, dissolved oxygen and variations of sea surface temperature also influenced, in a secondary way, MAA content in algae in their natural environments.

Red Seaweed (Hypnea Bryodies and Melanothamnus Somalensis) Extracts Counteracting Azoxymethane-Induced Hepatotoxicity in Rats

Background: Azoxymethane (AOM) is a well-known colon cancer-inducing agent in experimental animals via mechanisms that include oxidative stress in rat colon and liver tissue. Few studies have investigated AOM-induced oxidative stress in rat liver tissue. Red seaweeds of the genera Hypnea Bryodies and Melanothamnus Somalensis are rich in polyphenolic compounds that may suppress cancer through antioxidant properties, yet limited research has been carried out to investigate their anti-carcinogenic and antioxidant influence against AOM-induced oxidative stress in rat liver. Objective: This study aims to determine protective effects of red seaweed (Hypnea Bryodies and Melanothamnus Somalensis) extracts against AOM-induced hepatotoxicity and oxidative stress. Materials and Methods: Sprague–Dawley rats received intraperitoneal injections of AOM, 15 mg/kg body weight, once a week for two consecutive weeks and then orally administered red seaweed (100 mg/kg body-weight) extracts for sixteen weeks. At the end of the experiment all animals were overnight fasted then sacrificed and blood and liver tissues were collected. Results: AOM treatment significantly decreased serum liver markers and induced hepatic oxidative stress as evidenced by increased liver tissue homogenate levels of nitric oxide and malondialdehyde, decreased total antioxidant capacity and glutathione, and inhibition of antioxidant enzymes (catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase and superoxide dismutase). Both red seaweed extracts abolished the AOM-associated oxidative stress and protected against liver injury as evidenced by increased serum levels of liver function markers. In addition, histological findings confirmed protective effects of the two red seaweed extracts against AOM-induced liver injury. Conclusion: Our findings indicate that red seaweed (Hypnea Bryodies and Melanothamnus Somalensis) extracts counteracted oxidative stress-induced hepatotoxicity in a rat model of colon cancer.

A Cultivated Form of a Red Seaweed (Chondrus crispus), Suppresses β-Amyloid-Induced Paralysis in Caenorhabditis elegans

We report here the protective effects of a methanol extract from a cultivated strain of the red seaweed, Chondrus crispus, against β-amyloid-induced toxicity, in a transgenic Caenorhabditis elegans, expressing human Aβ_1-42 gene. The methanol extract of C. crispus (CCE), delayed β-amyloid-induced paralysis, whereas the water extract (CCW) was not effective. The CCE treatment did not affect the transcript abundance of amy1; however, Western blot analysis revealed a significant decrease of Aβ species, as compared to untreated worms. The transcript abundance of stress response genes; sod3, hsp16.2 and skn1 increased in CCE-treated worms. Bioassay guided fractionation of the CCE yielded a fraction enriched in monogalactosyl diacylglycerols (MGDG) that significantly delayed the onset of β-amyloid-induced paralysis. Taken together, these results suggested that the cultivated strain of C. crispus, whilst providing dietary nutritional value, may also have significant protective effects against β-amyloid-induced toxicity in C. elegans, partly through reduced β-amyloid species, up-regulation of stress induced genes and reduced accumulation of reactive oxygen species (ROS).

Proteins and Carbohydrates from Red Seaweeds: Evidence for Beneficial Effects on Gut Function and Microbiota

Based on their composition, marine algae, and namely red seaweeds, are good potential functional foods. Intestinal mucosal barrier function refers to the capacity of the intestine to provide adequate containment of luminal microorganisms and molecules. Here, we will first outline the component of seaweeds and will summarize the effects of these on the regulation of mucosal barrier function. Special attention will be paid to unique components of red seaweeds: proteins and derived peptides (e.g., phycobiliproteins, glycoproteins that contain “cellulose binding domains”, phycolectins and the related mycosporine-like amino acids) together with polysaccharides (e.g., floridean starch and sulfated galactans, such as carrageenans, agarans and “dl-hybrid”) and minerals. These compounds have been shown to exert prebiotic effects, to regulate intestinal epithelial cell, macrophage and lymphocyte proliferation and differentiation and to modulate the immune response. Molecular mechanisms of action of peptides and polysaccharides are starting to be elucidated, and evidence indicating the involvement of epidermal growth factor receptor (EGFR), insulin-like growth factor receptor (IGFR), Toll-like receptors (TLR) and signal transduction pathways mediated by protein kinase B (PKB or AKT), nuclear factor-κB (NF-κB) and mitogen activated protein kinases (MAPK) will also be summarized. The need for further research is clear, but in vivo experiments point to an overall antiinflammatory effect of these algae, indicating that they can reinforce membrane barrier function.

An improved method for estimating R-phycoerythrin and R-phycocyanin contents from crude aqueous extracts of Porphyra (Bangiales, Rhodophyta)

One frequently-cited method for determining phycoerythrin (PE) and phycocyanin (PC) contents from crude aqueous extracts of red seaweeds utilizes peaks and troughs of absorbance spectra. The trough absorbance values are used to establish a linear or logarithmic baseline attributable to background scatter of particulate cellular debris not removed by centrifugation. Pigment contents are calculated by subtracting baseline values from PE and PC absorbance peaks. The baseline correction is intended to make the method independent of centrifugation time and/or speed. However, when crude extracts of Porphyra were analyzed using this protocol, R-PE and R-PC estimates were significantly affected by centrifugation time, suggesting that the method was not reliable for the genus. The present study has shown that with sufficient centrifugation, background scatter in Porphyra extracts can be removed, the remaining spectrum representing the overlapping absorbance peaks of water-soluble pigments in the extract. Using fourth derivative analysis of Porphyra extract absorbance spectra, peaks corresponding to chlorophyll, R-PE, R-PC, and allophycocyanin (APC) were identified. Dilute solutions of purified R-PE, R-PC and chlorophyll were scanned separately to identify spectral overlaps and develop new equations for phycobilin quantification. The new equations were used to estimate R-PE and R-PC contents of Porphyra extracts and purified R-PE, R-PC and chlorophyll solutions were mixed according to concentrations corresponding to the sample estimates. Absorbances and fourth derivative spectra of the sample extract and purified pigment mixtures were compared and found to coincide. The newly derived equations are more accurate for determining R-PE and R-PC of Porphyra than previously published methods.