Edible Seaweed Research Articles

Dietary exposure and risk assessment to trace elements and iodine in seaweeds

IntroductionSeaweeds are a rich source of elements such as iodine, and are also able to accumulate contaminants such as trace elements. MethodsThe aim of this study was to assess the dietary exposure as well as the risk from iodine and trace elements in edible seaweeds for the French population using current consumption data. The contribution of seaweeds to overall dietary exposure to trace elements and iodine was evaluated, and for those substances with minimal contribution to overall dietary exposure, simulations were performed to propose increased maximal limits in seaweeds. ResultsCadmium, inorganic arsenic and mercury in seaweeds were very low contributors to total dietary exposure to these contaminants (0.7 % 1.1 % and 0.1 % on average, respectively). Dietary exposure to lead via seaweed may contribute up to 3.1 % of total dietary exposure. Dietary consumption of iodine via seaweed may contribute up to 33 % of total exposure to iodine, which makes seaweeds the strongest contributor to iodine in diet. DiscussionNew maximal values in seaweeds are proposed for the very low contributors to total dietary exposure: 1 mg/kg dw for cadmium, 10 mg/kg dw for inorganic arsenic and 0.3 mg/kg dw for mercury.

Formulation of Polymeric Microparticles Using Eco-Friendly Extracted Crude Fucoidans from Edible Brown Seaweed Undaria pinnatifida.

Several bioactive compounds that hold a potential interest in the food industry as phenolic compounds, polysaccharides, proteins and vitamins, among others, are present in seaweeds. Green extraction technologies are the preferred way to obtain these compounds. Pressurized hot water extraction, from 160 to 220 °C, was tested to achieve high yields of these components from the edible brown seaweed, Undaria pinnatifida. The maximum fucoidan content was recovered at 160 °C, while the phloroglucinol content and antioxidant activity were maximum at 220 °C. The possibility of encapsulating these bioactive fractions using mannitol was assessed. The highest production yield of the polymeric particles was found using the 220 °C fraction (close to 75%). In order to formulate microparticles with bioactive potential, several ratios of liquid phases were assessed, 3:1, 1:1 and 1:3 (w:w), using the liquid fractions obtained at 160 °C and 220 °C. The yield production was always above 67%, being in the 1:3 ratio (160 °C:220 °C) and close to 75%. The rheological results indicated that the presence of microparticles enhanced the apparent viscosity of the aqueous dispersions with non-Newtonian profiles, achieving the highest viscosity for those formulated with microparticles from 160 °C:200 °C (3:1).

Biochemical and Nutritional Characterization of Edible Seaweeds from the Peruvian Coast.

In Peru, the number of species of edible seaweeds within the genera Chondracanthus, Porphyra (hereafter P.), Pyropia (hereafter Py.), and Ulva has not been fully established, nor is there a significant level of information available related to their chemical and nutritional composition. This study involved the biochemical analysis of species belonging to ten genera of macroalgae, known edible and some of which have the potential to be used as food, including six red (Callophyllis, Chondracanthus, Mazzaella, Porphyra, Pyropia, and Rhodymenia), two green (Ulva and Codium), and two brown (Eisenia and Lessonia) species collected along the Peruvian coast (6°-17° S). In the evaluation of 37 specimens, differences were found in the proximal composition, amino acid composition, and fatty acid profiles, which were specific to subgroups and supported their taxonomic classification, mainly at the order level. The red algae Porphyra/Pyropia (Bangiales) had the highest average percentage of protein (24.10%) and carbohydrates (59.85%) and the lowest percentage of ash (7.95%). Conversely, the brown alga Eisenia (Laminariales) had the lowest average percentage of protein, with different values related to the structure: 14.11% at the level of the frond and 9.46% at the level of the stipe. On the other hand, Bryopsidales green algae showed the highest average percentages of lipids (5.38%). The moisture percentages ranged from 4 to 16%, and no relevant significant differences were shown between the orders. The characteristic amino acids in all of the studied groups were glutamic acid, aspartic acid, alanine, and leucine. The highest average of the essential amino acids ratio was obtained for the Gigartinales red algae (48.65%), and the highest values of the essential amino acid index (EAAI) were obtained for the Ulvales, Laminariales, Gigartinales, and Rhodymeniales algae (EAAI > 0.92). The highest average relative percentage of fatty acids was obtained for polyunsaturated fatty acids, followed by saturated fatty acids. The major component of the ω6 fatty acids from red and brown algae was arachidonic acid (C20:4n - 6). The highest level of ω3 fatty acids was observed for the eicosapentaenoic acids (EPA) in red algae. The highest median ω6/ω3 ratio was displayed by the red alga Callophyllis variegata (Gigartinales). A detailed knowledge of edible seaweeds, and those considered potentially edible, would help to diversify the diet based on macroalgae in Peru.

Survival of Inoculated Vibrio spp., Shigatoxigenic Escherichia coli, Listeria monocytogenes, and Salmonella spp. on Seaweed (Sugar Kelp) During Storage

Bacteria including Vibrio spp. persist in coastal waters and can contaminate edible seaweeds. Pathogens such as Listeria monocytogenes, shigatoxigenic Escherichia coli (STEC), and Salmonella have been associated with and present serious health risks in minimally processed vegetables including seaweeds. This study evaluated the survival of four pathogens inoculated onto two product forms of sugar kelp subjected to different storage temperatures. The inoculation comprised of a cocktail of two Listeria monocytogenes and STEC strains, two Salmonella serovars, and two Vibrio species. STEC and Vibrio were grown and applied in salt-containing media to simulate preharvest contamination, whereas L. monocytogenes and Salmonella inocula were prepared to simulate postharvest contamination. Samples were stored at 4°C and 10°C for 7 days, and 22°C for 8 h. Microbiological analyses were performed periodically (1, 4, 8, 24 h, etc.) to evaluate the effects of storage temperature on pathogen survival. Pathogen populations decreased under all storage conditions, but survival was greatest for all species at 22°C, with STEC exhibiting significantly less reduction (1.8 log CFU/g) than Salmonella, L. monocytogenes, and Vibrio (3.1, 2.7, and 2.7 log CFU/g, respectively) after storage. The largest population reduction (5.3 log CFU/g) was observed in Vibrio stored at 4°C for 7 days. Regardless of storage temperature, all pathogens remained detectable at the end of the study duration. Results emphasize the need for strict adherence to temperature control for kelp as temperature abuse may support pathogen survival, especially STEC, during storage, and the need for prevention of postharvest contamination, particularly with Salmonella.

Evaluation of Tropical Edible Seaweeds Across the Untapped Frontier of Gok for Boosting the Expanse’s Fiscal Valorization

Evaluation of Tropical Edible Seaweeds Across the Untapped Frontier of Gok for Boosting the Expanse’s Fiscal Valorization

Diphlorethohydroxycarmalol, a phlorotannin contained in brown edible seaweed Ishige okamurae, prevents AGE-related diabetic nephropathy by suppression of AGE-RAGE interaction

Advanced glycation end-products (AGEs) are complex and heterogeneous compounds generated through various steps and are naturally produced during the glycation reaction. Excessively generated AGEs bind to long-lived proteins such as collagen and cause renal dysfunction, leading to AGE-related diabetic nephropathy (DN). In this study, we aimed to confirm the therapeutic potential of marine biological resources by evaluating the role of diphlorethohydroxycarmalol (DPHC), a major phlorotannin compound contained in edible brown algae Ishige okamurae, in the key mechanisms involved in the pathogenesis and progression of AGE-induced DN. The AGE formation inhibitory and AGE-collagen cross-link inhibiting/breaking ability assay were performed to evaluate the anti-glycation effect of DPHC. The AGE-RAGE interaction inhibitory effect was evaluated through molecular docking study. The renoprotective effect of DPHC was confirmed in mouse glomerular mesangial cells. DPHC treatment exhibited anti-glycation ability through suppression of AGE formation and AGE-collagen cross-linking generation, and disruption of cross-links formed between AGE-collagen. In addition, DPHC pre-treatment significantly suppressed reactive oxygen species (ROS) production, intracellular methylglyoxal (MGO)/AGEs accumulation, and activation of apoptosis cascade by MGO. Moreover, DPHC suppressed AGE-receptor for AGE (RAGE) interaction by competing with MG-H1 for the binding site of RAGE. Furthermore, DPHC pre-treatment regulated apoptosis-related protein expression and increased Nrf2, Glo-1, HO-1, CAT, NQO1, and SOD1. These findings prove that the chemical structural characteristics of DPHC have the potential to prevent or manage AGE-induced DN by effectively mediating the key mechanisms responsible for its pathogenesis.

Pseudobangia corderoi sp. nov. (Bangiales, Rhodophyta) from the Philippines

ABSTRACT A new filamentous bangialean alga, Pseudobangia corderoi sp. nov., is described from the northern Philippines. Locally known as a sea vegetable, this species was previously identified as ‘Bangia fuscopurpurea’. Inferred combined analyses of the nucleus-encoded SSU rDNA and the plastid-encoded RubisCO LSU (rbcL) gene indicate that P. corderoi is sister to another unidentified species of Pseudobangia (originally referred to also as ‘Bangia fuscopurpurea’) from Taiwan. Together, these two taxa formed the closest diverging lineage from Pseudobangia kaycoleae (generitype). Current molecular phylogenies have also yielded monophyly of Pseudobangia and strong support for a sister relationship with the ‘Bangia 2’ lineage. Molecular and geographic analyses clearly differentiate P. corderoi from other filamentous Bangiales, whereas morpho-anatomical analysis identified only one distinguishing character, i.e. larger dimensions of the thalli.

Phytochemical Screening, Total Phenolic, Reducing Sugar Contents, and Antioxidant Activities of Gelidium spinosum (S.G. Gmelin) P.C. Silva

Gelidium spinosum is edible red seaweed with high economic values and potential pharmacological activities. This research aimed to evaluate phytochemicals, total phenolic content, reducing sugar content, and antioxidant properties of Gelidium spinosum methanolaqueous extracts. Maceration with different solvent ratios of methanol-water was employed to afford various crude extracts. The standard procedures of preliminary phytoconstituents determination were employed to screen the presence of various phytochemicals. Phenolic and reducing sugar contents were determined using Folin-Cioucalteu and 3,5-dinitro salicylic acid methods. The antioxidant activities of seaweed extracts were determined through DPPH and reducing power assays. The 100% methanol extract of G. spinosum was found to be rich in alkaloids, flavonoids, glycosides, polyphenols, proteins, reducing sugar, saponins, steroids and tannins. The aqueous extract of G. spinosum contained flavonoids, glycosides, polyphenols, reducing sugars, saponins and tannins at a moderate level. The total phenolic content range was 6.43 to 49.78 mg EGA/g extract. The highest reducing sugar content was shown by 100% methanol extract (1278.20 ± 21.25 mg GE/g extract). The highest antioxidant activities were found in 100% methanol extract for reducing power assay, and 75% methanol extract of G. spinosum for DPPH method. There was a positive correlation between reducing sugar, total phenolic contents and antioxidant activities. Results further confirmed the potential use of red seaweed in various ailments, however, should further be confirmed through more appropriate similar studies.

Effect of post-harvest processing methods on the microbial safety of edible seaweed

The American seaweed industry is growing, primarily into the edible sector, and more seaweed products are available for human consumption. It is necessary to evaluate the safety of industry’s current post-harvest storage and processing methods to ensure the risk of foodborne pathogens on edible seaweed remains low. We evaluated the pathogen load of edible kelp post-harvest under three different storage temperatures (4˚C, 10˚C, 20˚C) and two different drying methods (air- and freeze-drying). The focal pathogens for this research included: Listeria monocytogenes, Salmonella enterica, Staphylococcus aureus, pathogenic Escherichia coli, Vibrio vulnificus and Vibrio parahaemolyticus. We tested all six pathogens under each treatment condition on both sugar kelp (Saccharina latissima) and rockweed (Ascophyllum nodosum) as these are the most commonly farmed and wild-harvested species in Maine, respectively. We inoculated a known concentration of pathogen onto freshly harvested kelp, treated it under a storage temperature or drying method, and sampled it over time to determine the impact of treatment on pathogen load. Our results showed that storage at 20˚C can lead to replication while storage at 4˚C and 10˚C halted the replication of focal pathogens. Both air-drying and freeze-drying produced significant log scale reductions in surface pathogen load for all focal pathogens. Additionally, air-drying reduced pathogen load more than freeze-drying for a majority of pathogens and storing dried kelp for 6-weeks further reduced pathogen load across all cases. These results are promising for industry as they corroborate historical evidence that current post-harvest storage and processing conditions are producing products safe for human consumption.

Mineral profile of Edible Marine algae Padina tetrastromatica, Hauck

Seaweeds are an important ingredient of functional foods recommended for daily food due to their unique compositions and nutritional value. They are the vital source of rich nutrition in dietary fibre, low lipid content, high polysaccharide concentration, minerals, polyunsaturated fatty acids and vitamins. The nutritional and pharmacological potential of marine macroalgae drives our continuous interest in investigating the edible seaweeds. The present study mainly focuses on the mineral profile of the edible algae Padina tetrastromaica, collected from Thikkodi coast, Kerala. P. tetrastromatica, belongs to the family Dictyotacece, which have the copious source of pharmacologically active compounds and exhibits unalike properties such as antibiotic, anticoagulant, antihyperglycemic, antiviral and anti-cancerous. Thus the present study reveals the mineral profile of the edible marine algae P.tetrastromatica, which has higher amount of Calcium, Potassium, Magnesium and low amount of Iron . The results concluded that the marine brown algae selected for the present study holds a good amount of primary and secondary metabolites.

New Analytical Strategy for Bioaccessibility Evaluation of Bromine and Iodine from Edible Seaweeds.

A strategy for determining the bioaccessibility of bromine and iodine from edible seaweeds was proposed for the first time using microwave-induced combustion (MIC) and ion chromatography coupled to mass spectrometry (IC-MS) after in vitro digestion. The concentrations of bromine and iodine in edible seaweeds using the proposed methods (MIC and IC-MS) were not statistically different from those using MIC and inductively coupled plasma mass spectrometry (p > 0.05). Trueness was assessed by recovery experiments (101-110%, relative standard deviation <10%). Following an in vitro digestion protocol, MIC was proposed as sample preparation for bioaccessible and residual fractions. Using this strategy, the mass balance totaled from 97 to 111%. No statistical difference (p > 0.05) was observed between the total concentration of bromine or iodine and their concentration in bioaccessible and residual fractions for three edible seaweed species, indicating full analyte quantification in the fractions.

Lactobacillus-fermentation enhances nutritional value and improves the inhibition on pancreatic lipase and oral pathogens of edible red seaweed Bangia fusco-purpurea

Red seaweed contains abundant bioactive ingredients with health benefits. Fermentation is widely used in improving the bioactive ingredients of seaweed materials. However, the types of the active metabolite and changes in biological activity components by the fermentation process remain unknown. In this study, red seaweed Bangia fusco-purpurea was inoculated with Lactobacillus delbrueckii and Lactobacillus plantarum to study bioactive components in supernatants. Results showed that Lactobacillus-fermentation dramatically increased free essential amino acid, trace mineral elements, flavonoids, and polyphenols contents, while decreasing protein and sugar in supernatants. Meanwhile, inhibitions of pancreatic lipase enzyme activities and antibacterial activities against oral pathogenic bacteria were significantly increased by Lactobacillus-fermentation, up to 93.48% and 98.2%, respectively. It might be caused by the increase of polyphenols and flavonoids contents in fermentation supernatants. Also, the biological functions of L. delbrueckii-fermentation were better than that of L. plantarum. Overall, B. fusco-purpurea with Lactobacillus-fermentation has the potential to be special dietary food for improving hyperlipidemia and obesity.

Edible Seaweeds Extracts: Characterization and Functional Properties for Health Conditions

Seaweeds are popular foods due to claimed beneficial health effects, but for many there is a lack of scientific evidence. In this study, extracts of the edible seaweeds Aramé, Nori, and Fucus are compared. Our approach intends to clarify similarities and differences in the health properties of these seaweeds, thus contributing to target potential applications for each. Additionally, although Aramé and Fucus seaweeds are highly explored, information on Nori composition and bioactivities is scarce. The aqueous extracts of the seaweeds were obtained by decoction, then fractionated and characterized according to their composition and biological activity. It was recognized that fractioning the extracts led to bioactivity reduction, suggesting a loss of bioactive compounds synergies. The Aramé extract showed the highest antioxidant activity and Nori exhibited the highest potential for acetylcholinesterase inhibition. The identification of the bioactive compounds in the extracts allowed to see that these contained a mixture of phloroglucinol polymers, and it was suggested that Nori's effect on acetylcholinesterase inhibition may be associated with a smaller sized phlorotannins capable of entering the enzyme active site. Overall, these results suggest a promising potential for the use of these seaweed extracts, mainly Aramé and Nori, in health improvement and management of diseases, namely those associated to oxidative stress and neurodegeneration.

Pressurized Liquid Extraction for the Recovery of Bioactive Compounds from Seaweeds for Food Industry Application: A Review.

Seaweeds are an underutilized food in the Western world, but they are widely consumed in Asia, with China being the world's larger producer. Seaweeds have gained attention in the food industry in recent years because of their composition, which includes polysaccharides, lipids, proteins, dietary fiber, and various bioactive compounds such as vitamins, essential minerals, phenolic compounds, and pigments. Extraction techniques, ranging from more traditional techniques such as maceration to novel technologies, are required to obtain these components. Pressurized liquid extraction (PLE) is a green technique that uses high temperatures and pressure applied in conjunction with a solvent to extract components from a solid matrix. To improve the efficiency of this technique, different parameters such as the solvent, temperature, pressure, extraction time and number of cycles should be carefully optimized. It is important to note that PLE conditions allow for the extraction of target analytes in a short-time period while using less solvent and maintaining a high yield. Moreover, the combination of PLE with other techniques has been already applied to extract compounds from different matrices, including seaweeds. In this way, the combination of PLE-SFE-CO2 seems to be the best option considering both the higher yields obtained and the economic feasibility of a scaling-up approximation. In addition, the food industry is interested in incorporating the compounds extracted from edible seaweeds into food packaging (including edible coating, bioplastics and bio-nanocomposites incorporated into bioplastics), food products and animal feed to improve their nutritional profile and technological properties. This review attempts to compile and analyze the current data available regarding the application of PLE in seaweeds to determine the use of this extraction technique as a method to obtain active compounds of interest for food industry application.

Production of Ulva fasciata biomass through optimization of culture condition for viable tank-based edible seaweed farming

Production of Ulva fasciata biomass through optimization of culture condition for viable tank-based edible seaweed farming

Antiangiogenic drugs in combination with seaweed fucoidan: A mechanistic in vitro and in vivo study exploring the VEGF receptor and its downstream signaling molecules in hepatic cancer.

Hepatocellular carcinoma (HCC) is one of the most common cancers reported worldwide with poor morbidity and high mortality rates. HCC is a very vascular solid tumour as angiogenesis is not only a key driver for tumour progression but also an exciting therapeutic target. Our research investigated the use of fucoidan, a sulfated polysaccharide readily abundant in edible seaweeds commonly consumed in Asian diet due to their extensive health benefits. Fucoidan was reported to possess a strong anti-cancer activity, but its anti-angiogenic potential is still to be fully unraveled. Our research investigated fucoidan in combination with sorafenib (an anti-VEGFR tyrosine kinase inhibitor) and Avastin® (bevacizumab, an anti-VEGF monoclonal antibody) in HCC both in vitro and in vivo. In vitro on HUH-7 cells, fucoidan had a potent synergistic effect when combined with the anti-angiogenic drugs and significantly reduced HUH-7 cell viability in a dose dependent manner. Using the scratch wound assay to test cancer cell motility, sorafenib, A + F (Avastin and fucoidan) or S + F (sorafenib and fucoidan) treated cells consistently showed an unhealed wound and a significantly smaller %wound closure (50%-70%) versus untreated control (91%-100%) (p < 0.05, one-way ANOVA). Using RT-qPCR; fucoidan, sorafenib, A + F and S + F significantly reduced the expression of the pro-angiogenic PI3K/AKT/mTOR and KRAS/BRAF/MAPK pathways by up to 3 folds (p < 0.05, one-way ANOVA versus untreated control). While ELISA results revealed that in fucoidan, sorafenib, A + F and S + F treated cells, the protein levels of caspases 3, 8, and 9 was significantly increased especially in the S + F group showing 40- and 16-times higher caspase 3 and 8 protein levels, respectively (p < 0.05, one-way-ANOVA versus untreated control). Finally, in a DEN-HCC rat model, H&E staining revealed larger sections of apoptosis and necrosis in the tumour nodules of rats treated with the combination therapies and immunohistochemical analysis of the apoptotic marker caspase 3, the proliferation marker Ki67 and the marker for angiogenesis CD34 showed significant improvements when the combination therapies were used. Despite the promising findings reported herein that highlighted a promising chemomodulatory effect of fucoidan when combined with sorafenib and Avastin, further investigations are required to elucidate potential beneficial or adversary interactions between the tested agents.

Anti-Pollutant Activity of Porphyra yezoensis Water Extract and Its Active Compound, Porphyra 334, against Urban Particulate Matter-Induced Keratinocyte Cell Damage

Urban particulate matter (UPM) causes skin aging and inflammatory reactions by influencing skin cells through the aryl hydrocarbon receptor (AhR) signaling pathway. Porphyra yezoensis (also known as Pyropia yezoensis), a red alga belonging to the Bangiaceae family, is an edible red seaweed. Here, we examined the anti-pollutant effect of P. yezoensis water extract. While UPM treatment induced xenobiotic response element (XRE) promoter luciferase activity, P. yezoensis water extract reduced UPM-induced XRE activity. Next, we isolated an active compound from P. yezoensis and identified it as porphyra 334. Similar to the P. yezoensis water extract, porphyra 334 attenuated UPM-induced XRE activity. Moreover, although UPM augmented AhR nuclear translocation, which led to an increase in cytochrome P450 1A1 (CYP1A1) mRNA levels, these effects were reduced by porphyra 334. Moreover, UPM induced the production of reactive oxygen species (ROS) and reduced cell proliferation. These effects were attenuated in response to porphyra 334 treatment. Furthermore, our results revealed that the increased ROS levels induced by UPM treatment induced transient receptor potential vanilloid 1 (TRPV1) activity, which is related to skin aging and inflammatory responses. However, porphyra 334 treatment reduced this reaction by inhibiting ROS production induced by CYP1A1 activation. This indicates that porphyra 334, an active compound of P. yezoensis, attenuates UP-induced cell damage by inhibiting AhR-induced ROS production, which results in a reduction in TRPV1 activation, leading to cell proliferation. This also suggests that porphyra 334 could protect the epidermis from harmful pollutants.

Density regulation of aquaculture production and its effects on commercial profit and quality as food in the cosmopolitan edible seaweed Undaria pinnatifida

Aquaculture of marine macroalgae (i.e. seaweeds) such as the kelp Undaria pinnatifida is expected to contribute to future food and biomass production. Although macroalgal survival, biomass, and morphology are strongly affected by the density of individual plants in natural environments, little is known about the cultivation density (individuals per 1 m of cultivation rope) of macroalgae required to optimize aquaculture production, commercial profit (sales – labor expenses for processing), and quality as food. The present study examined the effect of increasing the cultivation density of U. pinnatifida from 10 to 200 individuals m-1 on survival rate, biomass production, profit, and morphological features related to quality as food. Survival rate was almost 100% in all treatments, indicating self-thinning did not occur. Biomass production increased with increasing density, suggesting that the maximum density possible is in excess of 200 individuals m-1. However, although profit rose with increasing density from 10 to 120 individuals m-1, it did not rise further if density was further increased. Moreover, some morphological features related to quality increased or decreased with increasing density. On balance, these results suggest that 80-120 individuals m-1 is an appropriate density range to optimize production of this species in terms of both profit and quality as food. However, only 10-30 individuals m-1 was the density best suited to enhance production of the sporophyll form, which is known to be a nutritious food both for humans and sea urchins.

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.

Effect of thermal processing on toxic heavy metals in edible seaweeds of Gulf of Mannar and their health risk assessment

A significant amount of toxic heavy metals (As, Cd, Hg, Pb, and Cr) in seafood has raised human health concern worldwide. This study investigates the effect of heat processing (boiling, steaming, and microwave cooking) on the toxic metals in wild-harvested (Ulva lactuca and Caulerpa racemosa) and cultured (Kappaphygus aliverzii) edible seaweeds and estimates its potential human health risks. Except As in raw seaweeds, other toxic metals in raw and processed seaweeds were found below the maximum residual limit (MRL) set by the French and the European Union. The target hazard quotient (THQ) of As in raw seaweeds and total THQ (TTHQ) of raw seaweeds were > 1, and other toxic metals were < 1 indicating no health risk from processed seaweeds. The lifetime cancer risk (LCR) value of processed seaweeds were found between the recommended guideline value of 10−6 and 10−4, indicating no carcinogenic risk from heat-processed seaweeds. The recommended maximum seaweed consumption limit (CRmm) was > 100 meals per month with no adverse health effects. Therefore, boiling, steaming, and microwave-cooking methods are recommended to reduce the toxic metal risk from seaweeds.