Poisoning by the red alga 'ogonori' (Gracilaria verrucosa) on the Nojima Coast, Yokohama, Kanagawa Prefecture, Japan

Toxicological effects of marine seaweeds: a cautious insight for human consumption

Marine environment is a rich and diverse source for many biologically active substances including functional foods and nutraceuticals. It is well exploited for useful compounds, natural products and aquaculture industry; and seaweeds is one of the major contributors in terms of both food security and healthy nutrition. They are well-known due to their enormous benefits and is consumed globally in many countries. However, there is lack of attention toward their toxicity reports which might be due toxic chemical compounds from seaweed, epiphytic bacteria or harmful algal bloom and absorbed heavy metals from seawater. The excess of these components might lead to harmful interactions with drugs and hormone levels in the human body. Due to their global consumption and to meet increasing demands, it is necessary to address their hazardous and toxic aspects. In this review, we have done extensive literature for healthy seaweeds, their nutritional composition while summarizing the toxic effects of selected seaweeds from red, brown and green group which includes- Gracilaria, Acanthophora, Caulerpa, Cladosiphon, and Laminaria sp. Spirulina, a microalgae (cyanobacteria) biomass is also included in toxicity discussion as it an important food supplement and many times shows adverse reactions and drug interactions. The identified compounds from seaweeds were concluded to be toxic to humans, though they exhibited certain beneficial effects too. They have an easy access in food chain and thus invade the higher trophic level organisms. This review will create an awareness among scientific and nonscientific community, as well as government organization to regulate edible seaweed consumption and keep them under surveillance for their beneficial and safe consumption.

Phospholipids of New Zealand Edible Brown Algae

Edible brown algae have attracted interest as a source of beneficial allenic carotenoid fucoxanthin, and glyco- and phospholipids enriched in polyunsaturated fatty acids. Unlike green algae, brown algae contain no or little phosphatidylserine, possessing an unusual aminophospholipid, phosphatidyl-O-[N-(2-hydroxyethyl) glycine], PHEG, instead. When our routinely used technique of 31P-NMR analysis of phospholipids was applied to the samples of edible New Zealand brown algae, a number of signals corresponding to unidentified phosphorus-containing compounds were observed in total lipids. NI (negative ion) ESI QToF MS spectra confirmed the presence of more familiar phospholipids, and also suggested the presence of PHEG or its isomers. The structure of PHEG was confirmed by comparison with a synthetic standard. An unusual MS fragmentation pattern that was also observed prompted us to synthesise a number of possible candidates, and was found to follow that of phosphatidylhydroxyethyl methylcarbamate, likely an extraction artefact. An unexpected outcome was the finding of ceramidephosphoinositol that has not been reported previously as occurring in brown algae. An uncommon arsenic-containing phospholipid has also been observed and quantified, and its TLC behaviour studied, along with that of the newly synthesised lipids.

Algae as nutritional and functional food sources: revisiting our understanding

Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value. The second issue is quantifying which fractions of algal foods are bioavailable to humans, and which factors influence how food constituents are released, ranging from food preparation through genetic differentiation in the gut microbiome. Third is understanding how algal nutritional and functional constituents interact in human metabolism. Superimposed considerations are the effects of harvesting, storage, and food processing techniques that can dramatically influence the potential nutritive value of algal-derived foods. We highlight this rapidly advancing area of algal science with a particular focus on the key research required to assess better the health benefits of an alga or algal product. There are rich opportunities for phycologists in this emerging field, requiring exciting new experimental and collaborative approaches.

Increased potential for wound activated production of Prostaglandin E2 and related toxic compounds in non-native populations of Gracilaria vermiculophylla

The capacity of the East Asian seaweed Gracilaria vermiculophylla ("Ogonori") for production of prostaglandin E₂ from arachidonic acid occasionally causes food poisoning after ingestion. During the last two decades the alga has been introduced to Europe and North America. Non-native populations have been shown to be generally less palatable to marine herbivores than native populations. We hypothesized that the difference in palatability among populations could be due to differences in the algal content of prostaglandins. We therefore compared the capacity for wound-activated production of prostaglandins and other eicosatetraenoid oxylipins among five native populations in East Asia and seven non-native populations in Europe and NW Mexico, using a targeted metabolomics approach. In two independent experiments non-native populations exhibited a significant tendency to produce more eicosatetraenoids than native populations after acclimation to identical conditions and subsequent artificial wounding. Fourteen out of 15 eicosatetraenoids that were detected in experiment I and all 19 eicosatetraenoids that were detected in experiment II reached higher mean concentrations in non-native than in native specimens. Wounding of non-native specimens resulted on average in 390% more 15-keto-PGE₂, in 90% more PGE₂, in 37% more PGA₂ and in 96% more 7,8-di-hydroxy-eicosatetraenoic acid than wounding of native specimens. Not only PGE₂, but also PGA₂ and dihydroxylated eicosatetraenoic acid are known to deter various biological enemies of G. vermiculophylla that cause tissue or cell wounding, and in the present study the latter two compounds also repelled the mesograzer Littorina brevicula. Non-native populations of G. vermiculophylla are thus more defended against herbivory than native populations. This increased capacity for activated chemical defense may have contributed to their invasion success and at the same time it poses an elevated risk for human food safety.

Identification of novel oxidized levuglandin D2 in marine red alga and mouse tissue

In animals, the product of cyclooxygenase reacting with arachidonic acid, prostaglandin(PG)H(2), can undergo spontaneous rearrangement and nonenzymatic ring cleavage to form levuglandin(LG)E(2) and LGD(2). These LGs and their isomers are highly reactive γ-ketoaldehydes that form covalent adducts with proteins, DNA, and phosphatidylethanolamine in cells. Here, we isolated a novel oxidized LGD(2) (ox-LGD(2)) from the red alga Gracilaria edulis and determined its planar structure. Additionally, ox-LGD(2) was identified in some tissues of mice and in the lysate of phorbol-12-myristate-13-acetate (PMA)-treated THP-1 cells incubated with arachidonic acid using LC-MS/MS. These results suggest that ox-LGD(2) is a common oxidized metabolite of LGD(2). In the planar structure of ox-LGD(2), H8 and H12 of LGD(2) were dehydrogenated and the C9 aldehyde was oxidized to a carboxylic acid, which formed a lactone ring with the hydrated ketone at C11. These structural differences imply that ox-LGD(2) is less reactive with amines than LGs. Therefore, ox-LGD(2) might be considered a detoxification metabolite of LGD(2).

Biochemical composition of two red seaweed species grown on the Brazilian coast

BACKGROUND

Algae species have been used as an important source of food because they are highly nutritive considering their vitamin, protein, mineral, fiber, essential fatty acid and carbohydrate contents. However, a large number of seaweeds have been poorly studied, especially Brazilian species. Two red macroalgae species from the Brazilian coast (Plocamium brasiliense and Ochtodes secundiramea) were assessed with respect to their total lipid, fatty acid, total nitrogen, protein, amino acid and total carbohydrate contents.

RESULTS

The total lipid contents (dry weight) were 36.3 and 35.4 g kg(-1); fatty acid contents were 9.3 and 12.1 g kg(-1); total nitrogen contents were 37.4 and 24.9 g kg(-1); protein contents were 157.2 and 101.0 g kg(-1); amino acid contents were 127.5 and 91.4 g kg(-1); and total carbohydrate contents were 520.3 and 450.7 g kg(-1) for P. brasiliense and O. secundiramea, respectively.

CONCLUSION

Considering these compositions, both algae species were determined to have sources of protein, essential amino acids and carbohydrates similar to the edible seaweeds Laminaria japonica and Palmaria palmata.

Anti-inflammatory constituents of the red alga Gracilaria verrucosa and their synthetic analogues

A chemical study on the anti-inflammatory components of the red alga Gracilaria verrucosa led to the isolation of new 11-deoxyprostaglandins ( 1- 4), a ceramide ( 5), and a C 16 keto fatty acid ( 6), along with known oxygenated fatty acids ( 7- 14). Their structures were elucidated on the basis of NMR and MS data. The absolute configurations of compounds 1- 5 were determined by Mosher's method. The anti-inflammatory activity of the isolated compounds ( 1- 14) was evaluated by determining their inhibitory effects on the production of pro-inflammatory mediators (NO, IL-6, and TNF-alpha) in lipopolysaccharide (LPS)-activated RAW 264.7 murine macrophage cells. Compounds 9 and 10 exhibited the most potent activity. In the evaluation of these two compounds and derivatized analogues ( 15- 40), the anti-inflammatory activity was enhanced in some synthetic analogues. These enone fatty acids were investigated as potential anti-inflammatory leads for the first time.

The innate immunity of a marine red alga involves oxylipins from both the eicosanoid and octadecanoid pathways

The oxygenated derivatives of fatty acids, known as oxylipins, are pivotal signaling molecules in animals and terrestrial plants. In animal systems, eicosanoids regulate cell differentiation, immune responses, and homeostasis. In contrast, terrestrial plants use derivatives of C18 and C16 fatty acids as developmental or defense hormones. Marine algae have emerged early in the evolution of eukaryotes as several distinct phyla, independent from the animal and green-plant lineages. The occurrence of oxylipins of the eicosanoid family is well documented in marine red algae, but their biological roles remain an enigma. Here we address the hypothesis that they are involved with the defense mechanisms of the red alga Chondrus crispus. By investigating its association with a green algal endophyte Acrochaete operculata, which becomes invasive in the diploid generation of this red alga, we showed that (1) when challenged by pathogen extracts, the resistant haploid phase of C. crispus produced both C20 and C18 oxylipins, (2) elicitation with pathogen extracts or methyl jasmonate activated the metabolism of C20 and C18 polyunsaturated fatty acids to generate hydroperoxides and cyclopentenones such as prostaglandins and jasmonates, and (3) C20 and C18 hydroperoxides as well as methyl jasmonate did induce shikimate dehydrogenase and Phe ammonialyase activities in C. crispus and conferred an induced resistance to the diploid phase, while inhibitors of fatty acid oxidation reduced the natural resistance of the haploid generation. The dual nature of oxylipin metabolism in this alga suggests that early eukaryotes featured both animal- (eicosanoids) and plant-like (octadecanoids) oxylipins as essential components of innate immunity mechanisms.

Chlorinated C12 fatty acid metabolites from the red alga Gracilaria verrucosa

Three compounds containing moieties rarely encountered in nature, viz., 3-nonyloxirane-2 carboxylic acid methyl ester (1), 2-chlorododec-2-en-1-ol (2), and 2-chlorododec-2,11-dien-1-ol (3), were isolated from the red alga Gracilaria verrucosa, and their structures were determined by spectroscopic methods.

Actions of prostanoids to induce emesis and defecation in the ferret

Several prostanoids were investigated for their ability to induce emesis and/or defecation and tenesmus in the ferret. The rank order of emetic potency (dose producing four episodes, D4) was: sulprostone (5 microg/kg)>11alpha,9alpha-epoxymethano-15S-hydroxyprosta-5Z,13E-dienoic acid (U46619; 8 microg/kg)>misoprostol (27 microg/kg)>17-phenyl-omega-trinor prostaglandin E2 (53 microg/kg)>prostaglandin E2 (94 microg/kg)>5-(6-carboxyhexyl)-1-(3-cyclohexyl-3-hydroxypropyl) hydantoin (BW245C; 148 microg/kg)>>prostaglandin F(2alpha) (13,500 microg/kg). Emesis was also induced by iloprost (D4 not determined) and prostaglandin E2 methyl ester (D4=350 microg/kg). Cicaprost and fluprostenol were virtually inactive; they also failed to modify copper sulphate (100 mg/kg, intragastric)-induced emesis (P>0.05), although cicaprost potentiated apomorphine (0.25 mg/kg, s.c.)-induced emesis (P<0.05). U46619-induced emesis was antagonised by vapiprost (P<0.05). The rank order of potency to produce defecation and tenesmus (dose producing three episodes) was: sulprostone (12 microg/kg)>misoprostol (15 microg/kg)>17-phenyl-omega-trinor prostaglandin E2 (94 microg/kg)>prostaglandin E2 (113 microg/kg)>fluprostenol (158 microg/kg)z.Gt;prostaglandin F(2alpha) (1759 microg/kg); prostaglandin E2 methyl ester also induced defecation (196 microg/kg). Data are discussed in relation to mechanisms involved in emesis and defecation.

Bleeding from the small intestine caused by aplysiatoxin, the causative agent of the red alga Gracilaria coronopifolia poisoning

The cause of death by aplysiatoxin poisoning was bleeding from the small intestine in mice. The pathological changes related to the cause and progression of bleeding were studied morphologically. Bleeding from the capillaries was observed 60 min after i.p. treatment at 250 microg/kg, and this was preceded by dilatation of the lymphatic vessel and congestion of capillaries in the lamina propria from 10 min after the injection. At 100 microg/kg i.v., the target vessels were in the lung, where fibrin deposition was observed in the dilated pulmonary artery, and blood flowed out through a gap in the artery. Then, in the small intestine, similar changes appeared to have occurred, and bleeding was induced in two characteristic ways, one through deposition of fibrin in the lumen and the other via distension of the capillary wall.

Identification of eicosanoids in the red algae, Gracilaria asiatica, using high-performance liquid chromatography and electrospray ionization mass spectrometry

Identification of eicosanoids which are metabolites of arachidonic acid in red algae Gracilaria asiatica, one of the popular seaweeds in Japan, was carried out using high-performance liquid chromatography (HPLC) interfaced with electrospray ionization mass spectrometry. Prostaglandin (PG) E2, 15-keto-PGE2, and 8-hydroxyeicosatetraenoic acid (HETE) were detected as major eicosanoids and PGA2, leukotriene B4 as minor ones in G. asiatica. 8- and 12-HETE had the same retention time in HPLC analysis, but using this analytical method, we were able to identify them.

Apparent paralytic shellfish poisoning in captive herring gulls fed commercial scallops

This report describes an acute poisoning event observed in captive herring gull (Larus argentatus) chicks fed a batch of store-bought scallops. They developed a characteristic acute syndrome, that has not hitherto been reported in birds and the cause of which remains to be identified. We suggest that it is a variant of paralytic shellfish poisoning (PSP) insofar as it was paralytic and caused by shellfish. However, analyses by the U.S. Food and Drug Administration to identify known toxins (saxitoxins, brevetoxins, domoic acid) in the scallops were negative.

Manauealides, some of the causative agents of a red alga Gracilaria coronopifolia poisoning in Hawaii

Manauealides A-C (1-3), compounds related to debromoaplysiatoxin (5), were isolated and characterized from a red alga Gracilaria coronopifolia. Compounds 1 and 2 are presumed to be the causative toxins of G. coronopifolia food poisoning in Hawaii. Manauealide A (1) and C (3) are new macrolides, whereas manauealide B (2) is a known semisynthetic product of 5.

Aplysiatoxin and debromoaplysiatoxin as the causative agents of a red alga Gracilaria coronopifolia poisoning in Hawaii

The causative toxins of a red alga Gracilaria coronopifolia poisonings in Hawaii, which broke out in succession in September of 1994, were studied. Two major toxins were isolated from both extracts of the two original algal samples which caused separate poisonings. By spectroscopic method, these toxins were shown to be completely identical with aplysiatoxin and debromoaplysiatoxin which have previously been obtained from the sea hare and also from blue green algae. The human symptoms and the amount of these toxins in the original algal samples indicate that aplysiatoxin and debromoaplysiatoxin were the causative agents of the human poisoning incidents. This is the first reported case of the implication of aplysiatoxin and debromoaplysiatoxin in food poisoning. The existence of these toxins in the residue of algae washed in saline was confirmed by HPLC analysis. Furthermore, we observed blue-green algal parasitism on the surface of the toxic G. coronopifolia. Therefore, epiphytic organisms such as blue-green algae might be the true origin of the toxins in G. coronopifolia.