A new digalactosyl diacylglycerol from a cultured marine dinoflagellate Heterocapsa circularisquama

Metabolomic Profiles of Dinophysis acuminata and Dinophysis acuta Using Non-Targeted High-Resolution Mass Spectrometry: Effect of Nutritional Status and Prey

Photosynthetic species of the genus Dinophysis are obligate mixotrophs with temporary plastids (kleptoplastids) that are acquired from the ciliate Mesodinium rubrum, which feeds on cryptophytes of the Teleaulax-Plagioselmis-Geminigera clade. A metabolomic study of the three-species food chain Dinophysis-Mesodinium-Teleaulax was carried out using mass spectrometric analysis of extracts of batch-cultured cells of each level of that food chain. The main goal was to compare the metabolomic expression of Galician strains of Dinophysis acuminata and D. acuta that were subjected to different feeding regimes (well-fed and prey-limited) and feeding on two Mesodinium (Spanish and Danish) strains. Both Dinophysis species were able to grow while feeding on both Mesodinium strains, although differences in growth rates were observed. Toxin and metabolomic profiles of the two Dinophysis species were significantly different, and also varied between different feeding regimes and different prey organisms. Furthermore, significantly different metabolomes were expressed by a strain of D. acuminata that was feeding on different strains of the ciliate Mesodinium rubrum. Both species-specific metabolites and those common to D. acuminata and D. acuta were tentatively identified by screening of METLIN and Marine Natural Products Dictionary databases. This first metabolomic study applied to Dinophysis acuminata and D.acuta in culture establishes a basis for the chemical inventory of these species.

Neuroenzymatic activity and physiological energetics in Manila clam, Ruditapes philippinarum, during short-term sublethal exposure to harmful alga, Heterocapsa circularisquama

The harmful alga, Heterocapsa circularisquama, causes recurrent mortalities of bivalve molluscs in Japan, with demonstrated hemolysis and cytotoxicity in rabbit erythrocytes, HeLa cells, and bivalve tissues. Nonetheless, the effects of exposure to sublethal cell densities on the physiological energetics of bivalves have not been investigated, nor the potential involvement of neurotoxicity. In the present study, two sets of experiments were conducted with adult clams, Ruditapes philippinarum. In the first set, the clearance rate (CR), respiration rate (RR), absorption efficiency (AE), ingestion rate (IR), and absorption rate (AR) were examined in clams exposed to H. circularisquama to quantify the scope for growth (SFG) as an indicative of the bioenergetic status of clams (5, 50, 2.5×10(2), and 5×10(2)cellsml(-1); under 15°C and 20°C). In the second set, the activity of the biomarker of neurotoxic exposure, acetylcholinesterase (AChE), was monitored following 3, 6, 24, and 48h of exposure (5, 50, 5×10(2), and 10(3)cellsml(-1), at 20°C) in gills of R. philippinarum, and compared to that in Mediterranean mussels, Mytilus galloprovincialis; a species also affected by H. circualrisquama and in which AChE activity was more extensively studied. At 15°C, CR, IR, and AR were decreased for exposures to 50-5×10(2) cells ml(-1) resulting in a significant decrease in the absorbed energy (A), and a significant decrease in SFG at 5×10(2)cellsml(-1). At 20°C, AE was null for exposures to 2.5×10(2) and 5×10(2)cellsml(-1). RR was decreased at 2.5×10(2) and 5×10(2)cellsml(-1), CR, IR, and AR were decreased at 5-5×10(2)cellsml(-1), and the AE was null for 2.5×10(2)-5×10(2)cellsml(-1) resulting in a significant decrease in the respired energy (R), but mainly in (A) especially at 2.5×10(2) and 5×10(2)cellsml(-1) decreasing the SFG over the entire range of cell density with negative values for 2.5×10(2) and 5×10(2)cellsml(-1). The activity of AChE in both clams and mussels was significantly reduced following 3-48h of exposure to 5-5×10(2)cellsml(-1). Reduction in the energy available for clams to grow and reproduce was induced mainly via decreased energy acquisition, and delayed and/or reduced functions of the digestive organs. In addition, this is the first report of decreased neuroenzymatic activity in two bivalve molluscs induced by exposure to H. circularisquama potentially via either neurotoxic compounds affecting the activity of gill cilia and/or gill muscles, and/or potentially via either neurotoxic compounds affecting the activity of gill cilia and/or gill muscles, and/or non-cholinergic affects associated with other functions; both resulting in decreased SFG. The relationship between the decreased AChE and decreased SFG should be corroborated in future research.

Examination of the structures of several glycerolipids from marine macroalgae by NMR and GC-MS

Several classes of glycerolipids were isolated from the total lipids of the algae Saccharina cichorioides, Eualaria fistulosa, Fucus evanescens, Sargassum pallidum, Silvetia babingtonii (Ochrophyta, Phaeophyceae), Tichocarpus crinitus, and Neorhodomela larix (Rhodophyta, Florideophyceae). The structures of these lipids were examined by nuclear magnetic resonance (NMR) spectroscopy, including 1D ((1) H and (13) C) and 2D (COSY, HSQC and HMBC) experiments. All of the investigated algae included common galactolipids and sulfonoglycolipids as the major glycolipids. Minor glycolipids isolated from S. cichorioides, T. crinitus, and N. laris were identified as lyso-galactolipids with a polar group consisted of the galactose. Comparison of the (1) H NMR data of minor nonpolar lipids isolated from the extracts of the brown algae S. pallidum and F. evanescens with the (1) H NMR data of other lipids allowed them to be identified as diacylglycerols. The structures of betaine lipids isolated from brown algae were confirmed by NMR for the first time. The fatty acid compositions of the isolated lipids were determined by gas chromatography-mass spectrometry.

Prevalence and intensity of pathologies induced by the toxic dinoflagellate, Heterocapsa circularisquama, in the Mediterranean mussel, Mytilus galloprovincialis

The harmful dinoflagellate, Heterocapsa circularisquama, has been causing mass mortalities of bivalve molluscs in Japan, at relatively low cell densities. Although several studies have been conducted to determine the toxicity mechanisms, the specific cause of death is still unclear. In a previous study, in our laboratory, it was shown that H. circularisquama (10(3) cells ml(-1)) caused extensive cytotoxicity in the gills of short-neck clams, Ruditapes philippinarum. In the present study, Mediterranean mussels, Mytilus galloprovincialis, were exposed to H. circularisquama at four cell densities (5, 50, 500, 10(3) cells ml(-1)), three temperatures (15, 20, and 25°C), and three exposure durations (3, 24, and 48 h), and the pathologies in nine organs (gills, labial palps, mantle, hepatopancreas, stomach, intestines, exhalant siphon, adductor muscles, and foot) were assessed. Foot, adductor muscles, and exhalent siphons of mussels were not affected; however, 16 inflammatory (hemocytic infiltration and aggregation, diapedesis, hyperplasia, hypertrophy, edema, melanization, and firbrosis) and degenerative (thrombus, thrombosed edema, cilia matting and exfoliation, epithelial desquamation, atrophy, and necrosis) pathologies were identified in the gills, labial palps, mantle, hepatopancreas, stomach, and intestines. The total prevalence and total intensity of pathology in each individual mussel, and the prevalence and intensity of pathology in each organ increased significantly with increased cell density, exposure duration, and temperature. The prevalence of pathology was the highest in gills, followed by the prevalence in labial palps, mantle, stomach, and intestines. Pathology was least prevalent in the hepatopancreas. The intensity of pathology was the highest in the gills, followed by the labial palps and mantle, the stomach and intestines, and the hepatopancreas. This detailed quantitative histopathological study demonstrates that exposure to H. circularisquama induces a broad cytotoxic effect in six vital organs, even at low density (5 cells ml(-1)) and low temperature (15°C), but not in muscular organs. Combining cell density, time, and duration of exposure, the organ most affected by the harmful alga was the gill, followed by the labial palps and mantle, the stomach and intestines, and the hepatopancreas. The results of this pathological analysis show that exposure to H. ciruclarisquama severely affects the gills, the labial palps, and mantle thereby interfering with particle clearance and sorting, cleansing, and respiration, but also affects the stomach, intestines, and hepatopancreas, altering the digestive processes and possibly detoxification pathways, if mussels are able to detoxify the toxins of H. circularisquama. In the most severe cases, bivalves would most likely have died as a result of combined severe alterations of the vital functions, failure of tissue repair, and moderate to heavy hemorrhaging in both the external organs and the digestive organs concomitantly with light to moderate alterations in the detoxifying processes.

Prymnesium parvum revisited: relationship between allelopathy, ichthyotoxicity, and chemical profiles in 5 strains

Bioassay-guided discovery of ichthyotoxic algal compounds using in vivo fish assays is labor intensive, costly, and highly regulated. Since the mode of action of most known algal-mediated fish-killing toxins is damage to the cell membranes in the gills, various types of cell-based bioassays are often used for bioassay guided purification of new ichthyotoxins. Here we tested the hypothesis that allelopathy is related to ichthyotoxicity and thus that a microalgal bioassay can be used as a proxy for ichthyotoxicity by comparing the toxicity of five strains of Prymnesium parvum toward rainbow trout (Oncorhynchus mykiss, 10 g) and the microalga Teleaulax acuta. No relationship between median effective concentrations (EC50s) on fish and median lethal concentrations (LC50s) on algae was observed in the 5 strains showing that a microalgal bioassay cannot be used as a proxy for ichthyotoxicity. Fish were more sensitive to P. parvum with EC50s ranging from 6×10(3) to 40×10(3) cells ml(-1), compared to the test alga where LC50s ranged from 30×10(3) to nearly non-toxic at 500×10(3) cells ml(-1). In addition, the cellular concentrations of two recently suggested ichthyotoxins produced by P. parvum, the "golden algae toxins", GAT 512 and a novel GAT 510, did not show any relationship to either ichthyotoxicity or allelopathy, and are not the biologically relevant toxins, but are simply lipids found in algal chloroplasts. Finally, we demonstrate that the recently suggested ichthyotoxin, oleamide, could not be detected in any of the five P. parvum strains above the limit of detection, nor was it found in a (13)C-labeled strain. Instead we document that oleamide can easily be extracted from plastic materials, which may have been the source of oleamide reported previously.

Biotechnological potential of the seaweed Cladophora rupestris (Chlorophyta, Cladophorales) lipidic extract

Recently, with the advent of modern technologies, various marine organisms including algae are being studied as sources of natural substances effective on classical microorganisms and able to also combat the new trend of acquired resistance in microbes. In the present study the antimicrobial activity of the lipidic extract of the green seaweed Cladophora rupestris collected in a Mediterranean area, in two sampling periods (January and April), was assayed. The chemical characterization of the lipidic fractions was performed by gas-chromatography and multinuclear and multidimensional NMR spectroscopy. In the lipidic extract of C. rupestris collected in January an antibacterial activity against Enterococcus sp., Streptococcus agalactiae and Vibrio cholerae non-O1 was recorded; by contrast, bacterial inhibition was measured on several Vibrio species only in April. The fatty acid profile of C. rupestris lipidic extract, analyzed by gas chromatography, resulted mainly composed of palmitic, myristic, oleic, α linolenic, palmitoleic and linoleic acids. Moreover, since α-linolenic acid was the predominant ω3 fatty acid in April, we suggest its involvement in the antibacterial activity observed in this month, taking also into account that pure α-linolenic acid resulted effective towards some vibrios strains. C. rupestris fatty acid profile revealed also an interesting composition in polyunsaturated fatty acids in both the considered periods with the ω6/ω3 ratio lower than 1, leading to conclude that this macroalga may be employed as a natural source of ω3. Finally, the (1)H NMR spectrum in CDCl3 of algal lipid fractions showed the characteristic signals of saturated (SAFAs) and unsaturated fatty acids (UFAs) as well as other metabolites and a marked difference in free fatty acids (FFAs) content for the two examined algal lipid fractions. It is noteworthy that C. rupestris lipidic extracts show, by NMR spectroscopy, the signal pattern of polyhydroxybutyrate, a natural biocompatible and biodegradable polymer. In conclusion, on account of its antimicrobial activity, nutritional value and bioplastic content, C. rupestris lipidic extract can be considered a promising source for future biotechnological applications.

Reassessing the ichthyotoxin profile of cultured Prymnesium parvum (golden algae) and comparing it to samples collected from recent freshwater bloom and fish kill events in North America

Within the last two decades, Prymnesium parvum (golden algae) has rapidly spread into inland waterways across the southern portion of North America and this organism has now appeared in more northerly distributed watersheds. In its wake, golden algae blooms have left an alarming trail of ecological devastation, namely massive fish kills, which are threatening the economic and recreational value of freshwater systems throughout the United States. To further understand the nature of this emerging crisis, our group investigated the chemical nature of the toxin(s) produced by P. parvum. We approached the problem using a two-pronged strategy that included analyzing both laboratory-grown golden algae and field-collected samples of P. parvum. Our results demonstrate that there is a striking difference in the toxin profiles for these two systems. An assemblage of potently ichthyotoxic fatty acids consisting primarily of stearidonic acid was identified in P. parvum cultures. While the concentration of the fatty acids alone was sufficient to account for the rapid-onset ichthyotoxic properties of cultured P. parvum, we also detected a second type of highly labile ichthyotoxic substance(s) in laboratory-grown golden algae that remains uncharacterized. In contrast, the amounts of stearidonic acid and its related congeners present in samples from recent bloom and fish kill sites fell well below the limits necessary to induce acute toxicity in fish. However, a highly labile ichthyotoxic substance, which is similar to the one found in laboratory-grown P. parvum cultures, was also detected. We propose that the uncharacterized labile metabolite produced by P. parvum is responsible for golden algae's devastating fish killing effects. Moreover, we have determined that the biologically-relevant ichthyotoxins produced by P. parvum are not the prymnesins as is widely believed. Our results suggest that further intensive efforts will be required to chemically define P. parvum's ichthyotoxins under natural bloom conditions.

Preliminary characterization of extracellular allelochemicals of the toxic marine dinoflagellate Alexandrium tamarense using a Rhodomonas salina bioassay

Members of the marine dinoflagellate genus Alexandrium are known to exude allelochemicals, unrelated to well-known neurotoxins (PSP-toxins, spirolides), with negative effects on other phytoplankton and marine grazers. Physico/chemical characterization of extracellular lytic compounds of A. tamarense, quantified by Rhodomonas salina bioassay, showed that the lytic activity, and hence presumably the compounds were stable over wide ranges of temperatures and pH and were refractory to bacterial degradation. Two distinct lytic fractions were collected by reversed-phase solid-phase extraction. The more hydrophilic fraction accounted for about 2% of the whole lytic activity of the A. tamarense culture supernatant, while the less hydrophilic one accounted for about 98% of activity. Although temporal stability of the compounds is high, substantial losses were evident during purification. Lytic activity was best removed from aqueous phase with chloroform-methanol (3:1). A “pseudo-loss” of lytic activity in undisturbed and low-concentrated samples and high activity of an emulsion between aqueous and n-hexane phase after liquid-liquid partition are strong evidence for the presence of amphipathic compounds. Lytic activity in the early fraction of gel permeation chromatography and lack of activity after 5 kD ultrafiltration indicate that the lytic agents form large aggregates or macromolecular complexes.

Apoptosis-inducing galactolipids from a cultured marine diatom, Phaeodactylum tricornutum

Two monogalactosyl diacylglycerols, 1 and 2, were isolated from the marine diatom Phaeodactylum tricornutum, using the patented ApopScreen cell-based screen for apoptosis-inducing, potential anticancer compounds. The molecular structures of the galactolipids were determined using a combination of NMR, mass spectrometry, and chemical degradation. The bioactivities were confirmed using a specific apoptosis induction assay based on genetically engineered mammalian cell lines with differential, defined capacities for apoptosis. The galactolipids induce apoptosis in micromolar concentrations. This is the first report of apoptosis induction by galactolipids.

Glyco- and sphingophosphonolipids from the medusa Phyllorhiza punctata: NMR and ESI-MS/MS fingerprints

The medusa Phyllorhiza punctata has been found in Brazilian waters where it is an exotic species, having arrived in ballasts from the Indo-Pacific Ocean in the general region of North Australia and Indonesia. Fatty acids of the intact animal and its component umbrella, oral arms, and mucus were identified. Two different groups of glycolipids and a sphingolipid were isolated by silica-gel column chromatography and characterized using GC-MS, ESI-MS, 1D, 2D (13)C, (1)H and (31)P NMR spectroscopy. They were sulfoquinovosyldiacylglycerol (SQDG), monogalactosyldiacylglycerol (MGDG), and ceramide aminoethylphosphonate (CAEP). The CAEP long chain base (LCB) and its polar head group (PHG) formed by partial hydrolysis, were analyzed by ESI-MS/MS. The probable origin of MGDG and SQDG in the jellyfish is the result of an endosymbiotic association with a microalga of the Dinoflagellate group, since these lipids are commonly found in photosynthetic membranes.

Syntheses of an α-d-Gal-(1→6)-β-d-Gal diglyceride, as lipase substrate

Two different routes were explored to afford 3-O-(6-O-alpha-D-galactopyranosyl-beta-D-galactopyranosyl)-1,2-di-O-dodecanoyl-sn-glycerol. In the first one, the key step was the glycosylation of the 3-O-(2,3,4-tri-O-benzyl-beta-D-galactopyranosyl)-1,2-O-isopropylidene-sn-glycerol acceptor with 2-pyridyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-galactopyranoside as the donor. In the second one, the key step was the coupling of 2,3,4-tri-O-acetyl-6-O-(2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl)-D-galactopyranosyl trichloroacetimidate donor with 1,2-O-isopropylidene-sn-glycerol. Even though the number of steps was the same in both pathways, the first one afforded a better overall yield (12.4%) than the second one (6.5%). This eight-step synthesis allowed the preparation of the expected glycolipid, which was used as substrate for recombinant GPLRP2 galactolipase using the monomolecular film technique.

On-line identification of secondary metabolites in freshwater microalgae and cyanobacteria by combined liquid chromatography–photodiode array detection-mass spectrometric techniques

The analysis and identification of a wide range of secondary metabolites biosynthesized by different algal taxa and cyanobacteria has been performed through a selective and sensitive methodology, mainly based on reversed-phase HPLC coupled both to UV photodiode array detection and to atmospheric pressure mass spectrometric techniques (HPLC-DAD-APIMS). Results are reported here with special attention to the analyses carried out both on the natural phytoplankton (mixed populations) of Lake Tovel (Northern Italy, Brenta Dolomites) and on enclosure-produced biomass of the dinoflagellate Glenodinium sanguineum Marchesoni (1941). This analytical procedure might represent a powerful tool for the fast screening of the taxonomic composition (broad groups, e.g. divisions) of natural mixed populations of phytoplankton, by providing a reliable distribution of accessory pigments extracted from microalgae, such as carotenoids and chlorophyll derivatives. Furthermore, we showed that in the same chromatographic analysis other classes of natural products, such as galactolipids, alkaloids, sterols and mycosporine-like amino acids, can be detected by using combined optical and mass spectrometric techniques. These metabolites represent distinctive biochemical signatures, sometimes even at the species level.

A New Unsaturated Glycoglycerolipid from a Cultured Marine Dinoflagellate Amphidinium carterae

From the cultured marine dinoflagellate Amphidinium carterae, a new unsaturated glycoglycerolipid (2S)-1,2-O-6,9,12,15-dioctadecatetraenoyl-3-O-[alpha-D-galactopyranosyl-(1''''-->6''')-O-beta-D-galactopyranosyl]-glycerol (1), has been isolated together with two known saturated ones, (2S)-1,2-distearoyl-3-O-(6-sulpho-alpha-D-quinovopyranosyl)-glycerol (2) and (2S)-1-stearoyl-3-O-(6-sulpho-alpha-D-quinovopyranosyl)-glycerol (3). Their structures were elucidated on the basis of chemical and spectral data.

New glyceroglycolipid and ceramide from Premna microphylla

Two new compounds (1,2) were isolated from the ethanolic extract of the leaves of Premna microphylla, together with five known compounds. The structures of compounds 1 and 2 were elucidated as (2S,3S,4R,11E)-2-[(2R)-2-hydroxytetracosanoylaminol-11-octadecene-1,3,4-triol (1) and 1-O-(9Z,12Z, 15Z-octadecatrienoyl)-3-O-[beta-D-galactopyranosyl-(1 --> 6)- O-beta-D-galactopyranosyl-(1 --> 6)-alpha-D-galactopyranosyl] glycerol (2) by means of spectroscopic and chemical methods.