The Genoa 2005 outbreak. Determination of putative palytoxin in Mediterranean Ostreopsis ovata by a new liquid chromatography tandem mass spectrometry method

A new method for sensitive, specific, and direct determination of palytoxin is proposed herein. It is based on combination of reversed-phase liquid chromatography with mass spectrometry (LC-MS). The new method was set up on a turbo ion spray-triple quadrupole MS instrument operating in selected ion monitoring (SIM) and multiple reaction monitoring (MRM) acquisition modes (positive ions). The minimum detection levels for matrix-free toxin on column were thus estimated from the data to be 200 and 125 pg in SIM and MRM modes, respectively. Spiking experiments before and after extraction allowed us to assess limits of detection and quantitation for palytoxin in matrix, accuracy, and intraday and interday reproducibility of the method. The developed method was decisive for the analysis of a plankton sample collected along Genoa coasts in July 2005 when respiratory illness in people exposed to marine aerosols occurred. It is suggested that putative palytoxin was the causative agent responsible for patients' symptoms and demonstrated for the first time the presence of such a toxin in Italian waters.

Putative palytoxin and its new analogue, ovatoxin-a, in Ostreopsis ovata collected along the Ligurian coasts during the 2006 toxic outbreak

In this article we report on the liquid chromatography tandem mass spectrometry (LC-MS) investigation of plankton samples collected in the summer of 2006 along the Ligurian coasts, coinciding with a massive bloom of the tropical microalga Ostreopsis ovata. LC-MS analyses indicated the occurrence of putative palytoxin along with a much more abundant palytoxin-like compound never reported so far, which we named ovatoxin-a. On the basis of molecular formula, fragmentation pattern, and chromatographic behavior, the structure of ovatoxin-a appeared to be strictly related to that of palytoxin. We report also on the analysis of cultured O. ovata, which was necessary to unequivocally demonstrate that putative palytoxin and ovatoxin-a contained in field samples were actually produced by O. ovata itself.

Isolation and structure elucidation of ovatoxin-a, the major toxin produced by Ostreopsis ovata

Since 2005, the benthic dinoflagellate Ostreopsis cf. ovata has bloomed across the Mediterranean basin, provoking serious toxic outbreaks. LC/MS studies have identified a number of palytoxin-like compounds, termed ovatoxins, along with trace amounts of putative palytoxin as the causative agents of the O. cf. ovata -related human sufferings. So far, any risk assessment for ovatoxins as well as establishment of their allowance levels in seafood has been prevented by the lack of pure toxins. The present paper reports on the isolation, NMR-based structural determination, and preliminary mouse lethality evaluation of ovatoxin-a, the major toxic compound contained in O. cf. ovata extracts. Availability of pure ovatoxin-a will open the double prospect of fully evaluating its toxicity and preparing reference standards to be employed in LC/MS quantitative analyses. Elucidation of ovatoxin-a's complex structure will ultimately herald the understanding of the molecular bases of ovatoxins bioactivity.

Yessotoxin in mussels of the northern Adriatic Sea

This study investigated the composition of diarrhoetic shellfish toxins in the hepatopancreas of mussels from the northern Adriatic Sea. The major toxins were shown to be yessotoxin, identified by its chromatographic properties and spectral data, and okadaic acid, detected both by fluorometric high-performance liquid chromatography and by comparison of its spectral properties with those of an authentic sample.

NMR-based identification of the phenolic profile of fruits of Lycium barbarum (goji berries). Isolation and structural determination of a novel N-feruloyl tyramine dimer as the most abundant antioxidant polyphenol of goji berries

Biological properties of fruits of Lycium barbarum (goji berries) have been ascribed to their high content of nutrients and phenolics. Comprehensive studies aimed at unambiguously identifying the phenolic components in goji berries are still lacking. In this paper, we report on the isolation and NMR-based identification of the major phenolics in commercially available goji berries. Together with already known phenolics, including caffeic acid, p-coumaric acid, rutin, scopoletin, N-trans-feruloyl tyramine, and N-cis-feruloyl tyramine, an unreported N-feruloyl tyramine dimer was characterized as the most abundant polyphenol isolated from the berries. Usually divalent molecules show enhanced biological activities than their corresponding monomers.

First finding of Ostreopsis cf. ovata toxins in marine aerosols

Since the late 1990s, a respiratory syndrome has been repetitively observed in humans concomitant with Ostreopsis spp. blooms (mainly O. cf. ovata) in the Mediterranean area. Previous studies have demonstrated that O. cf. ovata produces analogues of palytoxin (ovatoxins and a putative palytoxin), one of the most potent marine toxins. On the basis of the observed association between O. cf. ovata blooms, respiratory illness in people, and detection of palytoxin complex in algal samples, toxic aerosols, containing Ostreopsis cells and/or the toxins they produce, were postulated to be the cause of human illness. A small scale monitoring study of marine aerosol carried out along the Tuscan coasts (Italy) in 2009 and 2010 is reported. Aerosols were collected concomitantly with O. cf. ovata blooms, and they were analyzed by both PCR assays and LC-HRMS. The results, besides confirming the presence of O. cf. ovata cells, demonstrated for the first time the occurrence of ovatoxins in the aerosol at levels of 2.4 pg of ovatoxins per liter of air. Given the lack of toxicological data on palytoxins by inhalation exposure, our results are only a first step toward a more comprehensive understanding of the Ostreopsis-related respiratory syndrome.

Structural elucidation of a new cytotoxin isolated from mussels of the Adriatic sea

A detailed analysis of the toxic composition in the hepatopancreas of mussels from northern Adriatic sea has been performed. Along with some polyether toxins of DSP (diarrhetic shellfish poisoning) type, such as yessotoxin and its analogues, which are responsible for a variety of human seafood poisonings throughout the world, we have now isolated a new type of toxin, the chlorosulfolipid 1, which is completely different in structure from the polyether DSP-toxins isolated so far. The structural determination of the new toxin, including its absolute stereochemistry, has been performed by extensive NMR analysis and molecular mechanics and dynamics calculations.

Toxin profile of Alexandrium ostenfeldii (Dinophyceae) from the Northern Adriatic Sea revealed by liquid chromatography-mass spectrometry

This paper reports on the first occurrence of fairly high numbers of Alexandrium ostenfeldii along the Emilia Romagna coasts (Italy). Detailed liquid chromatography-mass spectrometry (LC-MS) analyses of the toxin profile were performed on a strain of the organism collected in November 2003, isolated during the event and grown in culture. Selected ion monitoring (SIM) and multiple reaction monitoring (MRM) experiments were carried out for detection of spirolides and paralytic shellfish poisoning (PSP) toxins. They revealed that the Adriatic A. ostenfeldii produces mainly spirolide 13-desmethyl C at levels of 3.7 pg/cell but not PSP toxins. Interestingly, low levels of some spirolide isomers that have not been reported so far in other strains of the dinoflagellate were also detected. This represents the first report of spirolide-type toxins in the Adriatic Sea.

Structure and stereochemistry of a new cytotoxic polychlorinated sulfolipid from Adriatic shellfish

A detailed analysis of the causative toxins contained in the hepatopancreas of toxic mussels from the northern Adriatic sea has been carried out. Along with some DSP (diarrhetic shellfish poisoning) type toxins, such as okadaic acid, yessotoxin, and their derivatives, which are involved in a number of human intoxications throughout the world, we have now isolated a new cytotoxin, a polychlorinated sulfolipid 1, whose gross structure has been elucidated by spectral analysis, including various 2D NMR techniques. The relative stereochemistry of 1 was elucidated by successful application of the J-based configuration analysis developed for acyclic compounds using carbon-proton spin-coupling constants ((2,3)J(C,H)) and proton-proton spin-coupling constants ((3)J(H,H)); its absolute stereochemistry was established by the Mosher method. Compound 1 possesses in vitro cytotoxicity against WEHI 164 and RAW 264.7 cells.

Complex palytoxin-like profile of Ostreopsis ovata. Identification of four new ovatoxins by high-resolution liquid chromatography/mass spectrometry

Over the past decades, Italian coastlines have been plagued by recurring presence of the benthic dinoflagellate Ostreopsis ovata. Such an alga has caused severe sanitary emergencies and economic losses due to its production of palytoxin-like compounds. Previous studies have confirmed the presence of ovatoxin-a (OVTX-a) as the major toxin of the algal toxin profile together with small amounts of putative palytoxin (PLTX). In our ongoing research on O. ovata toxins we report herein on in-depth investigation of an O. ovata culture carried out by high-resolution (HR) liquid chromatography/mass spectrometry (LC/MS) and tandem mass spectrometry (MS(2)). Particularly, the presence of putative PLTX and OVTX-a was confirmed and the occurrence in the extract of four new palytoxin-like compounds, OVTX-b, -c, -d, and -e, was highlighted. Elemental formulae have been assigned to the new ovatoxins and information has been gained about their structural features. A quantitative study of the O. ovata culture extract indicated that the whole of the new ovatoxins represents about 46% of the total toxin content and, thus, their presence has to be taken into account when LC/MS-based monitoring programs of either plankton or contaminated seafood are carried out.

Stereostructure and biological activity of 42-hydroxy-palytoxin: a new palytoxin analogue from Hawaiian Palythoa subspecies

This paper reports on the analysis of the toxin content from Palythoa tuberculosa and Palythoa toxica samples collected off of the Hawaiian coast. Our work, based on in-depth high-resolution liquid chromatography-mass spectrometry analysis along with extensive NMR study, led us to structurally characterize 42-hydroxy-palytoxin, a new palytoxin congener. This toxin and palytoxin itself appeared to be the major components of toxic extract from a P. tuberculosa sample, while 42-hydroxy-palytoxin was proven by far to be the main palytoxin derivative in P. toxica. Functional studies on this new palytoxin-like compound suggest that the new palytoxin analogue and palytoxin itself present similar biological activities.

Ostreopsis cf. ovata bloom in the northern Adriatic Sea during summer 2009: ecology, molecular characterization and toxin profile

Intense blooms of the benthic dinoflagellate Ostreopsis cf. ovata have occurred in the northern Adriatic Sea since 2006. These blooms are associated with noxious effects on human health and with the mortality of benthic organisms because of the production of palytoxin-like compounds. The O. cf. ovata bloom and its relationships with nutrient concentrations at two stations on the Conero Riviera (northern Adriatic Sea) were investigated in the summer of 2009. O. cf. ovata developed from August to November, with the highest abundances in September (1.3×10(6) cells g(-1) fw corresponding to 63.8×10(3) cells cm(-2)). The presence of the single O. cf. ovata genotype was confirmed by a PCR assay. Bloom developed when the seawater temperature was decreasing. Nutrient concentrations did not seem to affect bloom dynamics. Toxin analysis performed by high resolution liquid chromatography-mass spectrometry revealed a high total toxin content (up to 75 pg cell(-1)), including putative palytoxin and all the ovatoxins known so far.

Influence of temperature and salinity on Ostreopsis cf. ovata growth and evaluation of toxin content through HR LC-MS and biological assays

In the Mediterranean Sea, blooms of Ostreopsis cf. ovata and Ostreopsis siamensis have become increasingly frequent in the last decade and O. cf. ovata was found to produce palytoxin-like compounds (putative palytoxin, ovatoxin-a, -b, -c, -d and -e), a class of highly potent toxins. The environmental conditions seem to play a key role in influencing the abundance of Ostreopsis spp. High cell densities are generally recorded in concomitance with relatively high temperature and salinity and low hydrodynamics conditions. In this study the effects of temperature and salinity on the growth and toxicity of an Adriatic O. cf. ovata isolate were investigated. The highest growth rates of the Adriatic strain were recorded for cultures grown at 20 °C and at salinity values of 36 and 40, in accordance with natural bloom surveys. Toxicity was affected by growth conditions, with the highest toxin content on a per cell basis being measured at 25 °C and salinity 32. However, the highest total toxin content on a per litre basis was recorded at 20 °C and salinity 36, since under such conditions the growth yield was the highest. O. cf. ovata had lethal effects on Artemia nauplii and juvenile sea basses, and produced haemolysis of sheep erythrocytes. A comparison between haemolysis neutralization assay and HR LC-MS results showed a good correlation between haemolytic effect and total toxin content measured through HR LC-MS. Considering the increasing need for rapid and sensitive methods to detect palytoxin in natural samples, the haemolytic assay appears a useful method for preliminary quantification of the whole of palytoxin-like compounds in algal extracts.

Toxin levels and profiles in microalgae from the north-Western Adriatic Sea--15 years of studies on cultured species

The Northern Adriatic Sea is the area of the Mediterranean Sea where eutrophication and episodes related to harmful algae have occurred most frequently since the 1970s. In this area, which is highly exploited for mollusk farming, the first occurrence of human intoxication due to shellfish consumption occurred in 1989, nearly 10 years later than other countries in Europe and worldwide that had faced similar problems. Until 1997, Adriatic mollusks had been found to be contaminated mostly by diarrhetic shellfish poisoning toxins (i.e., okadaic acid and dinophysistoxins) that, along with paralytic shellfish poisoning toxins (i.e., saxitoxins), constitute the most common marine biotoxins. Only once, in 1994, a toxic outbreak was related to the occurrence of paralytic shellfish poisoning toxins in the Adriatic coastal waters. Moreover, in the past 15 years, the Adriatic Sea has been characterized by the presence of toxic or potentially toxic algae, not highly widespread outside Europe, such as species producing yessotoxins (i.e., Protoceratium reticulatum, Gonyaulax spinifera and Lingulodinium polyedrum), recurrent blooms of the potentially ichthyotoxic species Fibrocapsa japonica and, recently, by blooms of palytoxin-like producing species of the Ostreopsis genus. This review is aimed at integrating monitoring data on toxin spectra and levels in mussels farmed along the coast of the Emilia-Romagna region with laboratory studies performed on the species involved in the production of those toxins; toxicity studies on toxic or potentially toxic species that have recently appeared in this area are also reviewed. Overall, reviewed data are related to: (i) the yessotoxins producing species P. reticulatum, G. spinifera and L. polyedrum, highlighting genetic and toxic characteristics; (ii) Adriatic strains of Alexandrium minutum, Alexandrium ostenfeldii and Prorocentrum lima whose toxic profiles are compared with those of strains of different geographic origins; (iii) F. japonica and Ostreopsis cf. ovata toxicity. Moreover, new data concerning domoic acid production by a Pseudo-nitzschia multistriata strain, toxicity investigations on a Prorocentrum cf. levis, and on presumably ichthyotoxic species, Heterosigma akashiwo and Chattonella cf. subsalsa, are also reported.

Complex yessotoxins profile in Protoceratium reticulatum from north-western Adriatic sea revealed by LC-MS analysis

While the occurrence of yessotoxin (YTX) has been reported worldwide from Protoceratium reticulatum, the biogenetic origin of some YTX analogues is still unknown, thus raising an issue whether they are metabolites of YTX formed in mussels or true products of different dinoflagellate species. Findings reported herein suggest that P. reticulatum from the north-western Adriatic sea is responsible for production, together with YTX (1), of homoYTX (2), 45-OHYTX (3), carboxyYTX (5), and noroxoYTX (7). YTX and its analogues have been determined by high performance liquid chromatography coupled with electrospray ion trap mass spectrometry (HPLC-MS and HPLC-MSn experiments). The result is the first to confirm production of these YTX analogues from this species and indicate it as a producing organism of homoYTX, 45-OHYTX, carboxyYTX, and noroxoYTX found in shellfish.

LC-MS of palytoxin and its analogues: State of the art and future perspectives

The state of the art of LC-MS of palytoxin and its analogues is reported in the present review. MS data for palytoxin, 42-hydroxy-palytoxin, ostreocin-D, mascarenotoxins, and ovatoxins, obtained using different ionization techniques, namely fast-atom bombardment (FAB), matrix assisted laser desorption ionization (MALDI), and electrospray ionization (ESI), are summarized together with the LC-MS methods used for their detection. Application of the developed LC-MS methods to both plankton and seafood analysis is also reported, paying attention to the extraction procedures used and to limits of detection (LOD) and quantitation (LOQ) achieved. In a research setting, LC-MS has shown a good potential in determination of palytoxin and its analogues from various sources, but, in a regulatory setting, routine LC-MS analysis of palytoxins is still at a preliminary stage. The LOQ currently achieved in seafood analysis appears insufficient to detect palytoxins in shellfish extract at levels close to the tolerance limit for palytoxins (30 μg/kg) proposed by the European Food Safety Authority (EFSA, 2009). In addition, lacking of certified reference standard of palytoxins as well as of validation studies for the proposed LC-MS methods represent important issues that should be faced for future perspectives of LC-MS technique.

Caspase activation and death induced by yessotoxin in HeLa cells

We have studied the death response induced by yessotoxin (YTX) in cultured HeLa cells, and have compared it to that triggered by okadaic acid (OA) in the same experimental system. Sub-nanomolar concentrations of YTX were found to induce HeLa cell death after a 48-96-h incubation. YTX caused loss of intact poly(ADP-ribose)-polymerase (PARP) in HeLa cells, and detection of the 85kDa fragment, which is indicative of proteolytic attack by caspases. Measurements of caspase activities using extracts prepared from YTX-treated cells and substrates of the caspase-3/7 and caspase-2 isoforms, showed that the relative proteolysis of caspase-3/7 substrate was about eight-fold higher than that of caspase-2, the levels of which were about twice those measured with extracts from control cells. These findings were matched by Western blot analyses of caspase-2, -3 and -7 in HeLa cell extracts, which showed that the levels of pro-caspase-2 were not greatly affected by YTX treatment, whereas pro-caspase-3 and -7 were activated in YTX-treated cells. Taken together, these data complement others previously obtained with OA, and support the notion that caspase isoforms involved in cell death induced by OA and YTX are cell- and toxin-specific.

Structure determination of carboxyhomoyessotoxin, a new yessotoxin analogue isolated from adriatic mussels

The contamination of shellfish with marine biotoxins derived from microalgae represents a serious problem for shellfish industries and public health. This study investigated the composition of diarrhetic shellfish toxins in the digestive glands of mussels from the Northern Adriatic Sea. Along with known yessotoxins, identified by comparison of their chromatographic and spectral properties with those reported in the literature, we isolated a new analogue of yessotoxin, carboxyhomoyessotoxin, whose structure was determined by mass spectrometry and (1)H NMR spectroscopy.

Ostreopsis fattorussoi sp. nov. (Dinophyceae), a new benthic toxic Ostreopsis species from the eastern Mediterranean Sea

The new benthic toxic dinoflagellate, Ostreopsis fattorussoi sp. nov., is described from the Eastern Mediterranean Sea, Lebanon and Cyprus coasts, and is supported by morphological and molecular data. The plate formula, Po, 3', 7″, 6c, 7s, 5‴, 2'''', is typical for the Ostreopsis genus. It differs from all other Ostreopsis species in that (i) the curved suture between plates 1' and 3' makes them approximately hexagonal, (ii) the 1' plate lies in the left half of the epitheca and is obliquely orientated leading to a characteristic shape of plate 6″. The round thecal pores are bigger than the other two Mediterranean species (O. cf. ovata and O. cf. siamensis). O. fattorussoi is among the smallest species of the genus (DV: 60.07 ± 5.63 μm, AP: 25.66 ± 2.97 μm, W: 39.81 ± 5.05 μm) along with O. ovata. Phylogenetic analyses based on the LSU and internal transcribed spacer rDNA shows that O. fattorussoi belongs to the Atlantic/Mediterranean Ostreopsis spp. clade separated from the other Ostreopsis species. Ostreopsis fattorussoi produces OVTX-a and structural isomers OVTX-d and -e, O. cf. ovata is the only other species of this genus known to produce these toxins. The Lebanese O. fattorussoi did not produce the new palytoxin-like compounds (ovatoxin-i, ovatoxin-j₁ , ovatoxin-j₂ , and ovatoxin-k) that were previously found in O. fattorussoi from Cyprus. The toxin content was in the range of 0.28-0.94 pg · cell^-1 . On the Lebanon coast, O. fattorussoi was recorded throughout the year 2015 (temperature range 18°C-31.5°C), with peaks in June and August.