Screening of cyclic imine and paralytic shellfish toxins in isolates of the genus Alexandrium (Dinophyceae) from Atlantic Canada

Seasonal occurrence of toxic phytoplankton and phycotoxins at a mussel aquaculture site in Nova Scotia, Canada

A three-year field study at a mussel (Mytilus edulis) aquaculture site in Ship Harbour, Nova Scotia, Canada was carried out between 2004 and 2006 to detect toxic phytoplankton species and dissolved lipophilic phycotoxins and domoic acid. A combination of plankton monitoring and solid phase adsorption toxin tracking (SPATT) techniques were used. Net tow and pipe phytoplankton samples were taken weekly to determine the abundance of potentially toxic species and SPATT samplers were deployed weekly for phycotoxin analysis. Mussels were also collected for toxin analysis in 2005. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyse the samples for spirolides (SPXs), pectenotoxins (PTXs), okadaic acid group toxins (OA, DTXs) and domoic acid (DA). Phycotoxins were detected with SPATT samplers beginning from the time of deployment until after the producing organisms were no longer observed in pipe samples. Seasonal changes in toxin composition occurred over the sampling period and were related to changes in cell concentrations of Alexandrium Halim, Dinophysis Ehrenberg and Pseudo-nitzschia (Hasle) Hasle. Spirolides peaked in late spring and early summer, followed by DA in mid-July. Okadaic acid, DTX1 and PTXs occurred throughout the field season but peaked in late summer. Concentrations of some phycotoxins detected in SPATT samplers deployed within the area where mussels were suspended on lines were lower than in those deployed outside the mussel farm. The SPATT samplers provided a useful tool to detect the presence of phycotoxins and to establish trends in their appearance in the Ship Harbour estuary.

Anatoxins from benthic cyanobacteria responsible for dog mortalities in New Brunswick, Canada

In July 2018 three dogs died after visiting the Wolastoq (Saint John River) near Fredericton, New Brunswick, in Atlantic Canada. All showed signs of toxicosis, and necropsies revealed non-specific pulmonary edema and multiple microscopic brain hemorrhages. Liquid chromatography-high-resolution mass spectrometry (LC-HRMS) analysis of vomitus and stomach contents as well as water and biota from the mortality sites confirmed the presence of anatoxins (ATXs), a class of potent neurotoxic alkaloids. The highest levels were measured in a dried benthic cyanobacterial mat that two of the dogs had been eating before falling ill and in a vomitus sample collected from one of the dogs. Concentrations of 357 and 785 mg/kg for anatoxin-a and dihydroanatoxin-a, respectively, were measured in the vomitus. Known anatoxin-producing species of Microcoleus were tentatively identified using microscopy and confirmed by 16S rRNA gene sequencing. The ATX synthetase gene, anaC, was detected in the samples and isolates. The pathology and experimental results confirmed the role of ATXs in these dog mortalities. Further research is required to understand drivers for toxic cyanobacteria in the Wolastoq and to develop methodology for assessing occurrence.

Detection, occurrence, influencing factors and environmental risks of paralytic shellfish toxins in seawater in a typical mariculture bay

Paralytic shellfish toxins (PSTs) producing algae are widely distributed in the global coastal aquatic environment, posing a threat to coastal ecosystem health and mariculture safety. However, the levels and potential environmental risks of PSTs frequently detected in shellfish remain largely unexplored in seawater of mariculture zones. In this study, a new method for trace detection of 13 common PSTs (<1.0 ng/L) in seawater was established based on off-line solid phase extraction (SPE) and on-line SPE-liquid chromatography-tandem mass spectrometry (on-line SPE-LC-MS/MS), and a systematic investigation of PSTs in seawater of the Laizhou Bay, a typical aquaculture bay in China, was conducted to understand their pollution status, environmental impact factors and ecological risks for the first time. Eleven PSTs were detected in the seawater of Laizhou Bay with total concentrations ranging from 0.75 to 349.47 ng/L (mean, 176.27 ng/L), which indicates the rich diversity of PSTs in the mariculture bay and demonstrates the reliability of the proposed analytical method. C1, C2, GTX2, GTX3, dcGTX2, and dcGTX3 were found to be the predominant PSTs, which refreshed the knowledge of PST contamination in the coastal aquatic environment. PST levels in seawater exhibited the highest levels in the southeastern mouth of Laizhou Bay and decreased toward the inner bay. Correlation analyses showed that climatic factors, nutrient status and hydrological conditions had significant effects on the distribution of PST in mariculture bay. Preliminary environmental risk assessments revealed that aquatic organisms throughout the waters of Laizhou Bay are at risk of chronic PST toxicity. These findings imply that the risk of PST in seawater of mariculture bay has previously been grossly underestimated, and that the coastal aquatic environment in North China and even the world may be at more serious risk of PST pollution, which should be taken seriously.

Spirolides in Bivalve Mollusk of the Galician (NW Spain) Coast: Interspecific, Spatial, Temporal Variation and Presence of an Isomer of 13-Desmethyl Spirolide C

Spirolides are cyclic imines whose risks to human health have not been sufficiently evaluated. To determine the possible impact of these compounds in Galicia (NW Spain), their presence and concentration in bivalve mollusk were studied from 2014 to 2021. Only 13-desmethyl spirolide C (13desmSPXC) and an isomer have been detected, and always at low concentrations. Mussel, Mytilus galloprovincialis, was the species which accumulated more spirolides, but the presence of its isomer was nearly restricted to cockle, Cerastoderma edule, and two clam species, Venerupis corrugata and Polititapes rhomboides. On average, the highest 13desmSPXC levels were found in autumn-winter, while those of its isomer were recorded in spring-summer. Both compounds showed decreasing trends during the study period. Geographically, the concentration tends to decrease from the southern to the north-eastern locations, but temporal variability predominates over spatial variability.

LC-HRMS Profiling of Paralytic Shellfish Toxins in Mytilus galloprovincialis after a Gymnodinium catenatum Bloom

Saxitoxin and its more than 50 analogues are a group of naturally occurring neurotoxins collectively designated as paralytic shellfish toxins (PSTs). PSTs are toxic to humans and maximum legal limits in seafood have been implemented by regulatory authorities worldwide. In the European Union, monitoring of PSTs is performed using the AOAC Official Method 2005.06, based on liquid chromatography coupled with fluorescence detection (LC- FLD). However, this method has been suggested to not effectively detect the emerging C-11 hydroxyl (M-toxins) and benzoate (GC-toxins) analogues, with these analogues currently not being surveyed in monitoring programs. In this study, a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method was used to search for these emerging PSTs in mussels, Mytilus galloprovincialis, contaminated following an intense Gymnodinium catenatum bloom in the Tagus estuary (Lisbon, Portugal). Five M-toxins (M1, M2, M6, dcM6, and dcM10), but no GC-toxins, were detected in the mussels' whole-soft body tissue. Moreover, the classical PSTs (C1 to C4, GTX 4 to GTX6, dcGTX1 to dcGTX4, dcSTX, dcNEO, and STX) were also found and comprised the largest fraction of the PSTs' profile. The presence of unregulated PSTs in edible mussel samples suggests potential seafood safety risks and urges further research to determine the frequency of these analogues in seafood and their contribution to toxicity.

Current Situation of Palytoxins and Cyclic Imines in Asia-Pacific Countries: Causative Phytoplankton Species and Seafood Poisoning

Among marine biotoxins, palytoxins (PlTXs) and cyclic imines (CIs), including spirolides, pinnatoxins, pteriatoxins, and gymnodimines, are not managed in many countries, such as the USA, European nations, and South Korea, because there are not enough poisoning cases or data for the limits on these biotoxins. In this article, we review unregulated marine biotoxins (e.g., PlTXs and CIs), their toxicity, causative phytoplankton species, and toxin extraction and detection protocols. Due to global warming, the habitat of the causative phytoplankton has expanded to the Asia-Pacific region. When ingested by humans, shellfish that accumulated toxins can cause various symptoms (muscle pain or diarrhea) and even death. There are no systematic reports on the occurrence of these toxins; however, it is important to continuously monitor causative phytoplankton and poisoning of accumulating shellfish by PlTXs and CI toxins because of the high risk of toxicity in human consumers.

Selective extraction of gambierone and related metabolites in Gambierdiscus silvae using m-aminophenylboronic acid-agarose gel and liquid chromatography-high-resolution mass spectrometric detection

Gambierdiscus spp. are epi-benthic dinoflagellates that have been associated with ciguatera poisoning. These microalgae can have complex secondary metabolite profiles including ciguatoxins, maitotoxins, and gambierones, with varying compositions and toxicities across species and strains. Given this chemical diversity there is a need to develop selective and sensitive methods for secondary metabolite profiling. In this study, we used a cultured Caribbean strain of Gambierdiscus silvae to develop sample preparation and analysis strategies for characterizing vic-diol containing secondary metabolites. A pooled cellular extract was first screened by liquid chromatography-high-resolution mass spectrometry (LC-HRMS) for ciguatoxin-related compounds, which resulted in the confirmation of gambierone (1) and a novel isomer of 44-methylgambierone (3). Treatment of the extract with periodate confirmed that the gambierones each contained one reactive vic-diol, which was exploited for the development of a selective extraction procedure using m-aminophenylboronic acid gel and the non-aqueous binding solvent chloroform. Using this non-traditional boronate affinity procedure, LC-HRMS also revealed the presence of additional sulfated polycyclic ethers in the gambierone-containing vic-diol fraction, while pigments and other contaminants were removed. The developed tools could be applied to screen collections of Gambierdiscus and other benthic algae to provide additional chemical characterization of gambierone-related compounds. The selective extraction procedure may also prove useful as a step in the isolation of these sulfated polyethers for structural, toxicological and biotransformation studies.

Unknown Extracellular and Bioactive Metabolites of the Genus Alexandrium: A Review of Overlooked Toxins

Various species of Alexandrium can produce a number of bioactive compounds, e.g., paralytic shellfish toxins (PSTs), spirolides, gymnodimines, goniodomins, and also uncharacterised bioactive extracellular compounds (BECs). The latter metabolites are released into the environment and affect a large range of organisms (from protists to fishes and mammalian cell lines). These compounds mediate allelochemical interactions, have anti-grazing and anti-parasitic activities, and have a potentially strong structuring role for the dynamic of Alexandrium blooms. In many studies evaluating the effects of Alexandrium on marine organisms, only the classical toxins were reported and the involvement of BECs was not considered. A lack of information on the presence/absence of BECs in experimental strains is likely the cause of contrasting results in the literature that render impossible a distinction between PSTs and BECs effects. We review the knowledge on Alexandrium BEC, (i.e., producing species, target cells, physiological effects, detection methods and molecular candidates). Overall, we highlight the need to identify the nature of Alexandrium BECs and urge further research on the chemical interactions according to their ecological importance in the planktonic chemical warfare and due to their potential collateral damage to a wide range of organisms.

Performance of different extraction methods for paralytic shellfish toxins and toxin stability in shellfish during storage

Accurate analysis of paralytic shellfish toxins (PSTs) in shellfish is important to protect seafood safety and human health. In this study, the performance of different extraction protocols for PSTs from scallop tissues is compared and discussed, including regular extraction solvents hydrochloric acid (HCl) and acetic acid (AcOH) followed by heating and solid-phase extraction (SPE) purification, and a novel technique of matrix solid-phase dispersion (MSPD) without heating. The possible conversion of C1/2 and GTX2/3 standards after heating, and the stability of PSTs in wet scallop tissues stored at -20 °C for a 6-month period are also explored. Results showed that the MSPD technique could effectively mitigate matrix interference, but its recoveries of PSTs were significantly lower than those of the HCl and AcOH extraction methods followed by carbon SPE purification. The molar concentrations of M-toxins obtained by the MSPD method were generally lower than those analyzed by the HCl and AcOH extraction methods, which demonstrated a weak chemical conversion of C1/2 and GTX2/3 due to the heating process. Most of the PSTs were relatively stable in scallop tissues during 1-month storage at -20 °C, while the concentrations of PSTs in scallop tissues obviously changed after 6 months due to the degradation and transformation of PSTs during long-term storage at -20 °C. This work helps improve our understanding of the performance of different extraction methods and the stability of PSTs in scallop tissues stored at -20 °C.

Two new skeletal analogues of saxitoxin found in the scallop, Patinopecten yessoensis, as possible metabolites of paralytic shellfish toxins

The scallop, Patinopecten yessoensis, was screened for new saxitoxin analogues to study the metabolism of paralytic shellfish toxins (PSTs), and this resulted in the discovery of two new analogues: M5-hemiaminal (HA) and M6-HA. M5-HA was isolated and its structure was determined by using NMR spectroscopy. It contains hydrogen at C-4 with opposite stereochemistry to that in saxitoxin, and a hemiaminal was formed between 9-NH₂ and the hydrated ketone at C-12 in α-orientation. This is the first reported structural feature in a natural saxitoxin analogue, whereas the same ring system has previously been reported in a synthetic saxitoxin analogue, FD-saxitoxin. Acid hydrolysis of the carbamoyl N-sulfate in M5-HA produced M6-HA which was also identified in P. yessoensis by using LC-MSMS. M5-HA was not synthetically produced from M1 (11-hydroxy gonyautoxin-5) and M3 (11,11-dihydroxy gonyautoxin-5) through incubation in aqueous buffers. Furthermore, PSTs in the hepatopancreas of P. yessoensis, cultured in a bay located in northeastern Japan, were chronologically analyzed in 2018. The highest concentrations of M1/M3/M5-HA were observed two weeks after C-toxins had reached their highest concentrations, which provides evidence that M1/M3/M5-HA are metabolites of C-toxins. The voltage-gated sodium channel blockage activity of M6-HA was not detected at the concentration of 140 nM by using the Neuro-2A veratridine/ouabain assay.

Effects of Polystyrene Microplastics on Growth and Toxin Production of Alexandrium pacificum

Microplastics (MP) widely distributed in aquatic environments have adverse effects on aquatic organisms. Currently, the impact of MP on toxigenic red tide microalgae is poorly understood. In this study, the strain of Alexandrium pacificum ATHK, typically producing paralytic shellfish toxins (PST), was selected as the target. Effects of 1 and 0.1 μm polystyrene MP with three concentration gradients (5 mg L⁻¹, 25 mg L⁻¹ and 100 mg L⁻¹) on the growth, chlorophyll a (Chl a), photosynthetic activity (F_v/F_m) and PST production of ATHK were explored. Results showed that the high concentration (100 mg L⁻¹) of 1 μm and 0.1 μm MP significantly inhibited the growth of ATHK, and the inhibition depended on the size and concentration of MP. Contents of Chl a showed an increase with various degrees after MP exposure in all cases. The photosynthesis indicator F_v/F_m of ATHK was significantly inhibited in the first 11 days, then gradually returned to the level of control group at day 13, and finally was gradually inhibited in the 1 μm MP treatments, and promotion or inhibition to some degree also occurred at different periods after exposure to 0.1 μm MP. Overall, both particle sizes of MP at 5 and 25 mg L⁻¹ had no significant effect on cell toxin quota, and the high concentration 100 mg L⁻¹ significantly promoted the PST biosynthesis on the day 7, 11 and 15. No significant difference occurred in the cell toxin quota and the total toxin content in all treatments at the end of the experiment (day 21). All MP treatments did not change the toxin profiles of ATHK, nor did the relative molar percentage of main PST components. The growth of ATHK, Chl a content, F_v/F_m and toxin production were not affected by MP shading. This is the first report on the effects of MP on the PST-producing microalgae, which will improve the understanding of the adverse impact of MP on the growth and toxin production of A. pacificum.

A mussel tissue certified reference material for multiple phycotoxins. Part 5: profiling by liquid chromatography-high-resolution mass spectrometry

A freeze-dried mussel tissue-certified reference material (CRM-FDMT1) was prepared containing the marine algal toxin classes azaspiracids, okadaic acid and dinophysistoxins, yessotoxins, pectenotoxins, cyclic imines, and domoic acid. Thus far, only a limited number of analogues in CRM-FDMT1 have been assigned certified values; however, the complete toxin profile is significantly more complex. Liquid chromatography-high-resolution mass spectrometry was used to profile CRM-FDMT1. Full-scan data was searched against a list of previously reported toxin analogues, and characteristic product ions extracted from all-ion-fragmentation data were used to guide the extent of toxin profiling. A series of targeted and untargeted acquisition MS/MS experiments were then used to collect spectra for analogues. A number of toxins previously reported in the literature but not readily available as standards were tentatively identified including dihydroxy and carboxyhydroxyyessotoxin, azaspiracids-33 and -39, sulfonated pectenotoxin analogues, spirolide variants, and fatty acid acyl esters of okadaic acid and pectenotoxins. Previously unreported toxins were also observed including compounds from the pectenotoxin, azaspiracid, yessotoxin, and spirolide classes. More than one hundred toxin analogues present in CRM-FDMT1 are summarized along with a demonstration of the major acyl ester conjugates of several toxins. Retention index values were assigned for all confirmed or tentatively identified analogues to help with qualitative identification of the broad range of lipophilic toxins present in the material.

First determination of extracellular paralytic shellfish poisoning toxins in the culture medium of toxigenic dinoflagellates by HILIC-HRMS

Paralytic shellfish poisoning (PSP) toxins have received considerable attention in recent years because of their adverse effects on marine breeding industries and human health. In this study, a reliable method for the analysis of extracellular PSP toxins in the culture medium of marine toxic dinoflagellates was developed for the first time using graphitized carbon black-solid-phase extraction and hydrophilic interaction liquid chromatography-high-resolution mass spectrometry. The limit of quantification of typical PSP toxins in algal culture medium ranged from 0.072 μg/L to 0.151 μg/L under optimal conditions. Satisfactory absolute recoveries (87.5%-102.4%), precision (relative standard deviation ≤ 7.6%), and linearity (R² ≥ 0.9998) were also achieved. In addition, the proposed method was applied to screen and determine the extracellular PSP toxins of two typical toxigenic dinoflagellates, Alexandrium minutum and Alexandrium tamarense. The total concentrations of the extracellular PSP toxins in A. minutum and A. tamarense over the whole growth period were within 2.0-735.5 and 2.0-19.2 μg/L, respectively. The concentrations of extracellular PSP toxins varied remarkably in the different growth stages of A. minutum and A. tamarense, and the contents of some extracellular PSP toxins were substantially higher than those of intracellular PSP toxins. Therefore, the extracellular PSP toxins released by toxigenic red tide algae cannot be ignored, and their environmental fate, bioavailability, and potential harm to aquatic environment need to be investigated in future studies.

Mass Spectrometry-Based Characterization of New Spirolides from Alexandrium ostenfeldii (Dinophyceae)

Spirolides belong to a group of marine phycotoxins produced by the marine planktonic dinophyte Alexandrium ostenfeldii. Composed of an imine moiety and a spiroketal ring system within a macrocylcle, spirolides are highly diverse with toxin types that vary among different strains. This study aims to characterize the spirolides from clonal A. ostenfeldii strains collected from The Netherlands, Greenland and Norway by mass spectral techniques. The structural characterization of unknown spirolides as inferred from high-resolution mass spectrometry (HR-MS) and collision induced dissociation (CID) spectra revealed the presence of nine novel spirolides that have the pseudo-molecular ions m/z 670 (1), m/z 666 (2), m/z 696 (3), m/z 678 (4), m/z 694 (5), m/z 708 (6), m/z 720 (7), m/z 722 (8) and m/z 738 (9). Of the nine new spirolides proposed in this study, compound 1 was suggested to have a truncated side chain in lieu of the commonly observed butenolide ring in spirolides. Moreover, there is indication that compound 5 might belong to new spirolide subclasses with a trispiroketal ring configuration having a 6:5:6 trispiroketal ring system. On the other hand, the other compounds were proposed as C- and G-type SPX, respectively. Compound 7 is proposed as the first G-type SPX with a 10-hydroxylation as usually observed in C-type SPX. This mass spectrometry-based study thus demonstrates that structural variability of spirolides is larger than previously known and does not only include the presence or absence of certain functional groups but also involves the triketal ring system.

Semiquantitation of Paralytic Shellfish Toxins by Hydrophilic Interaction Liquid Chromatography-Mass Spectrometry Using Relative Molar Response Factors

Paralytic shellfish toxins (PSTs) are a complex class of analogs of the potent neurotoxin saxitoxin (STX). Since calibration standards are not available for many PSTs, including C-11 hydroxyl analogs called M-toxins, accurate quantitation by liquid chromatography–mass spectrometry (LC-MS) can be challenging. In the absence of standards, PSTs are often semiquantitated using standards of a different analog (e.g., STX), an approach with a high degree of uncertainty due to the highly variable sensitivity between analytes in electrospray ionization. Here, relative molar response factors (RMRs) were investigated for a broad range of PSTs using common LC-MS approaches in order to improve the quantitation of PSTs for which standards are unavailable. First, several M-toxins (M1-M6, M9 and dcM6) were semipurified from shellfish using preparative gel filtration chromatography and quantitated using LC-charged aerosol detection (LC-CAD). The RMRs of PST certified reference materials (CRMs) and M-toxins were then determined using selective reaction monitoring LC-MS/MS and full scan LC-high-resolution MS (LC-HRMS) methods in positive and negative electrospray ionization. In general, RMRs for PSTs with similar chemical structures were comparable, but varied significantly between subclasses, with M-toxins showing the lowest sensitivity. For example, STX showed a greater than 50-fold higher RMR than M4 and M6 by LC-HRMS. The MS instrument, scan mode and polarity also had significant impacts on RMRs and should be carefully considered when semiquantitating PSTs by LC-MS. As a demonstration of their utility, the RMRs determined were applied to the semiquantitation of PSTs in contaminated mussels, showing good agreement with results from calibration with CRMs.

Conversion and Stability of New Metabolites of Paralytic Shellfish Toxins under Different Temperature and pH Conditions

A number of new C-11 hydroxyl metabolites (so-called M-toxins) of paralytic shellfish toxins (PSTs) have been discovered in contaminated shellfish, and trace amounts have also been detected in some strains of PST-producing microalgae. To investigate the chemical conversion and stability of M-toxins, mussel extracts were purified with solid-phase extraction cartridges (Oasis HLB) and Biogel P-2 resin columns and four partially purified M-toxin fractions were stored at different temperatures (-20, 4, and 20 °C) and pH values (3, 4, and 5). The concentrations and profiles of M-toxins in these fractions were analyzed using liquid chromatography coupled with tandem mass spectrometry for 27 weeks. Results further confirmed the chemical conversion pathway M1 → M3 → M5 and determined for the first time two new transformation pathways: M2 → M4 → M6 and neosaxitoxin (NEO) → M10. The half-lives of M1, M2, M4, and M10 were calculated using a first-order degradation kinetics model, which indicated that the degradation of all M-toxins was dependent upon the temperature and pH, increasing with rising temperature and pH. In comparison to M4 and M10, M1 was more sensitive to the temperature, followed by M2. Results suggest that M-toxins should be maintained at a low temperature (-20 °C) and low pH (3) for their prolonged storage. M-toxins were less stable than all of the common analogues of PSTs, which may be beneficial for shellfish to achieve rapid detoxification through transformation of PSTs to M-toxins. These new findings are of significance because they enable further understanding of the metabolism of PSTs and their detoxification mechanisms in contaminated shellfish.

Fatty acid ester metabolites of gymnodimine in shellfish collected from China and in mussels (Mytilus galloprovincialis) exposed to Karenia selliformis

Marine shellfish exposed to the microalgae Karenia selliformis can accumulate gymnodimines (GYM). Shellfish samples collected from Beihai City in Guangxi Autonomous Region, and Ningde City in Fujian Province, in the South China Sea, as well as mussels Mytilus galloprovincialis fed on K. selliformis under laboratory conditions were analyzed. Gymnodimines and various fatty acid ester metabolites were detected in the clam Antigona lamellaris and pen shell Atrina pectinata, while no esters were found in the oyster Crassostrea sp. and the gastropod Batillaria zonalis despite positive detection of free GYM in both species. When present, the predominant acyl esters observed were 18:0-GYM-A and 20:1-GYM-A. Under laboratory conditions GYM-A was accumulated and metabolized to fatty acid esters in mussels exposed to K. selliformis, with 16:0-GYM-A and 20:1-GYM-A as the major variants. A novel compound with the same accurate mass as GYM-A and its 16:0 fatty acid ester were observed in the experimental mussels but was not present in the microalgal strain to which mussels were exposed. No significant differences of reactive oxygen species (ROS) levels and antioxidant enzymes were found between mussels fed on K. selliformis or GYM-free microalgae Isochrysis galbana. This suggests the accumulation of GYM and its metabolites does not significantly impact the physiological status of mussels. While it is currently not proven that GYM affects human health, risk assessments should consider the presence of GYM esters in naturally contaminated shellfish as part of exposure analysis.

Analysis of Cyclic Imines in Mussels (Mytilus galloprovincialis) from Galicia (NW Spain) by LC-MS/MS

Cyclic imines (CIs) are being considered as emerging toxins in the European Union, and a scientific opinion has been published by the European Food Safety Authority (EFSA) in which an assessment of the risks to human health related to their consumption has been carried out. Recommendations on the EFSA opinion include the search for data occurrence of CIs in shellfish and using confirmatory methods by liquid chromatography-tandem mass spectrometry (LC-MS/MS), which need to be developed and optimized. The aim of this work is the application of LC-MS/MS to the analysis of gymnodimines (GYMs), spirolides (SPXs), pinnatoxins (PnTXs), and pteriatoxins (PtTXs) in mussels from Galician Rias, northwest Spain, the main production area in Europe, and therefore a representative emplacement for their evaluation. Conditions were adjusted using commercially available certified reference standards of GYM-A, SPX-1, and PnTX-G and evaluated through quality control studies. The EU-Harmonised Standard Operating Procedure for determination of lipophilic marine biotoxins in molluscs by LC-MS/MS was followed, and the results obtained from the analysis of eighteen samples from three different locations that showed the presence of PnTXs and SPXs are presented and discussed. Concentrations of PnTX-G and SPX-1 ranged from 1.8 to 3.1 µg/kg and 1.2 to 6.9 µg/kg, respectively, and PnTX-A was detected in the group of samples with higher levels of PnTX-G after a solid phase extraction (SPE) step used for the concentration of extracts.

Structure Elucidation and Relative Toxicity of (24R)-24-Hydroxyyessotoxin from a Namibian Isolate of Gonyaulax spinifera

Liquid chromatography-high-resolution mass spectrometry (LC-HRMS) analysis of a Namibian strain of Gonyaulax spinifera showed the presence of a number of yessotoxins (YTXs). Principal among these were YTX (1), homoYTX (2), and a tentative hydroxylated analogue that did not correspond to any previously confirmed YTX structures. Culturing the G. spinifera strain afforded sufficient biomass for purification of the new analogue through a series of solvent partitioning and chromatographic steps, yielding ∼0.9 mg as a solid. NMR spectroscopy, ion-trap mass spectrometry, and HRMS identified the new analogue as 24-hydroxyYTX (7). Purified 24-hydroxyYTX was quantitated by NMR, and its relative toxicity evaluated using two embryonic zebrafish toxicity assays. 24-HydroxyYTX demonstrated reduced toxicity compared to YTX.

Dynamics of paralytic shellfish toxins and their metabolites during timecourse exposure of scallops Chlamys farreri and mussels Mytilus galloprovincialis to Alexandrium pacificum

New C-11 hydroxyl metabolites of paralytic shellfish toxins (PSTs) have been reported in shellfish. To gain further information on these metabolites, as well as the potential for formation of phase-II metabolites and acyl esters of PSTs, bivalves were fed with the PSTs-producing dinoflagellate Alexandrium pacificum (strain ATHK). Through independent experiments, scallops (Chlamys farreri) were fed for 9 days and mussels (Mytilus galloprovincialis) for 5 days plus an additional 5 days of depuration, with representative samples taken throughout. Several common PSTs (C1-4, GTX1-6 and NEO) and metabolites including M1, M3, M5, M7, M9, M2 and M8 were detected in the hepatopancreas of scallops during toxin accumulation and in the hepatopancreas of mussels during both toxin accumulation and elimination periods. The relative molar ratio of metabolites to precursor molecules was used to estimate relative metabolic conversion rates. Conversion rates of C1/2 and GTX2/3 were higher than those of C3/4 and GTX1/4, in scallops and mussels. The first metabolites observed in both bivalve species investigated were M1/3, which are formed from C1/2. However, the conversion of GTX2/3 to M2 was more complete than other biotransformation reactions in both mussels and scallops. In general, metabolic conversion of PSTs was observed after a shorter time and to a greater extent in mussels than in scallops in the exposure period. No acyl esters or conjugation products of PSTs with glucuronic acid, glutathione, cysteine and taurine were detected by liquid chromatography with high resolution tandem mass spectrometry in the samples investigated. Additionally, only GTX1/4 and GTX2/3 were detected in the kidney of scallops, which demonstrates that PSTs are mainly metabolized through the hepatic metabolism pathway in bivalves. This work improves the understanding of PST metabolism during toxin accumulation and depuration in commercially harvested shellfish.