The preparation of certified calibration solutions for azaspiracid-1, -2, and -3, potent marine biotoxins found in shellfish

Current Research Status of Azaspiracids

The presence and impact of toxins have been detected in various regions worldwide ever since the discovery of azaspiracids (AZAs) in 1995. These toxins have had detrimental effects on marine resource utilization, marine environmental protection, and fishery production. Over the course of more than two decades of research and development, scientists from all over the world have conducted comprehensive studies on the in vivo metabolism, in vitro synthesis methods, pathogenic mechanisms, and toxicology of these toxins. This paper aims to provide a systematic introduction to the discovery, distribution, pathogenic mechanism, in vivo biosynthesis, and in vitro artificial synthesis of AZA toxins. Additionally, it will summarize various detection methods employed over the past 20 years, along with their advantages and disadvantages. This effort will contribute to the future development of rapid detection technologies and the invention of detection devices for AZAs in marine environmental samples.

Preparation and characterization of an immunoaffinity column for the selective extraction of azaspiracids

The presence of azaspiracids (AZAs) in shellfish may cause food poisoning in humans. AZAs can accumulate in shellfish filtering seawater that contains marine dinoflagellates such as Azadinium and Amphidoma spp. More than 60 AZA analogues have been identified, of which AZA1, AZA2 and AZA3 are regulated in Europe. Shellfish matrices may complicate quantitation by ELISA and LC-MS methods. Polyclonal antibodies have been developed that bind specifically to the C-26-C-40 domain of the AZA structure and could potentially be used for selectively extracting compounds containing this substructure. This includes almost all known analogues of AZAs, including AZA1, AZA2 and AZA3. Here we report preparation of immunoaffinity chromatography (IAC) columns for clean-up and concentration of AZAs. The IAC columns were prepared by coupling polyclonal anti-AZA IgG to CNBr-activated sepharose. The columns were evaluated using shellfish extracts, and the resulting fractions were analyzed by ELISA and LC-MS. The columns selectively bound over 300 ng AZAs per mL of gel without significant leakage, and did not retain the okadaic acid, cyclic imine, pectenotoxin and yessotoxin analogues that were present in the applied samples. Furthermore, 90-92% of the AZAs were recovered by elution with 90% MeOH, and the columns could be re-used without significant loss of performance.

Co-localisation of Azaspiracid Analogs with the Dinoflagellate Species Azadinium spinosum and Amphidoma languida in the Southwest of Ireland

Phytoplankton and biotoxin monitoring programmes have been implemented in many countries to protect human health and to mitigate the impacts of harmful algal blooms (HABs) on the aquaculture industry. Several amphidomatacean species have been confirmed in Irish coastal waters, including the azaspiracid-producing species Azadinium spinosum and Amphidoma languida. Biogeographic distribution studies have been hampered by the fact that these small, armoured dinoflagellates share remarkably similar morphologies when observed by light microscopy. The recent releases of species-specific molecular detection assays have, in this context, been welcome developments. A survey of the south west and west coasts of Ireland was carried out in August 2017 to investigate the late summer distribution of toxic amphidomataceans and azaspiracid toxins. Azadinium spinosum and Am. languida were detected in 83% of samples in the southwest along the Crease Line and Bantry Bay transects between 20 and 70 m depth, with maximal cell concentrations of 7000 and 470,000 cells/L, respectively. Azaspiracid concentrations were well aligned with the distributions of Az. spinosum and Am. languida, up to 1.1 ng/L and 4.9 ng/L for combined AZA-1, -2, -33, and combined AZA-38, -39, respectively. Although a snapshot in time, this survey provides new insights in the late summer prominence of AZAs and AZA-producing species in the southwest of Ireland, where major shellfish aquaculture operations are located. Results showed a substantial overlap in the distribution of amphidomatacean species in the area and provide valuable baseline information in the context of ongoing monitoring efforts of toxigenic amphidomataceans in the region.

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.

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.

Effects of Temperature, Growth Media, and Photoperiod on Growth and Toxin Production of Azadinium spinosum

Azaspiracids (AZAs) are microalgal toxins that can accumulate in shellfish and lead to human intoxications. To facilitate their study and subsequent biomonitoring, purification from microalgae rather than shellfish is preferable; however, challenges remain with respect to maximizing toxin yields. The impacts of temperature, growth media, and photoperiod on cell densities and toxin production in Azadinium spinosum were investigated. Final cell densities were similar at 10 and 18 °C, while toxin cell quotas were higher (~3.5-fold) at 10 °C. A comparison of culture media showed higher cell densities and AZA cell quotas (2.5-5-fold) in f10k compared to f/2 and L1 media. Photoperiod also showed differences, with lower cell densities in the 8:16 L:D treatment, while toxin cell quotas were similar for 12:12 and 8:16 L:D treatments but slightly lower for the 16:8 L:D treatment. AZA1, -2 and -33 were detected during the exponential phase, while some known and new AZAs were only detected once the stationary phase was reached. These compounds were additionally detected in field water samples during an AZA event.

Identification of 21,22-Dehydroazaspiracids in Mussels ( Mytilus edulis) and in Vitro Toxicity of Azaspiracid-26

Azaspiracids (AZAs) are marine biotoxins produced by the genera Azadinium and Amphidoma, pelagic marine dinoflagellates that may accumulate in shellfish resulting in human illness following consumption. The complexity of these toxins has been well documented, with more than 40 structural variants reported that are produced by dinoflagellates, result from metabolism in shellfish, or are extraction artifacts. Approximately 34 μg of a new AZA with MW 823 Da (AZA26 (3)) was isolated from blue mussels ( Mytilus edulis), and its structure determined by MS and NMR spectroscopy. AZA26, possibly a bioconversion product of AZA5, lacked the C-20-C-21 diol present in all AZAs reported thus far and had a 21,22-olefin and a keto group at C-23. Toxicological assessment of 3 using an in vitro model system based on Jurkat T lymphocyte cells showed the potency to be ∼30-fold lower than that of AZA1. The corresponding 21,22-dehydro-23-oxo-analogue of AZA10 (AZA28) and 21,22-dehydro analogues of AZA3, -4, -5, -6, -9, and -10 (AZA25, -48 (4), -60, -27, -49, and -61, respectively) were also identified by HRMS/MS, periodate cleavage reactivity, conversion from known analogues, and NMR (for 4 that was present in a partially purified sample of AZA7).

Selective Extraction and Purification of Azaspiracids from Blue Mussels ( Mytilus edulis) Using Boric Acid Gel

Azaspiracids belong to a family of more than 50 polyether toxins originating from marine dinoflagellates such as Azadinium spinosum. All of the azaspiracids reported thus far contain a 21,22-dihydroxy group. Boric acid gel can bind selectively to compounds containing vic-diols or α-hydroxycarboxylic acids via formation of reversible boronate complexes. Here we report use of the gel to selectively capture and release azaspiracids from extracts of blue mussels. Analysis of the extracts and fractions by liquid chromatography-tandem mass spectrometry (LC-MS) showed that this procedure resulted in an excellent cleanup of the azaspiracids in the extract. Analysis by enzyme-linked immunoasorbent assay (ELISA) and LC-MS indicated that most azaspiracid analogues were recovered in good yield by this procedure. The capacity of boric acid gel for azaspiracids was at least 50 μg/g, making this procedure suitable for use in the early stages of preparative purification of azaspiracids. In addition to its potential for concentration of dilute samples, the extensive cleanup provided by boric acid gel fractionation of azaspiracids in mussel samples almost eliminated matrix effects during subsequent LC-MS and could be expected to reduce matrix effects during ELISA analysis. The method may therefore prove useful for quantitative analysis of azaspiracids as part of monitoring programs. Although LC-MS data showed that okadaic acid analogues also bound to the gel, this was much less efficient than for azaspiracids under the conditions used. The boric acid gel methodology is potentially applicable to other important groups of natural toxins containing diols including ciguatoxins, palytoxins, pectenotoxins, tetrodotoxin, trichothecenes, and toxin glycosides.

Absolute Quantification of Lipophilic Shellfish Toxins by Quantitative Nuclear Magnetic Resonance Using Removable Internal Reference Substance with SI Traceability

Okadaic acid (OA), a lipophilic shellfish toxin, was accurately quantified using quantitative nuclear magnetic resonance with internal standards for the development of an authentic reference standard. Pyridine and the residual proton in methanol-d4 were used as removable internal standards to limit any contamination. They were calibrated based on a maleic acid certified reference material. Thus, the concentration of OA was traceable to the SI units through accurate quantitative NMR with an internal reference substance. Signals from the protons on the oxygenated and unsaturated carbons of OA were used for quantification. A reasonable accuracy was obtained by integrating between the lower and upper (13)C satellite signal range when more than 4 mg of OA was used. The best-determined purity was 97.4% (0.16% RSD) when 20 mg of OA was used. Dinophysistoxin-1, a methylated analog of OA having an almost identical spectrum, was also quantified by using the same methodology.

Relative molar response of lipophilic marine algal toxins in liquid chromatography/electrospray ionization mass spectrometry

RATIONALE

Accurate quantitative analysis of lipophilic toxins by liquid chromatography/mass spectrometry (LC/MS) requires calibration solution reference materials (RMs) for individual toxin analogs. Untargeted analysis is aimed at identifying a vast number of compounds and thus validation of fully quantitative untargeted methods is not feasible. However, a semi-quantitative approach allowing for profiling is still required and will be strengthened by knowledge of the relative molar response (RMR) of analogs in LC/MS with electrospray ionization (ESI).

METHODS

RMR factors were evaluated for toxins from the okadaic acid (OA/DTXs), yessotoxin (YTX), pectenotoxin (PTX), azaspiracid (AZA) and cyclic imine (CI) toxin groups, in both solvent standards and environmental sample extracts. Since compound ionization and fragmentation influences the MS response of toxins, RMRs were assessed under different chromatographic conditions (gradient, isocratic) and MS acquisition modes (SIM, SRM, All-ion, target MS/MS) on low- and high-resolution mass spectrometers.

RESULTS

In general, RMRs were not significantly impacted by chromatographic conditions (isocratic vs gradient), with the exception of DTX1. MS acquisition modes had a more significant impact, with PnTX-G and SPX differing notably. For a given toxin group, response factors were generally in the range of 0.5 to 2. The cyclic imines were an exception.

CONCLUSIONS

Differences in RMRs between toxins of a same chemical base structure were not significant enough to indicate major issues for non-targeted semi-quantitative analysis, where there is limited or no availability of standards for many compounds, and where high degrees of accuracy are not required. Differences in RMRs should be considered when developing methods that use a standard of a single analogue to quantitate other toxins from the same group.

Separation and purification of two minor typical diarrhetic shellfish poisoning toxins from harmful marine microalgae via combined liquid chromatography with mass spectrometric detection

A novel method was developed for the purification of two typical diarrhetic shellfish poisoning toxins from toxin-producing marine microalgae using macroporous resin, high-speed countercurrent chromatography-mass spectrometry, and semipreparative high-performance liquid chromatography-mass spectrometry. Analytical high-performance liquid chromatography-mass spectrometry was used for identification and purity analysis of okadaic acid and dinophysistoxin-1 because they exhibit no visible or ultraviolet absorption. First, four kinds of macroporous resins were investigated, and HP-20 macroporous resin was selected for the preenrichment and cleanup of the two target toxins. Second, the resin-purified sample was further purified using high-speed countercurrent chromatography coupled with a mass spectrometer. The purities of the obtained okadaic acid and dinophysistoxin-1 were 89.0 and 83.0%, respectively, as determined through analytical high-performance liquid chromatography-mass spectrometry. Finally, further purification was carried out using semipreparative high-performance liquid chromatography with mass spectrometry, and the purities of the final okadaic acid and dinophysistoxin-1 products were both over 98.0% based on the analytical high-performance liquid chromatography-mass spectrometry chromatograms and fraction spectra. This work demonstrates that the proposed purification process is a powerful method for the preparation of high-purity okadaic acid and dinophysistoxin-1 from toxin-producing marine microalgae. Moreover, it is particularly important for the purification and preparation of minor toxins that exhibit no visible or ultraviolet absorption from harmful marine algae.

Effects of Heating on Proportions of Azaspiracids 1-10 in Mussels (Mytilus edulis) and Identification of Carboxylated Precursors for Azaspiracids 5, 10, 13, and 15

Azaspiracids (AZAs) are marine biotoxins that induce human illness following the consumption of contaminated shellfish. European Union regulation stipulates that only raw shellfish are tested, yet shellfish are often cooked prior to consumption. Analysis of raw and heat-treated mussels (Mytilus edulis) naturally contaminated with AZAs revealed significant differences (up to 4.6-fold) in AZA1-3 (1-3) and 6 (6) values due to heat-induced chemical conversions. Consistent with previous studies, high levels of 3 and 6 were detected in some samples that were otherwise below the limit of quantitation before heating. Relative to 1, in heat-treated mussels the average (n = 40) levels of 3 (range, 11-502%) and 6 (range, 3-170%) were 62 and 31%, respectively. AZA4 (4) (range, <1-27%), AZA5 (5) (range, 1-21%), and AZA8 (8) (range, 1-27%) were each ∼5%, whereas AZA7 (7), AZA9 (9), and AZA10 (10) (range, <1-8%) were each under 1.5%. Levels of 5, 10, AZA13 (13), and AZA15 (15) increased after heating, leading to the identification of novel carboxylated AZA precursors in raw shellfish extracts, which were shown by deuterium labeling to be precursors for 5, 10, 13, and 15.

Isolation, structure elucidation, relative LC-MS response, and in vitro toxicity of azaspiracids from the dinoflagellate Azadinium spinosum

We identified three new azaspiracids (AZAs) with molecular weights of 715, 815, and 829 (AZA33 (3), AZA34 (4), and AZA35, respectively) in mussels, seawater, and Azadinium spinosum culture. Approximately 700 μg of 3 and 250 μg of 4 were isolated from a bulk culture of A. spinosum, and their structures determined by MS and NMR spectroscopy. These compounds differ significantly at the carboxyl end of the molecule from known AZA analogues and therefore provide valuable information on structure-activity relationships. Initial toxicological assessment was performed using an in vitro model system based on Jurkat T lymphocyte cytotoxicity, and the potencies of 3 and 4 were found to be 0.22- and 5.5-fold that of AZA1 (1), respectively. Thus, major changes in the carboxyl end of 1 resulted in significant changes in toxicity. In mussel extracts, 3 was detected at low levels, whereas 4 and AZA35 were detected only at extremely low levels or not at all. The structures of 3 and 4 are consistent with AZAs being biosynthetically assembled from the amino end.

A mussel (Mytilus edulis) tissue certified reference material for the marine biotoxins azaspiracids

Azaspiracids (AZAs) are lipophilic biotoxins produced by marine algae that can contaminate shellfish and cause human illness. The European Union (EU) regulates the level of AZAs in shellfish destined for the commercial market, with liquid chromatography-mass spectrometry (LC-MS) being used as the official reference method for regulatory analysis. Certified reference materials (CRMs) are essential tools for the development, validation, and quality control of LC-MS methods. This paper describes the work that went into the planning, preparation, characterization, and certification of CRM-AZA-Mus, a tissue matrix CRM, which was prepared as a wet homogenate from mussels (Mytilus edulis) naturally contaminated with AZAs. The homogeneity and stability of CRM-AZA-Mus were evaluated, and the CRM was found to be fit for purpose. Extraction and LC-MS/MS methods were developed to accurately certify the concentrations of AZA1 (1.16 mg/kg), AZA2 (0.27 mg/kg), and AZA3 (0.21 mg/kg) in the CRM. Quantitation methods based on standard addition and matrix-matched calibration were used to compensate for the matrix effects in LC-MS/MS. Other toxins present in this CRM at lower levels were also measured with information values reported for okadaic acid, dinophysistoxin-2, yessotoxin, and several spirolides.

Epimers of azaspiracids: Isolation, structural elucidation, relative LC-MS response, and in vitro toxicity of 37-epi-azaspiracid-1

Since azaspiracid-1 (AZA1) was identified in 1998, the number of AZA analogues has increased to over 30. The development of an LC-MS method using a neutral mobile phase led to the discovery of isomers of AZA1, AZA2, and AZA3, present at ~2-16% of the parent analogues in phytoplankton and shellfish samples. Under acidic mobile phase conditions, isomers and their parents are not separated. Stability studies showed that these isomers were spontaneous epimerization products whose formation is accelerated with the application of heat. The AZA1 isomer was isolated from contaminated shellfish and identified as 37-epi-AZA1 by nuclear magnetic resonance (NMR) spectroscopy and chemical analyses. Similar analysis indicated that the isomers of AZA2 and AZA3 corresponded to 37-epi-AZA2 and 37-epi-AZA3, respectively. The 37-epimers were found to exist in equilibrium with the parent compounds in solution. 37-epi-AZA1 was quantitated by NMR, and relative molar response studies were performed to determine the potential differences in LC-MS response of AZA1 and 37-epi-AZA1. Toxicological effects were determined using Jurkat T lymphocyte cells as an in vitro cell model. Cytotoxicity experiments employing a metabolically based dye (i.e., MTS) indicated that 37-epi-AZA1 elicited a lethal response that was both concentration- and time-dependent, with EC50 values in the subnanomolar range. On the basis of EC50 comparisons, 37-epi-AZA1 was 5.1-fold more potent than AZA1. This data suggests that the presence of these epimers in seafood products should be considered in the analysis of AZAs for regulatory purposes.

Study of possible combined toxic effects of azaspiracid-1 and okadaic acid in mice via the oral route

Toxins from the okadaic acid (OA) and azaspiracid (AZA) group cause considerable negative health effects in consumers when present in shellfish above certain levels. The main symptoms, dominated by diarrhoea, are caused by damage to the gastrointestinal (GI) tract. Even though OA and AZAs exert toxicity via different mechanisms, it is important to find out whether they may enhance the health effects if present together since they act on the same organs and are regulated individually. In this study, the main issue was the possibility of enhanced lethality in mice upon combined oral exposure to OA and AZA1. In addition, pathological effects in several organs and effects on absorption from the GI tract were studied. Although the number of mice was small due to low availability of AZA1, the results indicate no additive or synergistic effect on lethality when AZA1 and OA were given together. Similar lack of increased toxicity was observed concerning pathological effects that were restricted to the GI-tract. OA and AZA1 were absorbed from the GI-tract to a very low degree, and when given together, uptake was reduced. Taken together, these results indicate that the present practice of regulating toxins from the OA and AZA group individually does not present an unwanted increased risk for consumers of shellfish.

Production and isolation of azaspiracid-1 and -2 from Azadinium spinosum culture in pilot scale photobioreactors

Azaspiracid (AZA) poisoning has been reported following consumption of contaminated shellfish, and is of human health concern. Hence, it is important to have sustainable amounts of the causative toxins available for toxicological studies and for instrument calibration in monitoring programs, without having to rely on natural toxin events. Continuous pilot scale culturing was carried out to evaluate the feasibility of AZA production using Azadinium spinosum cultures. Algae were harvested using tangential flow filtration or continuous centrifugation. AZAs were extracted using solid phase extraction (SPE) procedures, and subsequently purified. When coupling two stirred photobioreactors in series, cell concentrations reached 190,000 and 210,000 cell·mL⁻¹ at steady state in bioreactors 1 and 2, respectively. The AZA cell quota decreased as the dilution rate increased from 0.15 to 0.3 day⁻¹, with optimum toxin production at 0.25 day⁻¹. After optimization, SPE procedures allowed for the recovery of 79 ± 9% of AZAs. The preparative isolation procedure previously developed for shellfish was optimized for algal extracts, such that only four steps were necessary to obtain purified AZA1 and -2. A purification efficiency of more than 70% was achieved, and isolation from 1200 L of culture yielded 9.3 mg of AZA1 and 2.2 mg of AZA2 of >95% purity. This work demonstrated the feasibility of sustainably producing AZA1 and -2 from A. spinosum cultures.

Improved isolation procedure for azaspiracids from shellfish, structural elucidation of azaspiracid-6, and stability studies

Azaspiracids are a group of lipophilic polyether toxins produced by the small dinoflagellate Azadinium spinosum. They may accumulate in shellfish and can result in illnesses when consumed by humans. Research into analytical methods, chemistry, metabolism, and toxicology of azaspiracids has been severely constrained by the scarcity of high-purity azaspiracids. Consequently, since their discovery in 1995, considerable efforts have been made to develop methods for the isolation of azaspiracids in sufficient amounts and purities for toxicological studies, in addition to the preparation of standard reference materials. A seven-step procedure was improved for the isolation of azaspiracids-1-3 (1, 2, and 3) increasing recoveries 2-fold as compared to previous methods and leading to isolation of sufficiently purified azaspiracid-6 (6) for structural determination by NMR spectroscopy. The procedure, which involved a series of partitioning and column chromatography steps, was performed on 500 g of Mytilus edulis hepatopancreas tissue containing ~14 mg of 1. Overall yields of 1 (52%), 2 (43%), 3 (43%), and 6 (38%) were good, and purities were confirmed by NMR spectroscopy. The structure of 6 was determined by one- and two-dimensional NMR spectroscopy and mass spectrometry. The stability of 6 relative to 1 was also assessed in three solvents in a short-term study that demonstrated the greatest stability in aqueous acetonitrile.

Combined oral toxicity of azaspiracid-1 and yessotoxin in female NMRI mice

For many years, the presence of yessotoxins (YTXs) in shellfish has contributed to the outcome of the traditional mouse bioassay and has on many occasions caused closure of shellfisheries. Since YTXs do not appear to cause diarrhoea in man and exert low oral toxicity in animal experiments, it has been suggested that they should be removed from regulation. Before doing so, it is important to determine whether the oral toxicity of YTXs is enhanced when present together with shellfish toxins known to cause damage to the gastrointestinal tract. Consequently, mice were given high doses of YTX, at 1 or 5 mg/kg body weight, either alone or together with azaspiracid-1 (AZA1) at 200 μg/kg. The latter has been shown to induce damage to the small intestine at this level. The combined exposure caused no clinical effects, and no pathological changes were observed in internal organs. These results correspond well with the very low levels of YTX detected in internal organs by means of LC-MS/MS and ELISA after dosing. Indeed, the very low absorption of YTX when given alone remained largely unchanged when YTX was administered in combination with AZA1. Thus, the oral toxicity of YTX is not enhanced in the presence of sub-lethal levels of AZA1.

Screening for multiple classes of marine biotoxins by liquid chromatography-high-resolution mass spectrometry

Marine biotoxins pose a significant food safety risk when bioaccumulated in shellfish, and adequate testing for biotoxins in shellfish is required to ensure public safety and long-term viability of commercial shellfish markets. This report describes the use of a benchtop Orbitrap system for liquid chromatography-mass spectrometry (LC-MS) screening of multiple classes of biotoxins commonly found in shellfish. Lipophilic toxins such as dinophysistoxins, pectenotoxins, and azaspiracids were separated by reversed phase LC in less than 7 min prior to MS data acquisition at 2 Hz with alternating positive and negative scans. This approach resulted in mass accuracy for analytes detected in positive mode (gymnodimine, 13-desmethyl spirolide C, pectenotoxin-2, and azaspiracid-1, -2, and -3) of less than 1 ppm, while those analytes detected in negative mode (yessotoxin, okadaic acid, and dinophysistoxin-1 and -2) exhibited mass errors between 2 and 4 ppm. Hydrophilic toxins such as domoic acid, saxitoxin, and gonyautoxins were separated by hydrophilic interaction LC (HILIC) in less than 4 min, and MS data was collected at 1 Hz in positive mode, yielding mass accuracy of less than 1 ppm error at a resolving power of 100,000 for the analytes studied (m/z 300-500). Data were processed by extracting 5 ppm mass windows centered around the calculated masses of the analytes. Limits of detection (LOD) for the lipophilic toxins ranged from 0.041 to 0.10 μg/L (parts per billion) for the positive ions, 1.6-5.1 μg/L for those detected in negative mode, while the domoic acid and paralytic shellfish toxins yielded LODs ranging from 3.4 to 14 μg/L. Toxins were detected in mussel tissue extracts free of interference in all cases.