Macrocyclic-, polycyclic-, and nitro musks in cosmetics, household commodities and indoor dusts collected from Japan: implications for their human exposure

This paper reported the occurrence and concentrations of macrocyclic-, polycyclic- and nitro musks in cosmetics and household commodities collected from Japan. The high concentrations and detection frequencies of Musk T, habanolide, and exaltolides were found in commercial products, suggesting their large amounts of production and usage in Japan. Polycyclic musks, HHCB and OTNE, also showed high concentrations in cosmetics and products. The estimated dairy intakes of Musk T and HHCB by the dermal exposure to commercial products were 7.8 and 7.9 μg/kg/day in human, respectively, and perfume and body lotion are dominant exposure sources. We also analyzed synthetic musks in house dusts. Polycyclic musks, HHCB and OTNE, showed high concentrations in samples, but macrocyclic musks were detected only in a few samples, although these types of musks were highly detected in commercial products. This is probably due to easy-degradation of macrocyclic musks in indoor environment. The dairy intakes of HHCB by dust ingestions were 0.22 ng/kg/day in human, which were approximately five orders of magnitudes lower than those of dermal absorption from commercial household commodities.

A sensitive LC-MS/MS assay for brevisulcenal and brevisulcatic acid toxins produced by the dinoflagellate Karenia brevisulcata

A toxic dinoflagellate, Karenia brevisulcata, devastated almost all marine life in Wellington Harbour, New Zealand during the late summer of 1998. Brevisulcatic acids (BSXs) and brevisulcenals (KBTs), both polycyclic ether toxins, have been identified as the causative agents. A liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the sensitive and specific determination of BSXs and KBTs in culture medium, seawater and shellfish. Acidified algal culture, or seawater, was extracted using reverse phase solid phase extraction cartridges. Shellfish tissue homogenate was blended with methanol-water (9:1) and partitioned with hexane to remove non-polar lipids. This extraction protocol is similar to that used for analysis of lipophilic shellfish toxins. LC-MS/MS (triple quadrupole) was used for quantitative analysis with gradient elution (acidic buffer), positive electrospray ionization and multiple-reaction monitoring. Purified toxins were available for 4 KBTs (KBT-F, -G, -H and -I) and 4 BSXs (-1, -2, -4, and -5), and were used to calibrate the instrument responses. Relative response factors were used for semi-quantitative analysis of BSX-3 and BSX-6, using BSX-1 and BSX-4 respectively. Calibration curves for all toxins monitored were linear over the concentration range tested (5-200 ng mL(-1)) with r(2) values >0.99. The method limit of quantitation was determined to be 2 ng mL(-1) for BSXs and KBTs, except KBT-I, which was 5 ng mL(-1). Validation data was generated for culture medium and shellfish. Toxin recoveries were typically >70% with relative standard deviations <20% across all of the matrices tested. In addition, toxins specific to K. brevisulcata were able to be detected in seawater at a cell concentration of 10,000 cells L(-1), which represents the suggested trigger level for this harmful algal species. This method shows suitable performance characteristics to be regarded a useful tool to monitor toxin levels in a variety of sample matrices during future bloom events.

Advanced studies for the application of high-performance capillary electrophoresis for the analysis of yessotoxin and 45-hydroxyyessotoxin

Yessotoxins (YTXs) are a group of polyether toxins which have been previously reported as responsible for seafood contamination in several places worldwide. Despite their toxicity, which is not yet fully discussed, YTXs have been reported as an interference in the success of mouse bioassay for the determination of diarrhetic shellfish poisoning (DSP) toxins, and therefore, efficient and reliable analytical methodologies are required to evaluate their presence, avoiding false positives for DSP. High-performance capillary electrophoresis (HPCE) is presented in this work as an alternative to HPLC technique widely used for the analysis of YTXs. Improvements in the applicability of HPCE have been carried out through the development of different CE modes as well as different detection modes. With this aim, micellar electrokinetic chromatography (MEKC) has been considered for an increased selectivity while an increased sensitivity was achieved by using sample stacking. Moreover, the coupling of CE with mass spectrometry allowed the confirmation of YTXs present in the contaminated samples evaluated in this work. The results obtained showed the potential of CE as an alternative to HPLC for the analysis of YTXs present in naturally contaminated samples.

Extraction and cleaning methods to detect yessotoxins in contaminated mussels

Yessotoxin (YTX) and its analogues are a newly recognized group of toxins with increased presence in shellfish in recent years. They can be quantified by various functional assays due to their interaction with phosphodiesterases (PDEs). One of these assays detects the binding between the YTX and the fluorescently labeled PDE I using fluorescence polarization, a spectroscopic technique based on exciting a fluorescent molecule with plane-polarized light and measuring the polarization degree of the emitted light. The aim of this study was to develop a YTX extraction procedure from mussels that does not interfere with this detection method. YTX concentrations were measured in spiked mussel extracts obtained through use of different extraction methods and cleaning procedures. The percentages of toxin recovery in various steps of the processes were calculated using these concentrations. Six extraction methods and two cleaning steps were used and no matrix effects and high toxin recoveries were obtained in two cases. One case used acetone as extraction solvent followed by three dichloromethane partitions and the other case used methanol. The cleaning procedure includes a silica cartridge and a 10,000 NMWL filter. Finally these two extraction-cleaning-detection methods were applied to a naturally contaminated mussel sample and results showed that not only YTX but also homoYTX and hydroxyYTX can be quantified with a 85-90% recovery.

Feasibility of gamma irradiation as a stabilisation technique in the preparation of tissue reference materials for a range of shellfish toxins

The effect of gamma-irradiation on concentrations of hydrophilic and lipophilic phycotoxins has been investigated by use of HPLC-UV and LC-MS. Pure toxins in organic solvents and toxins in mussel (Mytilus edulis) tissues were irradiated at three different doses. In solution all toxin concentrations were reduced to some extent. Most severe decreases were observed for domoic acid and yessotoxin, for which the smallest dose of irradiation led to almost complete destruction. For pectenotoxin-2 the decrease in concentration was less severe but still continuous with increasing dose. Azaspiracid-1 and okadaic acid were the least affected in solution. In shellfish tissue the decrease in toxin concentrations was much reduced compared with the effect in solution. After irradiation at the highest dose reductions in concentrations were between ca. 5 and 20% for the lipophilic toxins and there was no statistical difference between control and irradiated samples for azaspiracids in tissue. Irradiation of shellfish tissues contaminated with domoic acid led to a more continuous decrease in the amount of the toxin with increasing dose. The effect of irradiation on the viability of microbial activity in shellfish tissues was assessed by using total viable counting techniques. Microbial activity depended on the type of shellfish and on the pretreatment of the shellfish tissues (with or without heat treatment). As far as we are aware this is the first investigation of the effectiveness of irradiation as a technique for stabilising tissue reference materials for determination of phycotoxins. Our results suggest that this technique is not effective for materials containing domoic acid. It does, however, merit further investigation as a stabilisation procedure for preparation of shellfish tissue materials for some lipophilic toxins, in particular azaspiracids. Chemical structures of the toxins investigated in the study.

Detection and identification of glycoyessotoxin A in a culture of the dinoflagellate Protoceratium reticulatum

The toxin composition of a culture of the dinoflagellate Protoceratium reticulatum was investigated using LC-FLD, after derivatization with DMEQ-TAD (4-(2-(6,7-dimethoxy-4-methyl-3-oxo-3,4-dihydroquinoxalimylethyl)-1,2,4-triazoline-3,5-dione)). Besides yessotoxin (YTX), the new YTX analogue, glycoyessotoxin A (G-YTXA) was detected in culture medium as well as in cells. The conditions for extraction were optimized and the production profile established. Retention time of the resulting fluorescent G-YTXA adduct was identified by comparison of the appropriate standard. Additionally, both G-YTXA and the DMEQ-TAD-G-YTXA adduct were confirmed by LC-MS showing ion peaks at m/z 1273 [M-2Na+H](-) and m/z 1618 [M-2Na+H](-), respectively. The LC-MS(n) displayed a fragmentation pattern similar to that of the YTX series.

Study of the effect of temperature, irradiance and salinity on growth and yessotoxin production by the dinoflagellate Protoceratium reticulatum in culture by using a kinetic and factorial approach

A complete first order orthogonal plan was used to optimize the growth and the production of yessotoxin (YTX) by the dinoflagellate Protoceratium reticulatum in culture by controlling salinity, temperature and irradiance. Initially, an approach to the kinetic data of cellular density and YTX production for each one of the experimental design conditions was performed. The P. reticulatum growth and YTX production were fitted to logistical equations and to a first-order kinetic model, respectively. The parameters obtained from this adjustment were used as dependent variables for the formulation of the empirical equations of the factorial design tested. The results showed that in practically all the cases for both, P. reticulatum growth and YTX production, irradiance is the primary independent variable and has a positive effect in the range 50-90 micromol photons m(-2) s(-1). Additionally, in certain specific cases, temperature reveals significant positive effects when maintained between 15 and 23 degrees C and salinity in the range of 20-34 displays negative effects. Despite the narrow ranges used in the work, results showed the suitability of factorial analysis to evaluate the optimal conditions for growth and yessotoxin production by the dinoflagellate P. reticulatum.

[Lipophilic toxin profiles associated with diarrhetic shellfish poisoning in scallops, Patinopecten yessoensis, collected in Hokkaido and comparison of the quantitative results between LC/MS and mouse bioassay]

Lipophilic toxins associated with diarrhetic shellfish poisoning (DSP) in scallops, Patinopecten yessoensis, collected in Hokkaido, Japan were quantified by liquid chromatography-mass spectrometry (LC/MS). Pectenotoxin-6 (PTX6) and yessotoxin (YTX) were the dominant toxins in the scallops, although the percentages of these toxins were different depending on the production area or the sampling period. The quantitative results obtained for the scallops in LC/MS and in mouse bioassay (MBA) were compared. Fifty of the 55 samples found to be exceeding the local quarantine level (0.025 MU/g whole meat) in Hokkaido by LC/MS were quantified by MBA as being below the quarantine level. It is suggested that this discrepancy is due to poor detection of YTX by MBA. These results indicate that LC/MS is a better method than MBA in terms of sensitivity and accuracy to quantify known lipophilic toxins, including YTX.

Systematic Assignment of the Configuration of Flexible Natural Products by Spectroscopic and Computational Methods: The Bistramide C Analysis

[reaction: see text] The combination of NMR NOE, chemical shift, and J-coupling measurements with molar rotation and circular dichroism (CD) determinations, including RI-DFT BP86/aug-cc-pVDZ calculations, reduced a candidate pool of 1024 possible stereoisomers of (+)-bistramide C to a single absolute configuration assignment for the 10 stereogenic carbons of the marine natural product.

Liquid chromatography with mass spectrometry--detection of lipophilic shellfish toxins

A rapid multiple toxin method based on liquid chromatography with mass spectrometry (LC/MS) was developed for the detection of okadaic acid (OA), dinophysistoxin-1 (DTX-1), DTX-2, yessotoxin (YTX), homoYTX, 45-hydroxy-YTX, 45-hydroxyhomo-YTX, pectenotoxin-1 (PTX-1), PTX-2, azaspiracid-1 (AZA-1), AZA-2, and AZA-3. Toxins were extracted from shellfish using methanol-water (80%, v/v) and were analyzed using a C8 reversed-phase column with a 5 mM ammonium acetate-acetonitrile mobile phase under gradient conditions. The method was validated for the quantitative detection of OA, YTX, PTX-2, and AZA-1 in 4 species (mussels, Mytilus edulis; cockles, Cerastoderma edule; oysters, Crassostrea gigas; king scallop, Pecten maximus) of shellfish obtained from United Kingdom (UK) waters. Matrix interferences in the determination of the toxins in these species were investigated. The validated linear range of the method was 13-250 microg/kg for OA, PTX-2, and AZA-1 and 100-400 microg/kg for YTX. Recovery and precision ranged between 72-120 and 1-22%, respectively, over a fortification range of 40-160 microg/kg for OA, PTX-2, and AZA-1 and 100-400 microg/kg for YTX. The limit of detection, reproducibility, and repeatability of analysis showed acceptable performance characteristics. A further LC/MS method using an alkaline hydrolysis step was assessed for the detection of OA, DTX-1, and DTX-2 in their esterified forms. In combination with the LC/MS multiple toxin method, this allows detection of all toxin groups described in Commission Decision 2002/225/EC.

Quantification of yessotoxin using the fluorescence polarization technique and study of the adequate extraction procedure

Yessotoxin (YTX) is a polycyclic ether toxin produced by phytoplanktonic microalgae from the group of dinoflagellates. It has been shown that YTX increases the 3',5'-cyclic nucleotide phosphodiesterases (PDEs) activity and that there is a binding between these proteins and the toxin. Fluorescence polarization (FP) is a spectroscopic technique that can be used to study the interactions between molecules. It is based on exciting a fluorescent molecule with plane-polarized light and measuring the polarization degree of the emitted light. In this study, the FP is applied to the study of the interaction between YTX and phosphodiesterases I and II (PDE I and II). The phosphodiesterases are labeled with a reactive succinimidyl esther of carboxyfluorescein, and the FP of the protein-dye conjugate is measured when the YTX concentration in the medium increases. The results show that in both cases the fluorescence polarization of the conjugates decreases when they bind to YTX. For the PDE I, it is possible to draw a Gaussian curve or a straight line that relates the two variables (FP and YTX concentration). The concentration of this toxin in a spiked mussel extract (which contains the conjugate) can be quantified measuring its FP and using the equations of those lines. Different extraction methods are tried in this study, and those that can be used to obtain an appropriate mussel extract to be quantified with this technique are determined.

Persistence of yessotoxin under light and dark conditions

The change in concentration of the disulfated polyether yessotoxin (YTX) produced by a culture of the marine dinoflagellate Protoceratium reticulatum was measured in laboratory experiments under light and dark conditions. Experimental cultures were inoculated and grew at a growth rate of 0.14 d(-1) until stationary phase was reached, after approximately 21 days. Cultures were maintained in the stationary phase until 31 days after inoculation. Cells of P. reticulatum contained a concentration of approximately 10-15 pg YTX cell(-1) during stationary phase but this was considerably lower (<5 pg cell-1) during the growth phase. Low amounts of 45-hydroxy-YTX were also detected. At day 32, P. reticulatum was killed by cooling to 1 degrees C (confirmed microscopically) and YTX concentrations were measured periodically under light and dark conditions. YTX concentrations decreased rapidly to approximately 10% of the initial concentration within the first 3 days and depleted to near zero within a week in the light treatment. In the dark environment, YTX persisted longer with approximately 10% of the initial YTX concentration still remaining after 18 days.

Comparison of ELISA and LC-MS analyses for yessotoxins in blue mussels (Mytilus edulis)

Blue mussels (Mytilus edulis) collected from Flødevigen Bay, Norway, in 2001 and 2002 were analysed for yessotoxins (YTXs) by ELISA and yessotoxin (YTX), 45-hydroxyYTX, and carboxyYTX by LC-MS. Results from the two methods were compared to evaluate the ELISA. The response in the ELISA was 3-13 times higher than LC-MS, probably due to the antibodies binding to other YTX analogues not included in the LC-MS analysis. Nevertheless, the correlation between ELISA and LC-MS was good, with r2 values> or =0.8. The results indicate that the ELISA is a reliable method for estimating the total level of YTXs in mussels, and are consistent with extensive metabolism of algal YTXs in mussels. YTX was a minor component in the blue mussels at all times compared to 45-hydroxyYTX and especially carboxyYTX, except when the P. reticulatum bloom occurred. The results also indicate the presence of significant amounts of YTX analogues in addition to those measured by LC-MS. All samples below 4 mg/kg by ELISA were below the current EU regulatory limit of 1 mg/kg by LC-MS. Therefore, we propose using ELISA as a screening tool with a cut-off limit at 4 mg/kg for negative samples, whereas samples above this limit would be reanalyzed by LC-MS.

Multiresidue method for determination of algal toxins in shellfish: single-laboratory validation and interlaboratory study

A method that uses liquid chromatography with tandem mass spectrometry (LC/MS/MS) has been developed for the highly sensitive and specific determination of amnesic shellfish poisoning toxins, diarrhetic shellfish poisoning toxins, and other lipophilic algal toxins and metabolites in shellfish. The method was subjected to a full single-laboratory validation and a limited interlaboratory study. Tissue homogenates are blended with methanol-water (9 + 1), and the centrifuged extract is cleaned up with a hexane wash. LC/MS/MS (triple quadrupole) is used for quantitative analysis with reversed-phase gradient elution (acidic buffer), electrospray ionization (positive and negative ion switching), and multiple-reaction monitoring. Ester forms of dinophysis toxins are detected as the parent toxins after hydrolysis of the methanolic extract. The method is quantitative for 6 key toxins when reference standards are available: azaspiracid-1 (AZA1), domoic acid (DA), gymnodimine (GYM), okadaic acid (OA), pectenotoxin-2 (PTX2), and yessotoxin (YTX). Relative response factors are used to estimate the concentrations of other toxins: azaspiracid-2 and -3 (AZA2 and AZA3), dinophysis toxin-1 and -2 (DTX1 and DTX2), other pectenotoxins (PTX1, PTX6, and PTX11), pectenotoxin secoacid metabolites (PTX2-SA and PTX11-SA) and their 7-epimers, spirolides, and homoYTX and YTX metabolites (45-OHYTX and carboxyYTX). Validation data have been gathered for Greenshell mussel, Pacific oyster, cockle, and scallop roe via fortification and natural contamination. For the 6 key toxins at fortification levels of 0.05-0.20 mg/kg, recoveries were 71-99% and single laboratory reproducibilities, relative standard deviations (RSDs), were 10-24%. Limits of detection were <0.02 mg/kg. Extractability data were also obtained for several toxins by using successive extractions of naturally contaminated mussel samples. A preliminary interlaboratory study was conducted with a set of toxin standards and 4 mussel extracts. The data sets from 8 laboratories for the 6 key toxins plus DTX1 and DTX2 gave within-laboratories repeatability (RSD(R)) of 8-12%, except for PTX-2. Between-laboratories reproducibility (RSDR) values were compared with the Horwitz criterion and ranged from good to adequate for 7 key toxins (HorRat values of 0.8-2.0).

Yessotoxins in Norwegian blue mussels (Mytilus edulis): uptake from Protoceratium reticulatum, metabolism and depuration

The Protoceratium reticulatum cell density at Flodevigen reached a maximum of 2200 cells/L on 16 May 2001. The levels of yessotoxins (YTXs) in blue mussels (Mytilus edulis) at the same site increased sharply by 14 May and peaked on 28 May, after which they steadily declined. No other algal species present showed a similar pattern of correspondence. Together with the recent finding that Norwegian strains of P. reticulatum produce YTXs, these results indicate that P. reticulatum causes yessotoxin (YTX) contamination of shellfish in Norway, and that only relatively low cell densities are necessary for this to occur. The mussels from Flodevigen were analyzed by LC-MS for YTX, 45-hydroxyYTX, carboxyYTX, and a new yessotoxin believed to be 45-hydroxycarboxyYTX, and by ELISA for YTXs. The seasonal variations in toxin content versus time measured by the two methods were qualitatively very similar, although the response in the ELISA was 3-9 times higher due to the antibodies detecting other YTXs that were not detected by the LC-MS method. Changes in the LC-MS profile for YTXs, and in the ratio of YTXs by LC-MS to YTXs by ELISA with time, were consistent with extensive metabolism of YTX in the mussels. Kinetic analysis of the LC-MS data showed an initial half-life of 20 days for YTX, and for YTX+45-hydroxyYTX, in the mussels. Similar analysis of the ELISA data gave a half-life of 24 days for YTXs. The depuration rate remained consistent over a 3-month period during which the temperature remained at 13-16 degrees C.

Solid phase adsorption toxin tracking (SPATT): a new monitoring tool that simulates the biotoxin contamination of filter feeding bivalves

A simple and sensitive in situ method for monitoring the occurrence of toxic algal blooms and shellfish contamination events has been developed. The technique involves the passive adsorption of biotoxins onto porous synthetic resin filled sachets (SPATT bags) and their subsequent extraction and analysis. The success of the method is founded on the observation that during algal blooms significant amounts of toxin, including the low polarity lipophilic compounds such as the pectenotoxins and the okadaic acid complex toxins, are dissolved in the seawater. The results of field trials during Dinophysis acuminata and Protoceratium reticulatum blooms are presented. These data prove the concept and demonstrate that the technique provides a means of forecasting shellfish contamination events and predicting the net accumulation of polyether toxins by mussels. As an early warning method it has many advantages over current monitoring techniques such as shellfish-flesh testing and phytoplankton monitoring. In contrast to the circumstantial evidence provided by genetic probe technologies and conventional phytoplankton monitoring methods, it directly targets the toxic compounds of interest. The extracts that are obtained for analysis lack many of the extraneous lipophilic materials in crude shellfish extracts so that many of the matrix problems associated with chemical and biological analysis of these extracts are eliminated. Analyses can confidently target parent compounds only, because analytical and toxicological uncertainties associated with the multiplicity of toxin analogues produced by in vivo biotransformation in shellfish tissues are reduced. Time integrated sampling provides a good simulation of biotoxin accumulation in filter feeders and the high sensitivity provides lengthy early warning and conservative estimates of contamination potential. The technique may reduce monitoring costs and provide improved spatial and temporal sampling opportunities. When coupled with appropriate analytical techniques (e.g. LC-MS/MS multi-toxin screens, ELISA assays, receptor binding assays), the technique has the potential to offer a universal early warning method for marine and freshwater micro-algae toxins.

Studies of polyether toxins in the marine phytoplankton, Dinophysis acuta, in Ireland using multiple tandem mass spectrometry

Diarretic shellfish poisoning (DSP) is a toxic syndrome associated with the consumption of bivalve molluscs. The DSP toxins are polyether compounds, which include okadaic acid (OA), dinophysistoxins (DTXs), pectenotoxins (PTXs) and pectenotoxin seco acids (PTX2SAs). These toxins originate in marine dinoflagellates, including Dinophysis spp. Phytoplankton samples were collected from the southwest coast of Ireland and D. acuta was the predominant species. Monocultures of D. acuta cells were prepared by hand picking from microscope slides in order to confirm their toxin profiles. There was a remarkable consistency in the toxin profiles in all of the phytoplankton samples collected during the summer months, irrespective of location, depth or mesh size. Analysis using liquid chromatography-multiple tandem mass spectrometry (LC-MS/MS) revealed that DTX2 and OA were the predominant toxins at a consistent ratio. The average toxin composition was: DTX2 (53+/-5%), OA (26.5+/-2.3%) and total pectenotoxins (20.8+/-4.7%). Toxin profiles in D. acuta from Europe were distinctly different from those found in New Zealand, where PTX2 was the predominant toxin and DTX2 was absent.

Nano liquid chromatography with hybrid quadrupole time-of-flight mass spectrometry for the determination of yessotoxin in marine phytoplankton

Studies of yessotoxin involving confirmation of fragmentation processes using a high-resolution orthogonal hybrid quadrupole time-of-flight (QqTOF) mass spectrometer and nanoLC hybrid quadrupole TOF MS have been undertaken. The fragmentation of YTX was studied in negative mode using nano electrospray (nanoESI) QqTOF mass spectrometry. Three major molecule-related ions were observed, [M - 2Na + H]-, [M - Na]- and [M - 2Na]2-, and fragmentation of the latter was studied in detail. This showed that product ions were formed as a consequence of charge-remote fragmentation processes that included a strong directional cleavage of the polyether rings of YTX. NanoLC coupled with QqTOF MS was used to determine YTX in small samples of the phytoplankton, Protoceratium reticulatum, by monitoring the [M - 2Na]2- ion at m/z 570. A PepMap C18 nanoLC column (75 microm x 10 cm, 100 A, 3 microm, LC Packings) was used and the solvent was acetonitrile/water (90:10 (v/v)) containing 1 mM ammonium acetate, at a flow rate of 400 nl/min, for 30 min. Calibrations obtained with YTX standard solutions were linear over four orders of magnitude, 0.75-250 ng/ml; r2 = 0.9947-0.9998. Phytoplankton cells (ca. 100-300) were picked, extracted with methanol/water (40:60), and the YTX concentration was determined over the range 0.011-0.020 ng/cell. The detection limit (3 x S/N) of this method was ca. 0.5 pg YTX on-column.

Enzyme-linked immunosorbent assay for the detection of yessotoxin and its analogues

Polyclonal antibodies were produced for the development of competitive enzyme-linked immunoassays for use in quantifying yessotoxins in shellfish, algal cells, and culture supernatants. Immunizing and plate coating antigens were prepared by derivatization of yessotoxin either by ozonolysis or bromination and conjugation to proteins. Two assays that were the most sensitive for yessotoxin were optimized and characterized. Cross-reactivity studies indicated that the antibodies raised have broad specificity and that binding to analogues was strongly affected by changes to the A-ring and, to a lesser extent, the K-ring regions of the toxin molecule. ELISA provides a sensitive and rapid analytical method that is suitable for screening large numbers of samples and detects all the yessotoxin analogues that the European Commission currently requires shellfish to be tested for. The assay limit of quantitation for yessotoxin in whole shellfish flesh is 75 microg/kg; therefore, assay sensitivity is sufficient to measure toxin levels well below the maximum permitted level set by the European Commission. The antibodies produced can be used in additional applications such as the immunolocalization of yessotoxins in shellfish and preparation of immunoaffinity columns.

A rapid microplate fluorescence method to detect yessotoxins based on their capacity to activate phosphodiesterases

This paper describes an easy and fast assay with enough sensitivity to detect yessotoxin (YTX) in shellfish samples. YTX decreases intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels by increasing the activity of phosphodiesterases (PDEs). Looking for new methods to detect YTXs, we developed a technique based on this effect. We use the fluorescent derivative of cAMP, anthranyloyl-cAMP, whose fluorescence decreases in time by hydrolysis effect of PDEs. The fluorescence fall is quantified in a plate reader. PDEs induce an anthranyloyl-cAMP hydrolysis rate that is increased in the presence of YTX. This effect is dose dependent, and the representation of YTX concentration versus rate of hydrolysis follows a lineal regression. The measurable range of YTX in this assay is 0.1 to 10microM, while by mouse bioassay, the official method to detect YTXs, the detection limit is 2microM. We determined by this method the concentration of YTX from alcoholic extracts whose concentrations were first determined by high performance liquid chromatography and the variation of concentration was from 5.26microM by fluorescence to 6microM by high performance liquid chromatography and from 3.16 by fluorescence to 3microM by HPLC.

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.

Development of a F actin-based live-cell fluorimetric microplate assay for diarrhetic shellfish toxins

A new cytotoxicity assay for detection and quantitation of diarrhetic shellfish toxins (DSP) is presented. This assay is based upon fluorimetric determination of F-actin depolymerization induced by okadaic acid (OA)-class compounds in the BE(2)-M17 neuroblastoma cell line. No interferences were observed with other marine toxins such as saxitoxin, domoic acid, or yessotoxin, thus indicating a good specificity of the assay as expected by the direct relationship between protein phosphatase inhibition and cytoskeletal changes. The proposed method is rapid (<2h) and shows a linear response in the range of 50-300 nM OA. The detection limit of the assay for crude methanolic extracts of bivalves lies between 0.2 and 1.0 microg OA per gram of digestive glands, depending on the type of samples (fresh or canned), thus being similar to that of the mouse bioassay. The performance of this assay has been evaluated by comparative analysis of 32 toxic mussel samples by the F-actin assay, mouse bioassay, HPLC and PP2A inhibition assay. Results obtained by the F-actin method showed no differences with HPLC and significant correlation with PP2A inhibition assay (r(2)=0.71). No false negative results were obtained with this new cell assay, which also showed optimum reproducibility.

Functional assay to measure yessotoxins in contaminated mussel samples

Yessotoxin (YTX) treatment of MCF-7 cells results in the accumulation of a 100-kDa fragment of E-cadherin (ECRA(100)) without a parallel loss of the intact protein in cytosoluble extracts. As a consequence, concentration-dependent increases in the total immunoreactivity detectable by anti-E-cadherin antibodies relative to controls (RTI) and in the relative immunoreactivity of ECRA(100) (RI) are observed. These responses have been exploited to develop a functional assay to measure YTX in samples from contaminated mussels by a three-step procedure, consisting of (i) treatment of MCF-7 cells with YTX standard in the concentration range 0-1nM and of unknown samples; (ii) preparation of cellular extracts, fractionation of proteins by polyacrylamide gel electrophoresis under denaturing conditions, and immunoblotting with anti-E-cadherin antibodies, followed by densitometric analyses of autoradiographies and calculation of RI of ECRA(100) and of RTI of the samples; and (iii) interpolation of the YTX concentrations in unknown samples on standard curves, by the RI of ECRA(100) and the RTI of the samples. The procedure has been used to measure yessotoxins in contaminated mussel samples, and the results obtained show that this functional assay is very sensitive (limit of detection of about 100ng equivalent YTX/g of digestive gland), and robust, as (i) it is insensitive to matrix effects in the range of toxin concentrations relevant for risk assessment to protect humans from exposure to YTX, (ii) calculations are based on a molecular parameter (the RI of ECRA(100)) which is not affected by errors in sample preparation, (iii) it can be performed by the use of antibodies commercially available from different companies, and (iv) it does not show an absolute need of calibration by a pure standard within each assay.

Nuclear magnetic resonance studies for the chiral recognition of (+)-(R)-18-crown-6-tetracarboxylic acid to amino compounds

Chiral recognition capability of (+)-(R)-18-crown-6-tetracarboxylic acid (18C6H(4)) to various amino compounds containing 16 amino acids, five alkyl amines, seven aminoalcohols and other amino compounds in nuclear magnetic resonance (1H-NMR) analysis was investigated. In general, amino compounds having an aromatic ring were well chiral recognized with 18C6H(4) compared with those having no aromatic ring. Effects of 18C6H(4) concentration and the kind of deuterated solvents (D(2)O, CD(3)OD and CD(3)CN) for measurement on the chiral recognition was investigated in detail. Concentration of 5 equivalent 18C6H(4) to the amino compounds was found to be sufficient for the chiral recognition. On the other hand, an effective deuterated solvent (D(2)O, CD(3)OD or CD(3)CN) for measurement was different in each compound. Distinguishment of 1.0% of the minor enantiomer (D-form) in L-alanine-beta-naphthylamide was found to be possible by 1H-NMR employing 18C6H(4) as a chiral shift reagent.

Complex toxin profiles in phytoplankton and Greenshell mussels (Perna canaliculus), revealed by LC-MS/MS analysis

Toxin profiles were determined in phytoplankton cell concentrates and Greenshell mussels (Perna canaliculus) exposed to a dinoflagellate bloom dominated by Dinophysis acuta and Protoceratium reticulatum. This was achieved by using a method for the simultaneous identification and quantification of a variety of micro-algal toxins by liquid chromatography-tandem mass spectrometry (LC-MS/MS) with electrospray ionisation (+/-) and monitoring of daughter ions in multiple reaction modes. Plankton concentrates and shellfish contained high levels of yessotoxins (YTXs) and pectenotoxins (PTXs) and low levels of okadaic acid (OA). A high proportion (>87%) of the OA in both plankton and shellfish was released by alkaline hydrolysis. An isomer of pectenotoxin 1 (PTX1i) was nearly as abundant as pectenotoxin 2 (PTX2) in the plankton and shellfish, and the latter contained high levels of their respective seco acids. DTX1, DTX2, and PTX6 were not detected. MS-MS experiments revealed that the shellfish contained several other oxygenated metabolites of YTX in addition to 45-hydroxy yessotoxin (45OH-YTX). Gymnodimine (GYM) was present in the shellfish but not plankton and it was probably the residue from a previous GYM contamination event. Unlike the other toxins, GYM was concentrated in tissues outside the digestive gland and levels did not decrease over 5 months. The depuration rates of YTX and PTXs from mussels were modelled.

Metal complexation of thiacrown ether macrocycles by electrospray ionization mass spectrometry

In the present study, electrospray ionization mass spectrometry is used to evaluate the metal-binding selectivities of an array of novel caged macrocycles for mercury(II), lead(II), cadmium(II), and zinc(II) ions. In homogeneous methanol/chloroform solutions as well as extractions of metals from aqueous solution by macrocycles in chloroform, it is found that the type of heteroatom (S, O, N), cavity size, and presence of other substituents influence the metal selectivities. Several of the macrocycles in this study bind mercury ion very selectively and efficiently in the presence of many other metal ions and have an avidity toward mercury that was tunable by the size and combination of heteroatoms in the macrocycle ring and the number of cage groups attached. The extraction mechanism was further investigated by determining the variation in extraction selectivity as a function of the counterions of the mercury salts.

Determination of brevetoxins in shellfish by the neuroblastoma assay

A neuroblastoma assay for determination of brevetoxins in shellfish was developed together with a method for sample cleanup that allows separation of brevetoxins from most of the components that cause matrix interference in the assay. This improved assay method was applied to a range of shellfish samples with different characteristics. Extracts of naturally contaminated and nontoxic shellfish together with extracts spiked with known amounts of toxin were tested. The results demonstrated that brevetoxins could be reliably detected in shellfish extracts at concentrations below the regulatory limit. Brevetoxin activity was detected in 15 of 23 samples from 5 separate toxicity incidents in which shellfish tested positive in the neurotoxic shellfish poisoning (NSP) mouse bioassay. Twelve of these positive NSP results came from 2 toxicity incidents. Yessotoxin was the major contributor to toxicity in 2 other incidents, although some samples contained both yessotoxin and brevetoxin. The sample from the remaining incident contained an unidentified toxin bioactivity, together with gymnodimine. In contrast to earlier versions of the neuroblastoma assay, gymnodimine was not detected by this modified method.

Direct detection of yessotoxin and its analogues by liquid chromatography coupled with electrospray ion trap mass spectrometry

A liquid chromatography mass spectrometry (LC-MS) method is proposed for the sensitive, specific and direct detection of yessotoxin and its analogues, marine biotoxins which are associated with diarrhetic shellfish poisoning (DSP) and which have been found in the North Adriatic sea since 1995. The LC-MS method provided a detection limit of 70 pg for yessotoxin in full scan mode and was applied to determine the toxic profiles of a number of extracts or partially purified fractions of toxic mussels collected along the Emilia Romagna coasts (Italy) in the period 1995-1999. Detection of a desulfo-yessotoxin derivative from Mytilus galloprovincialis collected in 1998 is also reported.

Repeatability and validity of a fluorimetric HPLC method in the quantification of yessotoxin in blue mussels (Mytilus edulis) related to the mouse bioassay

Repeatability and validity of a fluorimetric HPLC method in quantification of yessotoxin (YTX) in mussels related to the mouse bioassay was studied. Blue mussels (Mytilus edulis) from the Sognefjord, Norway were sampled from March to November, 1997, and October to December, 1998. A total of 75 samples were analysed for YTX by HPLC using 4-[2-(6,7-dimethoxy-4-methyl-3-oxo-3, 4-dihydroquinoxalinyl) ethyl]-1,2,4-triazoline-3, 5-dione (DMEQ-TAD) as a fluorimetric derivatization agent. Among these, 28 of the samples were analysed by HPLC in duplicate. All samples were analysed by the mouse bioassay using both chloroform and ether in the final step of extraction. The duplicate measurements using HPLC was found equal and the method repeatable (p<0.05). The absolute difference between the two measurements was found to increase with increasing level of measurements. This significant positive correlation (p<0.05) was mainly due to concentrations of YTX higher than 200 microg/100g mussel meat. However the precision of the results obtained was not found to be less in the upper level than in the lower level. Based on the internal correlation analysis including the mouse bioassay and the HPLC method a cut-off value of < or =10 microg YTX/5 g digestive gland was found preferable. The mouse bioassay of ether extracts often failed to detect high levels of YTX, and as demonstrated by the low kappa-values, the agreement between the mouse bioassay of ether extracts and the HPLC method was very weak. The HPLC method was found to give repeatable results and thereby found to be reliable. Consequently, the HPLC method seems to the method of choice for detection and quantification of YTX in mussels when compared with the mouse bioassay.

Integrated enzyme-linked immunosorbent assay screening system for amnesic, neurotoxic, diarrhetic, and paralytic shellfish poisoning toxins found in New Zealand

Enzyme-linked immunosorbent assays (ELISAs) were developed for amnesic, neurotoxic, and diarrhetic shellfish poisoning (ASP, NSP, and DSP) toxins and for yessotoxin. These assays, along with a commercially available paralytic shellfish poisoning (PSP) ELISA, were used to test the feasibility of an ELISA-based screening system. It was concluded that such a system to identify suspect shellfish samples, for subsequent analysis by methods approved by international regulatory authorities, is feasible. The assays had sufficient sensitivity and can be used on simple shellfish extracts. Alcohol extraction gave good recovery of all toxin groups. The ease of ELISAs permits the ready expansion of the system to screen for other toxins, as new ELISAs become available.

Confirmation of yessotoxin and 45,46,47-trinoryessotoxin production by Protoceratium reticulatum collected in Japan

Two different strains of the dinoflagellate Protoceratium reticulatum collected at Harima Nada and Yamada Bay in Japan were cultured and analyzed by fluorometric HPLC for yessotoxin production. Only the Yamada Bay strain produced yessotoxin. The toxin together with its analog, 45,46,47-trinoryessotoxin, were isolated from larger scale culture and unambiguously confirmed by (1)H NMR and MS measurements. This is the first confirmation of the biogenetic origin of yessotoxin in Japan, where the toxin was first reported. The results also indicate that the production of yessotoxins by P. reticulatum differs from strain to strain, in a similar way to that observed in many other toxigenic dinoflagellates such as Dinophysis spp. and Alexandrium spp.

Identification of Protoceratium reticulatum as the biogenetic origin of yessotoxin

Yessotoxin (YTX), a disulfated polyether toxin, was isolated from cultured cells of the marine dinoflagellate Protoceratium reticulatum and unambiguously identified by high-performance liquid chromatography, 1H NMR, and MS data. The result is the first to confirm toxigenicity of this species and demonstrate it as one of the biogenetic origins of YTX found in shellfish.

Adrenoceptor-induced changes of intracellular K+ and Ca2+ in astrocytes and neurons in rat cortical primary cultures

The calcium- and potassium sensitive fluorescent dyes fura-2 and K+-binding benzofuran isophtalate (PBFI) were used to detect changes in [Ca2+]i and [K+]i in type 1 astrocytes and neurons in mixed astroglial/neuronal rat cortical primary cultures after adrenoceptor stimulation. Noradrenalin (NA), phenylephrine (phe; alpha1-agonist), clonidine (clon; alpha2-agonist) and isoproterenol (iso; beta-agonist) were used. All agonists were able to increase [Ca2+]i and decrease [K+]i in the astrocytes with the exception of clon, which could not induce potassium responses. In the neurons, NA and phe evoked calcium transients while clon and iso did not. NA and clon were able to elicit reductions in [K+]i but no responses were seen after phe or iso stimulation. In neurons, the NA-evoked reductions in [K+]i always appeared immediately and gradually (after 30-50 s) returned to baseline even in the presence of the agonists. On the other hand, in the astrocytes, the NA-induced reductions in [K+]i appeared with some latency and always persisted at the lower level in the presence of the agonists. In addition, external tetraethylammonium (TEA) could severely reduce the NA-induced K+ responses in the astrocytes. The results indicate a clear heterogeneity regarding both adrenoceptor expression and response characteristics between astroglial cells and neurons.

Fluorometric measurement of yessotoxins in shellfish by high-pressure liquid chromatography

A rapid HPLC method with fluorescence detection of yessotoxin (YTX) and its two analogs (45-OHYTX and norYTX) in mussels and scallops is presented. A dienophile reagent, DMEQ-TAD, was used for fluorescence labeling. YTX was measured in the range 1-100 ng. The method confirmed the occurrence of YTX and 45-OHYTX for the first time in mussels from Chile and New Zealand.

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.

Determination of DSP toxins: comparative study of HPLC and bioassay to reduce the observation time of the mouse bioassay

The progressive increase of DSP toxic episodes in shellfish in the last few years has generated a series of criticisms centered on the suitability of the mouse bioassay as a reference method to regulate the harvest of mussels from the growth area. The observation time in injected mice is currently fixed in 12 h by the actual Spanish rules. The revision of this time period and the lack of a established DSP toxin threshold which permits the commercialization of mussels contaminated under certain levels, are some of the actual demands from the industry. In this study, the results obtained in a comparative study of DSP toxic mussels are shown using the HPLC method and the mouse bioassay. Based on these results, we consider feasible the reduction to 5 h of the observation times of the mouse bioassay currently established in the actual legislation, as well as the establishment of a DSP-toxin threshold of 2 micrograms okadaic acid/g hepatopancreas, which regulates the possibility of harvesting and commercialization of contaminated mussels.

Detection of okadaic acid esters in the hexane extracts of Spanish mussels

Two types of low polar derivatives of OA and dinophysitoxins have been reported in shellfish or in phytoplankton: 7-0-acyl esters containing a fatty acyl group attached through the 7-OH group and diol esters in which the carboxylic group of the toxins has been esterified. These compounds cannot be directly detected by liquid chromatography and fluorimetric detection as 9-anthryldiazomethane derivatives, owing in the first case to their low polarity and high molecular weight, and in the second case because they have the carboxylic group esterified. All of them must be hydrolysed before derivatization to be detected as Adam derivatives of the corresponding non-acylated toxins. In the Lee procedure, after extraction of the shellfish digestive glands with 80% methanol, a liquid-liquid partition with a non-polar solvent such as hexane is carried out in order to remove non-polar lipids. The presence of non-polar toxins was investigated in Spanish mussels and confirmed in the hexane layer, usually discarded in conventional extraction procedures, by analysis of the alkaline hydrolysis products. A preferred solubilization of these toxins in a non-polar solvent like hexane is reported. The inclusion of a hydrolytic step of the hexane extract in the general procedure is suggested in order to monitor the contribution of non-polar diarrhoetic shellfish poisons (DSPs) to the total DSP shellfish toxicity. This is the first report of DSPs other than OA and DTX2 in Spanish mussels.

Liquid chromatographic determination of okadaic acid and dinophysistoxin-1 in shellfish after derivatization with 9-chloromethylanthracene

The reagent 9-chloromethylanthracene was evaluated for derivatization of the diarrhetic shellfish poisons, okadaic acid and dinophysistoxin-1 (DTX-1), to form fluorescent products separable by liquid chromatography. The toxins were reacted with the reagent in acetonitrile in the presence of tetramethylammonium hydroxide for 1 h at 90 degrees C. The products were purified by using two silica solid-phase extraction cartridges before being determined by reversed-phase liquid chromatography with fluorescence detection. The results are comparable to those obtained using 9-anthryldiazomethane (ADAM) for okadaic acid and DTX-1 in mussel tissue. Detection limits were estimated to be about 70-100 ng/g hepatopancreas (equivalent to 12-20 ng/g whole tissue) for each toxin.

Influence of the extraction procedure on recovery of okadaic acid from experimentally contaminated mussels

Hepatopancreas samples from mussels (Mytilus galloprovincialis) experimentally contaminated with okadaic acid were analysed with Yasumoto's mouse bioassay and HPLC. A likely effect of some components of the hepatopancreas on the results (matrix effect) was evaluated, and a possible loss of toxin during the extraction phase was quantified. Experiments were conducted by comparing two different extraction procedures. Under our experimental conditions, the results obtained from mouse bioassay showed no matrix effect with either procedure. A certain quantity of the actual amount of okadaic acid contained in the sample was found to be lost after the extraction, i.e. 10.2-17.0% in samples extracted with acetone alone and 9.8-18.5% in samples extracted with acetone and ether.

Analysis of diarrhetic shellfish poisoning toxins in shellfish tissue by liquid chromatography with fluorometric and mass spectrometric detection

Diarrhetic shellfish poisoning (DSP) is a severe gastrointestinal illness caused by consumption of shellfish contaminated with toxigenic dinoflagellates. The main toxins responsible for DSP are okadaic acid (OA), DTX-1, DTX-2, and DTX-3, the latter being a complex mixture of 7-O-acyl derivatives of the first 3. In this study, existing methods based on liquid chromatography (LC) combined with mass spectrometry (LC-MS) and LC with fluorometric detection (LC-FLD) of anthryldiazomethane (ADAM) derivatives were improved upon to achieve a high degree of accuracy and precision for the determination of DSP toxins in a new mussel tissue reference material (MUS-2). All experimental parameters were examined comprehensively, and a new internal standard and a new solid-phase extraction cleanup method were introduced. Quantitative extraction of DSP toxins from shellfish tissue was achieved by exhaustive extraction with aqueous 80% methanol. Cleanup was accomplished by partitioning the crude aqueous methanol extract with hexane to remove lipids and then with chloroform to isolate the toxins. A further cleanup based on an aminopropylsilica column was useful for LC-MS and looks promising for the ADAM/LC-FLD method. The internal standard, 7-O-acetylokadaic acid, synthesized by partial acetylation of OA, improved accuracy and precision by correcting for incomplete recoveries in extraction, cleanup, and derivatization steps and for volumetric errors and instrumental drift. An improved silica cleanup after ADAM derivatization also was developed by controlling the activities of both sorbent and solvents. The methods were tested with various mussel tissue samples. The resulting improved methods will be useful to analysts involved in routine monitoring of DSP toxins.

Screening for okadaic acid by immunoassay

Increasing incidences of phytoplankton blooms with the potential danger of toxin release into the food chain have necessitated the search for new diagnostic methods that can detect toxins quickly and reliably. A competitive enzyme-linked immunosorbent assay (ELISA) was developed to quantitate okadaic acid in shellfish and phytoplankton extracts. To determine the specificity of the assay, a number of toxins, such as calyculin A, brevetoxin-1, and dinophysistoxins-1, -2, and -3 were analyzed. Both dinophysistoxins-2 and -1 could be detected by the assay but in concentration ranges 10- and 20-fold higher than that for okadaic acid, respectively. Dinophysistoxin-3, calyculin A, or brevetoxin-1 could not be detected with this assay. To validate the accuracy of the method, 18 mussel and 7 phytoplankton extracts were analyzed in parallel for okadaic acid content by ELISA and liquid chromatography combined with either fluorescence or mass spectrometric detection. Very high correlation between the results was found.

Comparison of mouse bioassay, HPLC and enzyme immunoassay methods for determining diarrhetic shellfish poisoning toxins in mussels

Mussel specimens (Mytilus galloprovincialis) collected from two different areas of the Adriatic Sea were analysed for diarrhoetic shellfish poisoning (DSP) toxin by three methods: mouse bioassay, the DSP Check enzyme immunoassay kit, and high-performance liquid chromatography (HPLC). The results obtained confirm that Yasumoto's mouse bioassay, capable of detecting all the components of the DSP group, is still necessary to determine the wholesomeness of the product. The ELISA method has not always given quantitatively reliable results. The HPLC method is advantageous in terms of sensitivity, accuracy, specificity and rapidity. However, its application is limited so far to the determination of okadaic acid in mussels.

A comparison of methods for diarrhoeic shellfish poison detection

Samples of diarrhoeic shellfish poison (DSP) mussels from several parts of the Italian Adriatic coastline were extracted and tested according to a number of different methods presently available, i.e. Yasumoto's mouse biotest, Kat's biotest, the ELISA test and the HPLC method. Results were compared for toxic levels detected in each sample. While a common qualitative result (toxic/non-toxic) was given by all the methods, no clear quantitative agreement was found. The differences between methods and consequent lack of agreement in results are discussed.

Specificity of mouse monoclonal anti-okadaic acid antibodies to okadaic acid and its analogs among diarrhetic shellfish toxins

The specificity of five mouse monoclonal antibodies to okadaic acid was studied for use in an enzyme-linked immunosorbent assay of okadaic acid and its analogs. OA8-2 and OA22-22 antibodies (IgG2a-kappa), which bind more strongly to dinophysistoxin-1 and 7-O-palmitoyl-dinophysistoxin-1 than to okaic acid or 7-O-palmitoyl-okadaic acid in 50% aqueous methanol, were useful in the detection of dinophysistoxins-1 and -3. OA10-8 (IgG1-kappa), which binds more strongly to 7-O-palmitoyl-okadaic acid and 7-O-palmitoyl-dinophysistoxin-1 than to okadaic or dinophysistoxin-1 in 50% aqueous methanol, was useful in the detection of dinophysistoxin-3. OA423-3 (IgG1-kappa), which binds weakly to dinophysistoxin-1 and 7-O-palmitoyl-dinophysistoxin-1 in 20% aqueous methanol, was useful in the selective detection of okadaic acid. OA958-2 (IgG1-kappa), which binds with equal strength to each of the four toxins in methanol, was useful in the detection of all okadaic acid analogs, and the minimum detectable concentration was 30 ng/ml. OA423-3 and OA958-2 retained their binding ability in 50% acetone, ethyl ether, or benzene in methanol.

Highly sensitive assay of okadaic acid using protein phosphatase and paranitrophenyl phosphate

A colorimetric phosphatase-inhibition bioassay was developed for the quantitative measurement of okadaic acid (OA) the main diarrhetic toxin responsible for diarrhetic shellfish poisoning. The assay used an artificial substrate, paranitrophenylphosphate, and a semi-purified protein phosphatase PP2Ac containing extract prepared from rabbit muscle. Calibration dose-inhibition curves were constructed using standard OA and they permitted easy determination of the enzyme concentration Et in their linear portion. In the range of linearity, the slope increased when Et decreased, thus giving a detecting limit of 0.04 pmol in the reaction mixture (1 ml). The lowest assayable concentration of OA was 4 ng/ml in aqueous solutions and 40 ng/ml (i.e., 100 ng of OA per g of mussel tissue) in crude methanol mussels extracts. The intra and interassay coefficients of variation in the measurement of OA for the toxin spiked aqueous samples averaged, respectively, 7.7% and 3.7%, and interexperiments coefficients of variation for the toxin spiked mussel extracts averaged 4.6%. The presence of OA was ascertained by a method in which one assay was performed at two or three different levels of enzyme concentration. The rapidity, accuracy, reproducibility, specificity, and simplicity of the procedure provides a simple way to assay okadaic acid in buffered or complex solutions.

Investigation of derivatization reagents for the analysis of diarrhetic shellfish poisoning toxins by liquid chromatography with fluorescence detection

Several derivatization reagents for the conversion of okadaic acid and related DSP toxins to fluorescent derivatives for analysis by liquid chromatography have been examined, viz: 9-anthryldiazomethane (ADAM), 1-pyrenyldiazomethane (PDAM), 4-diazomethyl-7-methoxycoumarin (DMMC), 4-bromomethyl-7-methoxycoumarin (BrMMC), 4-bromomethyl-7,8-benzcoumarin (BrMBC), 4-bromomethyl-7-acetoxycoumarin (BrMAC), and 4-bromomethyl-6,7-dimethoxycoumarin (BrDMC). The ADAM reagent provides the greatest selectivity and sensitivity, but its application on a routine basis has been limited by its instability and cost. Improvement of this method was achieved through the production of ADAM in situ from the stable 9-anthraldehyde hydrazone. A detection limit of 30 ng/g hepatopancreas (equivalent to 6 ng/g whole tissue) was achieved. The other aryldiazomethane reagents were found to have insufficient reactivity. Of the bromomethylcoumarin reagents, BrDMC was found to have the greatest promise. The reagent is inexpensive and has excellent stability and purity. Quantitative derivatization may be achieved in a 2 hour reaction at 45 degrees C with N,N-diisopropylethylamine as a catalyst. Unfortunately, the lower reaction selectivity of BrDMC compared to that of ADAM limits its application to isolated toxins, plankton samples, and shellfish tissues with high levels of DSP toxins. The use of BrDMC for the determination of how toxin levels in shellfish tissues will require development of a more extensive clean-up prior to derivatization. Successful application of the ADAM and coumarin derivatization methods to real-world samples has been demonstrated.

Evolution of methods for assessing ciguatera toxins in fish

Ciguatera toxins are odorless, tasteless, and generally undetectable by any simple chemical test; therefore, bioassays have traditionally been used to monitor suspect fish. Many native tests for toxicity in fish have been examined, including the discoloration of silver coins or copper wire or the repulsion of flies and ants, but all of these were rejected as invalid. Oral feeding of fish to cats or mongoose is a simple and relatively sensitive assay, but cats often regurgitate part of the meal. Feeding tests described above have been used in screening fish for toxicity, but they are cumbersome and nonquantitative. A mouse bioassay was developed; unfortunately, this procedure requires purification fish extracts, since mice are not very sensitive to ciguatoxin. An alternative to the use of mice is the mosquito bioassay, which was recently used to obtain a dose-response relationship between ingested ciguatoxin and clinical symptoms in man. This assay correlates reasonably well with cat and mouse bioassay. Many other bioassays have been developed using chicken, brine shrimp, and the guinea pig atrium. All traditional bioassays have one common disadvantage, the lack of specificity for individual toxins. Recent studies have also focused on the development of chemical methods, i.e., TLC and HPLC, for the detection and quantification of ciguatera-related toxins (okadaic acid and ciguatoxin and its analogs). Alternative assays based on immunochemical technology have been developed and show the greatest promise for use in seafood safety monitoring programs. For earlier methods (RIA and ELISA formats), liver extracts from ciguatoxic eels were used to prepare ciguatoxin antisera. The assay has been further adapted to a solid-phase immunobead assay (S-PIA), which has a very high potential for use as a marketplace screening tool to separate ciguateric fish. This assay can also be used to monitor reefs for ciguatera potential. Historically, attempts to validate methods used to measure ciguatera toxicity have been plagued with a lack of specificity and reference standards. These restrictions have been resolved, and a study is under way to evaluate the precision and accuracy of a low-cost, simplified field and laboratory S-PIA kit (Ciguatect, Hawaii Chemtect International, Pasadena, California, 91109), through an international interlaboratory trial using the AOAC/IUPAC validation mechanism.

Studies on the detection of okadaic acid in mussels: preliminary comparison of bioassays

Diarrheic toxins, especially okadaic acid, are detected nearly every year in mussels on French coasts. The monitoring network determines the toxicity of these shellfish by using a mouse test now considered unsatisfactory from an ethical point of view. Two alternative methods have been investigated: the daphnia test, for which there is a standardized method used routinely in ecotoxicology, and a cytotoxicity test on the KB cell line developed for this study. Using the same samples, the results of these two tests were compared with those obtained by chemical analysis (HPLC okadaic acid assay) or the mouse test. Linear regression studies showed that results for the two bioassays were well correlated with those for HPLC or the mouse test.

A unified bioscreen for the detection of diarrhetic shellfish toxins and microcystins in marine and freshwater environments

Capillary electrophoresis (CE) coupled with liquid chromatography (LC)-linked protein phosphatase (PPase) bioassay was used to detect sensitivity both diarrhetic shellfish toxins and hepatotoxic microcystins in marine and freshwater samples. This procedure provided a quantitative bioscreen for the rapid optical resolution of either of these toxin families in complex mixtures such as cultured marine phytoplankton, contaminated shellfish and cyanobacteria (natural assemblages). Following detection, identified toxins were purified by an enzyme bioassay-guided two-step LC protocol. Using the latter approach, at least four microcystins were rapidly isolated from a cyanobacteria bloom (largely Microcystis aeruginosa) collected from a Canadian drinking-water lake, including a novel microcystin termed microcystin-XR, where X is a previously unidentified hydrophobic amino acid of peptide residue molecular mass 193 Da. The unified CE/LC-linked PPase bioscreen described provides a powerful capability to dissect multiple toxin profiles in marine or freshwater samples contaminated with either okadaic acid or microcystin classes of toxin.

The use of Daphnia magna for detection of okadaic acid in mussel extracts

Okadaic acid (OA), the main toxin responsible for diarrheic shellfish poisoning (DSP) has toxicity for Daphnia magna (EC50 = 15 +/- 1.8 micrograms/l). A Daphnia bioassay was developed and used to analyse okadaic acid in mussel extracts. A linear correlation was found between OA concentration determined by the Daphnia bioassay and by HPLC assay (r = 0.85; p < 0.001). The Daphnia bioassay can measure OA levels 10 times below the threshold of the mouse bioassay method. It is an inexpensive sensitive tool which can be used in replacement of mouse bioassay for the screening of OA and some co-extracting toxins in mussel extracts.