Data/hora: 16/06/2024 03:48:50

Provedor de dados: | 5
País: | France
Título: | Contributions to the characterisation of risks posed by marine biotoxins
Autores: | Hess, Philipp.
Data: | 2010-10-26
Ano: | 2010
Resumo: | Toxic algae producing an array of bioactive compounds may accumulate in shellfish, which in turn cause poisoning, following human consumption of contaminated shellfish. The chemistry, occurrence and toxicity of the toxins involved was reviewed. Following this review, the risk analysis and management processes are outlined for the production of shellfish. Subsequent sections describe five elements of risk characterisation to which my studies have significantly contributed: methods of analysis, distribution of toxins in the marine environment, preparative isolation of toxins, quality control tools in the determination of the toxins and characterisation of the chemical hazard in terms of lipophilicity, stability, reactivity and toxicity.  The use of liquid chromatography coupled to mass spectrometry for the detection of both hydrophilic and lipophilic toxins is outlined, with emphasis on the contributions clarifiying critical parameters. For STX-group toxins, hydrophilic-lipophilic interaction chromatography has been introduced and demonstrated to achieve similar detection limits to the current regulatory bioassay, while providing a wealth of additional information in terms of toxin profiles. The determination of lipophilic toxins was critically evaluated. Matrix effects are systematically described and recommendations for their elimination or reduction are given.  The geographical distribution of AZAs has been shown to extend all along the Atlantic coast of Europe, and the biogeographic differences between European and a North American strain of Dinophysis were elucidated. Mussels were shown to accumulate higher levels of AZA- and OA-group toxins than oysters through the introduction of routine monitoring of lipophilic shellfish toxins by LC-MS in Ireland. The contamination of scallops with DA and the causes of its variability were studied in Scotland and Ireland, with results contributing to legislation implemented. The distribution of shellfish toxins was also studied using passive sampling techniques. Thanks to these techniques, the existence of toxins previously unreported in Ireland was demonstrated (DTX1, YTX, SPX). The capability of predicting the occurrence of shellfish toxins using passive samplers was not confirmed in our studies.  Compounds from three different toxin groups were isolated in the studies described: AZA, OA and PTX-group. Particular efforts were dedicated to the isolation of AZAs; these efforts have culminated in the production of a certified calibrant for AZA1 and in the discovery of 8 previously unknown analogues of AZAs, bringing the total number of analogues known to 20. DTX2 has been isolated to satisfactory purity, thus allowing further toxicological evaluation as well as the production of a standard currently undergoing certification at NRCC. The isolation of PTX2sa-fatty acid esters has outlined the complexity of natural products in shellfish.  Shellfish tissue reference materials were prepared, and factors affecting their homogeneity and stability were clarified. The materials were fit for in-house validation of methods, interlaboratory method validation, proficiency testing and certification. Two materials have been prepared for certification: an AZA-contaminated wet mussel material and a multitoxin-contaminated freeze-dried mussel tissue. Proficiency testing was introduced for DA-, OA-, AZA- and STX-group toxins. The applicability of LC-UV and –MS was demonstrated for the determination of DA. Immunoassays were compared to LC-methods for both DA- and OA-group toxins. The MBA was compared to an in-house validated LC-MS method for AZA-group toxins demonstrating that both were applicable for the current regulatory limit. The MBA has grave limitations as it cannot detect lower levels and is thus not fit-for-purpose, considering the transformation of AZAs observed in mussels following heat-treatments.  The acidity and lipophilicity constants of lipophilic shellfish toxins have been determined chromatographically. AZAs have been shown to be sensitive to alkaline and acidic treatments. AZA3 was also shown to be more sensitive to heat treatments than AZA1 and –2. OA was shown to degrade rapidly under the influence of strong acids. The heat treatments of mussels appear to affect the concentrations of AZA- and OA-group toxins, suggesting that the increase in concentrations need to be taken into account by shellfish producers in their HACCP plans. The toxicity of DTX2 was shown to be approximatevely half that of OA. The toxicity of AZA1 was investigated at cellular and molecular level. Cytotoxicity, teratogenicity and effects on gene regulation were investigated. The mechanism of action has not been completely elucidated, however, indicative results of gene-chip experiments suggest that lipid-biosynthesis and wound-healing pathways are affected by this toxin group.
Tipo: | Text
Idioma: | Inglês

Identificador:

http://archimer.ifremer.fr/doc/00015/12661/9548.pdf

http://archimer.ifremer.fr/doc/00015/12661/9549.pdf

Relação: | http://archimer.ifremer.fr/doc/00015/12661/
Formato: | application/pdf
Fonte: | Philipp Hess