LC/MS analysis of brevetoxin metabolites in the Eastern oyster (Crassostrea virginica). |
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Authors: | Zhihong Wang Steven M Plakas Kathleen R El Said Edward L E Jester H Ray Granade Robert W Dickey |
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Affiliation: | Gulf Coast Seafood Laboratory, U.S. Food and Drug Administration, P.O. Box 158, 1 Iberville Drive, Dauphin Island, AL 36528-0158, USA. |
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Abstract: | Brevetoxin (PbTx) metabolism was examined in the Eastern oyster (Crassostrea virginica) following exposure to a Karenia brevis red tide, by using LC/MS(/MS) and cytotoxicity assay. Metabolites observed in field-exposed oysters were confirmed in oysters exposed to K. brevis cultures in the laboratory. Previously, we identified a cysteine conjugate and its sulfoxide (MH(+): m/z 1018 and 1034) as metabolites of the brevetoxin congener PbTx-2. In the present study, we found a cysteine conjugate and its sulfoxide with A-type brevetoxin backbone structure (MH(+): m/z 990 and 1006), as probable derivatives of PbTx-1. We also found glycine-cysteine-PbTx (m/z 1047 and 1075), gamma-glutamyl-cysteine-PbTx (m/z 1147), and glutathione-PbTx (m/z 1176 and 1204) conjugates with A- and B-type backbone structures. Amino acid-PbTx conjugates react with fatty acids through amide linkage to form a series of fatty acid-amino acid-PbTx conjugates. These fatty acid conjugates are major contributors to the composite cytototoxic responses obtained in extracts of brevetoxin-contaminated oysters. Other brevetoxin derivatives found in oysters are consistent with hydrolytic ring-opening and oxidation/reduction reactions. |
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Keywords: | Brevetoxins Metabolism Eastern oyster Cytotoxicity Liquid chromatography/mass spectrometry |
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