title: LC/MS analysis of brevetoxin metabolites in the Eastern oyster (Crassostrea virginica).
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.
authors.affiliation: Gulf Coast Seafood Laboratory, U.S. Food and Drug Administration, P.O. Box 158, 1 Iberville Drive, Dauphin Island, AL 36528-0158, USA.
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Wang
authors.forename: Steven M
authors.initials: SM
authors.lastname: Plakas
authors.forename: Kathleen R
authors.initials: KR
authors.lastname: El Said
authors.forename: Edward L E
authors.initials: EL
authors.lastname: Jester
authors.forename: H Ray
authors.initials: HR
authors.lastname: Granade
authors.forename: Robert W
authors.initials: RW
authors.lastname: Dickey
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001681:Biological Assay; D002853:Chromatography, Liquid; D003601:Cytotoxicity Tests, Immunologic; D004141:Dinoflagellida; D005227:Fatty Acids / Q000378:metabolism*; D005431:Florida; D006868:Hydrolysis; D008387:Marine Toxins / Q000737:chemistry* / Q000378:metabolism*; D013058:Mass Spectrometry; D010125:Ostreidae / Q000378:metabolism*; D010084:Oxidation-Reduction; D035964:Oxocins / Q000737:chemistry* / Q000378:metabolism*; D013781:Texas; D000095702:Polyether Toxins
chemical_list: D000596:Amino Acids; D005227:Fatty Acids; D008387:Marine Toxins; D035964:Oxocins; C053342:brevetoxin; D000095702:Polyether Toxins