Direct evidence of transformation of dinophysistoxin-1 to 7-O-acyl-dinophysistoxin-1 (dinophysistoxin-3) in the scallop Patinopecten yessoensis.

Non-toxic scallops Patinopecten yessoensis were reared for 5 days with the toxic dinoflagellate Dinophysis fortii sampled from the sea. The total cell number ingested by five scallops during the feeding experiment was approximately 682 x 10(3). Okadaic acid (OA), dinophysistoxin-1 (DTX1) and esterified toxins of OA and DTX1 in D. fortii and scallop extracts were determined by liquid chromatography fluorescence detection (LC-FLD) as their 9-anthryldiazomethane (ADAM) derivatives. Only DTX1 was detected in D. fortii extracts used for the feeding experiment. The content of esterified DTXI in scallops fed on D. fortii was significantly higher than that of DTX1. Identification of esterified DTX1, 7-O-palmitoyl DTX1 (7-O-16:0 DTX1), in D. fortii and scallop extracts was carried out by LC equipped with an atmospheric pressure electrospray ionization-mass spectrometry (ESI-MS). Only extracts of scallops fed on D. fortii yielded a mass spectrum exhibiting abundant [M-H]- at m/z 1055 corresponding to 7-O-16:0 DTX1. These findings are the first direct evidence of the transformation of DTX1 to 7-O-acyl DTX1 in scallop tissues.