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The main toxins produced by the dinoflagellate Prorocentrum belizeanum, DTX5c and 7-hydroxymethyl-2methyleneocta- 4,7 dienyl okadaate, were studied by liquid chromatography-coupled with ion trap mass spectrometry (LC–MS/MS). Their retention times (RTs) and fragmentation patterns were established, in particular those of DTX5c, as there is a lack of data about these water soluble OA sulphated derivatives. As an application of the LC–MS methodology, a sample of the toxic P. belizeanum culture was analysed for these metabolites. Both metabolites were detected in cells as majority compounds, whereas levels of these compounds in the culture media were undetectable.

In the Diarrhetic Shellfish Poisoning (DSP) phenomena, the parent toxins, namely okadaic acid (OA) and/or dinophysistoxin-2 (DTX2), are predominantly found esterified. Therefore, a toxicity assessment of a sample can only be performed after an alkaline hydrolysis step in order to recover the parent molecules in their free form. The presence of several OA diol esters has already been confirmed in Prorocentrum lima and Prorocentrum belizeanum cultures. This paper reports on the analysis of OA diol esters using liquid chromatography coupled with mass spectrometry (LC–MS/MS), and establishes a method for their detection and identification based upon their retention times (RT) and the fragmentation patterns of their mass spectra.

Prorocentrum belizeanum is a dinoflagellate known for its okadaic acid (OA) and dinophysitoxins (DTXs) production, both OA and DTX are polyether toxins of the Diarrhetic Shellfish Poisoning (DSP) group. We have recently published the isolation of a new diol-ester of okadaic acid from cultures of P. belizeanum. On this occasion we present a new sulphated water-soluble derivative, DTX-5c, isolated from this microalga, whose structure was established on the basis of its spectroscopical data.