Production of 7-deoxy-okadaic acid by a New Caledonian strain of Prorocentrum lima (Dinophyceae)

7-Deoxy-okadaic acid and okadaic acid were identified as the major diarrhet ic shellfish poisoning (DSP) toxins produced by a New Caledonian strain of Prorocentrum lima Ehrenberg, Dinophysistoxin-1 was not produced by this str ain. The cellular concentrations of 7-deoxy-okadaic acid were about one ten th that of okadaic acid and were maximal (similar to1.4 pg.cell(-1)) during the stationary growth phase of batch culture. Autolytic hydrolysis of cell extracts did not increase the concentrations of 7-deoxy-okadaic acid, wher eas okadaic acid production increased more than 4-fold, indicating that 7-d eoxy-okadaic acid, unlike okadaic acid, is not directly derived from large sulfated precursors. 7-Deoxy-okadaic acid could be detected by liquid chrom atogaphy-selected reaction monitoring mass spectrometry, HPLC-fluorescence detection after derivatization with 9-anthryldiazomethane (ADAM), and inhib ition of protein phosphatases. The solvent washes currently used for solid- phase clean-up of ADAM-derivatized DSP samples elute derivatized 7-deoxy-ok adaic acid, indicating that the current sample clean-up protocol for HPLC-f luorescence detection would miss any contamination by this toxin.