Detection and identification of glycoyessotoxin A in a culture of the dinoflagellate Protoceratium reticulatum

The toxin composition of a culture of the dinoflagellate Protoceratium reticulatum was investigated using LC–FLD, after derivatization with DMEQ-TAD (4-(2-(6,7-dimethoxy-4-methyl-3-oxo-3,4-dihydroquinoxalimylethyl)-1,2,4-triazoline-3,5-dione)). Besides yessotoxin (YTX), the new YTX analogue, glycoyessotoxin A (G-YTXA) was detected in culture medium as well as in cells. The conditions for extraction were optimized and the production profile established. Retention time of the resulting fluorescent G-YTXA adduct was identified by comparison of the appropriate standard. Additionally, both G-YTXA and the DMEQ-TAD-G-YTXA adduct were confirmed by LC–MS showing ion peaks at m/z 1273 [M−2Na+H]− and m/z 1618 [M−2Na+H]−, respectively. The LC–MSn displayed a fragmentation pattern similar to that of the YTX series.