Analysis of Purified Okadaic Acid and Dinophysis Toxin 1 from Prorocentrum Lima Dodge

Abstract

Okadaic acid (OA) and dinophysis toxins (DTXs) are representative toxins corresponding for the diarrhetic shellfish poisoning (DSP) incidents. In the current study, the samples of OA and DTX1, which were purified previously from the cultured algal cells of dinoflagellate Prorocentrum lima Dodge, were analyzed for the identity and purity with high performance liquid chromatography coupled with fluorescence detector (HPLC-FLD) and ultraviolet detector (HPLC-UV), mass spectrometry (MS) and HPLC-MS. Commercially available toxin standards of OA and DTX1 were also analyzed to compare with the purified samples. After derivatized with 4-bromomethyl-7-methoxycoumarin (BrMmc), OA and DTX1 were detected in the purified samples with the HPLC-FLD method. In the HPLC-UV chromatogrphy detected at 200 nm, OA and DTX1 were found to be the most predominant peaks, and the purity calculated based on the peak area could reach 95% and 98% for the samples of OA and DTX1, respectively. In the MS spectrums of the purified samples and toxin standards, the highest signals in the positive mode or the negative mode had the same value of m/z, which could be identified as [M+Na](+) and [M-H](-) of OA and DTX1. The [M+Na](+) and [M-H](-) ions of the toxin samples showed similar fragmentation pattern as those of the toxin standards, further confirming the presence of OA and DTX1 in the purified samples. In the LC-MS analysis of the purified samples with the full-scan m/z range at 100-1300, a small amount of impurities in the OA sample was found, and no impurity presented in the DTX1 sample. The results suggested that the OA and DTX1 samples prepared previously had high purity and could be used as standards for the analysis of OA and DTX1 with HPLC-FLD and HPLC-MS methods in management and protection of seafood.