Diarrhetic Shellfish Poisoning, which is caused by ingestion of bivalves fed on toxic dinoflagellates, has become one of the largest natural food poisonings from marine source. The poisoning has broken out at various places in Japan as well as in Europe and a number of the total patients has exceeded ten thousand so far. The authers have already identified two toxins responsible for the poisoning, DTX1 (II) from Japanese mussels and okadaic acid (I) from Europian mussels. In the present work, a main toxic constituent of Japanese scallops has been elucidated to be 7-O-acylDTXl. Its acyl moiety consists of various unsaturated fatty acids (C18:4, C20:5, C22:5 etc.) and the highly unsaturated fatty acyloxy group seems to play a substantial roll in bioactivity of the toxin. Causative organism of the poisonings in Europe has identified as a dinoflagellate Dinophysis acuminata because okadaic acid was detected in the extract of the alga by a fluorometric HPLC analysis. A novel diol ester of okadaic acid (PLT1a, VIII) was isolated from a cultured dinoflagellate Prorocentrum lima. Five novel diol compounds (X-XIV) were also obtained from a hydrolysate of the ester fraction.
