Abstract
Two cases of human intoxication resulting from consumption of red marine algae Gracilaria verrucosa (Japanes name, ogonori) and G. chorda (tsurushiramo) have recently occurred in Japan. Large amounts of inorganic salts present in these seaweeds has been suggested to be responsible for the poisoning. We however found that the extracts prepared from these algae which had been steeped in freshwater evoked severe diarrhea in mice; the main symptom of human victims. Two active principles have been isolated pure from G. verrucosa that was soaked in distilled water for20h. The principal compound was identified to be prostaglandin E2 by spectral data, chemical transformation and direct comparison with authentic specimens, while the less active substance to be prostaglandin A2. Responsibility of the prostaglandins, particularly PGE2, for the “ ogonori ” poisoning has been suggested. It was also proposed that an inhibitor of prostaglandin synthesis is present in the algae of the genus Gracilaria.
