Since 1953, a total of 27 human poisoning cases caused by the consumption of blue humphead parrotfish, Scarus ovifrons, have been reported in Japan. Characteristic symptoms are severe muscle pain associated with rhabdomyolysis. Although it is believed that palytoxin, which is one of the most potent non-protein marine biotoxins, is the most likely causative toxin in blue humphead parrotfish poisoning, palytoxin has not been proven conclusively as the causative toxin because of lack of a reliable and sensitive analytical method for palytoxin. In 2011, human poisoning cases caused by the consumption of blue humphead parrotfish occurred in Miyazaki and Tokyo. In our present study, an LC-MS/MS method for palytoxin and its analogues in the blue humphead parrotfish samples causing the human poisoning cases in 2011 was developed and the samples were analysed by using the newly developed LC-MS/MS method. Palytoxin and its analogues were not detected in the samples from the food poisoning cases. The LC-MS/MS findings therefore do not support the recently accepted hypothesis that palytoxin is the causative agent in blue humphead parrotfish poisoning in Japan.

-Lipophilic toxin pectenotoxin-2 (PTX2) is oxidatively metabolized to pectenotoxin-1 (PTX1), pectenotoxin-3 (PTX3), and pectenotoxin-6 (PTX6) in the Japanese scallop Patinopecten yessoensis. This particular metabolism has been observed only in Japanese scallops, in which PTX6 is the most dominant lipophilic toxin. We investigated the cytotoxicity of PTX2 and its metabolites PTX1,3,6 in a rat cell line (L6) and a human cell line (RD). RD showed an approximately three-fold greater sensitivity than L6 upon exposure to PTXs. The cytotoxicity of PTXs decreased with degree of oxidation in the order PTX2 > PTX1 > PTX3 > PTX6. The calculated half maximal inhibitory concentration (IC 50 ) values of PTX2 obtained for the L6 and RD cell lines were 60 and 23 ng/mL, respectively, while those obtained for PTX6 for both cell lines were over 2,000 ng/mL. These results demonstrate that PTX6 has extremely low cytotoxicity or is non-toxic and that the oxidative metabolism of PTX2 in P. yessoensis is a detoxification process.