Determination of toxins involved in ciguatera fish poisoning in the Pacific by LC/MS.

Ciguatera fish poisoning is the most extensive and difficult to control of the seafood poisonings. To facilitate monitoring of fish toxicity, toxin profiles were investigated by an LC/MS/MS method using 14 reference toxins on eight representative species of fish collected in four different areas of the Pacific. Snappers and groupers from Okinawa contained ciguatoxin-1B (CTX1B) and two deoxy congeners at variable but species-specific ratios, while red snapper, Lutjanus bohar, from Minamitorishima, and amberjack, Seriola dumerili, from Hawaii, contained both CTX1B-type and CTX3C-type toxins. Spotted knifejaw, Oplegnathus punctatus, from Okinawan waters, contained mainly CTX4A and CTX4B, but the same species caught at Miyazaki was contaminated primarily with the CTX3C-type toxins. Otherwise, the toxin profiles were consistently species-specific in fish collected from various locations around Okinawa over 20 years. The LC/MS/MS and mouse bioassay results agreed well, indicating the LC/MS/MS method is a promising alternative to the mouse bioassay. Pure CTX1B and CTX3C were prepared for use in future LC/MS/MS analysis.

Inhibition of brevetoxin binding to the voltage-gated sodium channel by gambierol and gambieric acid-A.

Brevetoxins (BTXs) and ciguatoxins (CTXs) bind to site 5 of the voltage-gated sodium channel of excitable membranes. In the present study, we performed a competitive inhibition assay with other structurally distinct naturally occurring polyethers using isotope-labeled dihydro BTX-B ([3H]PbTx-3), which showed, for the first time, that gambierol and gambieric acid-A inhibit the binding of [3H]PbTx-3 while yessotoxins are inactive in this assay. The inhibition assay also suggested that there is a significant relationship between the size of the polycyclic region and inhibitory activity. Interestingly, the acute mouse toxicities of the compounds do not correspond directly to their inhibitory activities. These observations will serve as a guide for designing artificial polyethers with desired activity.