Characteristic Distribution of Ciguatoxins in the Edible Parts of a Grouper, Variola louti

Abstract

Ciguatera fish poisoning (CFP) is one of the most frequently encountered seafood poisoning syndromes; it is caused by the consumption of marine finfish contaminated with ciguatoxins (CTXs). The majority of CFP cases result from eating fish flesh, but a traditional belief exists among people that the head and viscera are more toxic and should be avoided. Unlike the viscera, scientific data to support the legendary high toxicity of the head is scarce. We prepared tissue samples from the fillet, head, and eyes taken from five yellow-edged lyretail (Variola louti) individuals sourced from Okinawa, Japan, and analyzed the CTXs by LC-MS/MS. Three CTXs, namely, CTX1B, 52-epi-54-deoxyCTX1B, and 54-deoxyCTX1B, were confirmed in similar proportions. The toxins were distributed nearly evenly in the flesh, prepared separately from the fillet and head. Within the same individual specimen, the flesh in the fillet and the flesh from the head, tested separately, had the same level and composition of toxins. We, therefore, conclude that flesh samples for LC-MS/MS analysis can be taken from any part of the body. However, the tissue surrounding the eyeball displayed CTX levels two to four times higher than those of the flesh. The present study is the first to provide scientific data demonstrating the high toxicity of the eyes.

Keywords: 52-epi-54-deoxyCTX1B; 54-deoxyCTX1B; CTX1B; LC-MS/MS; ciguatera; ciguatoxin.

Figure 1

Structures representative of ciguatoxin-1B (CTX1B), 52-epi-54-deoxyCTX1B, and 54-deoxyCTX1B, implicated in CFP in Okinawa, Japan.

Figure 2

A specimen (D, ID 160135) of V. louti used for this study (A) and the locations of samples used for LC-MS/MS analyses. (B) The half-body fillet was divided into six parts (#1–#6, bottom right). (C) From the head, the flesh samples taken from the cheek (#7), the collar (#8), and the cavalry (#9); the eyeball (#10) and the tissue surrounding eyeball (#11). The eyeball was further separated into samples #12–#14, as shown in Table 1.

Figure 3

LC-MS/MS chromatograms of reference toxin mixture (top), flesh (A-1, middle), and eye (A-10, bottom) samples of Specimen A.

Figure 4

The levels of CTX1B analogs detected in samples prepared from Specimens A–E.

Figure 4

The levels of CTX1B analogs detected in samples prepared from Specimens A–E.

Figure 5

LC-MS/MS chromatograms of reference toxin mixture (top) and flesh samples of the fillet (E-1, middle) and cheek (E-7, bottom) of Specimen E. The gradient systems used were conditions Gradient I (A) and II (B).