LC–MS/MS Analysis of Ciguatoxins Revealing the Regional and Species Distinction of Fish in the Tropical Western Pacific

Abstract

Ciguatera fish poisoning (CFP) is one of the most frequently reported seafood poisoning diseases. It is endemic to the tropical region and occurs most commonly in the regions around the Pacific Ocean, Indian Ocean, and Caribbean Sea. The principal toxins causing CFP are ciguatoxins (CTXs). In the Pacific region, more than 20 analogs of CTXs have been identified to date. Based on their skeletal structures, they are classified into CTX1B-type and CTX3C-type toxins. We have previously reported species-specific and regional-specific toxin profiles. In this study, the levels and profiles of CTXs in fish present in the tropical western Pacific regions were analyzed using the liquid chromatography–tandem mass spectrometry (LC–MS/MS) technique. Forty-two fish specimens, belonging to the categories of snappers, groupers, Spanish mackerel, and moray eel, were purchased from various places such as Fiji, the Philippines, Thailand, and Taiwan. Only the fish captured from Fijian coastal waters contained detectable amounts of CTXs. The toxin levels in the fish species found along the coastal regions of the Viti Levu Island, the main island in Fiji, and the toxin profiles were significantly different from those of the fish species present in other coastal regions. The toxin levels and profiles varied among the different fish samples collected from different coastal areas. Based on the toxin levels and toxin profiles, the coast was demarcated into three zones. In Zone-1, which covers the northern coast of the main island and the regions of the Malake Island and Korovau, CTXs in fish were below the detection level. In Zone-2, CTX3C-type toxins were present in low levels in the fish. CTX1B-type and CTX3C-type toxins co-occurred in the fish present in Zone-3. The toxin profiles may have reflected the variation in Gambierdiscus spp.

Extraction and LC-MS/MS Analysis of Ciguatoxins: A Semi-Targeted Approach Designed for Fish of Unknown Origin

“…Acidic conditions favor the epimerization of CTX congeners. This fact can be utilized for structure elucidation [ 14 ] or standard preparation [ 30 ]. For full conversion, strongly acidic conditions with HCl (0.1 M) and elevated temperatures (55 °C) were employed [ 30 ].…”

“…This fact can be utilized for structure elucidation [ 14 ] or standard preparation [ 30 ]. For full conversion, strongly acidic conditions with HCl (0.1 M) and elevated temperatures (55 °C) were employed [ 30 ]. Due to solvent evaporation during sample preparation, a concentration of acetic acid can occur, which might favor epimerization.…”

“…In general, sample preparation methods for CTX analysis are often time-consuming due to several clean-up steps needed for LC-MS/MS analyses [23,25,30]. Fast extraction methods have been developed, but these were typically designed with a focus on a specific congener (CTX1B in case of [31]) or only (medium) polar congeners with chromatograms displaying a pronounced increase in the baseline with increasing run time [32].…”

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

“…Extraction and preparation of the fish flesh followed the method in previous studies ( Figure S3) [18,19]. Flesh (5 g) was extracted with acetone (15 mL) twice, and the extracts were combined and evaporated to remove the acetone.…”

“…CTXs are naturally occurring macromolecules consisting of ladder-shaped polyether, with more than 20 analogs reported from the Pacific Ocean and classified into CTX1B-type and CTX3C-type toxins based on their skeletal structure [15]. In our previous studies, we reported the regional and species-specific features of the CTX profiles of fish in the Pacific using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis [16][17][18][19]. In the specimens captured in Hawaii, French Polynesia, Minamitorishima (Marcus Island), and mainland Japan, both CTX1B-type and CTX3C-type toxins were detected [16].…”