Caribbean Ciguatoxin-1 stability under strongly acidic conditions: Characterisation of a new C-CTX1 methoxy congener

ABSTRACT

The recent emergence of ciguatera in the eastern Atlantic, particularly in the Canary Islands (Spain) and Madeira (Portugal) prompted the development and implementation of liquid chromatography tandem–mass spectrometry (LC/MS-MS) methods for the detection of ciguatoxins in fish. The complexity of fish tissue matrices, low concentrations of ciguatoxins in hazardous fish, and the scarcity of ciguatoxin standards present challenging issues for successful implementation of routine ciguatoxin analysis. A laboratory reference material of Caribbean Ciguatoxin-1 (C-CTX1), which was previously confirmed in fish responsible for ciguatera outbreaks in the Canary Islands, was used to assess the toxin’s stability under strongly acidic conditions and solvent systems commonly used in LC-MS/MS. It was observed that strongly acidic conditions caused the transformation of C-CTX1 to a C56 methoxy congener, C-CTX1-Me. C-CTX1 was structurally characterised by LC-MS/MS and fragmentation pathways are presented showing the same fragmentation pattern as C-CTX1-Me. These results suggest that the use of strongly acidic conditions during sample pretreatment for C-CTX analysis, might produce significant artefacts, and risks failing to detect the presence of C-CTX1.

KEYWORDS:

• Ciguatoxins
• Ciguatera Fish Poisoning
• C-CTX1
• LC-MS/MS
• Emerging toxins

Acknowledgments

Prof. Takeshi Yasumoto for providing standards for Pacific Ciguatoxins. Dr Robert Dickey (previously, U.S. Food and Drug Administration) via Dr Ronald Manger (Fred Hutchinson Cancer Research Center, Seattle, USA) for providing the Caribbean Ciguatoxin-1 standard (C-CTX1). The authors also acknowledge the financial support through the project EuroCigua: “Risk Characterization of Ciguatera Fish Poisoning in Europe” GP/EFSA/AFSCO/2015/03, co-funded by the European Food Safety Authority (EFSA). Financial support from the Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2016–2019) and the European Union (European Regional Development Fund - ERDF), is also gratefully acknowledged. Pablo Estevez (P.E.) acknowledges the PhD fellowship from the Xunta de Galicia (Regional Government, Spain) under grant ED481A-2018/207.

Disclosure statement

No potential conflict of interest was reported by the authors

Additional information

Funding

This work was supported by the European Food Safety Authority [GP/EFSA/AFSCO/2015/03]; Xunta de Galicia [ED481A-2018/207].