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Characterization of maitotoxin‐4 (MTX4) using electrospray positive mode ionization high‐resolution mass spectrometry and UV spectroscopy
Author(s) -
Pisapia Francesco,
Sibat Manoëlla,
Watanabe Ryuichi,
Roullier Catherine,
Suzuki Toshiyuki,
Hess Philipp,
Herrenknecht Christine
Publication year - 2020
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.8859
Subject(s) - chemistry , electrospray ionization , mass spectrometry , electrospray , molecule , adduct , fragmentation (computing) , chromatography , spectroscopy , mass spectrum , analytical chemistry (journal) , organic chemistry , physics , quantum mechanics , computer science , operating system
Rationale The dinoflagellate genera Gambierdiscus and Fukuyoa are producers of toxins responsible for Ciguatera Poisoning (CP). Although having very low oral potency, maitotoxins (MTXs) are very toxic following intraperitoneal injection and feeding studies have shown they may accumulate in fish muscle. To date, six MTX congeners have been described but two congeners (MTX2 and MTX4) have not yet been structurally elucidated. The aim of the present study was to further characterize MTX4. Methods Chemical analysis was performed using liquid chromatography coupled to a diode‐array detector (DAD) and positive ion mode high‐resolution mass spectrometry (LC/HRMS) on partially purified extracts of G. excentricus (strain VGO792). HRMS/MS studies were also carried out to tentatively explain the fragmentation pathways of MTX and MTX4. Results The comparison of UV and HRMS (ESI + ) spectra between MTX and MTX4 led us to propose the elemental formula of MTX4 (C 157 H 241 NO 68 S 2 , as the unsalted molecule). The comparison of the theoretical and measured m/z values of the doubly charged ions of the isotopic profile in ESI + were coherent with the proposed elemental formula of MTX4. The study of HRMS/MS spectra on the tri‐ammoniated adduct ([M – H + 3NH 4 ] 2+ ) of both molecules gave additional information about structural features. The cleavage observed, probably located at C 99 –C 100 in both MTX and MTX4, highlighted the same A‐side product ion shared by the two molecules. Conclusions All these investigations on the characterization of MTX4 contribute to highlighting that MTX4 belongs to the same structural family of MTXs. However, to accomplish a complete structural elucidation of MTX4, an NMR‐based study and LC/HRMS n investigation will have to be carried out.