title: Multiple ciguatoxins present in Indian Ocean reef fish.
abstract: Optimised gradient reversed-phase high-performance liquid chromatography electrospray ionisation mass spectrometry (LC/MS) methods, in combination with a [3H]-brevetoxin binding assay (RLB), revealed multiple ciguatoxins in a partially purified extract of a highly toxic Lutjanus sebae (red emperor) from the Indian Ocean. Two major ciguatoxins of 1140.6 Da (I-CTX-1 and -2) and two minor ciguatoxins of 1156.6 Da (I-CTX-3 and -4) were identified. Accurate mass analysis revealed that I-CTX-1 and -2 and Caribbean C-CTX-1 had indistinguishable masses (1140.6316 Da, at 0.44 ppm resolution). Toxicity estimated from LC/MS/RLB responses indicated that I-CTX-1 and -2 were both approximately 60% the potency of Pacific ciguatoxin-1 (P-CTX-1). In contrast to ciguatoxins of the Pacific where the more oxidised ciguatoxins are more potent, I-CTX-3 and -4 were approximately 20% of P-CTX-1 potency. Interconversion in dilute acid or on storage, typical of spiroketal and hemiketal functionality found in P-CTXs and C-CTXs, respectively, was not observed to occur between I-CTX-1 and -2. The ratio of CTX-1 and -2 varied depending on the fish extract being analysed. These results suggest that I-CTX-1 and -2 may arise from separate dinoflagellate precursors that may be oxidatively biotransformed to I-CTX-3 and -4 in fish.
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Qld 4072, Australia.
authors.forename: Brett
authors.initials: B
authors.lastname: Hamilton
authors.forename: Mira
authors.initials: M
authors.lastname: Hurbungs
authors.forename: Alun
authors.initials: A
authors.lastname: Jones
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lewis
mesh_terms: D000818:Animals; D001681:Biological Assay; D002851:Chromatography, High Pressure Liquid; D002922:Ciguatoxins / Q000145:classification / Q000302:isolation & purification* / Q000633:toxicity; D005399:Fishes / Q000378:metabolism*; D019156:Indian Ocean; D008387:Marine Toxins / Q000378:metabolism; D051379:Mice; D035964:Oxocins / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D014316:Tritium; D000095702:Polyether Toxins
chemical_list: D002922:Ciguatoxins; D008387:Marine Toxins; D035964:Oxocins; D014316:Tritium; C053342:brevetoxin; D000095702:Polyether Toxins