Brevisulcenal-G, -H, and –I, Polycyclic Ether Marine Toxins from the Dinoflagellate Karenia brevisulcata

Members of two classes of marine polycyclic ether compounds, brevisulcenals (KBTs) and brevisulcatic acids (BSXs), were isolated as causative toxins from a red tide (Karenia brevisulcata) bloom event in New Zealand in 1998. The new analogues, brevisulcenals (KBTs)-G, -H, and -I, were isolated from neutral lipophilic extracts of bulk dinoflagellate culture extracts, and the molecular structures of these compounds were elucidated by detailed analyses of NMR and matrix -assisted laser desorption/ionization tandem mass spectrometry spectra, and by comparison with the spectra of KBT-F. All the analogues have the same size and arrangement of 24 ether rings, but differ in their backbone substitution patterns and degree of terminal oxidation. The cytotoxicity of these new KBT analogues was greater than that of the co-isolated, KBT-F.