Characterisation of new analogues of palytoxin isolated from an Ostreopsis mascarenensis bloom in the south-western Indian Ocean

A preliminary screening of toxins of the crude extract of Ostreopsis mascarenensis Quod, a benthic dinoflagellate from the south-western Indian Ocean, revealed a neurotoxicity in mice similar to that induced by palytoxin,one of the most potent marine toxins involved in seafood poisoning. The highest toxicity was retained in the butanol-soluble fraction, revealing a strong haemolytic activity, as found for palytoxin. Analyses usinghigh-performance liquid chromatography with ultraviolet detection allowed the detection of two new toxins named mascarenotoxins (McTXs). Their mass spectrum profile and fragmentation pattern, obtained by advancednano-ESI-Q-TOF mass spectrometry of purified McTXs, were similar to those of a reference palytoxin. They were identified as palytoxin analogues, with the characterisation of a specific fragment ion m/z 327. O. mascarenensisis a species not previously known to produce palytoxin analogues.