Complex Palitoxin-Like Profile Of Ostreopsis Ovata. Identification Of Four New Ovatoxins By High Resolution Liquid Chromatography-Mass Spectrometry

In the last decades, the Italian coastlines have been plagued by the recurring presence of the benthic dinoflagellate Ostreopsis ovata. Such an alga has caused severe sanitary emergencies and economic losses due to its production of palytoxin-like compounds. Previous studies evidenced the presence of ovatoxin-a, as the major toxin of the algal toxin profile together with small amounts of putative palytoxin. In our ongoing research on O. ovata toxins we report herein on high resolution LC-MS and MS2 investigation of an O. ovata culture, which revealed an algal toxin profile more complex than previously found. Particularly, the presence of putative palytoxin and ovatoxin-a was confirmed and the occurrence in the extract of four new palytoxin-like compounds, ovatoxin-b, -c, -d, and -e, was highlighted. Elemental formulae very close to palytoxin???s have been assigned to the new ovatoxins and information has been gained about their structural features. A quantitative study of the O. ovata culture extract indicated that ovatoxin-a represented almost 54% of the total toxin content with the remaining 46% being constituted by the whole of ovatoxin-b, -c, -d and -e. Thus, the presence of the new ovatoxins should be taken into account when LC-MS based monitoring programs of either plankton or contaminated seafood are carried out.