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Anal Bioanal Chem (2015) 407:11911204 DOI 10.1007/s00216-014-8338-y
RESEARCH PAPER
The novel ovatoxin-g and isobaric palytoxin (so far referred to as putative palytoxin) from Ostreopsis cf. ovata(NW Mediterranean Sea): structural insights by LC-high resolution MSn
Mara Garca-Altares & Luciana Tartaglione & Carmela DellAversano &
Olga Carnicer & Pablo de la Iglesia & Martino Forino &
Jorge Diogne & Patrizia Ciminiello
Received: 17 September 2014 /Revised: 7 November 2014 /Accepted: 10 November 2014 /Published online: 10 December 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Blooms of the benthic dinoflagellate Ostreopsis cf. ovata are a concern in the Mediterranean Sea, since this species produces a wide range of palytoxin-like compounds listed among the most potent marine toxins. This study focused on two analogs of palytoxin found in cultures of six strains of O. cf. ovata isolated from the south of Catalonia (NW Mediterranean Sea). In addition to some already known ovatoxins, our strains produced two minor compounds, ovatoxin-g and the so far called putative palytoxin, whose structures had not been elucidated before. Insufficient quantity of these compounds impeded a full nuclear magnetic resonance (NMR)-based structural elucidation; thus, we studied their structure in crude algal extracts through liquid chromatographyelectrospray ionization high-resolution mass spectrometryn (LC-ESI-HRMSn) in positive ion mode. Under the used MS conditions, the molecules underwent fragmentation at many sites of their backbone and a large number of diagnostic fragment ions were identified. As a result, tentative structures were assigned to both ovatoxin-g and the putative
palytoxin, the latter being identified as a palytoxin isomer and re-named as isobaric palytoxin.
Keywords Ostreopsis cf. ovata . Palytoxin . Putative palytoxin . Isobaric palytoxin . Ovatoxin-g . LC-HRMSn
Introduction
Ovatoxins (OVTXs) are complex macromolecules produced by the benthic dinoflagellate Ostreopsis cf. ovata (Fig. 1) [13]. Structurally, they are closely related to palytoxin (PLTX, C129H223N3O54), one of the most toxic non-peptidic
marine compounds (LD50 by intra-venous administration of0.15 g/kg in mice) [4] first isolated from soft corals of the genus Palythoa [5, 6] (Fig. 1).
Although little is known on their toxicity [7], ovatoxins have been frequently involved in several Ostreopsis-related toxic outbreaks following inhalation of marine aerosols in the Mediterranean basin [810]. The presence of ovatoxins and O. cf. ovata cells in the aerosols has been recently proven by chemical and...