Unique Toxin Profile of a Mediterranean Ostreopsis cf. ovata Strain: HR LC-MSⁿ Characterization of Ovatoxin-f, a New Palytoxin Congener

Abstract

Currently, the benthic dinoflagellate Ostreopsis cf. ovata represents a serious concern to human health in the whole Mediterranean basin due to the production of palytoxin congeners, a putative palytoxin and ovatoxins (ovatoxin-a, -b, -c, -d/-e), listed among the most potent marine toxins. High resolution liquid chromatography-mass spectrometry (HR LC-MS) based investigation of a North Western Adriatic strain of Ostreopsis cf. ovata collected at Portonovo (Italy) in 2008 is reported herein. Toxin profile was different from those previously reported for other O. cf. ovata, both qualitatively and quantitatively. For the first time, ovatoxin-a did not dominate the toxin profile, and a new palytoxin congener, here named ovatoxin-f, was detected. Ovatoxin-f and its elemental formula present C(2)H(4) more than ovatoxin-a. HR CID MS(n) experiments allowed us to restrict structural differences between ovatoxin-a and -f to the region between C-95 and C-102, a region not previously been described to be modified in other palytoxins. Ovatoxin-f represents the major component of the toxin profile of the analyzed strain accounting for 50% of the total toxin content, while ovatoxin-a, the dominant toxin in most of the Mediterranean O. cf. ovata strains we have analyzed so far, is the second major component of the toxin profile (23%). Thus, the presence of ovatoxin-f should be taken into account when monitoring programs for palytoxin-like compounds in microalgae and/or seawater are carried out.

Chemical, molecular, and eco-toxicological investigation of Ostreopsis sp. from Cyprus Island: structural insights into four new ovatoxins by LC-HRMS/MS

“…Considering that the B-side fragment due to cleavage #19 matched again that of ovatoxin-a, we could deduce that the oxygen was lacking in the region stretching from C53 to C78. We could not further restrict the region of difference as this part structure does not fragment further, as already observed for other palytoxin-like compounds [19,23,24], likely as a consequence of the formation of a conjugated polyene during the fragmentation process [37].…”

“…The employed approach [19] uses the fragmentation pattern of a structurally defined palytoxin congener, such as palytoxin [20,21] or ovatoxin-a (OVTX-a) [22] (Fig. 1), as a template for structural characterization of the unknown [23,24], providing tentative structures.…”

Warm Seawater Microalgae: Growth and Toxic Profile of Ostreopsis Spp. from European Coasts

“…In this sense, many times the results are shown as PLTX-like compounds because although several analogs have been identified, as far as we know, certified material or standards for these products are not yet available. Therefore the identification studies published are based on theoretical chemical approaches from a PLTX standard [5,[7][8][9][10]18].…”

“…The PLTX-group of toxins includes complex polyhydroxylated compounds with a lipophilic and a hydrophilic area. Different molecules related with the PLYX structure ( Figure 1) have been described: palytoxin-b, homopalytoxin, bishomopalytoxin, neopalytoxin, deoxypalytoxin, 42-hydroxypalytoxin, ostreocin-d, ovatoxin-a, -b,-c,-d, -e and -f and mascarenotoxin-a, -b and -c. However only the chemical structures of PLTX, ostreocin-d, ovatoxin-a and 42-hydroxypalytoxin have been characterized [4][5][6][7][8][9][10][11]. PLTX is a large molecule, with a molecular weight of 2659-2680 daltons depending on the origin [12,13].…”

Sanitary problems related to the presence of Ostreopsis spp. in the Mediterranean Sea: a multidisciplinary scientific approach

“…Since then, there has been increasing consensus in the scientific community regarding microalgae as at least one producer of the toxins, even though the biosynthetic pathways are still unclear and represent a field of open and ongoing research. In addition to O. siamensis, putative PLTX and analogues have been isolated from O. mascarenensis [29] and O. ovata [30][31][32][33][34][35]. Extensive studies on Ostreopsis samples has led to the identification of several PLTX congeners (Figure 2), including ostreocin-D [26,27], mascarenotoxins [29][30][31][32][33][34] and several ovatoxins, denoted ovatoxin-a, -b, -c, -d, -e [30][31][32][33][34] and ovatoxin-f [35].…”