Discovery of fatty acid ester metabolites of spirolide toxins in mussels from Norway using liquid chromatography/tandem mass spectrometry

Abstract

Cultured mussels sampled in the spring of 2002 and 2003 from Skjer, a location in the Sognefjord, Norway, tested positive in the mouse bioassay for lipophilic toxins. In a previous report, it was established that a number of spirolides, cyclic imine toxins produced by the phytoplankton Alexandrium ostenfeldii, were present in the mussels and were responsible for the observed toxicity. The main toxin proved to be a new compound named 20-methyl spirolide G. In subsequent studies, a delayed onset of spirolide-like symptoms in the mouse bioassay exceeding the usual time limit of 20 min was observed in some samples, with symptoms and death appearing as long as 45-50 min after injection. It is well known that shellfish can extensively metabolize other toxins, such as okadaic acid and the dinophysistoxins, to fatty acid acyl esters and it is also known that a delayed onset of toxic symptoms with such metabolites can occur. Analyses performed with liquid chromatography/ tandem mass spectrometry (LC/MS/MS) have revealed a complex mixture of esters of 20-methyl spirolide G in the contaminated mussels. Precursor ion scanning has delineated the range of fatty acid esters involved, while product ion scanning has provided information on structure. Identity was also supported through reaction of 20-methyl spirolide G with palmitic anhydride, which produced a derivative with a retention time and spectrum identical with one putative metabolite, 17-O-palmitoyl-20-methyl spirolide G.

Identification of Pinnatoxins and Discovery of Their Fatty Acid Ester Metabolites in Mussels (Mytilus edulis) from Eastern Canada

“…They were not detected in a survey of mussel samples from Norway, 18 despite the occurrence of esters of other toxin groups in mussels harvested in similar locations. 23,26 No acyl esters of 6 were observed following base hydrolysis of contaminated oysters (Crassostrea gigas) from South Australia. 6 A recent study looking at the occurrence of benthic toxins from harbors in New Zealand found significant quantities of pinnatoxins and okadaic acid in a variety of marine organisms.…”

“…The presence of 7-O-acyl derivates of okadaic acid and dinophysistoxins has been well documented, 20−23 and similar acyl esters of pectenotoxins, 24 brevetoxins, 25 and spirolides 26 have been reported. Because pinnatoxins also contain hydroxyl groups that could be acylated, it seems possible that similar metabolites of these compounds would occur.…”

Synthesis and biology of cyclic imine toxins, an emerging class of potent, globally distributed marine toxins

“…All known spirolides have so far been linked to two producing organisms, dinoflagellate Alexandrium ostenfeldii 14,17,19,31,32,33,34,40 and Alexandrium peruvianum . 13,35,36,37 A. ostenfeldii is a gonyaulacoid 38 dinoflagellate that has long been considered confined to Northern cold-temperature oceanic waters (Figure 3D).…”

Quantification and profiling of lipophilic marine toxins in microalgae by UHPLC coupled to high-resolution orbitrap mass spectrometry

“…Operating the software programme ToxID 2.1.2 (Thermo Fisher Scientific, San José, USA), the full-scan data of three culture extracts were efficiently screened. To this end, a ToxID database from Gerssen et al [15] was modified by adding new compounds and molecular formulas of 98 relevant toxins [24,[50][51][52][53][54][55][56][57][58][59][60][61][62], see Table S1 …”