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Open AccessFeature PaperArticle

Mass Spectrometry-Based Characterization of New Spirolides from Alexandrium ostenfeldii (Dinophyceae)

1
Alfred Wegener Institut-Helmholtz Zentrum für Polar- und Meeresforschung, Ökologische Chemie, Am Handelshafen 12, 27570 Bremerhaven, Germany
2
Helmholtz Institut für Funktionelle Marine Biodiversität an der Universität Oldenburg (HIFMB), Ammerländer Heerstraße 231, 26129 Oldenburg, Germany
*
Author to whom correspondence should be addressed.
Mar. Drugs 2020, 18(10), 505; https://doi.org/10.3390/md18100505
Received: 7 August 2020 / Revised: 23 September 2020 / Accepted: 28 September 2020 / Published: 2 October 2020
Spirolides belong to a group of marine phycotoxins produced by the marine planktonic dinophyte Alexandrium ostenfeldii. Composed of an imine moiety and a spiroketal ring system within a macrocylcle, spirolides are highly diverse with toxin types that vary among different strains. This study aims to characterize the spirolides from clonal A. ostenfeldii strains collected from The Netherlands, Greenland and Norway by mass spectral techniques. The structural characterization of unknown spirolides as inferred from high-resolution mass spectrometry (HR-MS) and collision induced dissociation (CID) spectra revealed the presence of nine novel spirolides that have the pseudo-molecular ions m/z 670 (1), m/z 666 (2), m/z 696 (3), m/z 678 (4), m/z 694 (5), m/z 708 (6), m/z 720 (7), m/z 722 (8) and m/z 738 (9). Of the nine new spirolides proposed in this study, compound 1 was suggested to have a truncated side chain in lieu of the commonly observed butenolide ring in spirolides. Moreover, there is indication that compound 5 might belong to new spirolide subclasses with a trispiroketal ring configuration having a 6:5:6 trispiroketal ring system. On the other hand, the other compounds were proposed as C- and G-type SPX, respectively. Compound 7 is proposed as the first G-type SPX with a 10-hydroxylation as usually observed in C-type SPX. This mass spectrometry-based study thus demonstrates that structural variability of spirolides is larger than previously known and does not only include the presence or absence of certain functional groups but also involves the triketal ring system. View Full-Text
Keywords: CID spectrum; fragmentation pattern; cyclic imine; elemental composition; triketal ring system; proposed structure CID spectrum; fragmentation pattern; cyclic imine; elemental composition; triketal ring system; proposed structure
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Nieva, J.A.; Tebben, J.; Tillmann, U.; Wohlrab, S.; Krock, B. Mass Spectrometry-Based Characterization of New Spirolides from Alexandrium ostenfeldii (Dinophyceae). Mar. Drugs 2020, 18, 505.

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