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

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.

Two novel azaspiracids from Azadinium poporum, and a comprehensive compilation of azaspiracids produced by Amphidomataceae, (Dinophyceae).

Two novel azaspiracids (AZA) with a molecular mass of 869 Da were found in Pacific strains of Azadinium poporum and characterized by tandem mass spectrometry and high resolution mass spectrometry (HRMS). One compound, AZA-42, was found in Az. poporum strains AZFC25 and AZFC26, both isolated from the South China Sea. AZA-42 belongs to the 360-type AZA that in comparison to AZA-1 has an additional double bond in the F-I ring system of AZA comprising C28-C40. The other compound, AZA-62, was detected in Az. poporum strain 1D5 isolated off Chañaral, Northern Chile. Mass spectral data indicate that AZA-62 is a variant of AZA-11 with an additional double bond in the C1-C9 region of AZA. In addition to the description of the two novel AZA, a comprehensive list of all AZA known to be produced by species of the genera Azadinium and Amphidoma comprising 26 AZA variants is presented.