Structural study of spirolide marine toxins by mass spectrometry

Abstract

A novel group of toxins, the spirolides, has been investigated by several mass spectrometric (MS) methods to enable structure elucidation and metabolite identification. These macrocyclic compounds, produced by the dinoflagellate Alexandrium ostenfeldii, are a new class of marine phycotoxin with characteristic spiro-linked tricyclic ether and imine moieties. A crude phytoplankton extract has been shown to contain known spirolides and several unknown compounds, present at low yet significant levels. This study has focused on mass spectrometric characterization of the main component of this extract, 13-desmethyl spirolide C. Collision-induced dissociation (CID) spectra were collected on triple-quadrupole and quadrupole linear ion-trap instruments. High-resolution Fourier-transform ion cyclotron resonance MS data revealed the accurate masses of the protonated molecule and the product ions formed by infrared multiphoton dissociation. A fragmentation scheme for this toxin has been proposed to explain the formation of the collision-induced fragments. Charge-remote fragmentations dominate the CID spectra, because there is only one predominantly basic site in this molecule, and prove to be structurally informative. Extensive MS characterization of 13-desmethyl spirolide C will undoubtedly be useful in the characterization of known and unknown spirolides and other related compounds.

Toxin Variability Estimations of 68 Alexandrium ostenfeldii (Dinophyceae) Strains from The Netherlands Reveal a Novel Abundant Gymnodimine

“…Precursor ion scans of the characteristic spirolide fragment at m/z 164, which is characteristic for SPX [41], revealed the presence of four more precursor ions with m/z 696 ( 2 ), m/z 710 ( 3 ), m/z 720 ( 4 ) and m/z 722 ( 5 ). The CID experiments of these precursor masses displayed the typical A- and B-type fragments characteristic for SPX (Figure 2).…”

“…The typical A-type SPX fragment cluster of ( 1 ) (Figure 2B) was downshifted of 16 Da in comparison to 13-desMethyl-spirolide C [41,42]. In addition to the B-type fragment at m/z 164, ions not commonly observed in SPX CID spectra appeared at m/z 248, 274 and 292.…”

“…The second characteristic SPX fragment group (A type, Figure 2A) is produced by the loss of the butenolide side chain of the molecule, which is formed after a retro-Diels–Alder opening of the SPX macrocycle and subsequent water losses. This fragment cluster typically occurs in the mass range of 400 to 500 Da [41], except for G-type SPX, where this cluster is shifted to lower masses [22]. The third SPX fragment group (B-type, Figure 2A) consists of the cyclic imine ring with an ethylene rest of the macrocycle at m/z 150, 164 or 180 (depending on the degree of methylation and/or hydroxylation).…”

Confirmation of Pinnatoxins and Spirolides in Shellfish and Passive Samplers from Catalonia (Spain) by Liquid Chromatography Coupled with Triple Quadrupole and High-Resolution Hybrid Tandem Mass Spectrometry

“…Product ions monitored were 674 m/z , 444 m/z and 164 m/z for SPX-1 (MRM1, MRM2 and MRM3, respectively); and 676 m/z , 458 m/z and 164 m/z for PnTX-G (MRM1, MRM2 and MRM3, respectively). MRM1 was the quantifier while MRM2 and MRM3 were qualifiers; these ions were selected according to their diagnostic power [8,16,17] and included the cyclic imine (MRM3). The precursor and product ions applied for the screening of analogs of PnTX-G and SPX-1 were the nominal m/z as those listed in Table 1.…”

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 …”