Studies on azaspiracid biotoxins. II. Mass spectral behavior and structural elucidation of azaspiracid analogs

Abstract

In this report, the mass spectral analysis of azaspiracid biotoxins is described. Specifically, the collision-induced dissociation (CID) behavior and differences between CID spectra obtained on a triple-quadrupole, a quadrupole time-of-flight, and an ion-trap mass spectrometer are addressed here. The CID spectra obtained on the triple-quadrupole mass spectrometer allowed the classification of the major product ions of the five investigated compounds (AZA 1-5) into five distinct fragment ion groups, according to the backbone cleavage positions. Although the identification of unknown azaspiracids was difficult based on CID alone, the spectra provided sufficient structural information to allow confirmation of known azaspiracids in marine samples. Furthermore, we were able to detect two new azaspiracid analogs (AZA 1b and 6) in our samples and provide a preliminary structural analysis. The proposed dissociation pathways under tandem mass spectrometry (MS/MS) conditions were confirmed by a comparison with accurate mass data from electrospray quadrupole time-of-flight MS/MS experiments. Regular sequential MS(n) analysis on an ion-trap mass spectrometer was more restricted in comparison to the triple-quadrupole mass spectrometer, because the azaspiracids underwent multiple [M + H - nH(2)O](+) (n = 1-6) losses from the precursor ion under CID. Thus, the structural information obtained from MS(n) experiments was somewhat limited. To overcome this limitation, we developed a wide-range excitation technique using a 180-u window that provided results comparable to the triple-quadrupole instrument. To demonstrate the potential of the method, we applied it to the analysis of degraded azaspiracids from mussel tissue extracts.

Formation of Azaspiracids-3, -4, -6, and -9 via Decarboxylation of Carboxyazaspiracid Metabolites from Shellfish

“…There was nothing in their structures suggesting the possibility of conversion to AZA3 upon heating, especially under the mild conditions in which the phenomenon was sometimes observed. The possibility of carboxylic acid derivatives of AZAs had been suggested on the basis of MS data, but no structures were proposed (8). Recent work demonstrated the existence of carboxylated AZAs (AZA17, -19, -21, and -23), although the location of the carboxylic acid group could not be definitively Proposed oxidative metabolism of AZA1 and -2 in shellfish to form 22-carboxylated metabolites (AZA17 and -19), which undergo decarboxylation when heated to form AZA3 and -6, respectively.…”

Structural study of spirolide marine toxins by mass spectrometry

“…3). Multiple water losses, characteristic of several polyether compounds [28,37,38,39], are observed, as well as a cluster of ions in the region of m/z 444, also related by several water losses. The base fragment is represented as a cyclic imine with stabilizing conjugation at m/z 164 (Fig.…”

“…The HPLC system employed was an Agilent 1100 (Palo Alto, CA, USA) binary pump, with modifications, as previously described [28], to reduce gradient delay times. A Phenomenex ODS (30) 150×3.2 mm i.d.…”

Mediterranean Azadinium dexteroporum (Dinophyceae) produces six novel azaspiracids and azaspiracid-35: a structural study by a multi-platform mass spectrometry approach

“…The MS behavior of AZAs is indeed characteristic and it has been studied widely using either tandem MS or high resolution MS analyzers [9,[23][24][25]. Over the last years, new dinophycean species other than A. spinosum have been identified as AZA producers, including Amphidoma languida from Bantry Bay and two species in the genus Azadinium, i.e., Azadinium poporum from the North Sea, Korea [12], and the China Sea [26], and Azadinium dexteroporum from the Mediterranean Sea [13].…”