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Rontani J.-F.,Aix - Marseille University | Rontani J.-F.,CNRS Mediterranean Institute of Oceanography (MIO) | Aubert C.,Laboratoire Of Pharmacocinetique Et Toxicocinetique Ea 3286 | Belt S.T.,University of Plymouth
Journal of the American Society for Mass Spectrometry | Year: 2015

EI mass fragmentation pathways of TMS derivatives οf 7α/β-hydroxy-dehydroabietic acids resulting from NaBH4-reduction of oxidation products of dehydroabietic acid (a component of conifers) were investigated and deduced by a combination of (1) low energy CID-GC-MS/MS, (2) deuterium labeling, (3) different derivatization methods, and (4) GC-QTOF accurate mass measurements. Having identified the main fragmentation pathways, the TMS-derivatized 7α/β-hydroxy-dehydroabietic acids could be quantified in multiple reaction monitoring (MRM) mode in sea ice and sediment samples collected from the Arctic. These newly characterized transformation products of dehydroabietic acid constitute potential tracers of biotic and abiotic degradation of terrestrial higher plants in the environment. [Figure not available: see fulltext.] © 2015 American Society for Mass Spectrometry. Source


Rontani J.-F.,Aix - Marseille University | Rontani J.-F.,CNRS Mediterranean Institute of Oceanography (MIO) | Belt S.T.,University of Plymouth | Brown T.A.,University of Plymouth | Aubert C.,Laboratoire Of Pharmacocinetique Et Toxicocinetique Ea 3286
Rapid Communications in Mass Spectrometry | Year: 2014

RATIONALE C25 tri-unsaturated highly branched isoprenoid (HBI) alkenes are produced by a number of marine diatoms around the world yet are very easily oxidized during senescence to yield several isomeric allylic 9-hydroperoxides. Elucidation of the electron ionization mass spectrometry (EIMS) fragmentation pathways of the trimethylsilyl (TMS) derivatives of the alcohols (obtained by reduction of the corresponding 9-hydroperoxides) is essential for their characterization and quantification in natural samples. METHODS EIMS fragmentation pathways of TMS derivatives of isomeric allylic alcohols resulting from NaBH4 reduction of photo- and autoxidation products of HBI alkenes were investigated. These pathways were deduced by: (i) low-energy collision-induced dissociation gas chromatography/tandem mass spectrometry (CID-GC/MS/MS) and (ii) deuterium labelling. RESULTS CID-MS/MS analyses and deuterium labelling allowed us to elucidate EIMS fragmentations of TMS derivatives of several isomeric allylic alcohols resulting from NaBH 4 reduction of HBI alkene oxidation products and to propose some specific fragment ions for differentiating individual isomers. As an application of some of the described fragmentations, these oxidized compounds in phytoplanktonic cells collected from the Antarctic were characterized and quantified in multiple reaction monitoring (MRM) mode. CONCLUSIONS EIMS fragmentations of TMS derivatives of several isomeric allylic alcohols resulting from NaBH4 reduction of HBI alkene oxidation products are shown to be strongly dependent on the position and configuration of double bonds, allowing simple, yet robust differentiation of individual isomers in natural samples. Copyright © 2014 John Wiley & Sons, Ltd. Source


Ea S.,Laboratoire Of Pharmacocinetique Et Toxicocinetique Ea 3286 | Aubert C.,Laboratoire Of Pharmacocinetique Et Toxicocinetique Ea 3286 | Rontani J.-F.,Aix - Marseille University | Rontani J.-F.,CNRS Mediterranean Institute of Oceanography (MIO) | And 2 more authors.
Rapid Communications in Mass Spectrometry | Year: 2014

RATIONALE Formation of vicinal diols was observed after in vitro and in vivo studies of the natural product haplamine (9-methoxy-2,2-dimethyl-2,6- dihydropyrano[3,2-c]quinolin-5-one). These compounds, identified as trans- and cis-3,4-dihydroxy-9-methoxy-2,2-dimethyl-2,3,4,6-tetrahydropyrano[3,2-c] quinolin-5-ones and trans- and cis-3,4,9-trihydroxy-2,2-dimethyl-2,3,4,6- tetrahydropyrano[3,2-c]quinolin-5-ones, have a potential interest in oncology. It is therefore essential to elucidate their electron ionization mass spectrometric (EIMS) fragmentation pathways. METHODS EIMS fragmentation pathways of trimethylsilyl (TMS) derivatives of 3,4-dihydroxy- and 3,4,9- trihydroxyhaplamines were investigated. These pathways have been substantiated by: (i) comparison with EI mass spectra of structural homologues (silylated diols obtained from various chromenes and 1,2-dihydronaphthalene), (ii) low-energy collision-induced dissociation (CID) gas chromatography/tandem mass spectrometry (GC/MS/MS) and (iii) 18O labelling. RESULTS CID-MS/MS analyses and 18O labelling demonstrated that EI mass spectral fragmentation of these TMS derivatives involves a transannular cleavage of the pyran ring with formation of a characteristic intense cyclic ion. The study of the mass spectra of TMS derivatives of different chromenes and 1,2-dihydroxynaphthalene allowed to confirm the proposed fragmentation pathways and to show that they act only when the pyran ring is present. CONCLUSIONS Elimination of the neutral element [(CH3)2=C(H)OSi(CH 3)3] and formation of cyclic ions play a key role during EI mass spectral fragmentation of the TMS derivatives of 3,4-dihydroxy- and 3,4,9-trihydroxyhaplamines. These fragmentation pathways could be generalized to TMS derivatives of cyclic compounds possessing vicinal diols close to a pyran ring. Copyright © 2014 John Wiley & Sons, Ltd. Source

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