Use of gas chromatography-mass spectrometry techniques (GC-MS, GC-MS/MS and GC-QTOF) for the characterization of lipid photooxidation and autoxidation products in senescent autotrophic organisms
Résumé
This paper reviews applications of gas chromatography-mass spectrometry techniques for the characterization of lipid photooxidation and autoxidation products in senescent phototrophic organisms. Particular attention is given to: (i) the selection of oxidation products that are sufficiently stable and specific to each lipid class and degradation route, (ii) the description of electron ionization mass fragmentation of trimethylsilyl derivatives of these compounds and (iii) the use of specific fragment ions for monitoring the oxidation of the main unsaturated lipid components of phototrophs. The techniques best geared for this task were gas chromatography-quadrupole-time of flight to monitor fragment ions with very high resolution and accuracy, and gas chromatography-tandem mass spectrometry to monitor very selective transitions in multiple reaction monitoring mode. The extent of the degradation processes can only be estimated if the oxidation products are unaffected by fast secondary oxidation reactions, as it is notably the case of 5-sterols, monounsaturated fatty acids, chlorophyll phytyl side-chain, and di-and triterpenoids. In contrast, the primary degradation products of highly branched isoprenoid alkenes possessing more than one trisubstituted double bond, alkenones, carotenoids and polyunsaturated fatty acids, appear to be too unstable with respect to secondary oxidation or other reactions to serve for quantification in senescent phototrophs.
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