Evaluation of lipid peroxidation by the analysis of volatile aldehydes in the headspace of synthetic membranes using selected ion flow tube mass spectrometry

Rationale: Oxidative stress of cell membranes leads to a number of pathological processes associated with some diseases and is accompanied by the release of volatile aldehydes, which potentially can be used as biomarkers. Thus, the aim was to investigate peroxidation of defined synthetic membranes by direct quantitative analysis of volatile aldehydes. Methods: The concentration spectra of volatile compounds present in the headspace of synthetic membranes under peroxidation stress and following mechanical stress due to sonication were obtained using solid-phase microextraction (SPME) in combination with gas chromatography/mass spectrometry (SPME-GC/MS) and selected ion flow tube mass spectrometry (SIFT-MS). The focus was on the direct, real-time quantification of volatile aldehydes. In addition, the total aldehydes in the aqueous membrane suspensions were quantified using the thiobarbituric acid reactive substances (TBARS) method. Results: Propanal, butanal, pentanal, hexanal, heptanal and malondialdehyde were detected and quantified in the humid headspace of the media containing the synthetic membranes following peroxidation. The composition and concentration of these saturated aldehydes strongly depend on the representation of unsaturated fatty acids in the liposomes. Some protective effect of cholesterol was observed especially for membranes peroxidised by Fenton reagents and after application of a mechanical stress. Conclusions: This study demonstrates that peroxidation of model synthetic membranes in vitro can be tracked in real time using direct quantification by SIFT-MS of several specific aldehydes in the headspace of the membrane suspensions. Cholesterol plays an important role in retaining membrane structure and can indirectly protect membranes from lipid peroxidation.