Chlorinated and brominated phosphatidylcholines are generated under the influence of the Fenton reagent at low pH—a MALDI-TOF MS study

Lipid (phospholipid) oxidation is an increasingly important research topic due to the significant physiological relevance. The Fenton reaction, i.e. the transition metal catalyzed decomposition of H2O2 is frequently used to generate hydroxyl radicals (HO). Lipids with unsaturated fatty acyl residues are primarily converted by HO radicals into peroxides. In contrast, chloro- and bromohydrins as well as dihalogenides are formed by the addition of HOCl or HOBr to the olefinic groups of the fatty acyl residues of lipids or under the influence of the enzyme myeloperoxidase (MPO) from Cl− and H2O2. We will show here by using MALDI-TOF MS for product analysis that halogenated products may also be generated in the presence of the Fenton reagent, if either FeCl2 or FeBr2 is used. In the presence of FeSO4, however, peroxides are exclusively generated. It will also be shown that the generation of halogen-containing products is a competing reaction with the cleavage of the double bond under generation of the corresponding aldehyde or carboxylic acid that is favored at prolonged incubation times and at elevated pH.