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Reactive oxygen species (ROS) play important physiological roles and are of particular relevance in the pathogenesis of inflammatory diseases. At inflammatory conditions, the enzyme myeloperoxidase generates hypochlorous acid (HOCl) which adds to the double bonds of fatty acyl residues of (phospho)lipids under the formation of chlorohydrins. This may lead to the development of many inflammatory diseases, such as atherosclerosis or arthritis, if the ROS generation exceeds a certain extent. Using oleic acid as the simplest unsaturated fatty acid which contains just a single double bond, as a model system, we investigated all products - including the chlorohydrin - after its reaction with HOCl by a combination of thin-layer chromatography and electrospray ionization mass spectrometry. Unlike the general acceptance, the reaction of oleic acid and HOCl leads not exclusively to the formation of chlorohydrin (isomers) but is much more complex: there are also considerable amounts of dimeric and (to a minor extent) trimeric products which can be assigned to isomeric ethers and esters. The obtained products after oleic acid chlorination were also compared with the reaction products of 1-palmitoyl-2-oleoyl-sn-phosphatidylcholine (POPC) and HOCl. The reasons why different products are obtained will be discussed and the involvement of the carboxylic acid emphasized., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Free fatty acids (FFA) are released through phospholipase A 2 (PLA 2 ), which cleaves the fatty acyl residue at the sn -2 position of phospholipids (PL). During inflammatory diseases, reactive oxygen species (such as HOCl) lead to the formation of oxidatively modified PL (e.g., chlorohydrin generation). It is still widely unknown to which extent the oxidation of PL influences their digestibility by PLA 2 . Additionally, investigations on the impact of the position of the unsaturated fatty acyl residue ( sn -1 versus sn -2 position) and modifications of the headgroup (for instance phosphatidylcholine (PC) versus phosphatidylethanolamine (PE)) are also lacking. Therefore, the aim of this study is the investigation of these aspects using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry to elucidate the PL/lysophospholipid (LPL) ratios as measures of the PLA 2 digestibility. We will show that oxidative modifications of PL by HOCl have a considerable impact on the PLA 2 digestibility, i.e., oxidation of the unsaturated fatty acyl residues leads to a reduced digestibility of both PC and PE. Besides, it will be shown that MALDI MS is a convenient and reliable tool to investigate the related changes. [ABSTRACT FROM AUTHOR]