Identification and Quantitation of C═C Location Isomers of Unsaturated Fatty Acids by Epoxidation Reaction and Tandem Mass Spectrometry

摘要

src="http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2017/ancham.2017.89.issue-19/acs.analchem.7b01870/20170927/images/medium/ac-2017-018709_0006.gif">Unsaturated fatty acids (FAs) serve as nutrients, energy sources, and signaling molecules for organisms, which are the major components for a large variety of lipids. However, structural characterization and quantitation of unsaturated FAs by mass spectrometry remain an analytical challenge. Here, we report the coupling of epoxidation reaction of the C═C in unsaturated FAs and tandem mass spectrometry (MS) for rapid and accurate identification and quantitation of C═C isomers of FAs in a shotgun lipidomics approach. Epoxidation of the C═C leads to the production of an epoxide which, upon collision induced dissociation (CID), produces abundant diagnostic ions indicative of the C═C location. The total intensity of the same set of diagnostic ions for one specific FA C═C isomer was also used for its relative and absolute quantitation. The simple experimental setup, rapid reaction kinetics (<2 min), high reaction yield (>90% for monounsaturated FAs), and easy-to-interpret tandem MS spectra enable a promising methodology particularly for the analysis of unsaturated FAs in complex biological samples such as human plasma and animal tissues.