A widely targeted analytical method for oxylipins including enantiomers using chiral liquid chromatography tandem...

Oxylipins are lipids formed when polyunsaturated fatty acids are oxidized. Several oxylipins play important roles in the body, such as regulation of inflammatory responses. Although oxylipin measurement is commonly performed using reversed-phase liquid chromatography tandem mass spectrometry, conventional methods cannot resolve enantiomers. The aim of this study was to develop a widely targeted analysis method for oxylipins that could separate enantiomers. First, seven polysaccharide-derived chiral columns were screened, and the CHIRALPAK IG column, which achieved the highest resolution of eicosanoid isomers, was selected. Next, the set of targeted compounds was expanded, and the chromatographic separation of 151 compounds, including 40 pairs of enantiomers, was evaluated. The constructed method successfully separated 55 out of 59 pairs of isomers, including enantiomers. Finally, the established method was used to analyze mouse plasma and five types of tissues, and approximately 100 compounds exhibiting characteristic profiles were detected in each tissue. After evaluating hydroxyeicosatetraenoic acids (HETEs), monohydroxy compounds of arachidonic acid, it was found that the S-enantiomer of 12-HETE was more prevalent than the R-enantiomer in the lungs and spleens. Conversely, R-enantiomer of 9-HETE and 11-HETE was more abundant than the S-enantiomer. The amounts of R- and S-enantiomers of 5-HETE and 8-HETE were nearly equal in certain tissues. This analytical method is useful for biomarker discovery and accurately understanding the pathways of oxylipin formation because it can perform a widely targeted analysis of oxylipins, including enantiomers.