Novel Isotope-Labeled Derivatization Strategy for the Simultaneous Analysis of Fatty Acids and Fatty Alcohols and Its Application in Idiopathic Inflammatory Myopathies and Pancreatic Cancer

Fattyacids (FAs) and fatty alcohols (FOHs) are essentialcompoundsfor maintaining life. Due to the inherent poor ionization efficiency,low abundance, and complex matrix effect, such metabolites are challengingto precisely quantify and explore deeply. In this study, a pair ofnovel isotope derivatization reagents known as d0/d5-1-(2-oxo-2-(piperazin-1-yl)ethyl) pyridine-1-ium (d0/d5-OPEPI) were designed and synthesized,and an in-depth screening strategy for FAs and FOHs was establishedbased on d0/d5-OPEPI coupled with liquid chromatography-tandem high-resolutionmass spectrometry (LC-HRMS/MS). Using this approach, a total of 332metabolites were identified and annotated (some of the FAs and FOHswere reconfirmed by standards). Our results demonstrated that OPEPIlabeling could significantly enhance the MS response of FAs and FOHsvia the introduction of permanently charged tags. The detection sensitivitiesof FAs were increased by 200-2345-fold compared with the nonderivatizationmethod. At the same time, for FOHs, due to the absence of ionizablefunctional groups, sensitive detection was achieved utilizing OPEPIderivatization. One-to-one internal standards were provided by usingd5-OPEPI labeling to minimize the errors in quantitation. Moreover,the method validation results showed that the method was stable andreliable. Finally, the established method was successfully appliedto the study of the FA and FOH profiles of two heterogeneous severeclinical disease tissues. This study would improve our understandingof the pathological and metabolic mechanisms of FAs and FOHs for inflammatorymyopathies and pancreatic cancer and also prove the generality andaccuracy of the developed analytical method for complex samples.