Screening and Identification of Epoxy/Dihydroxy-Oxylipins by Chemical Labeling-Assisted Ultrahigh-Performance Liquid Chromatography Coupled with High-Resolution Mass Spectrometry

Abstract

Epoxy/dihydroxy-oxylipins are important biologically active compounds that are mainly formed from polyunsaturated fatty acids (PUFAs) in the reactions catalyzed by the cytochrome P450 (CYP 450) enzyme. The analysis of epoxy/dihydroxy-oxylipins would be helpful to gain insights into their landscape in living organisms and provide a reference for the biological studies of these compounds. In this work, we employed chemical labeling-assisted liquid chromatography (LC) coupled with high-resolution mass spectrometry (CL-LC-HRMS) to establish a highly sensitive and specific method for screening and annotating epoxy/dihydroxy-oxylipins in biological samples. The isotope reagents 2-dimethylaminoethylamine (DMED) and DMED-d 4 were employed to label epoxy/dihydroxy-oxylipins containing carboxyl groups so as to improve the analysis selectivity and MS detection sensitivity of epoxy/dihydroxy-oxylipins. Based on a pair of diagnostic ions with a mass-to-charge ratio (m/z) difference of 15.995 originating from the fragmentation of derivatives via high-energy collision dissociation (HCD), the potential epoxy/dihydroxy-oxylipins were rapidly screened from the complex matrix. Furthermore, the epoxy/dihydroxy groups could be readily localized by the diagnostic ion pairs, which enabled us to accurately annotate the epoxy/dihydroxy-oxylipins detected in biological samples. The applicability of our method was demonstrated by profiling epoxy/dihydroxy-oxylipins in human serum and heart samples from mice with high-fat diet (HFD). By the proposed method, a total of 32 and 62 potential epoxy/dihydroxy-oxylipins including 42 unreported ones were detected from human serum and the mice heart sample, respectively. Moreover, the relative quantitative results showed that most of the potential epoxy/dihydroxy-oxylipins, especially the oxidation products of linoleic acid (LA) or α-linolenic acid (ALA), were significantly decreased in the heart of mice with HFD. Our developed method is of high specificity and sensitivity and thus is a promising tool for the identification of novel epoxy/dihydroxy-oxylipins in biological samples.

Carboxylic submetabolome-driven signature characterization of COVID-19 asymptomatic infection

“…S10 ), the terminal aldehyde-containing ion of 278.2115 and terminal alkenyl-containing ion of 262.2165 with a m/z difference of 15.995 (-O), were generated via fragmentation of the three-membered epoxide ring of the fragment ion m/z 320.2572. According to our previous report [ 17 ], it was a fragmentation characteristic of DMED labelled epoxy/dihydroxy-oxylipins. Furthermore, above diagnostic ion pairs revealed the epoxy groups are located at C-15 and C-16.…”

In-depth profiling of carboxyl compounds in Chinese Baijiu based on chemical derivatization and ultrahigh-performance liquid chromatography coupled to high-resolution mass spectrometry

“…Currently, there are still some difficulties in conducting chemical derivatization for comprehensive annotation of carboxyl compounds in complex samples. On one hand, for the annotation of carboxyl compounds, most derivatization methods applied the chemical isotope labeling strategy, in which labeled compounds were extracted by peak pairs obtained from light and heavy isotope derivatization reagents ( An et al, 2021 , Li et al, 2019 , Xiong et al, 2021 ). However, heavy isotope derivatization reagents are expensive and even commercially unavailable, which limits the application of the chemical isotope labeling strategy.…”

Analytical Strategy for Oxylipin Annotation by Combining Chemical Derivatization-Based Retention Index Algorithm and Feature Tandem Mass Spectrometric Fragmentation as a Biomarker Discovery Tool

“…Recently, Bian et al established a fast cholamine-derivatization to label oxylipins within 1 min at room temperature. Xiong et al employed 2-dimethylaminoethylamine derivatization coupled with LC-high-resolution mass spectrometry for identifying epoxy and dihydroxy-oxylipins in biological samples with high sensitivity and specificity. Nevertheless, there is still no effective method for the comprehensive analysis and identification of isomers of oxylipins, especially for the unknown oxylipins without standards.…”