Pseudotargeted Lipidomics Strategy Enabling Comprehensive Profiling and Precise Lipid Structural Elucidation of Polyunsaturated Lipid-Rich Echium Oil

Echium
oil has great nutritional value as a result of its high
content of α-linolenic acid (ALA, 18:3ω-3) and stearidonic
acid (SDA, 18:4ω-3). However, the comprehensive lipid profiling
and exact structural characterization of bioactive polyunsaturated
lipids in echium oil have not yet been obtained. In this study, we
developed a novel pseudotargeted lipidomics strategy for comprehensive
profiling and lipid structural elucidation of polyunsaturated lipid-rich
echium oil. Our approach integrated untargeted lipidomics analysis
with a targeted lipidomics strategy based on Paternò–Büchi
(PB)–tandem mass spectrometry (MS/MS) using 2-acetylpyridine
(2-AP) as the reaction reagent, allowing for high-coverage lipid profiling
and simultaneous determination of CC locations in triacylglycerols
(TGs), diacylglycerols (DGs), free fatty acids (FFAs), and sterol
esters (SEs) in echium oil. A total of 209 lipid species were profiled,
among which 162 unsaturated lipids were identified with CC
location assignment and 42 groups of ω-3 and ω-6 CC
location isomers were discovered. In addition, relative isomer ratios
of certain groups of lipid CC location isomers were revealed.
This pseudotargeted lipidomics strategy described in this study is
expected to provide new insight into structural characterization of
distinctive bioactive lipids in food.