Abstract
Cholesteryl esters of ω-(O-acyl)-hydroxy FAs (Chl-ωOAHFAs) were identified for the first time in vernix caseosa and characterized using chromatography and MS. Chl-ωOAHFAs were isolated using adsorption chromatography on silica gel and magnesium hydroxide. Their general structure was established using high-resolution and tandem MS of intact lipids, and products of their transesterification and derivatizations. Individual molecular species were characterized using nonaqueous reversed-phase HPLC coupled to atmospheric pressure chemical ionization. The analytes were detected as protonated molecules, and their structures were elucidated in the negative ion mode using controlled thermal decomposition and data-dependent fragmentation. About three hundred molecular species of Chl-ωOAHFAs were identified in this way. The most abundant Chl-ωOAHFAs contained 32:1 ω-hydroxy FA (ω-HFA) and 14:0, 15:0, 16:0, 16:1, and 18:1 FAs. The double bond in the 32:1 ω-HFA was in the n-7 and n-9 positions. Chl-ωOAHFAs are estimated to account for approximately 1-2% of vernix caseosa lipids.
Highlights
IntroductionRapid identification of fatty acids and (O-acyl) -hydroxy fatty acids in human meibum by liquid chromatography/ high-resolution mass spectrometry
A group of FA methyl ester (FAME) at unusually high retention times was identified as methyl esters of -hydroxy FA (HFA) (HFAMEs)
HFAs form 2–3% of free FAs in vernix caseosa [5]. They have been identified in hydrolysates of sterol esters, wax esters, diol diesters, and triacylglycerols [5], intact neutral lipids containing HFAs have not yet been reported
Summary
Rapid identification of fatty acids and (O-acyl) -hydroxy fatty acids in human meibum by liquid chromatography/ high-resolution mass spectrometry. Mass spectrometry of methyl esters: hydroxy fatty acids - trimethylsilyl derivatives. Localization of double bonds in wax esters by highperformance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry utilizing the fragmentation of acetonitrile-related adducts. Identification of the double-bond position in fatty acid methyl esters by liquid chromatography/ atmospheric pressure chemical ionisation mass spectrometry. Localization of double bonds in triacylglycerols using high-performance liquid chromatography/ atmospheric pressure chemical ionization ion-trap mass spectrometry. In High-Performance Liquid Chromatography and Lipids: A Practical Guide. Analysis of wax ester molecular species by high performance liquid chromatography/ atmospheric pressure chemical ionisation mass spectrometry. Epidermal barrier lipids in human vernix caseosa: corresponding ceramide pattern in vernix and fetal skin.
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