Cholesteryl esters of ω-(O-acyl)-hydroxy fatty acids in vernix caseosa

Cholesteryl esters of omega-(O-acyl)-hydroxy FAs (Chl. OAHFAs) were identified for the first time in vernix caseosa and characterized using chromatography and MS. Chl-omega OAHFAs 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-omega OAHFAs were identified in this way. The most abundant Chl. OAHFAs contained 32: 1 omega-hydroxy FA (omega-HFA) and 14:0, 15:0, 16:0, 16: 1, and 18: 1 FAs. The double bond in the 32: 1 omega-HFA was in the n-7 and n-9 positions. Chl-omega OAHFAs are estimated to account for approximately 1-2% of vernix caseosa lipids.