Biased distribution of the branched-chain fatty acids in ceramides of vernix caseosa.

The compositions of ester- and amide-linked fatty acids from ceramides of human vernix caseosa were described with emphasis on the distribution of the branched-chain fatty acid (BCFA). Two novel ceramides were isolated from vernix caseosa in the course of this study: the acylated type of esterified alpha-OH-hydroxyacid/sphingosine ceramide (Cer[EAS]) and nonacylated type of non-OH fatty acid/hydroxysphingosine ceramide (Cer[NH]). Their chemical structures were identified by nuclear magnetic resonance and chemical procedure. The Cer[EAS] was an acylceramide and consisted of the highest concentrations of ester- and amide-linked BCFA (62 and 67%, respectively). The iso- or anteiso-branching structures of the aliphatic chains were confirmed by the mass spectra of their picolinyl or pyrrolidide derivatives. As a whole, amide-linked fatty acids of ceramides 1-7 and Cer[NH] were normal types of straight-chain fatty acids with or without alpha- or omega-hydroxylation. The BCFA concentrations of amide-linked fatty acids in these ceramides (ceramides 1-7 and Cer[NH]) were low and less than 10%. The BCFA thus occurred exclusively in a novel acylceramide of Cer[EAS] in the vernix caseosa.