Nonhydroxylated 1--acylceramides in vernix caseosa.

Vernix caseosa, the waxy substance that coats the skin of newborn babies, has an extremely complex lipid composition. We have explored these lipids and identified nonhydroxylated 1--acylceramides (1--ENSs) as a new class of lipids in vernix caseosa. These ceramides mostly contain saturated C11-C38 ester-linked (1-) acyls, saturated C12-C39 amide-linked acyls, and C16-C24 sphingoid bases. Because their fatty acyl chains are frequently branched, numerous molecular species were separable and detectable by HPLC/MS: we found more than 2,300 molecular species, 972 of which were structurally characterized. The most abundant 1--ENSs contained straight-chain and branched fatty acyls with 20, 22, 24, or 26 carbons in the 1- position, 24 or 26 carbons in the position, and sphingosine. The 1--ENSs were isolated using multistep TLC and HPLC and they accounted for 1% of the total lipid extract. The molecular species of 1--ENSs were separated on a C18 HPLC column using an acetonitrile/propan-2-ol gradient and detected by APCI-MS, and the structures were elucidated by high-resolution and tandem MS. Medium-polarity 1--ENSs likely contribute to the cohesiveness and to the waterproofing and moisturizing properties of vernix caseosa.