Structures of the ceramides from porcine palatal stratum corneum.

Ceramides are the major type of lipid found in stratum corneum from the skin, gingiva and hard palate. The present study examined the ceramides of the stratum corneum from the hard palate. Six fractions of ceramides were isolated by preparative thin-layer chromatography. The least polar fraction contained an unusual acyl ceramide (EOS) consisting of long omega-hydroxy acids amide-linked to sphingosine with mostly saturated fatty acids ester-linked to the omega-hydroxyl group. The second and third fractions contained normal fatty acids amide-linked to sphingosine (NS) and phytosphingosine (NP), respectively. In each of these ceramides, the fatty acids consisted of a mixture of saturated and monoenoic species. The three most polar fractions all contain amide-linked alpha-hydroxy acids. The fourth fraction contained long alpha-hydroxy acids amide-linked to sphingosine (ASl), while the fifth fraction contained short alpha-hydroxy acids amide-linked to sphingosine (ASs). The most polar ceramide contained alpha-hydroxy acids amide-linked to phytosphingosine (AP). EOS, NS and NP differed from their epidermal counterparts in terms of the compositions of the normal fatty acids. ASl, ASs and AP from palatal stratum corneum were essentially identical to their epidermal counterparts. The differences between palatal and epidermal EOS, NS and NP contribute to the differences in permeability of palate compared to skin.