The monoene and other Wax alcohols of human skin surface lipid and their relation to the fatty acids of this lipid

Abstract

Wax alcohols (as acetates) were isolated from human skin surface lipid and separated into a saturated and a monoene fraction. Four main chain types were found for both saturated and monoene alcohols: normal even, normal odd, iso and anteiso. (“Even” and “odd” refer to the number of C-atoms in the straight chain.) The monoene alcohol acetates were separated into homologues of each chain type by preparative gas-liquid chromatography (GLC) and the positions of the double bonds for each homologue were determined by analytical GLC of the original fraction, its hydrogenated derivative, and the products it formed by reductive ozonolysis. The fragments formed by reductive ozonolysis of the monoene alcohol acetates were compared to those formed from the total monoenoic fatty acids (as methyl esters), both obtained from the same sample of surface lipid. (Comparisons were best made by ozonolysis of a portion of the entire sample of each ester group. The terminal ends of both groups of monoene fatty chains yielded a very similar pattern of aldehydes in terms of types and amounts. This could be explained by the hypothesis that both fatty acid and fatty alcohol chains of lengths ranging mainly from C₁₄ to C₁₈ were first biosynthesized, then desaturated at Δ6. The functional group ends gave a distinct pattern of aldehyde esters for the acids and another for the alcohols. Both patterns consisted nearly entirely of members having aneven number of C-atoms from the double bond to the functional group. This suggested that the members of each pattern were formed by chain extensions of an integral number of C₂ units beyond the lengths arrived at in 4a). Thus 71% of the fatty acid monoenes were not extended, 25% were extended by 1 C₂ unit and the remainder extended from 2 to 5 C₂ units, whereas nearly all the fatty alcohols were extended mainly by 2, 3 or 4 C₂ units, with decreasing amounts up to 8 C₂ units. A small amount (∼5%) of odd chain aldehyde esters for both fatty acids and fatty alcohols were found and some unidentified alcohols were detected.