Fatty acid composition of the living layer and stratum corneum lipids of human sole skin epidermis

Abstract

Lipids from the living layer and stratum corneum of human sole epidermis were extracted, saponified and the fatty acids analyzed. The proportion of fatty acids to unsaponifiables (mainly cholesterol), was higher in the living layer than in the stratum corneum. Fatty acids of the living layer and stratum corneum of human sole epidermis comprise saturates, monoenes, dienes, traces of polyenes and α-hydroxy fatty acids. Homologs of monoenoic and dienoic fatty acids for both living layer and stratum corneum lipids have a similar distribution. C₁₆ and C₁₈ were major components for each type of acids. There appeared to be two clusters, especially for saturates of both living layer and stratum corneum acids. One of these clusters ranged from C₁₂ to C₂₀ with C₁₆ or C₁₈ as a maximum and the other ranged from C₂₁ to C₃₀ with C₂₄ as a maximum. The proportion of saturated acids with chain length C₂₀ and above was much higher in the stratum corneum than in the living layer. Position isomers of the monoenoic fatty acids for both the living layer and stratum corneum show a predominance of ω9 acids, due to the overwhelmingly large amount of oleic acid. Linoleic acid was by far the major component of the dienoic acids. Homolog distribution of α-hydroxy fatty acids for the living layer was similar to that of the stratum corneum and again two clusters of acids below and above C₂₀ with maxima at C₁₆ and C₂₄ were noticeable. Comparison of epidermal acids with those of sebaceous glands showed that each tissue can synthesize the same kind of acids but in widely different amounts. Oxidation of palmitate and stearate could supply the necessary energy for the late stages of keratinization.