Chemometric approach for investigating the skin surface lipids (SSLs) composition: influence of geographical localization.

Skin surface lipids (SSLs), arising from both sebaceous glands and skin removal, form a complex lipid mixture composed of free fatty acids and neutral lipids. They are present in the hydrolipidic film and have a close relationship with the stratum corneum lipids. Thus, SSLs participate in the barrier function. One can expect a physiological adaptation of the SSLs composition according to geographical localization or skin pigmentation. In this study, SSLs obtained from three groups of volunteers (light and dark skin, living in France and dark skin, living in Ivory Coast) have been investigated. High-temperature gas chromatography/mass spectrometry has been used to study SSLs composition. The variability in the SSLs chromatographic profiles has been investigated, using chemometric methods which allowed us to highlight the sapienic acid (C16: 1Δ6) as discriminant according to geographical localization. This result is of a great interest regarding sapienic acid properties. However, no significant variation has been detected following skin pigmentation. In parallel, SSLs Raman spectra were collected in order to determine the organization and the conformational order of lipids. The spectral data treatment revealed discriminant variation in the υ C-C stretching region revealing changes in the conformational order of the SSLs following geographical localization.