RESUMO
INTRODUCTION: Skin surface lipids (SSLs) greatly affect the skin physiology and are thought to be involved in skin processes such as thermoregulation, bacterial colonization, and barrier function and maintenance. SSLs are primarily composed of fatty acids, triglycerides, cholesterol, steryl esters, wax esters, and squalene. The objective of this research was to evaluate and better understand the SSL composition and variation in an age- and sex-controlled population, and create an appropriate botanically derived mimetic. METHODS: SSL samples taken from the foreheads of 59 healthy, 22-year-old females were analyzed by gas chromatography mass spectrometry (GC-MS). Using botanically derived raw materials from Macadamia integrifolia, Simmondsia chinensis, and Olea europaea, a mimetic was engineered via a series of esterification reactions and lipid components quantitated with GC-MS. The glyceride and wax ester components were produced by the interesterification of M. integrifolia and S. chinensis under specified conditions. The steryl ester component was produced by the esterification of the fatty acids of M. integrifolia and phytosterols under similar conditions. RESULTS: The following major classes of lipids were found and quantified by percent composition: glycerides, free fatty acids, squalene, wax esters, steryl esters, and cholesterol. The variability between subjects for each component was minimal; however, the greatest variation was seen for free fatty acids and cholesterol. Correlations among the components were calculated and found to be statistically or directionally significant with few exceptions. The esterification reactions of jojoba, macadamia, and tall oils, along with a precise addition of squalene derived from O. europaea, produced a suitable SSL mimetic. When applied to delipidized skin, the mimetic helped restore barrier function, increased skin hydration, and increased skin elasticity and firmness in aged skin. DISCUSSION: The present research indicates that, overall, the SSL composition is quite consistent in a controlled population of 22-year-old females. Furthermore, there were strong correlations between the SSL components among subjects, with the exception of squalene and steryl esters. This was expected due to the fact that of the six major SSL components, steryl esters and squalene also showed higher variation over time for each individual. The variation in free fatty acids may be attributable to the potential differences in the microflora of the subjects. The variation in this study's results, as compared to previously published work, could indicate that the collection methods, geographic location, gender, and age specificity contribute to the distribution or collection of different lipid components on the skin surface. Since the excretion of sebum is known to decrease in females after 40 years of age, the proposed mimetic could be a beneficial supplement to human SSLs in aged skin, as well as in skin where the stratum corneum is defective, by aiding in the restoration of barrier function, while increasing skin hydration, elasticity, and firmness.