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j. Soc. Cosmet. Chem., 47, 351-362 (November/December 1996) Lipo-amino acid cholesteryl derivatives promote recovery effect for damaged skin HIROJI ISHII, NAOKO MIKAMI, and KAZUTAMI SAKAMOTO, Ajinomoto Central Research Laboratories, Tokyo, Japan. Accepted for publication January 15, 1997. Synopsis The ability of cholesteryl derivatives to promote the recovery effect in skin damaged by sodium lauryl sulfate was investigated. Among cholesteryl derivatives, acylglutamic acid cholesteryl ester (AGCE) was shown to be effective, either by itself or as a substitute for ceramide (type III). Recovery was evaluated in vivo on human skin using dermal scores, water-holding capacity (conductance), and transepidermal water loss (TEWL). When substituted for ceramide in an artificial stratum corneum lipid model, AGCE also formed a lameliar structure. INTRODUCTION It is well known that the softness of the skin is related to its water content (1). Skin damage caused by external stimulation or irritation results in the destruction of the barrier function of the stratum corneum, which in turn reduces the water-holding capacity and water content of the skin (2,3). Skin characterized by a pathological stratum corneum, such as senile xerotic skin, also has a much lower water content than that of healthy skin (4). This marked decrease in the water-holding capacity of damaged skin is often accompanied by a selective loss of intercellular lipids in the stratum corneum (5). Thus, the use of intercellular lipids as emollients is increasing in recognition as a means of maintaining the softness and flexibility of skin. Stratum corneum lipids consist mainly of ceramides, cholesteryl esters, cholesterol, and fatty acids (6). Ceramides are reported to be the main components of the stratum corneum lipids, and to play an important role in promoting the water-holding capacity of skin by forming a lameliar structure that acts as a moisture evaporation barrier (5,7). Cholesterol and cholesteryl derivatives are also thought to be effective components in these lipid bilayers for retaining water and promoting the recovery of water-holding capacity in damaged skin (7). For example, it has been reported that stratum corneum lacking cholesterol and cholesteryl derivatives exhibits a decrease in its water content and high rates of skin disease (8). Although ceramides are recognized as the key com- 351