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© 1989 Society of Cosmetic Chemists
Journal of the Society of Cosmetic Chemists, Vol. 40, No. 5, 273-285


Water-retaining function in the stratum corneum and its recovery properties by synthetic pseudoceramides
Genji Imokawa , Shuichi Akasaki , Akira Kawamata , Shinji Yano , Naotake Takaishi

ABSTRACT

Synopsis

We have recently found that lipids that form lamellar structures in the intercellular spaces of the stratum corneum can be specific modulators for water-retaining properties of the stratum corneum. Among the intercellular lipids, ceramide (A) fractions exhibit the highest capacity for recovering diminished water-retaining properties. In order to clarify the role of ceramides in the water-retaining function of the stratum corneum, we have synthesized pseudoceramide (B) derivatives and examined their potential for repairing the lipid-depleted stratum corneum, in which a marked decrease in the water-retaining properties is found. Synthesized pseudoceramide derivatives are characterized by structures having both amide or nitrogen bonds and hydroxyl groups as hydrophilic units, as well as two long alkyl chains. When the polar group has an amide bond in the main linkage with hydroxyl ether binding at nitrogen atom, topical applications of these compounds (solubilized at 1–3% in squalane or W\/O cream) to acetone\/ether or sodium dodecyl sulfate-induced dry skin showed a significant recovery of water-retaining properties—accompanied by an improvement in scaling—over that induced by base cream. Analysis of alkyl chain properties has revealed that a structural requirement for the recovery of the water-retaining capacity is the presence of saturated-straight alkyl chains whose structural characteristics are very similar to naturally occurring ceramide in the stratum corneum and the absence of unsaturation or methyl branching. However, the observed alkyl chain length (14–18 carbons) preferred for water-retaining function is different from that of the major naturally occurring ceramides, indicating differential contributions of ceramide structures to stratum corneum functions. The present evidence suggests that ceramides with relatively shorter alkyl chain lengths serve as water modulators in the multilipid bilayers within the stratum corneum.

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© 1989 Society of Cosmetic Chemists
Journal of the Society of Cosmetic Chemists