HAGA, Japan—According to researchers at Kao Corp., eucalyptus extract may have a therapeutic effect on the stratum corneum by increasing its content of ceramide, and improving its water-holding and barrier functions(Int J Cosm Sci. 2011;34(1):17-22).
Japanese researchers aimed to identify a plant extract that would improve stratum corneum functions and to elucidate the mechanism(s) involved. Based on the information that stratum corneum functions depend on the level of ceramide in the stratum corneum, researchers identified a eucalyptus extract that was able to increase the level of ceramide in human keratinocytes in culture and in human stratum corneum, and improve the stratum corneum water-holding and barrier functions. Addition of the eucalyptus extract to human keratinocytes in culture increased the level of ceramide in a dose-dependent manner and also increased the biosynthesis of ceramide, glucosylceramide and sphingomyelin. Topical application of the eucalyptus extract on the dry skin of human subjects induced by acetone and diethylether treatment resulted in a significant increase in ceramide level in the stratum corneum, a significant improvement in its water-holding function and an improvement in its barrier function. The addition of macrocarpal A, one of the main components of the eucalyptus extract, to human keratinocytes in culture increased the level of ceramide and the mRNA expression of serine palmitoyltransferase, acid sphingomyelinase, neutral sphingomyelinase, glucosylceramide synthase and glucocerebrosidase in a dose-dependent manner.
“Our results indicate the possibility that macrocarpal A is the key component that stimulates the synthesis of ceramide in the stratum corneum," the researchers noted.
