Limonoids and unsaturated fatty acids present in Melia toosendan increase ceramide production in keratinocytes.

The skin barrier prevents moisture evaporation and the entry of foreign substances such as allergens. Ceramides are one of the most important factors for maintaining skin barrier function. Melia toosendan is a plant of the Meliaceae family, and its fruit extracts have been used in Traditional Chinese Medicine as analgesics and anthelmintics; however, its ability to increase ceramide levels has not been reported.

Changes in hydration of the stratum corneum are the most suitable indicator to evaluate the irritation of surfactants on the skin.

Background/purpose: Irritancy levels of surfactants on human skin have not been clarified completely. The relationships between skin damage and changes of skin properties caused by various surfactants were investigated using non-invasive measurements.

Methods: Aqueous solutions of seven kinds of anionic, non-ionic, and amphoteric surfactants were exposed to the inside of forearm skin of 20 human subjects in two separate studies using the cup method.

The inhibitory effect of a Platycodon root extract on ultraviolet B-induced pigmentation due to a decrease in Kit expression.

The signaling of stem cell factor (SCF) through its receptor Kit is known to play an important role in regulating cutaneous melanogenesis. In the course of UVB-induced pigmentation, the expression of membrane-bound SCF by epidermal keratinocytes is upregulated at an early phase and subsequently activates neighboring melanocytes via their Kit receptors. In order to identify effective skin-lightening materials, we screened botanical extracts to determine their abilities to diminish Kit expression in melanocytes.

Variations in the ceramide profile in different seasons and regions of the body contribute to stratum corneum functions.

The objective of this study was to clarify variations of the ceramide (CER) profile in human stratum corneum (SC) in different seasons and in different regions of the body and to estimate the contributions of CERs to the SC barrier and water-holding functions. Based on the information that there are great variations of SC functions among body sites, we compared the CER profiles obtained from ten different anatomical sites in healthy Japanese males in four seasons. Not only the physiological parameters of skin but also the CER profile showed body region and seasonal variations.

Eucalyptus increases ceramide levels in keratinocytes and improves stratum corneum function.

The objectives of this study were 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, we identified a Eucalyptus extract that was able to increase the level of ceramide in human keratinocytes in culture and in human stratum corneum and that improves 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.