Oligopeptides in Sensory, Proteins in Winter Skin and Carotenoids: Literature Findings

By: Charles Fox, Independent Consultant

Posted: November 26, 2008, from the December 2008 issue of Cosmetics & Toiletries.

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Alpha-arbutin glycosylation for industrial production, applied in skin lightening: Sugimoto et al. reviewed the development of alpha-arbutin production on an industrial scale, and its application as a skin-lightening cosmetic ingredient.⁴ The investigators discovered a new enzyme that was shown to efficiently catalyze transglycosylation reaction toward phenolic hydroxyl groups. This enzyme, hydroquinone glucosylating enzyme, catalyzed selective glycosylation of hydroquinone, and the yield of the resulting product, 4-hydroxyphenyl-O-alpha-d-glucopyranoside (alpha-arbutin), reportedly was high enough for industrial production.

Kojic acid, caffeic acid and many other phenolic compounds also were glycosylated by the reaction of this enzyme; however, alcohols were not. Application studies of alpha-arbutin were carried out and indicated that the material strongly inhibited human tyrosinase. Researchers also noted that its inhibitory effect on human tyrosinase was much higher than that of its isomer, 4-hydroxyphenyl-O-beta-d-glucopyranoside (arbutin).

Glycosides of alpha-arbutin and arbutin were then synthesized and their inhibitory effects compared; human tyrosinase indicated that the molecular size and electrostatic potential around the benzene ring are important for inducing the inhibitory effect of hydroquinone glycosides toward human tyrosinase. Further, the inhibitory effects of alpha-arbutin on melanin biosynthesis were examined. Alpha-arbutin was found to inhibit melanin syntheses of HMV-II cells and the human skin model in a dose-dependent manner, and at a noncytotoxic concentration. These results demonstrate that alpha-arbutin is an effective and safe ingredient for skin lightening.

Skin lipid review: Bouwstra et al. review skin lipid organization, composition and barrier function.5 As is generally known, the primary function of skin is to act as a barrier against unwanted influences from the environment and to protect the body from water loss. This barrier function is located in the superficial layer of the skin, the stratum corneum (SC). The SC consists of dead cells filled with keratin and water-the corneocytes-embedded in lipid regions. The lipid regions are the only continuous structure in the SC and thus are considered key to the skin barrier function.

The main lipid classes are ceramides, cholesterol, and free fatty acids. In this review paper, the authors examined lipid organization in human SC and the role the various classes play in lipid organization by studying mixtures prepared either from native human ceramides or synthetic ceramides. Finally, the paper describes a model to study the relationships between lipid composition, organization and barrier function. This model is referred to as the SC substitute.