Majmudar, G., Jacob, G., Laboy, Y., Fisher, L. Mary Kay Holding Corp., Dallas, TX 75247.

Melanoderm™ (MatTek) is an in vitro model of the human epidermis consisting of well-differentiated, cultured human keratinocytes and melanocytes. We utilized this model to evaluate the efficacy, stability, and cytotoxicity of whitening agents. Magnesium ascorbyl phosphate (MAP), kojic acid and lactic acid in aqueous or anhydrous base were applied to Melanoderm. Following incubation, tyrosinase activity was measured using L-dihydroxyphenylalanine (L-DOPA). Melanocyte staining was observed under the microscope. Melanoderm treated with either MAP, kojic acid, or lactic acid showed 33%, 48%, and 46% reduction, respectively, of tyrosinase activity. Microscopic examination of treated Melanoderm clearly showed the dendritic nature of melanocytes, and normal morphology of keratinocytes and MTT assay suggested that the test materials were not cytotoxic. The kojic acid effect declined with the age of the preparation, and subsequent analysis via high performance liquid chromatography (HPLC) showed kojic acid to be unstable in the aqueous base. Clinical tests using a chromameter to evaluate skin color indicated that kojic acid in an anhydrous base can induce more skin lightening than in the aqueous base. We obtained a good correlation between the Malanoderm, HPLC, and clinical tests. The data show that Melanoderm is a suitable tool for screening whitening agents and developing whitening products. A combination of two in vitro tests, such as the Melanoderm and HPLC methods, is useful to evaluate the relative activity, stability, and cytotoxicity of whitening ingredients and products before testing on humans.


Kojic acid, L-dihydroxyphenylalanine (L-DOPA), Lactic acid, Magnesium ascorbyl phosphate (MAP), MelanoDerm, Melanocytes, Skin lightening, Tyrosinase activity, Whitening agents, Whitening products

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