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J. Cosmet. Sci., 63, 197–203 (May/June 2012) 197 Melanosome transfer evaluation by quantitative measurement of Pmel 17 in human normal melanocyte–keratinocyte co-cultures: Effect of an Alaria esculenta extract CLOTILDE VERDY, JEAN-ERIC BRANKA, and NICOLE MEKIDECHE, BIOTECHMARINE, Zone industrielle, BP 65, 22260 Pontrieux (N.M.), and EFFISCIENCE, 178 rue de Brest, 35000 Rennes (C.V., J.-E.B.), France. Accepted for publication November 8, 2011. Synopsis Numerous strategies have been proposed to evaluate melanosome transfer. Methods allowing quantitative measurements of this transfer in human normal cellular models, however, are very few and often require ex- tremely specialized devices that are expensive and diffi cult to use. As a part of the melanosome-specifi c membrane-bound glycoprotein, Pmel 17 is released from the melano- some membrane by ectodomain shedding. We reasoned, therefore, that it should be possible to evaluate melanosome transfer by quantifying this “soluble” Pmel 17. The Pmel 17 ELISA assay developed permits a detection of 10 to 1000 ng/ml of this glycoprotein in human normal melanocyte–keratinocyte co-culture media. As expected, niacinamide, a well-known melanosome transfer inhibitor, signifi cantly reduced the Pmel 17 quantities found in the culture media. This validated our experimental design. We then used our model to show that a whitening cosmetic active compound, i.e., an Alaria esculenta extract, can (at least in part) enable a signifi cant decrease in the melanosome transfer to produce a lightening effect without affecting melanin production. This research provides a simple and effi cient method to quantify melanosome transfer in a human normal co-culture model. It is a particularly useful tool with which to facilitate the development of new active whit- ening compounds. INTRODUCTION Quantifi cation of melanosome transfer is important in cosmetics for the development of new whitening compounds. Although several methodological approaches have already been proposed (for a review, see reference 1), they often require complicated and expensive devices that preclude rapid and effi cient screenings. Address all correspondence to Jean-Eric Branka at jebranka@effi science.fr.