Biol. Pharm. Bull. 30(4) 719—723 (2007)

due to the destruction of the ozone layer. Our skin is more exposed to UV radiation and often suffers from various harmful effects of UV. Melanin prodcution in human skin is an important defense mechanism against UV and a major determinant of skin color. Melanocytes residing within the basal layer of the epidermis synthesize melanin in specialized organelles, designated as melanosomes, by coordinated action of various melanogenic enzymes such as tyrosinase, tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2 (TRP-2). Then, melanin-containing melanosomes are transferred to keratinocytes, providing protection against UV radiation and eventually disappear with desquamation of the skin. Despite the protective role of melanins, abnormal hyperpigmentation such as freckles, chloasma, and other forms of melanin hyperpigmentation sometimes can be serious aesthetic problems. Therefore potent active agents for the improvement of hyperpigmentation have been sought for cosmetic use. Many chemicals such as hydroquinone, arbutin, kojic acid, and ascorbic acid are well known for their melanogenicinhibitory functions. Even though these chemicals are often used in many skin-lightening, cosmetic formulations, they have some disadvantages such as poor safety and limited effectiveness. In this study, we screened more than 200 medicinal herbal extracts that have been known for their skin-lightening effects to develop a skin-lightening agent from traditional medicinal plants and found that Atractylodis Rhizoma Alba, which has been used in the treatment and prevention of diabetes and ulceration, has strong melanogenic-inhibitory activity. Its active compound was purified using bioactivityguided fractionation and identified as selina-4(14),7(11)dien-8-one (compound 1) by spectroscopic methods. The effects of compound 1 were evaluated on melan-a cells. Compound 1 markedly inhibited melanogenesis of melan-a cells by regulating the expression of melanogenic enzymes. MATERIALS AND METHODS