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J. Cosmet. Sci., 64, 145–158 (March/April 2013) 145 Inhibitory effects of Korean indigenous plants on tyrosinase and melanogenesis KYUNG HUN SON and MOON YOUNG HEO, Cosmetics Evaluation Division, Korea Food and Drug Administration, Chungcheongbuk-do 363-700 (K.H.S.), and College of Pharmacy, Kangwon National University, Chunchon 200-701 (M.Y.H.), Republic of Korea. Accepted for publication August 6, 2012. Synopsis To search for new depigmenting cosmetic ingredients from Korean herbal extracts of traditional Korean medicines (TKMs), we screened about 17 TKM extracts collected in the Republic of Korea. Samples were prepared from the natural plants, including medicinal plants such as Chrysanthemum indicum (fl ower), using methanol, methylene chloride, ethyl acetate (EtOAc), n-butyl alcohol, and water as the extraction and/or the partitioning solvents. We then tested their inhibitory effects on melanogenesis by using in vitro tyrosinase inhibition assay, in vitro L -3,4-dihydroxy-indole-2-carboxylic acid (L-DOPA) auto-oxidation assay, and B16 melanoma cells. In addition, cytotoxicity testing (NR50 and MTT50) was conducted to evaluate safety. From the results of these assays, four fractions with good effi cacy and low toxicity were selected among them, in- cluding EtOAc fraction of Smilax china (rhizome), Paeonia lactifl ora (root), and Polyporus umbellatus (sclero- tium), and BuOH fraction of Evodia offi cinalis (fruit). In the inhibition assay of intracellular tyrosinase activity and melanogenesis in B16 melanoma cell line, the four plant fractions showed dose-dependent inhibitory effects, and the EtOAc fraction of P. lactifl ora showed the highest activity among the four fractions. The EtOAc fraction of P. lactifl ora was found to be the most effective substrate. INTRODUCTION Skin color is determined by the type, amount, and size of melanin formed by melanocytes between the dermis and epidermis (1,2). Therefore, in the development of depigmenting agents, it is important to understand the skin structure, physiological functions, and mechanisms of melanin biosynthesis. Melanin is formed in the melanosome, a unique intracellular structure of the melanocyte. Melanosomes contain enzymes that are involved in melanin biosynthesis, such as tyrosi- nase, tyrosinase-related protein-1 (TRP-1), and tyrosinase-related protein-2. It has been reported that TRP-1 stabilizes enzymes in the melanosome. Furthermore, melanosomes contain matrix proteins, which are thought to act as the location of enzyme synthesis. Address all correspondence to Moon Young Heo at myheo@kangwon.ac.kr.