J. Cosmet. Sci., 62, 41–48 (January/February 2011) 41 Inhibitory effect of a water extract from Pemphis acidula on melanogenesis in mouse B16 melanoma cells HSIOU-YU DING, TE-SHENG CHANG, CHIEN-MIN CHIANG, and SORGAN SHOU-KU TAI, Institute of Cosmetics Science, Chia Nan University of Pharmacy and Science (H.-Y.D.), Department of Biological Science and Technology, National University of Tainan (T.-S.C.), Department of Biotechnology, Chia Nan University of Pharmacy and Science (C.-M.C.), and Department of Biotechnology, National Formosa University (S.S.-K.T.), Taiwan, R.O.C. Accepted for publication November 3, 2010. Synopsis The inhibitory effect of a water extract from Pemphis acidula on melanogenesis in mouse B16 melanoma cells was investigated. The results showed that the P. acidula extract (PAE) inhibited melanogenesis in 3-isobutyl- 1-methylxanthin (IBMX)-stimulated B16 cells in a dose-dependent manner, with an IC50 value of 33.5 μg/ml. In addition, PAE also inhibited cellular tyrosinase activity. Moreover, western blot and real-time reverse transcriptase polymerase chain reaction (qRT-PCR) analyses respectively confi rmed that PAE down-regulated levels of tyrosinase protein and its mRNA in IBMX-stimulated B16 cells. These results demonstrated that PAE inhibits melanogenesis of B16 cells by reducing tyrosinase gene expression. From the present study, PAE is proven to be a good candidate as a skin-whitening agent for treatment of skin hyperpigmentation. INTRODUCTION Skin pigmentation is produced by dermal melanocytes. Melanogenesis has been defi ned as the entire process leading to the formation of dark macromolecular pigments, i.e., melanin, which are formed by a combination of enzymatically catalyzed and chemical reactions (1). Melanogenesis is initiated in melanosomes, the special organelles of mela- nocytes, with the fi rst step of l-tyrosine oxidation to l-dopa (l-3,4-dihydroxyphenylala- nine) and then to dopaquinone, which is catalyzed by tyrosinase. This is a rate-limiting step in melanin synthesis because the remainder of the reaction sequence can proceed spontaneously at a physiological pH value. Although melanin mainly plays a photopro- tective role, the accumulation of abnormal amounts of melanin in different parts of the skin, which results in pigmented patches of skin, might become an esthetic problem. Address all correspondence to Sorgan Shou-Ku Tai at 64 Wun-Hua Road, Huwei, Yunlin, Taiwan, R.O.C. (sorgan@nfu.edu.tw).