在1997年，台灣的皮膚科醫生發現許多臉上患有嚴重黑白斑的病例，他們都使用篜過的荖葉來作臉部的美白，為何會造成黑白斑的機轉不明。荖葉是檳榔塊的一個組成物，裡面含有許多酚類化合物，像丁香油酚等。已知有一些酚類化合物具有去色素的作用，有時也會引起發炎後過度色素化的反應。在此計畫中，我們就假設荖葉會誘發黑白班症是因為抑制黑色素的合成及/或細胞毒性的產生所致。我們首先藉由測試酪胺酸酵素的活性來篩選荖葉萃取液中是否具有抑制黑色素合成的成分，再以老鼠的黑色素瘤細胞來偵測荖葉萃取液的細胞毒性，最後再偵測荖葉萃取液是否可以降低黑色素的量。實驗結果發現荖葉萃取液在體外實驗可抑制酪胺酸酵素的活性，同時也具有細胞毒性且成劑量相關性，因此荖葉萃取液之所以造成黑白斑的現象可能就是因為抑制黑色素的產生及細胞毒性所致。 In 1997, dermatologists documented a kind of severe facial leukomelanosis to the use of facial dressing with steamed Piper betle leaf (PBL) as a bleaching agent in Taiwan. The underlying mechanisms for this leukomelanosis have yet to be resolved. Piper betle leaf (PBL) is a component of areca quid and it contains many phenolic ingredients including eugenol, chavicol and hydroxychavicol. Phenolic derivatives are known for depigmentation, such as hydroquinone and sometimes even induce postinflammatory hyperpigmentation. In this study, we hypothesizes that PBL extracts induces leukomelanosis through inhibition of melanin synthesis and/or melanocytotoxicity. We first screened the inhibition potential of PBL on tyrosinase activity in the presence of L-Dopa as a substrate. We further determined the cytotoxicity of PBL extracts in mouse melanoma B16 cells by using tetrazolium salt and trypan blue exclusion assays. The effects of PBL extracts on melanin content in B16 cells were also measured by UV at OD405. The data showed that PBL extracts were cytotoxic to B16 cells in a dose-dependent manner (10~100 g/ml) and inhibited mushroom tyrosinase activity in vitro. These results demonstrate that PBL extracts induced leukomelanosis may through the inhibition of melanin synthesis and melanocytotoxicity.