摘要
紫外光乃色素沉著之主要肇因，一旦暴露於紫外光，會令黑色素細胞內的一氧化氮釋出增加，進而觸動訊息傳遞系統，引發酪胺酸酶活性，促進黑色素生成；紫外光亦可透過角質細胞的參與，藉由旁分泌調節，而影響黑色素生成。雖然諸多降低黑色素沉著之產品問世，天然物製品仍較受歡迎，亦將成為市場之主流；越來越多之活性成分如酚類、黃酮類及香豆素等及其衍生物自天然物分離出來。本文乃依這些天然物美白之作用機轉，將之分為兩大類，一為藉由阻斷酪胺酸酶，諸如酚類及多酚類等；另一為非藉由抑制酪胺酸酶作用之美白天然物，如α-MSH阻斷劑、黑色素轉移抑制劑、細胞激素抑制劑等，並分別說明其美白作用及作用機轉研究現況；而目前絕大多數降低黑色素沉著之效果，多藉由抑制酪胺酸酶的作用，然而，其他阻斷黑色素生成上游路徑之成分，未來於美白成分之開發將深具潛力。
並列摘要
UV radiation is widely considered as a major cause of skin pigmentation. Upon exposure to UV radiation, the melanocytes increase the production of intracellular nitric oxide, which triggers signal transduction cascades to initiate melanogenesis by tyrosinase. UV radiation also influences melanogenesis through a paracrine regulation process involving the keratinocytes. Although a number of hypopigmenting products have been developed, those from natural sources are preferred and will predominate in the cosmetics market. More active compounds such as phenols, flavonoids, coumarins and other derivatives have been identified from natural sources. This article summarized natural skin whitening products involving tyrosinase blockers like phenols and polyphenols, and non-tyrosinase blockers like CL-MSH, melanosome transferase and cytokine inhibitors. In addition, the skin-whitening effects and the mechanisms of these natural products were also reviewed. Most of the compounds achieve the hypopigmenting effect by inhibiting tyrosinase; however, some interesting compounds blocking the upstream regulation points of melanogenesis are extraordinarily promising for developing novel whitening agents.