Natural Products of Cosmetics: Analysis of Extracts of Plants Endemic to Taiwan for the Presence of Tyrosinase-inhibitory, Melanin-reducing, and Free Radical Scavenging Activities

天然物應用在化妝品中已成為目前市場趨勢，近來有許多關於天然成分於抑制酪氨酸酶或活性氧產生之相關報導。由於黑色素是決定皮膚色素的主要原因之一，而酪胺酸酶則是形成黑色素時的速率限制步驟酵素，因此酪氨酸酶抑制劑常被視為有皮膚美白作用，而抑制活性氧的產生則與老化延緩有關，可應用於延遲皮膚老化。本研究乃採集、製備二十六種臺灣產植物之酒精萃取物，探討其對人類正常黑色素細胞內酪氨酸酶與黑色素抑制作用以及體外自由基清除活性。於人類黑色素細胞試驗分析中發現台灣火刺木(M-165)具有低細胞毒細與最佳的酪氨酸酶抑制活性(IC50, 54.8 μg/mL)；樟葉槭(M-51)、大安水簑衣(M169)，大葉楠(M-67)以及山枇杷(M-50)具有較佳的自由基清除作用，包括清除氫氧自由基（IC50分別為3.1，0.8，6.6和1.8 μg/mL）、超氧自由基(IC(下標 50)分別為5.3, 12.8, 12.4和6.1μg/mL)及ABTS自由基（IC50分別為2.4，7.9，5.7和2.9 μg/mL），但與酚性成分含量並非呈絕對相關，這些具潛力的植物萃取物互相混合使用，提供為功能性化妝品添加物之參考，將來亦可繼續純化分離其中具有酪胺酸酶抑制與自由基清除作用之成分應用於化妝品中。
Non-toxic natural products useful in the formulation of cosmetics are of considerable interest. Recent efforts have focused on the identification of substances that inhibit tyrosinase activity or suppress formation of reactive oxygen species (ROS) in skin cells. Since tyrosinase is the rate-limiting enzyme in the synthesis of melanin, the pigment responsible for the color of human skin, tyrosinase inhibitors may have skin-whitening effects. Since ROS have been implicated in the aging of human skin, agents that suppress the production of ROS may retard such aging. In the present study, ethanol (95%) extracts of 26 plants endemic to Taiwan were examined for their tyrosinase-inhibitory or melanin-reducing activities in human epidermal melanocytes, as well as in vitro free radical scavenging activity. Among the preparations tested, extracts of Pyracantha koidzumii (M-165) were found to be the least cytotoxic and to possess the highest cellular tyrosinase inhibitory activity (IC50, 54.8 μg/mL). Extracts of Acer albopurpurascens (M-51), Hygrophila pogonocalyx (M169), Machilus japonica var. kusanoi (M-67), and Eriobotrya deflexa (M-50) exhibited the most potent free radical scavenging activity against hydroxyl, superoxide, and 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) anion radicals. The IC(subscript 50) values of M-51, M169, M-67, and M-50 were 3.1, 0.8, 6.6, and 1.8 μg/mL for hydroxyl radical; 5.3, 12.8, 12.4, and 6.1 μg/mL for superoxide radical; 2.4, 7.9, 5.7, and 2.9 μg/mL for ABTS anion radical, respectively. Nevertheless, the phenolic contents were not all correlated with these activities. These plants thus serve as potential sources of ingredients, which could be combined in cosmetic products. Further investigation of the substances responsible for the observed tyrosinase-inhibitory and free radical scavenging activities is therefore warranted.