洛神葉萃取物抑制黑色素生成作用之研究

The study of inhibitory effect of Hibiscus sabdariffa leaf extracts on melanogenesis

林菁薇(Jing-Wei Lin)

指導教授 ： 陳璟賢

中山醫學大學/健康管理學院/營養學研究所/碩士(2013年)

摘要

黑色素生成作用 (melanogenesis)是一種皮膚對抗紫外線照射的重要防禦機制，可使皮膚免於紫外線照射傷害，然而皮膚異常的色素沉澱不僅會造成美觀問題，也會增加罹患皮膚癌的風險。洛神葉 (Hibiscus sabdariffa leaf)富含多酚成分，已有研究指出洛神葉具有抗氧化及抗癌之活性，但對於美白之應用仍是未知。鞣花酸 (ellagic acid, EA)為洛神葉主要之多酚成分，亦是合法的美白試劑，因此本篇研究以EA作為對照物質，利用黑色素瘤細胞 (B16F0)及裸鼠模式，探討洛神葉水萃物 (Hibiscus sabdariffa leaf extract , HLE)對於黑色素生成作用之影響，並分析其分子機轉。在細胞實驗中以α-黑色素細胞刺激素(α-melanocyte stimulating hormone, α-MSH)為誘導因子促進黑色素 (melanin)生成，再給予不同劑量HLE (25, 50, 100 μg/ml)或EA (5 μM)，結果顯示HLE及EA皆能顯著降低酪胺酸酶 (tyrosinase)活性和黑色素生成；以西方墨點法分析，結果顯示HLE顯著抑制tyrosinase及其相關蛋白TRP-1 (tyrosinase-related protein 1)的蛋白表現，並且降低細胞內cAMP的含量。進一步分析其中機轉發現，HLE抑制黑色素生成作用是透過干擾CREB (cAMP responsive element- binding protein)活化，進而影響MITF (microphthalmia-associated transcription factor)表現，導致tyrosinase的表現減少和黑色素合成下降。最後再以裸鼠進行實驗，我們也發現HLE可以減少曝照UVB之裸鼠皮膚黑色素的形成，並且抑制tyrosinase、TRP-1、TRP-2等調控黑色素合成之酵素的表現。綜合以上研究結果顯示，HLE可能有潛力應用於美容醫學、化妝品等行業。

關鍵字

黑色素生成作用 ； 洛神葉 ； 鞣花酸 ； 黑色素瘤細胞 ； α-黑色素細胞刺激素 ； 黑色素 ； 酪胺酸酶

並列摘要

Melanogenesis has many important physiological functions, including photo-protection of human skin from UV irradiation. Melanin synthesis is stimulated by α-melanocyte stimulating hormone (α-MSH) and cyclic AMP (cAMP) elevating agents. However, abnormal melanogenesis causes hyperpigmentation in the skin, which results in serious aesthetic issues and increases the risk of skin cancer. Previous studies have indicated Hibiscus sabdariffa leaf extract (HLE) has antioxidant and anticancer activities. Therefore, in this study we examined the effect of HLE on melanogenesis and signaling pathways in vitro and in vivo. Results showed that non-cytotoxic doses of HLE and its main composition ellagic acid (EA) reduced α-MSH-induced both tyrosinase activity and melanin production in mouse melanoma B16F0 cells. Western blotting data showed HLE and EA inhibited the expression of tyrosinase and TRP-1 (tyrosinase-related protein 1), cooperative with intracellular cAMP content. Further, HLE also suppressed the nuclear levels of CREB causing the consequent disturbed activation of MITF in α-MSH-stimulated B16F0 cells. The HLE-inhibited α-MSH-induced tyrosinase expression appeared be a consequence of MITF inactivation, because its DNA binding activity was suppressed by HLE. Besides, HLE inhibited melanin production in the dorsal skin of hairless mice exposed to UVB and the molecules involved in the melanogenesis. These findings suggested that HLE might be used as a potential natural whitening agent.

並列關鍵字

melanogenesis ； melanin ； α-MSH ； Hibiscus sabdariffa leaf extract ； ellagic acid ； tyrosinase

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