蓮蓬萃取物抑制黑色素生成作用之研究

The study of inhibitory effect of lotus seedpod extract on melanogenesis

李庭暄(Ting-Shuan-Lee)

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(2014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。蓮蓬 (lotus seedpod)富含多酚 (polyphenoe)成分，已有研究指出蓮蓬具有抗氧化、抗老化及抗癌之活性，但對於美白之應用仍是未知。表沒食子兒茶素(epigallocatechin, EGC)為蓮蓬萃取物中主要之多酚成分，過去研究證實EGC可做為美白試劑。因此本篇研究以蓮蓬主要成分EGC作為對照物質，利用黑色素瘤細胞 (B16F0)及C57BL/6小黑鼠模式，探討蓮蓬萃物 (Lotus seedpod extract , LSE)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)誘導促進黑色素(melanin)之生成，並給予不同劑量的LSE (10、15、20 μg/ml)或EGC (15 μM)，其結果顯示LSE與EGC皆能降低酪胺酸脢 (tyrosinase)活性和黑色素生成作用；以西方墨點法分析，結果顯示LSE能顯著抑制tyrosinase及其相關蛋白TRP-1 (tyrosinase-related protein 1)蛋白表現。本研究分析參與LSE抑制黑色素生成當中的分子機轉，發現LSE能透過抑制PKA (protein kinase A)和p38之磷酸化，進而干擾CREB (cAMP responsive element-binding protein)活化，影響下游轉錄因子MITF (microphthalmia-associated transcription factor)表現，導致tyrosinase的表現和黑生素合成下降。在動物實驗中發現，當C57BL/6小鼠耳朵皮膚暴露於UVB之下，處理LSE可以減少其黑色素之生成。綜合以上研究結果顯示，未來LSE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 ； 蓮蓬 ； 表沒食子兒茶素 ； 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). 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 lotus seedpod extract (LSE) has antioxidant, anti-aging and anticancer activities. Therefore, in this study we examined the effect of LSE on melanogenesis and signaling pathways in vitro and in vivo. Results showed that non-cytotoxic doses of LSE and its main composition Epigallocatechin (EGC) reduced α-MSH-induced both tyrosinase activity and melanin production in mouse melanoma B16F0 cells. Western blotting data showed LSE and EGC inhibited the expression of tyrosinase and TRP-1 (tyrosinase-related protein 1), Phosphorylation of p38 MAPK and PKA by α-MSH stimulation was efficiently blocked by LSE treatment. Further, LSE also suppressed the nuclear levels of CREB causing the consequent disturbed activation of MITF in α-MSH-stimulated B16F0 cells. The LSE-inhibited α-MSH-induced tyrosinase expression appeared be a consequence of MITF inactivation, because its DNA binding activity was suppressed by LSE. Besides, LSE inhibited melanin production in the ear skin of C57BL/6 mice exposed to UVB and the molecules involved in the melanogenesis. These findings suggested that LSE might be used as a potential natural whitening agent.

並列關鍵字

melanogenesis ； melanin ； α-MSH ； lotus seedpod extract ； Epigallocatechin ； tyrosinase

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