利用細胞模式評估Bracteanolide A的抗氧化生物功能

Investigate the anti-oxidant effects of Bracteanolide A by cell model

游雅茹(Ya-Ju Yu)

指導教授 ： 謝淑貞

國立臺灣大學/生物資源暨農學院/食品科技研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.00333

摘要

氧化壓力會造成活性氧化物(ROS)的累積，並透過傷害體內DNA、蛋白質，以及細胞膜等，導致許多慢性疾病，例如癌症、心血管疾病、神經退化性疾病，以及老化等等。因此，服用具抗氧化功效之保健食品漸漸成為現代人生活中的一部分。然而，對於天然物質抗氧化功能的研究常僅止於體外的試管化學反應試驗，例如：DPPH 清除能力測定、硫氰胺酸加上氯化亞鐵針對樣品進行抗氧化性測定的化學呈色法等。若能以較接近生物體的方式進行分析，定能更確認該物質的抗
氧化功效。NF-E2 相關因子2 (Nuclear factor-E2 (Erythroid 2)-related factor 2, Nrf-2) 為轉錄因子，亦為抗氧化路徑的重要調控因子。當體內受到氧化壓力傷害時，此因子可轉移至核內與抗氧化反應因素(Antioxidant response element, ARE)結合，接著可誘導其調控的下游基因，包含許多與抗氧化相關的酵素與蛋白質，使其發揮作用而降低氧化壓力所帶來的傷害。本篇研究先以RT-q-PCR 的方式作為篩選方法，偵測此途徑下游基因-NQO1 的表現，最後在11 個化合物中，發現白花水竹草萃取物中含量較高的純化合物，Bracteanolide A，於濃度50μM可明顯誘導NAD(P)H:Quinone 氧化還原酵素1(NQO1) mRNA 的表現。後續的實驗結果顯示，此化合物可在轉譯層次對Nrf2、NAD(P)H: Quinone 氧化還原酵素1(NQO1)，以及血基質氧化酶-1(HO-1)的蛋白質表現量有提升之效果，並能增加Nrf2 進入細胞核中的蛋白量，促進其作用活性。若先以Bracteanolide A 預先處理細胞，可有效減少過氧化氫誘發的活性氧化物生成並強烈降低其導致的DNA 傷害，最後抑制過氧化氫引起的細胞死亡。綜合上述，白花水竹草萃取物中的主要成分，Bracteanolide A 對遭受氧化傷害的細胞具有保護效果。

關鍵字

抗氧化 ； NF-E2相關因子 ； 抗氧化反應因素 ； NAD(P)H:Quinone氧化還原酵素1 ； 血基質氧化酶-1 ； Bracteanolide A

並列摘要

Oxidative stress will contribute to the accumulation of ROS, and result in many chronic diseases, such as cancers, cardiac diseases, neurodegenerative diseases, and aging etc. via damaging DNA, proteins, and cellular membranes in the body. Therefore, intaking the dietary supplement containing antioxidants is gradually becoming a portion of modern life. However, the researches about the antioxidant functions always merely focus on the in vitro chemical reactions, for example, DPPH radical scavenging activity, chemical colorimetric methods using Ammonium thiocyanate and iron (II) chloride tetrahydrate solution, and so forth. If we can analyze these materials by the ways which are more closed to the actual organism, the antioxidant functions of them can be more convinced.
Nuclear factor-E2 (Erythroid 2)-related factor 2, Nrf-2, is a transcription factor and also an important regulation factor of antioxidation pathway. When our bodies are damaged by oxidative stress, the factor can translocate into the nucleus and binds to the antioxidant response element (ARE) to induce the expression of downstream genes, including many related enzymes and proteins about antioxidation, and then act to reduce oxidative damages. At first, the study utilizes RT-q-PCR as a screening method to detect the expression of the downstream gene- NQO1. Finally, we discovered that Bracteanolide A , the pure compound contained higher in Tradescantia albiflora Kunth, at the concentration of 50 μM can apparently induce the expression of NQO1 mRNA among the 11 compounds. Other experiments also indicate the compound has the ability to induce the expression of Nrf2, NQO1, and HO-1 on the protein level. Besides, it can increase the amount of Nrf2 which translocates into the nucleus to elevate its activity. If pretreating the cells with Bracteanolide A, ROS induced by hydrogen peroxide can be effectively reduced and DNA damages will be strongly lowered. Last but the most important, it can inhibit the cell death caused by hydrogen peroxide. Overall, the main component of Tradescantia albiflora Kunth, Bracteanolide A, possesses the protective effect on oxidative damaged cells.

並列關鍵字

Antioxidation ； Nuclear factor-E2 (Erythroid 2)-related factor 2 (Nrf-2) ； Antioxidant response element (ARE) ； NAD(P)H: Quinoneoxidoreductase 1 (NQO1) ； Heme oxidase-1 ； Bracteanolide A

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