臺灣博碩士論文加值系統

在生物體中會產生一些自由基如：超氧自由基 ( superoxide )、氫氧自由基 ( hydroxy radicals ) 以及烷氧自由基 ( alkoxy radicals )…等，這些以氧為中心的自由基與其代謝物 ( 如：過氧化氫，hydrogen peroxide) 通稱為活性氧物質 ( reactive oxygen species， ROS )。 目前已知有許多疾病與自由基有關，包括：細胞膜的損傷 ( membrane damage)、風濕性關節炎 ( rheumatoid arthrutis)、缺氧後再給氧對組織造成的傷害 ( ischemia-reperfusion injury) 以及癌症的形成( carcinogenesis processing )..等。在過去一些研究證實，一些過氧化物或是一些會產生自由基的物質對老鼠皮膚具有促進癌化的能力，而抗氧化物會抑制此種促進腫瘤形成的能力。 癌瘤促進劑 如phorbol esters會刺激吞噬細胞活化NADPH oxidase而產生ROS，以及在小鼠皮膚上會活化xanthine oxidase以促進ROS量的累積。本篇偵測六種植物中的多酚類 ( phytopolyphenols ) 對ROS的清除能力以及對xanthine oxidase 和NADPH oxidase 的影響。其中theaflavin ( TF1 ) 、theaflavin-3-gallate( TF2 )、 theaflavin-3,3'-digallate ( TF3 ) 是紅茶中的成分，(-)-epigallocatechin-3-gallate ( EGCG )和gallic acid是綠茶中的主要成分，以及propyl gallate。EGCG、TF1、TF2和TF3會抑制xanthine oxidase 活性，並且會清除O2- 和H2O2 , 其中TF3對xanthine oxidase 的抑制能力最強 ( IC50 = 4.5mM) ，且屬於競爭型抑制劑 ( competitive inhibitor)。這些植物多酚類除了gallic acid 以外其他五種phytopolyphenoly在20mM對PMA引發HL60 O2- 的產生有明顯的抑制.在10mM時只有EGCG、 propyl gallate 和TF3的抑制效果大於50%，其中propyl gallate 對PMA引發HL60 H2O2 的產生抑制能力最強。由於PMA引發HL60產生ROS的機制主要是經由PKC的活化，再經由PKC去活化NADPH oxidase 產生O2-。我們發現TF3會明顯抑制PKC從細胞質轉移到細胞膜但對p47phox的磷酸化並沒有顯著的抑制。從這些結果我們發現TF3會抑制xanthine oxidase的活性以及抑制PMA促進NADPH oxidase ROS的產生，TF3不只本身會清除自由基同時也參與在訊息傳遞的調控中。

Reactive oxygen species (ROS) such as superoxide, hydrogen peroxide, hypohalides, and hydroxyl radicals are implicated in the pathogenesis of many diseases, e.g. membrane damage, respiratory disease syndromes, rheumatoid arthritis, ischemia-reperfusion injury and carcinogenesis processing. For instance, organic peroxides and free radical generators have tumor-promoting activity in mouse skin, and inversely, antioxidants and free radical scavengers inhibit the biochemical and biological effects of tumor promoters and tumorigenesis. Tumor promoters such as PMA enhance the generation of ROS, in phagocyte it through PKC pathway to activated NADPH oxidase. In some organs such as mouse skin, TPA triggers ROS accumulation through the activation of xanthie/xanthine oxidase system. The six Phytopolyphenols were selected that theaflavin (TF1), theaflavin-3-gallate (TF2), theaflavin-3,3'-digallate (TF3) were as black tea polyphenols, (-)-epigallocatechin-3-gallate (EGCG) and gallic acid were the major components in green tea，and propyl gallate (PG) which gallic acid was as a miain part of its structure . These six compounds are antioxidants , and it has been suggested that they can reduce oxidative stress by their antioxidant properties, we found that theaflavins and EGCG could prevent xanthine oxidase to produce uric acid (TF1, IC50 = 25.5mM; TF2, IC50 = 7.6mM; TF3, IC50 = 4.5mM; EGCG, IC50 = 12.5mM ) and they were as scanvengers of superoxide. TF3 is regarded as a competitive inhibitor, was the most potent inhibitor on the inhibition of xanthine oxidase in these compounds. Tea polyphenols and propyl gallate all have a potent inhibitory effects on PMA stimulated superoxide production at 20~50mM and their inhibitory effects were more than 50% that compared with PMA only. Gallic acid ( GA ) have no effects on the inhibition of superoxide production by PMA stimulated HL-60. At 10 mM, only EGCG, TF3, and propyl gallate ( PG )that the inhibitory effects were more than 50%, and the inhibition ability is Propyl gallate > EGCG > TF3. Superoxide scavenging ability of these 6 compunds were EGCG > TF2 > TF1 > GA > TF3 > PG. PG also was the most potent inhibitor on PMA stimulated H2O2 production and the H2O2 scavenging ability was TF2 >TF3 >TF1 > EGCG >PG >GA. PMA stimulated PKC translocation from cytosol to membrane were inhibited by TF3. From these data we suggest that inhibition of PG and TF3 were not only by its scavenging ability but most was involved in the signal transduction of NADPH oxidase activation.

Contents
Chapter 1. Abstract in Chinese (中文摘要)………………………………1
Chapter 2. Abstract in English (英文摘要)…………………………………3
Chapter 3. Introduction ....……………………………………………………5
Chapter 4. Material and Methods ..……………………………………………9
Chapter 5. Results ....……………………………………………………………15
Chapter 6. Discussion ………………………………………………………….20
Reference ………………………………………………………………………….26
Figures ……………………………………………………………………………31

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