Green tea extract and (-)-epigallocatechin-3-gallate, the major tea catechin, exert oxidant but lack antioxidant activities
Green tea extract and (-)-epigallocatechin-3-gallate, the major tea catechin, exert oxidant but lack antioxidant activities
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DOI：
10.1096/fj.04-2915fje
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发表时间：
2005-02-01
期刊：
影响因子：
4.8
通讯作者：
Mickshe, M
中科院分区：
文献类型：
--
作者：
Elbling, L;Weiss, RM;Mickshe, M
绿色茶是消费最广泛的饮料。由于其主要多酚成分（-）-表没食子儿茶素-3-没食子酸酯（EGCG）的抗氧化活性，它作为促进健康的膳食成分获得了很高的声誉。越来越多的证据表明，茶成分本身可以破坏细胞和促氧化剂。这些效应被认为是由于多酚在溶液中自发产生H（2）O（2）。在本研究中，我们研究了氧化剂和抗氧化剂特性的绿色茶提取物（GTE）和表没食子儿茶素没食子酸酯通过啮齿类巨噬细胞样RAW 264.7和人早幼粒细胞白血病HL 60细胞系。所得结果表明，无论是在无细胞条件下还是在细胞存在下，GTE和EGCG的氧化活性均超过自发产生的H（2）O（2）（FOX测定）。通过2 '，7'-二氯荧光素探测表明细胞内氧化应激增加，通过碱性彗星试验和微核试验（胞质分裂阻滞）证明遗传毒性增强。通过台盼蓝拒染法、MTT法和Hoechst染色法监测细胞死亡的时间和剂量依赖性诱导。此外，在我们的体外系统中，EGCG既不直接清除H（2）O（2），也不介导其他抗氧化活性，而是增加H（2）O（2）诱导的氧化应激和DNA损伤。总之，我们的数据表明，详细的机制研究GTE和EGCG的影响，应在体内过量摄入和/或局部应用的绿色茶产品之前，可以推荐给健康和/或患病的人。
Green tea is the most widely consumed beverage. It has attained high reputation as a health-promoting dietary component ascribed to the antioxidant activity of(-)-epigallocatechin-3-gallate(EGCG), its main polyphenolic constituent. Evidence is increasing that tea constituents can be cell damaging and pro-oxidant themselves. These effects were suggested to be due to spontaneous H(2)O(2) generation by polyphenols in solution. In the present study, we investigated the oxidant and antioxidant properties of green tea extracts(GTE) and of EGCG by means of the rodent macrophage-like RAW 264.7 and human promyelocytic leukemic HL60 cell lines. The results obtained show that both under cell-free conditions and in the presence of cells the oxidant activities of GTE and EGCG exceeded those of spontaneously generated H(2)O(2)(FOX assay). Increase of intracellular oxidative stress was indicated by 2',7'-dichlorofluorescin probing,and the enhanced genotoxicity was demonstrated by the alkaline comet assay and by the micronucleus assay(cytokinesis block). Time-and dose-dependent induction of cell death was monitored by trypan blue exclusion, MTT assay,and Hoechst staining. Furthermore,in our systems in vitro,EGCG neither directly scavenges H(2)O(2) nor mediates other antioxidant activities but rather increased H(2)O(2)-induced oxidative stress and DNA damage. In conclusion, our data suggest that detailed mechanistic studies on the effects of GTE and EGCG should be performed in vivo before excessive intake and/or topical application of green tea products can be recommended to healthy and/or diseased persons.