Division of Food Chemistry & Toxicology, Department of Chemistry, University of Kaiserslautern, Kaiserslautern, Germany.
Mol Nutr Food Res. 2009 Oct;53(10):1226-36. doi: 10.1002/mnfr.200800456.
Beneficial health effects of diets containing fruits have partly been attributed to polyphenols which display a spectrum of bioactive effects, including antioxidant activity. However, polyphenols can also exert prooxidative effects in vitro. In this study, polyphenol-mediated hydrogen peroxide (H(2)O(2)) formation was determined after incubation of apple juice extracts (AEs) and polyphenols in cell culture media. Effects of extracellular H(2)O(2 )on total glutathione (tGSH; =GSH + GSSG) and cellular reactive oxygen species (ROS) level of HT-29 cells were studied by coincubation +/- catalase (CAT). AEs ( > or =30 microg/mL) significantly generated H(2)O(2) in DMEM, depending on their composition. Similarly, H(2)O(2) was measured for individual apple polyphenols/degradation products (phenolic acids > epicatechin, flavonols > dihydrochalcones). Highest concentrations were generated by compounds bearing the o-catechol moiety. H(2)O(2) formation was found to be pH dependent; addition of CAT caused a complete decomposition of H(2)O(2) whereas superoxide dismutase was less/not effective. At incubation of HT-29 cells with quercetin (1-100 microM), generated H(2)O(2) slightly contributed to antioxidant cell protection by modulation of tGSH- and ROS-level. In conclusion, H(2)O(2) generation in vitro by polyphenols has to be taken into consideration when interpreting results of such cell culture experiments. Unphysiologically high polyphenol concentrations, favoring substantial H(2)O(2 )formation, are not expected to be met in vivo, even under conditions of high end nutritional uptake.
富含水果的饮食对健康有益，其部分原因可归因于多酚，多酚具有一系列生物活性作用，包括抗氧化活性。然而，多酚在体外也可能产生促氧化作用。在这项研究中，在细胞培养基中孵育苹果汁提取物（AE）和多酚后，测定了多酚介导的过氧化氢（H2O2）的形成。通过共孵育 +/- 过氧化氢酶（CAT）研究了细胞外 H2O2 对 HT-29 细胞总谷胱甘肽（tGSH；= GSH + GSSG）和细胞内活性氧（ROS）水平的影响。AE（≥30μg/mL）在 DMEM 中显著生成 H2O2，这取决于其组成。同样，测量了单个苹果多酚/降解产物（没食子酸>表儿茶素，黄酮醇>二氢查耳酮）的 H2O2。具有邻儿茶酚结构的化合物产生的 H2O2 浓度最高。发现 H2O2 的形成依赖于 pH 值；添加 CAT 会导致 H2O2 的完全分解，而过氧化氢酶则效果较差/无效。在 HT-29 细胞孵育槲皮素（1-100μM）的过程中，生成的 H2O2 通过调节 tGSH-和 ROS 水平，对细胞抗氧化保护略有贡献。总之，在解释此类细胞培养实验的结果时，必须考虑多酚在体外产生的 H2O2。即使在高营养摄入的情况下，体内也不会达到高浓度的多酚，这不利于大量生成 H2O2。
