Boots Agnes W, Bast Aalt, Haenen Guido R M M
Department of Pharmacology and Toxicology, Faculty of Medicine, University of Maastricht, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
FEBS Lett. 2005 Jan 31;579(3):677-82. doi: 10.1016/j.febslet.2004.12.044.
Quercetin is one of the most studied alimentary antioxidants. During its antioxidant activity, quercetin becomes oxidized into its ortho-quinone/quinone methide, denoted as QQ. QQ is toxic since it is highly reactive towards thiols. DT-diaphorase (NQO1) might protect against QQ toxicity by reducing QQ to quercetin. However, conflicting data have been reported. The aim of the present study is to elucidate the role of DT-diaphorase in the protection against QQ-mediated thiol reactivity. It was found that QQ is indeed a substrate for DT-diaphorase. However, QQ reacted much faster with glutathione or protein thiols than with DT-diaphorase in experiments with isolated compounds as well as with human liver cytosol or blood plasma. This indicates that DT-diaphorase has no role in the protection against QQ.
槲皮素是研究最多的膳食抗氧化剂之一。在其抗氧化活性过程中，槲皮素被氧化成其邻醌/醌甲基化物，记为QQ。QQ具有毒性，因为它对硫醇具有高度反应性。DT-黄递酶（NQO1）可能通过将QQ还原为槲皮素来防止QQ毒性。然而，已报道了相互矛盾的数据。本研究的目的是阐明DT-黄递酶在防止QQ介导的硫醇反应性中的作用。研究发现QQ确实是DT-黄递酶的底物。然而，在分离化合物以及人肝细胞溶胶或血浆的实验中，QQ与谷胱甘肽或蛋白质硫醇的反应比与DT-黄递酶的反应快得多。这表明DT-黄递酶在防止QQ方面不起作用。
