Lehrstuhl für Phytopathologie, Wissenschaftszentrum Weihenstephan, Technische Universität München, Emil-Ramann-Str. 2, 85354 Freising, Germany.
Free Radic Res. 2010 Dec;44(12):1435-44. doi: 10.3109/10715762.2010.515216. Epub 2010 Nov 1.
The chemopreventive chalcone xanthohumol (Xh) has been reported to decrease xanthine oxidase (XOD) catalysed formation of formazan from nitroblue tetrazolium (NBT) and is discussed as a potent scavenger of superoxide. Re-evaluation of the scavenging capacity indicated that Xh disturbed detection of superoxide with NBT, in case of an insufficient NBT/Xh ratio. Xh lacked superoxide scavenging activity in contrast to the Xh-derivative 3'-hydroxy-Xh with catechol substructure, used as positive control. This was shown by the use of sufficient concentration of NBT and other detectors such as hydroxylamine, XTT, cytochrome c and hydroethidine. HPLC analysis of reaction products in a xanthine/XOD/peroxidase system demonstrated beside enhanced inhibition of NBT-formazan by Xh that NBT even prevented oxidation of Xh. p-coumaric acid or ferulic acid could replace Xh in that system, indicating that superoxide detection using NBT is likely jeopardized by interference of phenoxyl-radicals. Furthermore, this study provides evidence that Xh can moderately generate superoxide via auto-oxidation.
类黄酮查尔酮（Xh）具有化学预防作用，据报道可减少黄嘌呤氧化酶（XOD）催化硝基四唑蓝（NBT）形成甲臜，被认为是超氧阴离子的有效清除剂。重新评估其清除能力表明，Xh 在 NBT/Xh 比例不足的情况下，会干扰 NBT 对超氧阴离子的检测。与具有儿茶酚结构的 Xh 衍生物 3'-羟基-Xh 不同，Xh 缺乏超氧阴离子清除活性，后者被用作阳性对照。这一点通过使用足够浓度的 NBT 和其他检测剂，如羟胺、XTT、细胞色素 c 和羟乙基啶，得到了证实。在黄嘌呤/XOD/过氧化物酶体系中的反应产物的 HPLC 分析表明，除了增强 Xh 对 NBT 甲臜的抑制作用外，NBT 甚至可以阻止 Xh 的氧化。对香豆酸或阿魏酸可以在该体系中替代 Xh，表明使用 NBT 检测超氧阴离子可能会受到苯氧自由基的干扰。此外，本研究提供的证据表明，Xh 可以通过自动氧化适度产生超氧阴离子。
