Damiani Elisabetta, Castagna Riccardo, Astolfi Paola, Greci Lucedio
Istituto di Biochimica, Via Ranieri, Università Politecnica delle Marche, I-60131 Ancona, Italy.
Free Radic Res. 2005 Mar;39(3):325-36. doi: 10.1080/10715760400028019.
Nitroxide radicals are an emerging class of interesting compounds with versatile antioxidant and radioprotective properties. All literature studies have so far concentrated on compounds bearing only one nitroxide function. Here, we now investigate and compare the radical scavenging behaviour and antioxidant activity of aromatic indolinonic and aliphatic piperidine bis-nitroxides, i.e compounds bearing two nitroxide functions. Their corresponding mono-derivatives were also studied for comparison. Radical scavenging activity was investigated using EPR and UV-Vis spectroscopy by following spectral changes in acetonitrile of the nitroxides in the presence of alkyl and peroxyl radicals generated, respectively, under anoxic or aerobic conditions from thermal decomposition of AMVN [2,2'-azobis(2,4-di-methylvaleronitrile)]. Antioxidant activity of the nitroxides was evaluated by monitoring conjugated dienes (CD) formation during methyl linoleate micelles peroxidation and by measuring carbonyl content in oxidized bovine serum albumin (BSA). The results show that: (a) each nitroxide moiety in bis-nitroxides scavenges radicals independent of each other; (b) aliphatic nitroxides do not scavenge peroxyl radicals, at least under the experimental conditions used here, whereas indolinonic aromatic ones do: their stoichiometric number is 1.14 and 2.17, respectively, for mono- and bis-derivatives; (c) bis-nitroxides are roughly twice more efficient at inhibiting lipid peroxidation compared to their corresponding mono-derivatives. Although this study provides only comparative information on the relative radical-scavenging abilities of mono- and bis-nitroxides, it helps in understanding further the interesting reactivity of these compounds especially with regards to peroxyl radicals where many controversies in the literature exist.
氮氧自由基是一类新兴的有趣化合物，具有多种抗氧化和辐射防护特性。迄今为止，所有文献研究都集中在仅带有一个氮氧官能团的化合物上。在此，我们现在研究并比较芳香吲哚啉酮类和脂肪族哌啶双氮氧自由基（即带有两个氮氧官能团的化合物）的自由基清除行为和抗氧化活性。还研究了它们相应的单衍生物以作比较。通过电子顺磁共振（EPR）和紫外可见光谱研究自由基清除活性，分别在无氧或有氧条件下，通过AMVN[2,2'-偶氮二(2,4-二甲基戊腈)]热分解产生烷基自由基和过氧自由基，跟踪氮氧自由基在乙腈中的光谱变化。通过监测亚油酸甲酯胶束过氧化过程中共轭二烯（CD）的形成以及测量氧化牛血清白蛋白（BSA）中的羰基含量来评估氮氧自由基的抗氧化活性。结果表明：（a）双氮氧自由基中的每个氮氧部分彼此独立地清除自由基；（b）脂肪族氮氧自由基至少在本文所用的实验条件下不清除过氧自由基，而吲哚啉酮芳香族氮氧自由基则能清除：它们的化学计量数对于单衍生物和双衍生物分别为1.14和2.17；（c）与相应的单衍生物相比，双氮氧自由基在抑制脂质过氧化方面的效率大约高两倍。尽管本研究仅提供了关于单氮氧自由基和双氮氧自由基相对自由基清除能力的比较信息，但它有助于进一步理解这些化合物有趣的反应性，特别是关于过氧自由基，这在文献中有许多争议。
