Weaver John, Tsai Pei, Pou Sovitj, Rosen Gerald M
Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201, USA.
J Org Chem. 2004 Nov 26;69(24):8423-8. doi: 10.1021/jo0485029.
Given that spin trapping/electron paramagnetic resonance (EPR) spectroscopy has become the primary technique to identify important biologically generated free radicals, such as superoxide (O(2)(-)), in vitro and in vivo models, evaluation of the efficiency of specific spin traps to identify this free radical is paramount. Recently, a family of ester-containing nitrones has been prepared, which appears to have distinct advantages for spin trapping O(2)(-) compared to the well-studied spin traps 5,5-dimethyl-1-pyrroline N-oxide 1 and 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide 2. An important determinant in the selection of a spin trap is the rate constant (k(app)) for its reaction with O(2)(-), and several different methods have been employed in estimating this k(app). In this paper, the two most frequently used scavengers of O(2)(-), ferricytochrome c and Cu/Zn-SOD, were evaluated as competitive inhibitors for spin trapping this free radical. Data presented herein demonstrate that SOD is the preferred compound when determining the k(app) for the reaction of O(2)(-) with spin traps. Using this model, the k(app) for the reaction of nitrone 1, 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide 3, and 5-methoxycarbonyl-5-methyl-1-pyrroline N-oxide 4 with O(2)()(-) was estimated to be 24.6 +/- 3.1, 73.0 +/- 12, and 89.4 +/- 1.0 M(-1) s(-1) at pH 7.0, respectively. Several other comparative studies between known spin traps were also undertaken.
鉴于自旋捕获/电子顺磁共振（EPR）光谱已成为在体外和体内模型中识别重要的生物产生自由基（如超氧阴离子（O₂⁻*））的主要技术，评估特定自旋捕获剂识别该自由基的效率至关重要。最近，已制备了一类含酯硝酮，与经过充分研究的自旋捕获剂5,5-二甲基-1-吡咯啉N-氧化物1和5-（二乙氧基磷酰基）-5-甲基-1-吡咯啉N-氧化物2相比，它们在自旋捕获O₂⁻*方面似乎具有明显优势。选择自旋捕获剂的一个重要决定因素是其与O₂⁻*反应的速率常数（k(app)），并且已经采用了几种不同的方法来估计该k(app)。在本文中，评估了两种最常用的O₂⁻*清除剂，即高铁细胞色素c和铜/锌超氧化物歧化酶（Cu/Zn-SOD），作为自旋捕获该自由基的竞争性抑制剂。本文提供的数据表明，在确定O₂⁻*与自旋捕获剂反应的k(app)时，SOD是首选化合物。使用该模型，在pH 7.0时，硝酮1、5-叔丁氧羰基-5-甲基-1-吡咯啉N-氧化物3和5-甲氧基羰基-5-甲基-1-吡咯啉N-氧化物4与O₂⁻*反应的k(app)估计分别为24.6±3.1、73.0±12和89.4±1.0 M⁻¹ s⁻¹。还进行了其他几种已知自旋捕获剂之间的比较研究。
