Formation and decay of the ABTS derived radical cation: A comparison of different preparation procedures
Formation and decay of the ABTS derived radical cation: A comparison of different preparation procedures
复制标题
DOI：
10.1002/kin.10094
复制
发表时间：
2002-12-01
影响因子：
1.5
通讯作者：
Lissi, E
中科院分区：
文献类型：
--
作者：
Henriquez, C;Aliaga, C;Lissi, E
蓝绿色自由基阳离子2，2-连氮基双-（3-乙基苯并噻唑-6-磺酸）（ABTS（+））预溶液的漂白已被广泛用于评估复杂混合物和单个化合物的抗氧化能力。通过跟踪样品在734 nm处吸光度的衰减，可以容易地监测预形成的自由基与自由基清除剂的反应。ABTS自由基阳离子可以使用不同的氧化剂制备。用MnO 2作为氧化剂得到的结果表明，锰离子的存在增加了[ABTS]（+.）以浓度依赖性方式自漂白。也可以通过用2，2 '-偶氮双（2-脒基丙烷）盐酸盐（AAPH）或过硫酸盐（PDS）氧化ABTS来获得自由基。在ABTS体系中，AAPH的氧化反应具有较高的活化能和较低的反应级数。数据支持的机制，其中AAPH的均裂是限速步骤，然后由ABTS反应后的偶氮化合物热处理产生的过氧自由基。另一方面，采用PDS测得的低活化能以及动力学定律与氧化剂和ABTS之间的双分子反应的发生是相容的。关于使用基于ABTS的方法来评估自由基清除剂，采用AAPH作为氧化剂获得的自由基阳离子仅可在低温下使用，在低温下剩余AAPH的进一步分解最小化的条件下。在ABTS/PDS浓度比等于（或高于）2的PDS反应中产生的ABTS衍生自由基获得最佳结果。然而，即使与自由基制备的这一程序，化学计量系数大大大于两个得到的自由基阳离子的消耗，采用环烷或对叔丁基苯酚作为还原剂。这使人怀疑使用ABTS为基础的程序来估计抗氧化能力。(C)2002 Wiley Periodicals，Inc.
Bleaching of a preformed solution of the blue-green radical cation 2,2-azinobis-(3-ethylbenzothizoline-6-sulfonic acid) (ABTS(+.)) has been extensively used to evaluate the antioxidant capacity of complex mixtures and individual compounds. The reaction of the preformed radical with free-radical scavengers can be easily monitored by following the decay of the sample absorbance at 734 nm. The ABTS radical cation can be prepared employing different oxidants. Results obtained using MnO2 as oxidant show that the presence of manganese ions increases the rate of [ABTS](+.) autobleaching in a concentration-dependent manner. The radicals can also be obtained by oxidizing ABTS with 2,2'-azobis(2-amidinopropane)hydrochloride (AAPH) or peroxodisulfate (PDS). The oxidation by AAPH takes place with a large activation energy and a low reaction order in ABTS. The data support a mechanism in which the homolysis of AAPH is the rate-limiting step, followed by the reaction of ABTS with the peroxyl radicals produced after the azocompound thermolysis. On the other hand, the low activation energy measured employing PDS, as well as the kinetic law, are compatible with the occurrence of a bimolecular reaction between the oxidant and ABTS. Regarding the use of ABTS-based methodologies for the evaluation of free radical scavengers, radical cations obtained employing AAPH as oxidant can be used only at low temperatures, conditions where further decomposition of the remaining AAPH is minimized. The best results are obtained with ABTS derived radicals generated in the reaction of PDS with an ABTS/PDS concentration ratio equal (or higher) to two. However, even with radicals prepared by this procedure, stoichiometric coefficients considerably larger than two are obtained for the consumption of the radical cation employing tryptophane or p-terbutylphenol as reductants. This casts doubts on the use of ABTS-based procedures for the estimation of antioxidant capacities. (C) 2002 Wiley Periodicals, Inc.