Department of Chemistry, Faculty of Science and Graduate School of Science and Engineering, Ehime University , Matsuyama 790-8577, Japan.
J Agric Food Chem. 2013 Oct 23;61(42):10054-62. doi: 10.1021/jf402811m. Epub 2013 Oct 10.
A new free radical absorption capacity assay method is proposed with use of an aroxyl radical (2,6-di-tert-butyl-4-(4'-methoxyphenyl)phenoxyl radical) and stopped-flow spectroscopy and is named the aroxyl radical absorption capacity (ARAC) assay method. The free radical absorption capacity (ARAC value) of each tocopherol was determined through measurement of the radical-scavenging rate constant in ethanol. The ARAC value could also be evaluated through measurement of the half-life of the aroxyl radical during the scavenging reaction. For the estimation of the free radical absorption capacity, the aroxyl radical was more suitable than the DPPH radical, galvinoxyl, and p-nitrophenyl nitronyl nitroxide. The ARAC value in tocopherols showed the same tendency as the free radical absorption capacities reported previously, and the tendency was independent of an oxygen radical participating in the scavenging reaction and of a medium surrounding the tocopherol and oxygen radical. The ARAC value can be directly connected to the free radical-scavenging rate constant, and the ARAC method has the advantage of treating a stable and isolable radical (aroxyl radical) in a user-friendly organic solvent (ethanol). The ARAC method was also successfully applied to a palm oil extract. Accordingly, the ARAC method would be useful in free radical absorption capacity assay of antioxidative reagents and foods.
提出了一种新的自由基吸收能力测定方法，使用了一种烷氧自由基（2,6-二叔丁基-4-（4'-甲氧基苯基）苯氧自由基）和停流光谱法，并将其命名为烷氧自由基吸收能力（ARAC）测定法。通过测量乙醇中自由基清除率常数来确定每种生育酚的自由基吸收能力（ARAC 值）。也可以通过测量清除反应中烷氧自由基的半衰期来评估 ARAC 值。对于自由基吸收能力的估计，烷氧自由基比 DPPH 自由基、半胱氨酸和对硝基苯基硝酮更合适。生育酚中的 ARAC 值与先前报道的自由基吸收能力具有相同的趋势，并且该趋势与参与清除反应的氧自由基以及生育酚和氧自由基周围的介质无关。ARAC 值可以直接与自由基清除率常数相关联，并且 ARAC 方法具有在用户友好的有机溶剂（乙醇）中处理稳定和可分离自由基（烷氧自由基）的优势。ARAC 方法还成功应用于棕榈油提取物。因此，ARAC 方法将有助于抗氧化剂和食品的自由基吸收能力测定。
