Kinetics and Mechanisms of Antioxidant Activity using the DPPH.Free Radical Method
Kinetics and Mechanisms of Antioxidant Activity using the DPPH.Free Radical Method
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DOI：
10.1006/fstl.1997.0240
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发表时间：
1997-09
期刊：
影响因子：
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通讯作者：
V. Bondet;W. Brand-Williams;C. Berset
中科院分区：
文献类型：
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作者：
V. Bondet;W. Brand-Williams;C. Berset
摘要提出了三种抗氧化剂的反应机理，以解释先前在我们实验室采用自由基2,2-二苯基-1-吡啶肼（DPPH）方法进行的动力学研究的实验结果。它的激进形式是DPPH。在515 nm处显示最大吸光度，经抗自由基化合物还原后消失。BHT是一种合成抗氧化剂，与DPPH缓慢反应。在5h内达到稳定状态。这个2.8级的化学计量完全反应对DPPH来说是1.5级的。0.5到BHT。在20℃时，反应的动力学速率常数k为5.0 L/(mol·s)，在甲醇中的活化能Ea为35 kJ/mol。丁香酚与DPPH反应。在2小时内达到稳定状态。这个1.9-化学计量反应对DPPH和DPPH都是2级反应。丁香酚在20℃和30 kJ/mol时的k和Ea分别为5.4 × 10 10 L 3 /（mol 3·s）。丁香酚的机制可能涉及两个苯氧基自由基之间的二聚化。与异丁香酚的反应快速可逆，化学计量量为1.1。对于异丁香酚，在10℃下，k（直接反应）等于8.9 × 10−2 s−1，为一级反应。该反应符合伪单分子机理。
Abstract The reaction mechanisms of three antioxidants are proposed in order to explain experimental results obtained from a kinetic study using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH . ) method, previously adapted in our laboratory. In its radical form, DPPH . shows an absorbance maximum at 515 nm which disappears upon reduction by an antiradical compound. BHT, a synthetic antioxidant, slowly reacts with DPPH . reaching a steady state within 5 h. This 2.8-stoichiometric complete reaction follows a 1.5-order with respect to DPPH . and 0.5 to BHT. The kinetic rate constant, k, is estimated to be 5.0 L/(mol·s) at 20 °C and the energy of activation, Ea , is equal to 35 kJ/mol in methanol. Eugenol reacts with DPPH . reaching a steady state within 2 h. This 1.9-stoichiometric reaction follows a 2-order with respect to both DPPH . and eugenol, k and Ea are estimated to be 5.4 × 10 10 L 3 /(mol 3 ·s) at 20 °C and 30 kJ/mol, respectively. The eugenol mechanism may involve a dimerization between two phenoxyl radicals. The reaction with isoeugenol is rapid and reversible, with a stoichiometry of 1.1. It is first order with respect to isoeugenol with k (direct reaction) equal to 8.9 × 10 −2 s −1 at 10 °C. This reaction is consistent with a pseudo-monomolecular mechanism.