Rutgers University, Department of Food Science, 65 Dudley Road, New Brunswick, New Jersey 08901, USA.
J Agric Food Chem. 2013 Jun 12;61(23):5511-9. doi: 10.1021/jf4010725. Epub 2013 May 31.
Reaction kinetics in the Trolox equivalent antioxidant capacity (TEAC) assay between ABTS(+•) [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) cation radical] and compounds with different structure, molecular weight, number of OH groups, and redox potential were investigated by recording loss of ABTS(+•) absorbance (734 nm) continuously over time. Curves showed six distinguishable kinetic patterns, including both immediate and extended reaction components. Radical quenching rates in the immediate component most relevant to reactions in foods and tissues depended on phenol structure and steric accessibility to the hindered radical, while reaction stoichiometry correlated with the number of phenol groups (>0.81) but not redox potential. Current assay procedures measure antioxidant capacity under conditions not relevant to actual applications and do not determine radical quenching rates. Results raise serious questions regarding the ability of reactions with the hindered ABTS(+•) to rank actual radical quenching by compounds with different structures and invalidate reporting antioxidant activity as Trolox equivalents.
通过连续记录 ABTS(+)吸收值的损失（734nm），研究了 Trolox 当量抗氧化能力（TEAC）测定中 ABTS(+)与不同结构、分子量、OH 基团数量和氧化还原电位的化合物之间的反应动力学。曲线显示了六种可区分的动力学模式，包括直接和扩展反应成分。与食物和组织中的反应最相关的直接成分中的自由基猝灭速率取决于酚的结构和受阻自由基的空间可及性，而反应计量学与酚基团的数量（>0.81）相关，但与氧化还原电位无关。目前的测定程序在与实际应用无关的条件下测量抗氧化能力，并且不测定自由基猝灭速率。结果对受阻 ABTS(+)与不同结构的化合物之间实际自由基猝灭能力的反应能力提出了严重质疑，并使以 Trolox 当量报告抗氧化活性无效。
