Department of Food Science and Technology, University of Ljubljana, Ljubljana, Slovenia.
J Agric Food Chem. 2012 Dec 19;60(50):12282-8. doi: 10.1021/jf3041512. Epub 2012 Dec 5.
Solvent composition has a large influence on measured antioxidant potential (AOP) of model polyphenols and red wines with 2,2-diphenyl-1-picrylhydrazyl (DPPH). We have shown that incorporation of aqueous buffer in the assay medium results in higher reactivity of catechin and caftaric acid, which are among major polyphenolic constituents of wines. Consequently, AOPs of red wines determined after 60 min of incubation at 25 °C in buffered methanol are 1.5-1.6-fold of values determined in methanol. Even in buffered methanol, wine polyphenols are not fully oxidized after 60 min. Only about half of Trolox equivalents were determined in comparison to the Folin-Ciocalteu assay. Buffer composition, pH, time of incubation, temperature, and concentration of antioxidants and DPPH all contribute to the resulting value of the AOP being standardized or at least strictly reported because minor differences in experimental procedures can account for large variations in determined AOP with DPPH for the same samples.
溶剂组成对模型多酚和含 2,2-二苯基-1-苦基肼（DPPH）的红葡萄酒的测定抗氧化活性（AOP）有很大影响。我们已经表明，在测定介质中加入水缓冲液会导致儿茶素和卡塔酸的反应性更高，儿茶素和卡塔酸是葡萄酒中主要的多酚成分之一。因此，在 25°C 下缓冲甲醇中孵育 60 分钟后测定的红葡萄酒 AOP 值是在甲醇中测定的值的 1.5-1.6 倍。即使在缓冲甲醇中，葡萄酒多酚在 60 分钟后也没有完全氧化。与福林-希奥考尔特（Folin-Ciocalteu）测定法相比，仅测定了大约一半的 Trolox 当量。缓冲液组成、pH 值、孵育时间、温度以及抗氧化剂和 DPPH 的浓度都会影响标准化的 AOP 结果，或者至少要严格报告，因为实验程序的微小差异可能会导致对相同样品使用 DPPH 测定的 AOP 产生很大变化。
