Mortensen A, Skibsted L H
Food Chemistry, Department of Dairy and Food Science, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark.
FEBS Lett. 1998 Apr 24;426(3):392-6. doi: 10.1016/s0014-5793(98)00382-2.
Peroxyl radicals, as model for peroxyl radicals formed during autoxidation of lipids, have been generated in three solvent systems (cyclohexane, tetrahydrofuran and tert-butanol/water) by steady-state and laser flash photolysis, and their reaction with beta-carotene studied. Steady-state photolysis experiments showed that alkyl, alkoxyl and alkylperoxyl radicals all react with beta-carotene. However, laser flash photolysis experiments indicated that the reaction with peroxyl radicals (second-order rate constant estimated to be less than 10(6) M(-1) s(-1)) is slower than with alkyl and alkoxyl radicals, and that beta-carotene is hence a poor direct scavenger of peroxyl radicals. Scavenging of peroxyl radicals by beta-carotene is suggested not to proceed via electron transfer but rather by adduct formation and/or hydrogen abstraction. For different phenoxyl radicals, differences in reactivity towards beta-carotene seem to be correlated with standard reduction potential.
作为脂质自氧化过程中形成的过氧自由基模型，过氧自由基已在三种溶剂体系（环己烷、四氢呋喃和叔丁醇/水）中通过稳态和激光闪光光解产生，并对其与β-胡萝卜素的反应进行了研究。稳态光解实验表明，烷基、烷氧基和烷基过氧自由基均与β-胡萝卜素发生反应。然而，激光闪光光解实验表明，与过氧自由基的反应（二阶速率常数估计小于10(6) M(-1) s(-1)）比与烷基和烷氧基自由基的反应慢，因此β-胡萝卜素是一种较差的过氧自由基直接清除剂。β-胡萝卜素对过氧自由基的清除作用被认为不是通过电子转移进行，而是通过加合物形成和/或氢原子提取。对于不同的苯氧基自由基，对β-胡萝卜素的反应性差异似乎与标准还原电位相关。
