Liebler D C, McClure T D
Department of Pharmacology and Toxicology, University of Arizona, Tucson 85721, USA.
Chem Res Toxicol. 1996 Jan-Feb;9(1):8-11. doi: 10.1021/tx950151t.
beta-Carotene and other carotenoids are thought to exert disease preventive actions by scavenging reactive free radicals, but the mechanisms of these reactions are poorly understood. We detected products formed by reaction of beta-carotene with alkoxyl, and alkylperoxyl free radicals generated by thermolysis of azobis(2,4-dimethylvaleronitrile) (AMVN) in benzene. Analyses by atmospheric pressure chemical ionization mass spectrometry identified two previously unknown classes of beta-carotene oxidation products. Substitution products contain one AMVN-derived radical adduct group and result from hydrogen transfer from the carotenoid polyene followed by radical recombination. Addition products contain two AMVN-derived adduct groups and result instead from sequential radical additions to the polyene. These product structures provide the first mechanistic explanation for the radical scavenging reactions of carotenoids.
β-胡萝卜素和其他类胡萝卜素被认为通过清除活性自由基发挥预防疾病的作用，但这些反应的机制尚不清楚。我们检测了β-胡萝卜素与通过偶氮二（2,4-二甲基戊腈）（AMVN）在苯中热解产生的烷氧基和烷基过氧自由基反应形成的产物。通过大气压化学电离质谱分析确定了两类以前未知的β-胡萝卜素氧化产物。取代产物含有一个源自AMVN的自由基加合物基团，是类胡萝卜素多烯氢转移后自由基重组的结果。加成产物含有两个源自AMVN的加合物基团，而是多烯连续自由基加成的结果。这些产物结构为类胡萝卜素的自由基清除反应提供了第一个机理解释。
