Importance of carotenoid structure in radical-scavenging reactions
Importance of carotenoid structure in radical-scavenging reactions
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DOI：
10.1021/jf970010s
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发表时间：
1997-08-01
影响因子：
6.1
通讯作者：
Skibsted, LH
中科院分区：
文献类型：
--
作者：
Mortensen, A;Skibsted, LH
类胡萝卜素和苯氧基之间的（平行）反应速率产生(i)类胡萝卜素/苯氧基加合物和（ii）类胡萝卜素自由基阳离子（实际上通过还原再生苯酚）已被发现随着类胡萝卜素中（共面）共轭双键数量的增加而增加，而羟基特别是酮基的存在则减少。生成类胡萝卜素自由基的反应的半衰期为十分之一毫秒，用纳秒激光闪光光解的瞬态可见光和近红外吸收光谱研究自由基的生成，在20℃下，过氧化二叔丁基/苯（7/3,v/v）的相对速率为番茄红素（1.66）、β -胡萝卜素(1)、玉米黄质（0.79）、叶黄素（0.70）和紫锥烯酮（0.68），而角黄素和β -apo-8′-胡萝卜素几乎不反应，虾青素根本不反应。当形成时，类胡萝卜素自由基是相当稳定的（在毫秒时间尺度上的二阶衰变）。自由基阳离子的近红外跃迁能量越低，类胡萝卜素作为苯氧基的清除剂越有效，番茄红素是更有效的抗氧化剂。
The rate of (parallel) reaction between carotenoids and phenoxyl radical to yield (i) carotenoid/ phenoxyl adducts and (ii) carotenoid radical cations (in effect regenerating the phenol by reduction) has been found to increase for an increasing number of(coplanar) conjugated double bonds in the carotenoid and to decrease in the presence of hydroxy and especially keto groups. The reactions to yield the carotenoid radical have half-lives of tenths of milliseconds, and when studied by transient visible and near-infrared absorption spectroscopy using nanosecond laser flash photolysis for radical generation, the relative rates in di-tert-butyl peroxide/benzene (7/3, v/v) at 20 degrees C were lycopene (1.66), beta-carotene (1), zeaxanthin (0.79), lutein (0.70), and echinenone (0.68), while canthaxanthin and beta-apo-8'-carotenal hardly reacted and astaxanthin not at all. When formed, the carotenoid radicals are rather stable (second-order decay on a millisecond time scale). The lower the energy of the near-infrared transition in the radical cation, the more effective is the carotenoid as phenoxyl scavenger, and lycopene is concluded to be the more efficient antioxidant.