Free-Radical Scavenging Reation of beta-Carotene

类胡萝卜素，如β-胡萝卜素，被认为是有效的脂质过氧化抑制剂。为了了解β-胡萝卜素的抗氧化作用机制，分析其作为抗氧化剂可能产生的氧化产物是很重要的。本研究对β-胡萝卜素与过氧化氢自由基的反应产物进行了分离和表征。在37ﾟC下苯中，β-胡萝卜素与烷基过氧基反应。用2，2‘-偶氮二(2，4-二甲基戊腈)(AMVN)生成烷基过氧基。反应产物经结构鉴定为12-甲酰基-11-去甲基-β、β-胡萝卜素(1)、15‘-甲酰基-15-去甲基-β、β-胡萝卜素(2)、19-氧甲基-10-去甲基-β-胡萝卜素(3)、5，6-环氧基-5，6-二氢-β、β-胡萝卜素(4)、13，15’-环氧乙烯-13，15‘-二氢-β、β-胡萝卜素(5)、15’-环氧乙烯-13，15‘-二氢-β、β-胡萝卜素(6)、11，15’-cyclo-12，15-epoxy-11，12，15，15‘-tetrahydro-beta，β-胡萝卜素(7)。研究了AMVN诱导的体相亚油酸甲酯过氧化过程中β-胡萝卜素的反应产物。在亚油酸甲酯的过氧化过程中，除化合物1-7外，还生成了大量的β-胡萝卜素与亚油酸甲酯的加合物。结果表明，β-胡萝卜素能清除脂质过氧化自由基，形成化合物1-7和β-胡萝卜素与脂质的加合物。

Carotenoids such as beta-carotene are considered to be effective inhibitors of lipid peroxidation. To know the mechanism of antioxidant activity of beta-carotene, it is important to analyze its oxidation products that may arise during its action as an antioxidant. In this research, the reaction products of beta-carotene with peroxyl radicals were isolated and characterized. beta-Carotene was reacted with an alkylperoxyl radical at 37ﾟC in benzene. 2,2'-Azobis(2,4-dimethylvaleronitrile) (AMVN) was used to generate the alkylperoxyl radical. The reaction products were identified as 12-formyl-11-nor-beta, beta-carotene(1), 15'-formyl-15-nor-beta, beta-carotene(2), 19-oxomethyl-10-nor-beta, beta-carotene(3), 5,6-epoxy-5,6-dihydro-beta, beta-carotene(4), 13,15'-epoxyvinyleno-13,15'-dihydro-beta, beta-carotene(5), 15'13-epoxyvinyleno-13,15'-dihydro-beta, beta-carotene(6), and 11,15'-cyclo-12,15-epoxy-11,12,15,15'-tetrahydro-beta, beta-carotene(7). The reaction products of beta-carotene during the AMVN-induced peroxidation of methyl linoleate in bulk phase were also studied. In addition to compounds 1-7, a large amount of adducts of beta-carotene with methyl linoleate were formed during the peroxidation of methyl linoleate. The results indicate that beta-carotene can scavenge lipid-peroxyl radicals to form compounds 1-7 and adducts of beta-carotene with lipids.