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用AM 1方法对若干黄酮类抗氧化剂做了计算 .发现 :( 1 )黄酮化合物邻二酚羟基清除自由基的活性强于间二酚羟基 .原因一是前者半醌式自由基与邻位酚羟基形成分子内氢键 ,从而更稳定 ;二是前者半醌式自由基通过共振形成邻苯醌 ,这使其未成对电子密度在邻位氧上有较多分布 ,内能更低 .( 2 )色原酮类黄酮化合物C环的吸电子性质使它对A环酚羟基有钝化作用 ,使其更不活泼 .由于B环受C环影响较小 ,而且大多数黄酮类抗氧化剂B环为邻二酚羟基取代 ,因此实验总结出的B环酚羟基活性高的规律得以解释 .
A number of flavonoid antioxidants were calculated by the AM 1 method and found that: (1) the activity of hydroxyl radical scavenging free radicals of flavone compounds is stronger than that of the meta-diphenolic hydroxyl group. One reason is that the former semiquinone-type free radical and orthophenol Hydroxyl forms an intramolecular hydrogen bond, which is more stable. Second, the former semiquinone-based radical forms p-benzoquinone by resonance, which makes its unpaired electron density more distributed on the ortho-oxygen and has lower internal energy. ) Chromone ketone flavonoid C ring electron-withdrawing nature of its A ring phenolic hydroxyl passivation, making it more inactive because the B ring by the C ring less affected, and most flavonoids B ring Is substituted for the hydroxyl group of the ortho-diphenol. Therefore, the experimentally concluded rule that the activity of the B-ring phenolic hydroxyl group is high is explained.