Department of Chemistry, Renmin University of China, Beijing 100872, China.
J Agric Food Chem. 2010 Aug 25;58(16):9221-7. doi: 10.1021/jf1015413. Epub 2010 Jul 30.
Antioxidant synergism (or antagonism) between plant (iso)flavonoids (daidzein, baicalein, and quercetin) or their glycosides (puerarin, baicalin, and rutin) and β-carotene in phosphatidylcholine liposomes (pH 7.4) with oxidation initiated thermally by the lipophilic free radical initiator 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) and followed by the formation of conjugated dienes did not depend simply on the bond dissociation enthalpy (BDE) of the phenol O-H bond or the HOMO/LUMO energy gap based on density functional theory (DFT) calculations. Rate of regeneration of β-carotene from the β-carotene radical cation as the one-electron oxidation product of the lipid phase antioxidant by the monoanion form of the (iso)flavonoids in homogeneous (1:9 v/v methanol/chloroform) solution, as studied by laser flash photolysis and occurring on a microsecond time scale with biphasic kinetics, was in better agreement with the observed nonadditive antioxidative effects. However, correcting the observed (pseudo)-first-order rate constant for β-carotene regeneration for water/lipid distribution of the (iso)flavonoids provided an almost correct ordering of the (iso)flavonoids, according to the nonadditive effects with β-carotene on lipid oxidation.
植物（异）黄酮（大豆苷元、黄芩素和槲皮素）或其糖苷（葛根素、黄芩苷和芦丁）及其与β-胡萝卜素在磷脂双层体（pH7.4）中的抗氧化协同作用（或拮抗作用），通过亲脂性自由基引发剂 2,2'-偶氮双（2,4-二甲基戊腈）（AMVN）引发热氧化，随后形成共轭二烯，这并不简单地取决于酚类 O-H 键的键离解焓（BDE）或基于密度泛函理论（DFT）计算的 HOMO/LUMO 能隙。在均相（1:9v/v 甲醇/氯仿）溶液中，作为脂相抗氧化剂的单电子氧化产物，β-胡萝卜素自由基阳离子由（异）黄酮的单阴离子形式从β-胡萝卜素中再生的速率，如通过激光闪光光解研究并在微秒时间尺度上发生双相动力学，与观察到的非加性抗氧化效果更吻合。然而，根据（异）黄酮与β-胡萝卜素对脂质氧化的非加性效应，为（异）黄酮的水/脂质分配校正观察到的β-胡萝卜素再生的（伪）一级速率常数，几乎可以正确地对（异）黄酮进行排序。
