Ueda J, Saito N, Shimazu Y, Ozawa T
National Institute of Radiological Sciences, Chiba-shi, Japan.
Arch Biochem Biophys. 1996 Sep 15;333(2):377-84. doi: 10.1006/abbi.1996.0404.
The reactivities of various antioxidative compounds including catechol derivatives and endogenous radical scavengers toward hydroxyl radical (.OH) were investigated by an electron spin resonance-spin trapping method, thiobarbituric acid method, and DNA strand scission assay. Hydroxyl radical was generated by both the reaction of Cu(II) complex with hydrogen peroxide (H2O2) and ultraviolet (uv) photolysis of H2O2. At physiological pH, catechol derivatives such as protocatechuic acid and catechin greatly suppressed the DNA strand scission by .OH produced from the reaction of Cu(en)2 with H2O2, whereas ascorbic acid and acetylcysteine accelerated DNA strand scission. The former case is due to the chelation of catechol derivatives to Cu(II) ion, forming of Cu(II) complexes being unable to react with H2O2, and the latter case is due to the acceleration of the reduction rate of Cu(II) to Cu(I). On the other hand, all compounds used here suppressed the DNA strand scission by .OH produced from uv photolysis of H2O2. The differences of the reactivities between the reaction system of Cu(en)2-H2O2 and the uv photolysis of H2O2 have been discussed.
通过电子自旋共振-自旋捕获法、硫代巴比妥酸法和DNA链断裂分析，研究了包括儿茶酚衍生物和内源性自由基清除剂在内的各种抗氧化化合物对羟基自由基（·OH）的反应活性。羟基自由基通过Cu（II）络合物与过氧化氢（H2O2）的反应以及H2O2的紫外（uv）光解产生。在生理pH值下，原儿茶酸和儿茶素等儿茶酚衍生物极大地抑制了由Cu（en）2与H2O2反应产生的·OH导致的DNA链断裂，而抗坏血酸和乙酰半胱氨酸则加速了DNA链断裂。前一种情况是由于儿茶酚衍生物与Cu（II）离子螯合，形成了无法与H2O2反应的Cu（II）络合物，而后一种情况是由于Cu（II）还原为Cu（I）的速率加快。另一方面，这里使用的所有化合物都抑制了由H2O2的紫外光解产生的·OH导致的DNA链断裂。讨论了Cu（en）2-H2O2反应体系与H2O2紫外光解之间反应活性的差异。
