Hiramoto K, Ojima N, Sako K, Kikugawa K
Tokyo University of Pharmacy and Life Sciences, School of Pharmacy, Japan.
Biol Pharm Bull. 1996 Apr;19(4):558-63. doi: 10.1248/bpb.19.558.
The effect of plant phenolics, including flavonoids and green tea polyphenolics, on hydroxyl radical was examined by a common method using an electron spin resonance (ESR) technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trapping agent. The intensity of the ESR signals of DMPO-OH adduct formed by the interaction of DMPO with Fenton reagent was reduced in the presence of each phenolic in a dose-dependent manner. However, the decrease in the intensity of the signals was due partly to the enhanced disappearance of the spin adduct by the phenolics, as has been previously shown. This spin trapping method was unreliable for evaluation of the effect of the phenolics against hydroxyl radical. Hydroxyl radical induced-DNA single-strand breaks may be a better index for evaluation of the activity of the phenolics regarding hydroxyl radical. The effect of the phenolics on DNA single-strand breaks induced by Fenton reagent was examined. While sesamol and esculetin were inhibitory, most polyphenolics, especially (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG), were rather stimulatory. The results indicate that sesamol and esculetin scavenged hydroxyl radical, and EGC and EGCG generated hydroxyl radical under the conditions where hydroxyl radical was generating.
采用以5,5-二甲基-1-吡咯啉氮氧化物（DMPO）作为自旋捕获剂的电子自旋共振（ESR）技术这一常用方法，研究了包括黄酮类化合物和绿茶多酚在内的植物酚类物质对羟基自由基的影响。在每种酚类物质存在的情况下，DMPO与芬顿试剂相互作用形成的DMPO-OH加合物的ESR信号强度均呈剂量依赖性降低。然而，信号强度的降低部分归因于酚类物质使自旋加合物的消失加快，正如之前所表明的那样。这种自旋捕获方法对于评估酚类物质对羟基自由基的作用并不可靠。羟基自由基诱导的DNA单链断裂可能是评估酚类物质对羟基自由基活性的更好指标。研究了酚类物质对芬顿试剂诱导的DNA单链断裂的影响。芝麻酚和七叶亭具有抑制作用，而大多数多酚，尤其是（-）-表没食子儿茶素（EGC）和（-）-表没食子儿茶素没食子酸酯（EGCG），则具有促进作用。结果表明，芝麻酚和七叶亭能清除羟基自由基，而EGC和EGCG在羟基自由基产生的条件下会产生羟基自由基。
