EFFECT OF PLANT PHENOLICS ON THE FORMATION OF THE SPIN-ADDUCT OF HYDROXYL RADICAL AND THE DNA STRAND BREAKING BY HYDROXYL RADICAL

The effect of plant phenolics, including flavonoids and green tea poly phenolics, on hydroxyl radical was examined by a common method using a n electron spin resonance (ESR) technique with 5,5-dimethyl-1-pyrrolin e N-oxide (DMPO) as a spin trapping agent. The intensity of the ESR si gnals of DMPO-OH adduct formed by the interaction of DMPO with Fenton reagent was reduced in the presence of each phenolic in a dose-depende nt manner. However, the decrease in the intensity of the signals was d ue partly to the enhanced disappearance of the spin adduct by the phen olics, as has been previously shown. This spin trapping method was unr eliable for evaluation of the effect of the phenolics against hydroxyl radical. Hydroxyl radical induced-DNA single-strand breaks may be a b etter index for evaluation of the activity of the phenolics regarding hydroxyl radical. The effect of the phenolics on DNA single-strand bre aks induced by Fenton reagent was examined. While sesamol and esculeti n were inhibitory, most polyphenolics, especially (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG), were rather stimulator y. The results indicate that sesamol and esculetin scavenged hydroxyl radical, and EGC and EGCG generated hydroxyl radical under the conditi ons where hydroxyl radical was generating.