Electron spin resonance spectroscopic evaluation of scavenging activity of tea catechins on superoxide radicals generated by a phenazine methosulfate and NADH system

The scavenging effects of tea catechins on superoxide radicals ( O-2(-)) generated non-enzymatically by a phenazine methosulfate (PMS) and reduced beta-nicotinamide adenine dinucleotide (NADH) system, was studied using an electron spin resonance (ESR) spectrometer along with a spin-trapping agent, 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO). The presence of 3', 4', 5'-trihydroxyl groups attached to the B-ring of the flavan skeleton enhanced the radical scavenging efficiency displayed by the catechin family in comparison to those with 3', 4'-dihydroxyl groups, and the insertion of a galloyl moiety into three positions of the C-ring exerted a synergistic impact on O-2(-) scavenging activity. Catechin constituents accounted for 86% of the total O-2(-) scavenging capacity of green tea extract. with a particularly high contribution ascribed to (-)-epigallocatechin gallate [(-)-EGCG] (48%) and (-)-epigallocatechin [(-)-EGC] (26%). (C) 2002 Elsevier Science Ltd. All rights reserved.