Alkyl peroxyl radical-scavenging activity of catechins

Alkyl peroxyl radical (ROO.) generated from the reaction between 20 mM t-butyl hydroperoxide (t-BuOOH) and 200 microM hematin could kill E. coli. The minimum concentrations of catechins sufficient to rescue the bacteria treated with ROO. were found to be 70 microM for (-)-epicatechingallate, 100 microM for (-)-epicatechin and 125 microM for (+)-catechin. These values were comparable with the value of alpha-tocopherol, a typical ROO. scavenger. On the other hand, L-ascorbate and beta-carotene revealed about one tenth the scavenging activity of catechins. No scavenging activity was found for superoxide dismutase even at 86 mM. These facts indicate that catechins have high ROO. scavenging activity.