Effect of catechins and tannins on depleted uranium-induced DNA strand breaks

Abstract

The effects of polyphenols on plasmid DNA strand breaks by depleted uranium were studied using four catechins: (+)-catechin, (−)-epicatechin, (−)-epigallocatechin (EGC), and (−)-epigallocatechin gallate (EGCG); seven tannins: Chinese gallotannin, persimmon tannin (PST), mimosa tannin (MMT), myrobalan tannin, quebracho tannin, gambir tannin, and chestnut tannin; and gallic acid. The plasmid DNA strand breaks by uranyl ion (UO22+) with hydrogen peroxide (H2O2) were strongly enhanced by EGC, EGCG, MMT, and PST (condenced tannins). The obtained results showed that the DNA strand breaks are caused by UO22+ through the direct interaction between the uranyl complex and the negatively charged DNA phosphate backbone. The additional DNA strand breaks by the addition of polyphenols occurred through an indirect process by the reduction of UO22+ to UO2+ and hydroxyl radical formation through a Fenton-type reaction with H2O2.