In this study, the inhibitory activities against DNA polymerases (pols) and DNA topoisomerases (topos) by eight major green tea catechin derivatives (flavan-3-ols) were investigated. Some catechins inhibited mammalian pols (alpha and beta) and human topos (I and II), with (-)-epigallocatechin gallate (EGCg) the strongest inhibitor of both enzyme types, showing IC50 values of 3.8-21.5 and 2.0-20.0 mu M, respectively. EGCg did not affect the activities of plant (cauliflower) pol alpha or prokaryotic pols and showed no effect on the activities of other DNA metabolic enzymes tested. Next, a method was established for assay of mouse one-cell zygote development inhibition, the catechin derivatives screened for bioactivity, and the inhibition was assessed and their effects ranked as: EGCg > GCg > Cg >> others. In the mouse one-cell zygote assay, EGCg at 50 mu M increased abnormal cells and 75 mu M of EGCg-induced apoptosis. The observed ranking of catechin derivative inhibition effects against mouse one-cell zygote development in vivo was similar to their ranking by topo inhibition in vitro rather than by pol inhibition; therefore, topo inhibition might have been effecting zygote development inhibition. These results suggested that catechin derivatives indeed reached the nuclear DNA where topo inhibition can occur, thus causing the observed cellular effects. From these findings, this zygote development inhibition assay will be useful as an anti-pregnant agent screening. (C) 2012, The Society for Biotechnology, Japan. All rights reserved.