Reevaluating the role of 1,10-phenanthroline in oxidative reactions involving ferrous ions and DNA damage.

It is widely believed that the iron chelator 1,10-phenanthroline (phen) is able to fully block the Fenton reaction by forming a complex (Fe(phen)3(2+), also known as ferroin) that cannot react with H2O2. We observed that phen cannot fully prevent 2-deoxyribose (5 mM) degradation induced by Fenton reagents (30 microM Fe(II) plus 100-500 microM H2O2); protection varied from 55% to 66% when the phen/Fe(II) ratio was 3:1 to 20:1. Inhibition of 2-deoxyribose damage was nearly unchanged if phen was pre-incubated with Fe(II).