Redox Potential of Iron-Bleomycin

The oxidation-reduction potential of the iron complex of bleomycin, an antitumor agent that cleaves deoxyribonucleic acid (DNA), was measured at 25 °C, pH 7.0, by using both a microcoulometric and an optical absorption method. A value of 129 ± 12 mV was obtained vs. the standard hydrogen electrode for a single-electron process. Thus, ferrous bleomycin, the active form of the antitumor drug, can be regenerated under physiological conditions from ferric bleomycin, a product of the DNA cleavage reaction.