Absence of generation of oxygen-containing free radicals with 4'-deoxydoxorubicin, a non-cardiotoxic anthracycline drug

In vitro ESR studies of doxorubicin and 4'-deoxydoxorubicin have been conducted using the spin traps PBN and DMPO. Solutions prepared in the presence of atmospheric oxygen at pH = 12 exhibited a typical semiquinone signal preceded by a short-lived signal attributed to perhydroxyl radical, HO2. At physiological pH the perhydroxyl signal was observed in the doxorubicin solution but not in 4'-deoxydoxorubicin. In the absence of oxygen, at pH = 7.5, neither drug exhibited a signal. A relationship is proposed between the perhydroxyl radical and the cardiotoxicity observed in doxorubicin but not in 4'-deoxydoxorubicin.