Kinetics and mechanism of the reactions of superoxide ion in solution. Part 6. Interaction of superoxide ion with adriamycin in aprotic and protic media

Abstract

The interaction of superoxide ion with adriamycin has been studied in aprotic and protic solutions by the use of electronic absorption and n.m.r. spectroscopy. It was found that superoxide ion reacted with adriamycin by one-electron transfer in both aprotic and protic media (in the latter case against the reduction potential) due to irreversible transformation of the adriamycin semiquinone via dimerisation and deglycosation. The one-electron mechanism was confirmed by electrochemical reduction of adriamycin and by its reduction with NaBH_4′ benzosemiquinone, and ascorbate. In both aprotic and protic media one-electron reduction of adriamycin by superoxide ion was favoured over deprotonation.The possible application of this mechanism to the raction of O₂^–˙ with other anthraquinones was also considered.