Mechanism of the interaction of superoxide ion and ascorbate with anthracycline antibiotics.

The interaction of superoxide ion and ascorbate anion with anthracycline antibiotics (adriamycin and aclacinimycin A) as well as with their Fe3+ complexes has been studied in aprotic and protic media. It was found that both superoxide and ascorbate reduce anthracyclines to deoxyaglycons via a one-electron transfer mechanism under all conditions studied. The reaction of ascorbate anion with adriamycin and aclacinomycin A in aqueous solution proceeded only in the presence of Fe3+ ions; it is supposed that an active catalytic species was Fe3+ adriamycin. It is also supposed that the reduction of anthracycline antibiotics by O2-. and ascorbate in cells may increase their anticancer effect.