CHELATION OF COPPER(II) IONS BY DOXORUBICIN AND 4'-EPIDOXORUBICIN - ELECTRON-SPIN-RESONANCE EVIDENCE FOR A NEW COMPLEX AT HIGH ANTHRACYCLINE COPPER MOLAR RATIOS

Doxorubicin and 4′-epidoxorubicin form chelate complexes with Cu(II), the structures of which are dependent on the drug-to-metal ratio r. The complex stoichiometry is defined by the structure of the drug, the pH and the r values. The cupric ion is able to evidence minor structural differences (doxorubicin versus 4′-epidoxorubicin), the substitution pattern of the antraquinone moiety and the self-association of the anthracycline ligand.