Electrochemical Properties of Adriamycin Adsorbed on a Mercury Electrode Surface

The electrochemical behavior of adriamycin has been studied by means of cyclic d.c. and a.c. voltammetry with a hanging mercury drop electrode, quinizarin being used as a model compound. Both adriamycin and quinizarin are strongly adsorbed on the mercury electrode with their aromatic ring planes oriented parallel to the electrode surface, and give two sets of reduction waves. The first wave, due to the quinone moieties of the adsorbed adriamycin and quinizarin, has been explained on terms of a two-step one-electron surface redox reaction. The formal standard redox potentials, semiquinone formation constants, and charge transfer rate constants of the surface redox reaction of the quinone moieties have been determined. Although the reduced form of adriamycin is not very stable chemically, it is converted to a stable and electrochemically active form for a few minutes at pH 4.54. The second wave appearing at more negative potential would be due to a kinetic or catalytic process.