Electrochemical oxidation of guanosine-5 '-monophosphate at the pyrolytic graphite electrode

The electrochemical oxidation of guanosine-5'-monophosphate has been invest igated in phosphate containing supporting electrolytes at pH 2.5-10.8 at a pyrolytic graphite electrode by cyclic sweep voltammetry, spectral studies, controlled potential electrolysis and related techniques. The initial cour se of the electrode reaction has been deduced to involve a pH dependent 4e, 4H(+) oxidation to give a diimine species which undergoes a series of chem ical reactions to give different products. The kinetics of the decay of the UV-absorbing intermediate generated during electrooxidation has been studi ed at different pH values and first-order rate constants for the disappeara nce of the UV-absorbing intermediate have been calculated. The electrooxida tion of guanosine-5'-monophosphate has been found to be an EC reaction (ele ctrode reaction followed by chemical reactions) in which charge transfer is followed by competitive chemical reactions. The ultimate products of oxida tion, urea riboside phosphate, alloxan (pyrimidine-2,4,5,6(1H,3H)-tetraone) and a dimer were characterized by IR, H-1 NMR and mass spectrometry at pH 3.4. A detailed interpretation of the redox mechanism for the formation of these products is presented.