We have studied the potential electrocatalytic activity towards the oxidation of NADH of several oxidation products of guanine and its derivative guanosine-5'-monophosphate (5'-GMP) on pyrolytic graphite electrodes (PGE). The distribution of products generated strongly depends on the experimental conditions. Our investigations focused on the oxidation products that are adsorbed on the electrode surface, are redox active and, exhibited electrocatalytic activity toward the oxidation of NADH. These compounds were electrochemically and kinetically characterized in terms of dependence of the formal potential on pH and electron transfer rate constant (k(s)). The voltammetric and catalytic behavior of both guanine and 5'-GMP oxidation products was compared with that of other guanine derivatives we have previously studied. Some mechanistic aspects concerning the generation of the catalysts are also discussed. (c) 2007 Elsevier Ltd. All rights reserved.