The electrochemical behaviour of biliverdin and bilirubin on platinum electrodes in N, Ndimethylformamide has been investigated hy means of voltammetric as well as controlled-potential electrolysis techniques. Bilirubin can be oxidized to biliverdin and the latter, in turn, to further oxidation products; conversely, biliverdin can be reduced to bilirubin, end the latter to further reduction products: however, the potential for the anodic oxidation of bilirubin to biliverdin and that for the cathodic reductionof biliverdin to bilirubin are about 1.6V auart from each other. The reduction of biliverdin to bilirubin is shown to be amenable to preparative electrochemistry. INTRODLJCIION Though a great deal is known about the electrochemistry of porphyrins and their metal complexes[ 11, there are few reports on the electrochemical bebaviour of open-chain tetrapyrrole compounds (bile pigments). These studies have been confined to the electrooxidation and/or electroreduction of 10, 21, 22, 24 tetrahydrobilin-1, 19-diones[2] such as mesobilirubin[3], bilirubinC3-81 (and its metal complexes[6,7]), and of 21, 24-dihydrobilin-1, 19-diones such as mesobiliverdin dimethyl ester[9], biliverdin dimethyl ester[9] (and their metal complexes[9]), and of 21, 24-dihydro-3, 8, 12, 17-tetraethyl-2, 7, 13, 18tetramethyl-1, 19-dione[lO]. To our knowledge, however, no detailed study has been so far reported on the electrochemistry of biliverdin (1) itself, despite the key role played by this pigment in the catabolism of heme: it is the first isolable compound of the oxidative breakdown of the protoporphyrin ring in oivo and is reduced enzymatically to bilirubin (2)[11]. The only data so far reported deal with the electrooxidation of commercial biliverdin dihydrochloride (and its zinc complex) of SO-85 'A purity[4,7]. It must be noted that commercial biliverdin contains, in addition to nonverdinoid products, substantial amounts of two positional isomers formed by acid-catalysed isomeric scrambling of bilirubin during the oxidation step[12]. The recent finding that the green bile pigment can be easily prepared in isomerically pure form[l3] prompted us to investigate its electrochemical reactions and redox potentials. In the present paper are reported the results obtained upon applying voltammetry and controlled-potential electrolysis to electrareduction and electrooxidation of biliverdin at a platinum electrode in N, N-dimethylformamide.