ELECTROCHEMICAL OXIDATION OF IYSERGIC ACID-TYPE ERGOT ALKALOIDS IN ACETONITRILE .1. STOICHIOMETRY OF THE ANODIC-OXIDATION ELECTRODE-REACTION

The ergot alkaloids are an important group of compounds used extensive ly in medicine. An intrinsic property of these molecules is that the e rgoline compounds decompose spontaneously in an oxidative process. A s ystematic study was carried out with the aim of describing the stoichi ometry of the electrochemical oxidation reaction which simulates the o xidative degradation. Eight ergo- and 9,10-dihydroergopeptides were in vestigated, including the group of 9,10-dihydroergotoxine alkaloids an d simple ergoline derivatives. Cyclic voltammetry, controlled-potentia l coulometry and isolation and identification of the electrochemically oxidized forms led to the conclusion that the electrochemical oxidati on of all lysergic acid-type ergot alkaloids takes place in the same w ay. The main oxidation product is always a highly conjugated dimer, an d the dimerization is located at the indole part of the ergoloid skele ton. The study of the stoichiometry of the oxidative electrode reactio n of lysergic acid-type ergot alkaloids is described, which provides a theoretical and experimental basis for the liquid chromatographic or flow-injection determination with amperometric detection of these alka loids in different pharmaceutical formulations.