Linert, Wolfgang and Herlinger, Erwin (1994) New facets in coordination chemistry: the spontaneous autoxidation of dopamine and the involvement of metal ions in the progress of degenerative mental disease. Atti della Accademia Peloritana dei Pericolanti, LXXII. pp. 129-151.
A detailed kinetic study has been carried out of the reaction of dopamine, 2-(3,4-dihydroxyphenyl)-ethylamine, with dioxygen over the pH range 7-9, where it reacts spontaneously without the necessity of metalion catalysis. Stoichiometric amounts of H2O2 were shown to be produced. The other product of oxidation is, initially, the pink dopaminochrome which is not stable and reacts further (without the consumption of dioxygen) to form the insoluble polymeric material known as "melanine". The rate determining step is assumed to be hydrogen atom abstraction from the monodeprotonated species by O2. Based on these results the in vitro chemistry of the reactions of dopamine (DA), 5-hydroxydopamine (5-OHDA), and 6-hydroxydopamine (6-OHDA) under the presence of iron(III) and dioxygen has been studied. The reaction pathway then essentially involves a FeL intermediate, which decomposes releasing Fe(II) and the above mentioned dopaminochrome, which reacts further under involvement of both Fe(III) and dioxygen. The important relevance of these reactions to the development of Parkinson's disease is examined. A mechanism for its initialisation and its progress is suggested by which the presence of excess iron(III) could arise and its consequences are discussed.
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