ELECTROCHEMICAL OXIDATION OF 5-HYDROXYTRYPTAMINE IN AQUEOUS-SOLUTION AT PHYSIOLOGICAL PH

The electrochemical oxidation of the indolic neurotransmitter 5-hydroxytryptamine (5-HT) has been studied in aqueous solution at physiological pH using a pyrolytic graphite electrode. The initial step in the oxidation involves a 2e,1H+ reaction leading to a reactive carbocation intermediate (28b). This intermediate is attacked by 5-HT in an ion-substrate reaction to give 5,5′-dihydroxy-4,4′-bitryptamine (1) as the major product along with the C(4)OC(5′) bridged dimer 9. Alternatively cation 28b is attacked by water to yield, ultimately, tryptamine-4,5-dione (5). Many additional reactions occur between primary dimers 1 and 9 and carbocation 28b such that a very complex mixture of ultimate products are formed. A total of 15 products have been isolated and partially or completely characterized. It is possible that the oxidation reaction pathways and product profile elucidated might have a bearing on, as yet hypothetical, aberrant oxidation reactions of 5-HT in the central nervous system which could play a role in the etiology of mental illnesses such as diseases of the Alzheimer's type. © 1990.