REACTION OF MALONDIALDEHYDE WITH AMINE NEUROTRANSMITTERS - FORMATION AND OXIDATION CHEMISTRY OF FLUORESCENT 1,4-DIHYDROPYRIDINE ADDUCTS

Under physiologically relevant conditions, malondialdehyde reacts smoothly with amine neurotransmitters, i.e. dopamine, norepinephrine and serotonin, to give the fluorescent dihydropyridines 1, 4 and 5, respectively, as the relatively most abundant products. Small amounts of enaminal derivatives, such as 2 and 6, could also be obtained in the reactions with dopamine and serotonin. Oxidation of 1 with hydrogen peroxide/peroxidase leads to a complex pattern of unstable products, the major of which has been isolated and identified as the o-quinone epoxide 7. Similar oxidation of 4 and 5 affords mainly the dihydropyridine 8 and the 4,4'-biindolyl 9, respectively. These results provide new clues to the role of malondialdehyde in neuronal degeneration and lipofuscin formation.