Formation of active oxygen species during autoxidation of DOPA

The light emission during DOPA autoxidation and the transition metal ion-catalyzed oxidation of this amine to melanins has been studied. Chemiluminescence and fluorescence spectra from both systems were measured. The light emission was inhibited by quenchers of singlet oxygen (1O2) and scavengers of superoxide anion radical ) hydroxyl radical (HO.) and by catalase. The generation of 1O2 was confirmed using electron spin resonance (ESR) and 2,2,6,6-tetramethylpiperidine as a trap as well as by spectrophotometry method. The formation of HO. was demonstrated by the technique of ESR spin trapping with DMPO as a spin trap.