Formation of active oxygen species during autoxidation of DOPA

The light emission during DOPA autoxidation and the transition metal ion-ca talyzed oxidation of this amine to melanins has been studied. Chemiluminesc ence and fluorescence spectra from both systems were measured. The light em ission was inhibited by quenchers of singlet oxygen (O-1(2)) and scavengers of superoxide anion radical (O-2(radical anion)), hydroxyl radical (HO.) a nd by catalase. The generation of O-1(2) 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. (C) 1999 Elsevier Science Ltd. All righ ts reserved.