Evaluation of scavenging rate constants of DOPA and tyrosine enantiomers against multiple reactive oxygen species and methyl radical as measured with ESR trapping method.

Abstract

The scavenging rates of DOPA (dl- and l-3-(3,4-dihydroxyphenyl)alanine) and Tyr (tyrosine (dl- and l-3-(4-hydroxyphenyl)alanine)) against five reactive oxygen species (ROS) and methyl radical were measured with the use of electron spin resonance (ESR) spin-trapping method and the scavenging rate constants of DOPA and Tyr were determined. The scavenging rate constants for multiple active species increased in the order of O2(-)<RO<(1)O2<H3C<HO for Tyr and RO≈O2(-)<(1)O2≈H3C<HO for DOPA, and the differences in the radical scavenging abilities for l-enantiomers and dl-mixtures of DOPA and Tyr were shown. Further, based on the redox potentials, we have suggested that the primary chemical process of antioxidant reactions with O2(-) and (1)O2 can be characterized with the electron transfer of antioxidants (DOPA and Tyr).