Pitfalls in the ABTS Peroxidase Activity Test: Interference of Photochemical Processes.

ABTS (2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid) oxidation to form its radical cation in the presence of H2O2 is frequently used as a test for determining the peroxidase activity of enzyme mimics. Detailed studies using salen-type Mn(III) complexes show that photochemical processes involving H2O2, ABTS, and the complex itself can lead to erroneous results. The capability of the complexes to act as •OH scavengers can be also relevant when the mechanism of their biological activity is considered.