Enzymatic oxidation of ansa-ferrocifen leads to strong and selective thioredoxin reductase inhibition in vitro

Enzymatic oxidation of 1 by the horseradish peroxidase/H2O2 mixture afforded a short-life species with high inhibitory activity towards cytosolic thioredoxin reductase in vitro (IC50 = 0.125 μM). This species was identified as the radical 1* in its two mesomeric forms by UV-Vis and EPR spectroscopy and ab-initio calculations.