Purity >95%. EUK 8 and EUK 134 are synthetic catalytic scavengers of reactive oxygen species with superoxide dismutase (SOD) and catalase mimetic activity. EUK 118 is a structural analog of EUK 8 and EUK 134 with significantly reduced activity. EUK 118 exhibits a catalase activity of 35 μM O2 formed/minute from 10 mM hydrogen peroxide, which is more than four times lower that that observed for EUK 8 under the same conditions. Superoxide-mediated reduction of an electron acceptor (i.e., SOD mimetic activity) was inhibited by EUK 118 and EUK 8 with IC50 values of 2 and 0.7 μM, respectively. EUK 118 did not protect human dermal fibroblasts against hydrogen peroxide-induced cell death.