Prooxidant and antioxidant action of 4-(4-phenoxybenzoyl)benzoic acid derivatives

4‐(4‐Phenoxybenzoyl)benzoic acid derivatives (PBADs) were found to inhibit rat and human α‐reductase isozymes 1 and 2 in vitro. Chemiluminescence (CL), electron spin resonance, spin trapping techniques, and spectrophotometry were used to examine the effect of PBADs on reactive oxygen species (superoxide radical, ; hydroxyl radical, HO•; singlet oxygen, 1O2) generating systems. All test compounds at a concentration of 0.5 mM enhanced the CL from up to fivefold, which was recorded as the light sums during 1 min. At 0.38 mM PBAD enhanced production of HO• from H2O2 in the presence of Co(II) up to 90%, as measured by a deoxyribose assay. Using the spin trap agent 5,5‐dimethyl‐1‐pyrroline‐N‐oxide, it was found that the amplitude of the signal arising from the Fenton‐like reaction [Co(II)/H2O2] was significantly diminished by the test compounds. The compounds also inhibited the 1O2 dependent 2,2,6,6‐tetramethylpiperidine‐N‐oxide radical, which is generated in the acetonitrile/H2O2 system. The measured rate constants of 1O2‐dimol quenching by PBAD were in the range of (0.8–2.6) × 108 M−1 s−1. The interaction between PBAD and 1O2 was also checked using a spectrophotometry method based on bleaching of p‐nitrosodimethylaniline. These results indicate that PBAD may directly scavenge HO• and 1O2, but not . However, the compounds that wer examined had prooxidant ability under some reaction conditions. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004