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, 1 O 2 ) generating systems. All test compounds at a concentration of 0.5 m M enhanced the CL from up to fivefold, which was recorded as the light sums during 1 min. At 0.38 m M PBAD enhanced production of HO • from H 2 O 2 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)/H 2 O 2 ] was significantly diminished by the test compounds. The compounds also inhibited the 1 O 2 dependent 2,2,6,6‐tetramethylpiperidine‐ N ‐oxide radical, which is generated in the acetonitrile/H 2 O 2 system. The measured rate constants of 1 O 2 ‐dimol quenching by PBAD were in the range of (0.8–2.6) × 10 8 M −1 s −1 . The interaction between PBAD and 1 O 2 was also checked using a spectrophotometry method based on bleaching of p ‐nitrosodimethylaniline. These results indicate that PBAD may directly scavenge HO • and 1 O 2 , but not . However, the compounds that wer examined had prooxidant ability under some reaction conditions. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004