White-rot fungus-mediated degradation of the analgesic ketoprofen and identification of intermediates by HPLC–DAD–MS and NMR

Ketoprofen is a nonsteroidal anti-inflammatory drug that has been detected in the environment in the range of ng L−1–μg L−1 due to its low degradability in some wastewater treatment plants. In this study, the use of the white-rot fungus Trametes versicolor to effectively degrade ketoprofen in a defined liquid medium was assessed. The fungus eliminated ketoprofen to nondetectable levels in 24 h when it was added at 10 mg L−1 whereas at low concentration of 40 μg L−1 it was almost completely removed (95%) after 5 h. Low extracellular laccase activity was detected in the T. versicolor cultures but the addition of the laccase-mediator system did not lead to ketoprofen oxidation. The cytochrome P-450 inhibitor 1-aminobenzotriazole reduced ketoprofen oxidation. These data suggest that the first oxidation step is cytochrome P450 mediated. During time-course degradation experiments, three intermediates were structurally elucidated and quantified by HPLC–DAD–MS and NMR: 2-[3-(4-hydroxybenzoyl)phenyl]-propanoic acid, 2-[(3-hydroxy(phenyl)methyl)phenyl]-propanoic acid, and 2-(3-benzoyl-4-hydroxyphenyl)-propanoic acid. The latter was reported for the first time in biological systems. After 7 d of incubation, only small amounts of 2-[(3-hydroxy(phenyl)methyl)phenyl]-propanoic acid (0.08 mg) remained in the liquid medium in comparison with the initial ketoprofen dose (1.0 mg), suggesting possible mineralization of ketoprofen.