TY - JOUR T1 - Differential Inhibition of Cytochromes P450 3A4 and 3A5 by the Newly Synthesized Coumarin Derivatives 7-Coumarin Propargyl Ether and 7-(4-Trifluoromethyl)coumarin Propargyl Ether JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 2234 LP - 2243 DO - 10.1124/dmd.108.021493 VL - 36 IS - 11 AU - Chitra Sridar AU - Ute M. Kent AU - Kate Noon AU - Alecia McCall AU - Bill Alworth AU - Maryam Foroozesh AU - Paul F. Hollenberg Y1 - 2008/11/01 UR - http://dmd.aspetjournals.org/content/36/11/2234.abstract N2 - The abilities of 7-coumarin propargyl ether (CPE) and 7-(4-trifluoromethyl)coumarin propargyl ether (TFCPE) to act as mechanism-based inactivators of P450 3A4 and 3A5 in the reconstituted system have been investigated using 7-benzyloxy-4-(trifluoromethyl)coumarin (BFC) and testosterone as probes. CPE inhibited the BFC O-debenzylation activity of P450 3A4 in a time-, concentration-, and NADPH-dependent manner characteristic of a mechanism-based inactivator with a half-maximal inactivation (KI) of 112 μM, a maximal rate of inactivation (kinact) of 0.05 min-1, and a t½ of 13.9 min. Similarly, TFCPE inhibited the BFC O-debenzylation activity of P450 3A4 in a time-, concentration-, and NADPH-dependent manner with a KI of 14 μM, a kinact of 0.04 min-1, and a t½ of 16.5 min. Parallel losses of P450 3A4 enzymatic activity and heme were observed with both compounds as measured by high-performance liquid chromatography and reduced CO spectra. Interestingly, neither compound inhibited the BFC O-debenzylation activity of P450 3A5. Reactive intermediates of CPE and TFCPE formed by P450 3A4 were trapped with glutathione, and the resulting adducts were identified using tandem mass spectral analysis. Metabolism studies using TFCPE resulted in the identification of a single metabolite that is formed by P450 3A4 but not by P450 3A5 and that may play a role in the mechanism-based inactivation. The American Society for Pharmacology and Experimental Therapeutics ER -