Simultaneous determination of taxol and its metabolites in microsomal samples by a simple thin-layer chromatography radioactivity assay — inhibitory effect of NK-104, a new inhibitor of HMG-CoA reductase

Abstract The inhibitory effect of NK-104, a potent inhibitor of HMG-CoA reductase, on taxol metabolism was examined using radio-TLC. This method is described for in vitro measurement of taxol metabolites as an alternative to the commonly used HPLC assay. After incubation of 14 C-taxol with human liver microsomes, the supernatants were developed using a solvent system consisting of toluene–acetone–formic acid (60:39:1, v/v) and quantified with a bioimaging analyzer. The described method provides a valuable tool for the simultaneous determination of unchanged taxol and its major metabolites. There was no inhibitory effect of NK-104 on CYP-mediated metabolism of taxol in human liver microsomes.