Study of coumarin metabolism by human liver microsomes using capillary electrophoresis

A method for the rapid determination of 7-hydroxycoumarin, based on separation by capillary electrophoresis (CE), with UV absorbance detection at 210 nm, was applied to a study of the metabolism of coumarin in human liver microsomes. The linear detection range for 7-hydroxycoumarin was 0–50 μg/ml, while the limit of detection was 1 μg/ml. Human liver microsomes from 5 patients were used in metabolic studies and the profiles clearly indicated that there is inter-individual variability in coumarin 7-hydroxylase activity. The CE method allowed the investigation of NADP+NADPH cofactor reactions involved in coumarin metabolism. The CE method was also compared to a liquid chromatographic method for the analysis of the metabolite and it was found that the results did not differ but the CE method was more rapid and needed no sample preparation. The very short time between sampling and analysis makes the method suitable for automated sample transfer and measurement.