Simultaneous determination of 6β-hydroxycortisol and cortisol in human urine and plasma by liquid chromatography with ultraviolet absorbance detection for phenotyping the CYP3A activity

This study describes an high-performance liquid chromatographic (HPLC)–UV method for the simultaneous determination of 6β-hydroxycortisol (6β-OHF) and cortisol (F) in human urine and plasma. The within-day relative standard deviation of the three concentrations for both analytes was less than 6.2%. Accuracy determined at three concentrations ranged between 95 and 107%. The extraction recoveries were 64.1 ± 4.3 and 88.1 ± 2.4% at three concentrations for 6β-OHF and F in urine, respectively. The extraction recoveries were 88.7 ± 1.4% at three concentrations for F in plasma. This is the first HPLC method that can simultaneously determine 6β-OHF and F in human urine and plasma and is suitable for routine assessment of the CYP3A activity expressed as 6β-hydroxylation clearance.