The enantioseparation and determination of sulconazole enantiomers in rat plasma and tissues by a chiral HPLC–ESI–MS/MS method and its application to studies on stereoselective pharmacokinetics and tissue distribution

Abstract

In this research, a sensitive method based on reverse-phase high performance liquid chromatography–electrospray ionization coupled with tandem mass spectrometry (HPLC–ESI–MS/MS) for the rapid and sensitive enantioselective analysis of sulconazole in rat plasma and tissue samples was developed and validated. A newly developed solid phase extraction (SPE) procedure using a C₁₈ cartridge was used for the extraction of sulconazole and an internal standard (IS, ornidazole) from plasma and tissue samples. The excellent enantioseparation of sulconazole enantiomers was achieved on a CHIRALPAK IC column using acetonitrile/5 mM aqueous CH₃COONH₄ (90 : 10, v/v) as a mobile phase, and the detection of the targeted compounds and the IS was performed in multiple reaction monitoring (MRM) mode with a positive ESI source. Using the measured electronic circular dichroism (ECD) spectrum combined with the calculated ECD spectrum, the absolute configuration of the sulconazole enantiomers was confirmed and was used to identify the order of the elution of the peaks. S-(+)-sulconazole was eluted first. After comprehensive validation following FDA guidelines, the established method was successfully applied to a study of the stereoselective pharmacokinetics and tissue distribution in Sprague–Dawley rats after the transdermal administration of a rac-sulconazole spray. The results showed that, in the pharmacokinetic study, the C_max and AUC_0–∞ values of S-(+)-sulconazole were 2.0 and 31.6 times higher than those of the R-(−)-isomer, respectively, but the CLz/F value of R-(−)-sulconazole was 1.7 times higher than its enantiomer. However, in the tissue distribution study, the heart, liver, and kidneys were the three main distribution organs, and different tissue samples presented completely opposite concentration distribution tendencies for S-(+)- and R-(−)-sulconazole. It should be noted that this is the first report involving the stereospecific study of sulconazole enantiomers in vivo.