Purpose: To develop a stereoselective high performance liquid chromatographic assay for determination of desbutylhalofantrine (DHF) enantiomers in rat plasma.
Methods: After protein precipitation of 100 microL of rat plasma, racemic DHF and internal standard (quinidine sulfate) were extracted into hexane in the presence of pH 8 phosphate buffer. After transfer and evaporation of the hexane, the residue was derivatized using 0.25 M (+)-di-O-acetyl-L-tartaric acid anhydride at 4 degrees C. After 5 min the reaction was stopped by addition of methanol in water, and the tube contents were dried, reconstituted in the mobile phase, and injected into a C(18) analytical column under reverse phase conditions.
Results: The derivatized enantiomers were baseline resolved and free of interference from endogenous components in plasma. Standard curves were linear (r(2)>0.99) over the range of enantiomer concentrations from 25-1000 ng/mL. The assay was validated to concentrations as low as 25 ng/mL, based on 100 microL of rat plasma. The nature of diastereomers formed was found to be dependent on the temperature used during the derivatization step. In a preliminary experiment in the rat, stereoselectivity in the plasma concentrations of DHF were observed, indicating stereoselectivity in the pharmacokinetics of the metabolite.
Conclusions: The assay was sensitive and appropriate for use in pharmacokinetic studies of DHF in the rat.