Simultaneous estimation of E- and Z- isomers of guggulsterone in rabbit plasma using liquid chromatography tandem mass spectrometry and its application to pharmacokinetic study

Abstract

A sensitive and selective liquid chromatography / tandem mass spectrometric method was developed for simultaneous determination of E- and Z-guggulsterone isomers (antihyperlipidemic drug) in rabbit plasma. Both the isomers were resolved on Symmetry-Shield C18 (5µm, 4.6 X 150 mm) column, using gradient elution comprising mobile phase of methanol, 0.5% v/v formic acid and acetonitrile. With dexamethasone as internal standard, plasma samples were extracted by an automated solid-phase extraction method using C-18 cartridges. Detection was performed by electrospray ionization in multiple reaction monitoring (MRM) in positive mode. Calibration curve was linear over the concentration range of 1.56-200 ng/ml (r2  0.998) for both analytes. The intra-day and inter-day accuracy and precision were within -0.96 to 4.12 (% bias) and 2.73 to 8.00 (% R.S.D.) respectively. The analytes were stable after three freeze-thaw cycles. The method was successfully applied to study steriospecific pharmacokinetics of E- and Z-guggulsterone in NZ rabbit.