Simultaneous determination of saikosaponin a, paeonol, and imperatorin, components of DA-9805, in rat plasma by LC-MS/MS and application to a pharmacokinetic study

DA-9805 is a new botanical antiparkinson drug candidate formulated using an ethanolic extract of the root of Bupleurum falcatum, the root cortex of Paeonia suffruticosa, and the root of Angelica dahurica. In this study, a sensitive and rapid LC-MS/MS method was developed to simultaneously determine, saikosaponin a, paeonol, and imperatorin, three active/representative ingredients of DA-9805, in rat plasma. Plasma was extracted by mixture of ethyl acetate and methyl tertiary butyl ether. Chromatographic separation was carried out using a C-18 column and a gradient elution of mobile phases consisting of 5 mM formic acid in water and acetonitrile. Total chromatographic run time was 10.5 min. Multiple reaction monitoring mode was used for mass spectrometry; the transitions were m/z 779.5 -> 617.2 for saikosaponin a in negative-ion mode, m/z 167 149 for paeonol and m/z 271.1 -> 203 for imperatorin in positive-ion mode. Calibration curves were constructed in the range of 0.5-1000 ng/mL for saikosaponin a, 20-10000 ng/mL for paeonol, and 0.2-1000 ng/mL for imperatorin. All the validation data, including the selectivity, linearity, precision, accuracy, recovery, matrix effect, and stability satisfied the acceptance requirements. The method was successfully applied in a pharmacokinetic study of saikosaponin a, paeonol, and imperatorin following oral administration of DA-9805.