A highly sensitive HPLC–MS/MS method for quantification of 20(S)-protopanaxadiol in human plasma and its application in phase IIa clinical trial of a novel antidepressant agent

•We established an HPLC–MS/MS method for quantification of protopanaxadiol in human plasma.•The lower limit of quantification is 0.05 ng/mL and the limit of determination is 0.01 ng/mL.•The method was successfully applied to phase IIa clinical trial of protopanaxadiol capsule.•The measured plasma protopanaxadiol concentration is linearly related to the oral dosage.•Measurements help to detect and prevent errors in the results of clinical trial.

A highly sensitive HPLC–MS/MS assay method was established to quantify 20(S)-protopanaxadiol (PPD) in human plasma with dexamethasone as an internal standard. The electrospray ion mass spectrometry (ESI–MS) was operated under the multiple reactions monitoring mode (MRM) using positive ion mode. PPD was extracted from 500 μL plasma samples by liquid–liquid extraction then separated by a C18 analytical column with gradient elution. The concentration of PPD could be determined by this HPLC–MS/MS method over the range of 0.05–20 ng/mL with the lower limit of quantification (LLOQ) of 0.05 ng/mL. The method was successfully applied to phase IIa clinical trial of Yuxintine (PPD capsule) in which plasma samples of 87 subjects were analyzed following 6 weeks of oral administration of placebo or PPD capsules in 5 different doses. In this study, the measured concentration was linearly related to the oral dosage with R = 0.9901. The minimum and maximum values of measured concentration were 0.06 and 11.60 ng/mL, respectively. In addition, plasma concentrations of PPD in depression patients were reported for the first time in our study.