Simultaneous Determination of Danshensu and Puerarin in Rat Plasma by LC-MS-MS and Its Application to a Pharmacokinetics and Bioequivalence Study after Oral Administration of Tongmai Dripping Pill and Tongmai Oral Solutions

The active components danshensu (DS) and puerarin (PA) of Tongmai dripping pills (TDP) and oral solution (TOS) were detected in rat plasma after liquid-liquid extraction and oral administration of formulated TDP and TOS. Simultaneous determinations were carried out using electrospray negative ionization mass spectrometry in multiple reaction monitoring mode. The corresponding ion transitions selected for quantitation of DS and PA were at m/z 197.1, 135.0 and m/z 415.2, 294.9, respectively. 3,4-Dihydroxybenzoic acid was used as the internal standard and was monitored at m/z 153.1, 108.9. The linear calibration curves ranged from 9.56 to 637.00 ng mL(-1) and 9.02 to 601.00 ng mL(-1) for DS and PA, respectively. The lowest detectable limit and the lowest quantification limit for both DS and PA in rat plasma were 2.00 and 9.00 ng mL(-1), respectively. The intra-day precision of the assay was less than 10.7% and 8.99% for DS and PA and inter-day precision was less than 14.8% and 14.2% for DS and PA, respectively. The accuracy ranged from 80.56 to 115.3% and 86.91 to 110.6% for DS and PA. This analytical method was applied to a pharmacokinetics and bioequivalence study of DS and PA. Statistical and bioequivalence analyses of DS and PA data for AUC(0-24h) and C (max) revealed that the 90% confidence intervals for the mean ratio (T/R) of DS and PA for AUC(0-24h) and C (max) were 91%-106% and 98%-116%, respectively.