ABSTRACT
A highly sensitive ultra-high-performance liquid chromatographic-tandem mass spectrometry (UPLC/MS/MS) method was developed for the quantification of the synthetic peptide drug of exenatide in monkey plasma. Sample preparation was carried out by solid-phase extraction (SPE), and bivalirudin was used as the internal standard (IS). An excellent chromatographic separation was obtained on a reversed-phase C18 column with a gradient elution. Detection utilized a Qtrap 5500 system operated in the positive ion mode with multiple reaction monitoring (MRM). The proposed method was validated by assessing the specificity, linearity, intra- and inter-day precision and accuracy, recovery, and stability. The method resulted in a linear calibration range of 0.10-30 ng/mL, extracting with only 50 µL monkey plasma aliquots. The intra- and inter-day precisions (as relative standard deviation) were less than 7.5% and 9.6%, respectively. The method could be successfully utilized for the pharmacokinetic study of exenatide in monkeys following a single subcutaneous injection of Byetta.
ABSTRACT
ETHNOPHARMACOLOGICAL RELEVANCE: Cimicifuga foetida L., a traditional Chinese medicine, has been used as an anti-inflammatory, antipyretic and analgesic remedy. The primary active constituents are believed to be present in the triterpene glycoside fraction. MATERIALS AND METHODS: To develop an LC-MS/MS assay for four major cimicifugosides [cimicifugoside H-1 (Cim A), 23-epi-26-deoxyactein (Cim B), cimigenolxyloside (Cim C) and 25-O-acetylcimigenoside (Cim D)] obtained from C. foetida L. and apply it to investigate their pharmacokinetic (PK) properties and bioavailabilities through oral administration of C. foetida L. extract (12.5, 25 and 50mg/kg) and single intravenous (i.v.) doses (5mg/kg) of the individual cimicifugosides in rat. PK parameters were estimated by non-compartmental analysis. RESULTS: All calibration curves showed excellent linear regressions (all r>0.995) within the range of tested concentrations. The intra- and inter-day variations were <15% in terms of RSD. The molar ratio of Cims A, B, C, and D in the extract was 20.7:1.4:2.9:1. PK parameters for Cims A, B, C, and D following oral administration of the extract were respectively: C(max) 4.05-17.69, 90.93-395.7, 407.1-1180 and 21.56-45.09pmol/mL; T(max) 0.46-1.28, 2.00-4.67, 14.67-19.67 and 8.08-14.27h; absolute oral bioavailability (F) 1.86-6.97%, 26.8-48.5%, 238-319% and 32.9-48%. PK parameters after i.v. administration of individual cimicifugosides were respectively: elimination half-life 1.1, 2.5, 5.7 and 4.2h; clearance 15.7, 0.48, 0.24 and 1.13mL/hkg. CONCLUSIONS: Systemic exposure to Cims B, C and D following oral administration of the extract was significantly greater than to Cim A despite the predominance of Cim A in the extract. Significantly different clearance and interconversion from Cim A to Cim C probably accounts for the different exposure to the four cimicifugosides.
