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In this study, a simple, sensitive, and rapid analytical method was developed by ultra-performance liquid chromatography (UPLC) coupled with tandem quadrupole mass spectrometry (MS) for the determination of nootkatone in normal and chronic kidney disease (CKD) rat plasma using clarithromycin as internal standard. After sample preparation by simple liquid–liquid extraction, chromatography was performed on an Acquity UPLC BEH C18 column (2.1 × 50 mm, 1.7 mm particle size) using gradient elution with the mobile phase composed of acetonitrile and water acidified with 0.1% (v/v) formic acid. Detection was achieved by electrospray ionisation MS under the multiple selective reaction monitoring mode. The linear range was 0.01‒500 ng/mL with the square regression coefficient (r) of 0.9975. The lower limit of quantification was 0.01 ng/mL. The intra- and inter-day precision was under 5% and the stability accuracy was between 3.6 and 7.0%. The average recoveries from spiked plasma samples were >83% and matrix effect was over 81%. The developed method was successfully applied to the pharmacokinetic study of nootkatone in normal and CKD rats after an oral administration of 50 mg/kg nootkaone. The results showed the cmax and area under curve of nootkaone were greatly decreased, meanwhile Vd/F and t1/2 were markedly increased in CKD rats. The pharmacokinetic characteristics of nootkatone in rats were significantly altered in CKD rats.

The evaluation of efficacy and safety should be paralleled with the assessment of comprehensive pharmacokinetic (PK) properties for a drug candidate, and a robust bioanalytical method is a prerequisite for obtaining PK information. α-Hederin is reported to have various in vitro and in vivo activities; however, very little is known about its PK and metabolic characteristics. In this study, we have developed an efficient LC-ESI(−)-MS/MS assay for α-hederin and its sapogenin hederagenin in rat plasma. Sample cleanup involved methanol precipitation for identification analysis and liquid–liquid extraction with ethyl acetate for quantification assay. LC analysis was performed under reversed-phase conditions in the modified “pulse gradient elution” mode. Analyte identification and quantification were conducted using multiple reaction monitoring (MRM) mode with euscaphic acid as the internal standard. Under these conditions, deglycosylated metabolites and their sulfate conjugates were detected; however, hederagenin was not detected in rat plasma samples after both oral and intravenous treatments. The mean plasma clearance (CL), volume of distribution (VSS) and elimination half-life (t1/2) of α-hederin were 0.24 L h−1 kg−1, 0.25 L kg−1 and 2.67 h, respectively. The oral bioavailability (F) of α-hederin in rats was about 0.14%, which might result from the poor intestinal absorption and/or extensive biliary excretion. It is hoped that this validated method will be useful for future PK studies of α-hederin.

Euscaphic acid, a triterpene acid, exists ubiquitously in medicinal plants and demonstrates various pharmacological activities. This active compound is often used as a marker compound for quality control. Hitherto, the pharmacokinetic (PK) information is relatively scarce; therefore, it remains open to question whether the euscaphic acid reaches the target sites in the body at concentrations high enough for the claimed biological effects. A robust analytical method is prerequisite for obtaining enough PK information of euscaphic acid, which is useful for interpreting its pharmacological effects. In this study, we developed and validated a rapid liquid chromatographic tandem mass spectrometric (LC-MS/MS) method for the measurement of euscaphic acid in rat plasma. The rat plasma samples were precipitated with acetonitrile and the resulting supernatants were separated by a 4 min pulse gradient method on a Synergi Fusion-RP C18 column (4 μm, 2.0 mm i.d. × 50 mm). Ursolic acid was used as an internal standard for quantification of euscaphic acid. Deprotonated euscaphic acid and its internal standard were generated in negative electrospray ionization (ESI) mode and their precursor-to-product ion pairs (m/z 487.4→469.3 and 455.5→455.4, respectively) were used for measurement. Notably, the commonly used concentration of formic acid (HCOOH; 1‰ and 5‰, v/v) in the mobile phase seriously suppressed the signal intensity, but this mobile phase additive at a much lower concentration level (0.1‰ and 0.2‰) could overcome the matrix effects and therefore increase the sensitivity of MS detection of euscaphic acid. The newly developed bioanalytical assay possessed favorable accuracy and precision with a lower limit of quantification of 2.0 ng mL−1 and was successfully applied to PK studies in rats. The experimental strategies presented herein may be helpful for measurement of other triterpene acids in biological matrices.

Background Galangin (3,5,7-trihydroxyflavone) is present in high concentrations in herbal medicine such as Alpinia officinarum Hance. Galangin shows multifaceted in vitro and in vivo biological activities. The number and position of hydroxyl groups in this molecule play an important role in these biological activities. However, these hydroxyl groups undergo glucuronidation and sulfation in in vitro assay system. However, the systemic exposure to galangin after dosing in animals and/or humans remains largely unknown. Thus it is not clear whether the galangin exists in the body at concentrations high enough for the biological effects. Furthermore, the metabolite identification and the corresponding plasma pharmacokinetics need to be characterized. Results Two LC-MS/MS methods were developed and validated and successfully applied to analyze the parent drug molecules and aglycones liberated from plasma samples via β-glucuronidase hydrolysis. Our major findings were as follows: (1) The routes of administration showed significant influences on the systemic exposure of galangin and its metabolites. (2) Galangin was preferentially glucuronidated after p.o. dosing but sulfated after i.v. medication. (3) Kaempferol conjugates were detected demonstrating that oxidation reaction occurred; however, both glucuronidation and sulfation were more efficient. (4) Oral bioavailability of free parent galangin was very low. Conclusions Systemic exposure to galangin and its metabolites was different in rat plasma between oral and intravenous administration. Further research is needed to characterize the structures of galangin conjugates and to evaluate the biological activities of these metabolites.

Rehmannia glutinosa Libosch (RG), is officially listed in the Chinese Pharmacopoeia and is widely used in China. In this paper, a sensitive and rapid ultra-performance liquid chromatography-mass spectrometry method including multiple-reaction monitoring mode was developed and applied to study the pharmacokinetic effect of acteoside from total glycoside extracted from the leaves of Rehmannia (TLR) and Dihuangye total glycoside capsule (DTG) in normal and diabetic nephropathy rats. The diabetic nephropathy rat model was induced by intraperitoneal injection of a small dose of streptozotocin and high-fat diet and plus 5% glucose drinking water. Samples of plasma of rats were obtained at different times after rats were administered TLR (7.2 g/kg) and DTG (360 mg/kg). After deproteinization by acetonitrile, the concentrations of acteoside in rats at different time points were detected by UPLC-TQ-MS method and pharmacokinetics parameters were calculated using DAS 3.2.8 software. A good linearity of acteoside was shown in the range of 8.51-3404.8 ng/m L (r2 = 0.9987). The mean extraction recovery of analyte was in the range of 63.55-79.49%, and the intra- and inter-day RSD values were