LC-ESI-MS/MS method for quantification of ambrisentan in plasma and application to rat pharmacokinetic study

A sensitive high‐performance liquid chromatography–positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of ambrisentan in plasma. The analyte and the internal standard (armodafinil) were extracted from plasma by acetonitrile precipitation and they were separated on a reversed‐phase C₁₈ column with a gradient program. The MS acquisition was performed with multiple reaction monitoring mode using the respective [M + H]⁺ ions, m/z 379–347 for ambrisentan and m/z 274–167 for the IS. The assay exhibited a linear dynamic range of 1–2000 ng/mL for ambrisentan in plasma. Acceptable precision (<10%) and accuracy (100 ± 8%) were obtained for concentrations over the standard curve range. The method was successfully applied to quantify ambrisentan concentrations in a rodent pharmacokinetic study after a single oral administration of ambrisentan at 2.5 mg/kg to rats. Following oral administration the maximum mean concentration in plasma (C_max; 1197 ± 179 ng/mL) was achieved at 1.0 ± 0.9 h (T_max), and the area under the curve (AUC) was 6013 ± 997 ng h/mL. Therefore, development of such a simple and sensitive method in rat plasma should translate into a method for ambrisentan in human plasma for clinical trials. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and validation of an LC-ESI-MS/MS method for simultaneous quantitation of olmesartan and pioglitazone in rat plasma and its pharmacokinetic application

A simple, high‐throughput and specific high‐performance liquid chromatography tandem mass spectrometry method has been developed and validated according to the FDA guidelines for simultaneous quantification of olmesartan and pioglitazone in rat plasma. The bioanalytical method consists of liquid–liquid extraction and quantitation by triple quadrupole mass spectrometry using electrospray ionization technique, operating in multiple reaction monitoring and positive ion modes. The compounds were eluted isocratically on a C₁₈ column with a mobile phase consisting of a mixture of methanol and water (containing 0.5% formic acid) in a ratio of 9:1. The response to olmesartan and pioglitazone was linear over the range 0.01–10 µg/mL. The validation results demonstrated that the method had satisfactory precision and accuracy across the calibration range. Intra‐ and inter‐day precisions ranged from 0.66 to 3.32 and from 0.94 to 2.93% (%CV), respectively. The accuracy determined at three quality control levels was within 91.27–107.28%. There was no evidence of instability of the analytes in rat plasma following the stability studies. The method proved highly reproducible and sensitive and was successfully applied in a pharmacokinetic study after single dose oral administration of olmesartan and pioglitazone to the rat. Copyright © 2010 John Wiley & Sons, Ltd.     

Development and validation of a rapid and sensitive LC-ESI-MS/MS method for ondansetron quantification in human plasma and its application in comparative bioavailability study

The validation of a high throughput and specific method using a high‐performance liquid chromatography coupled to electrospray (ES+) ionization tandem triple quadrupole mass spectrometric (LC‐ESI‐MS/MS) method for ondansetron quantification in human plasma is described. Human plasma samples were extracted by liquid–liquid extraction (LLE) using methyl tert‐butyl ether and analyzed by LC‐ESI‐MS/MS. The limit of quantification was 0.2 ng/mL and the method was linear in the range 0.2–60 ng/mL. The intra‐assay precisions ranged from 1.6 to 7.7%, while inter‐assay precisions ranged from 2.1 to 5.1%. The intra‐assay accuracies ranged from 97.5 to 108.2%, and the inter‐assay accuracies ranged from 97.3 to 107.0%. The analytical method was applied to evaluate the relative bioavailability of two pharmaceutical formulations containing 8 mg of ondansetron each in 25 healthy volunteers using a randomized, two‐period crossover design. The geometric mean and respective 90% confidence interval (CI) of ondansetron test/reference percent ratios were 90.15% (81.74–99.44%) for C_max and 93.11% (83.01–104.43%) for AUC_0–t. Based on the 90% confidence interval of the individual ratios (test formulation/reference formulation) for C_max and AUC_0‐inf, it was concluded that the test formulation is bioequivalent to the reference one with respect to the rate and extent of absorption of ondansetron. Copyright © 2010 John Wiley & Sons, Ltd.     

A novel LC-MS/MS method for simultaneous quantification of tenofovir and lamivudine in human plasma and its application to a pharmacokinetic study

A new, rapid, sensitive and specific LC‐MS/MS method has been developed and validated for the simultaneous quantification of tenofovir and lamivudine in human plasma using abacavir as an internal standard. An API‐4000 LC‐MS/MS with electrospray ionization was operated in multiple‐reaction monitoring mode for the analysis. The analytes were extracted from plasma by solid‐phase extraction technique using an Oasis HLB cartridge. The reconstituted samples were chromatographed on a Chromolith ROD speed C₁₈ column using a mixture of 0.1% formic acid in water and acetonitrile (90:10 v/v) at a flow‐rate of 1 mL/min. The method was validated as per the FDA guidelines. The calibration curves were found to be linear in the range of 5–600 ng/mL for tenofovir and 25– 4000 ng/mL for lamivudine. The intra‐ and inter‐day precision and accuracy results were well within the acceptable limits. A run time of 2.8 min consumed for each sample made it possible to analyze more samples per day. The proposed assay method was found to be applicable to a pharmacokinetic study in human male volunteers. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and validation of a highly sensitive LC-MS/MS method for simultaneous quantitation of ethionamide and ethionamide sulfoxide in human plasma: application to a human pharmacokinetic study

A highly sensitive and specific LC‐MS/MS method has been developed for simultaneous quantification of ethionamide and ethionamide sulfoxide in human plasma (300 µL) using prothionamide as an internal standard (IS). Solid‐phase extraction was used to extract ethionamide, ethionamide sulfoxide and IS from human plasma. The chromatographic separation of ethionamide, ethionamide sulfoxide and IS was achieved with a mobile phase consisting of 0.1% acetic acid : acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a Peerless Basic C₁₈ column. The total run time was 3.5 min and the elution of ethionamide, ethionamide sulfoxide and IS occurred at 2.50, 2.18 and 2.68 min, respectively. A linear response function was established for the range of concentrations 25.7–6120 ng/mL (r > 0.998) for ethionamide and 50.5–3030 ng/mL (r > 0.998) for ethionamide sulfoxide. The intra‐ and inter‐day precision values for ethionamide and ethionamide sulfoxide met the acceptance as per FDA guidelines. Ethionamide and ethionamide sulfoxide were stable in battery of stability studies, viz. bench‐top, autosampler and freeze–thaw cycles. The developed assay was applied to a pharmacokinetic study in humans. Copyright © 2011 John Wiley & Sons, Ltd.     

A sensitive UHPLC–MS/MS method for the simultaneous quantification of three lignans in human plasma and its application to a pharmacokinetic study

The aim of this study was to develop an analytical method to simultaneously analyze schizandrin, schizandrol B, and gomisin N lignans in human plasma using ultra high performance liquid chromatography with tandem mass spectrometry. The three lignans were separated using a mobile phase of water and acetonitrile containing 0.02% acetic acid equipped with a Kinetex C₁₈ column (2.1 mm × 50 mm, 1.7 μm). This analysis was achieved by multiple reaction monitoring mode in an electrospray interface. The mass transitions were m /z 433.1→384.0 for schizandrin, 398.8→367.8 for schizandrol B, and 400.6→299.8 for gomisin N. Liquid–liquid extraction with methyl tert‐butyl ether was used to obtain the three lignans. The chromatograms showed high resolution, sensitivity, and selectivity with no interference with plasma constituents. The calibration curves for the three lignans in human plasma were 0.05–50 ng/mL and displayed excellent linearity with correlation coefficients greater than 0.99. Precision for all three lignans was within 11.23%. The accuracy was 88.3–99.0% for schizandrin, 90.6–103.4% for schizandrol B, and 90.2–103.5% for gomisin N. The developed simultaneous analytical method satisfied the criteria of international guidance and could be successfully applied to the pharmacokinetic study of three lignans after oral administration of Schisandrae Fructus extract powder to humans.     

Development and validation of a rapid LC-ESI-MS/MS method for quantification of fluoxetine and its application to MS binding assays

In the present study, a rapid and sensitive LC-ESI-MS/MS method for quantification of (S)-fluoxetine as a native marker in mass spectrometry (MS) binding assays addressing the human serotonin transporter (hSERT) was developed and validated. The concept of MS binding assays based on mass spectrometric quantification of a nonlabeled marker recently introduced by us represents a promising alternative to conventional radioligand binding without the drawbacks inherently connected with radioisotope labeling. For high-performance liquid chromatography (HPLC), a 20 × 2-mm RP-18 column with a mobile phase composed of acetonitrile and ammonium bicarbonate buffer (5 mmol L⁻¹, pH 9.5) at a ratio of 80:20 (v/v) and a flow rate of 800 μL min⁻¹ in an isocratic mode were used, resulting in a chromatographic cycle time of 60 s. Employing [²H₅]fluoxetine as internal standard enabled ESI-MS/MS quantification of (S)-fluoxetine between 3 nmol L⁻¹ and 50 pmol L⁻¹ (LLOQ) in matrix obtained from binding experiments without the need of any sample preparation. Validation of the method showed that linearity, intra-, and inter-batch accuracy as well as precision meet the requirements of the FDA guidance for bioanalytical method validation. Considering sensitivity and speed, the established method is clearly superior to those published for biological matrices so far. Furthermore, the method was transferred to other RP-18 columns of different lengths and respective validation experiments demonstrated its versatility and chromatographic robustness. Finally, the newly developed method was successfully applied to MS binding assays for hSERT. The affinity determined for (S)-fluoxetine in saturation experiments was in good agreement with literature data obtained in respective radioligand binding assays.     

Rapid and sensitive LC-MS/MS method for quantification of lamotrigine in human plasma: application to a human pharmacokinetic study

A highly sensitive, specific and fully validated LC‐MS/MS method as per general practices of industry has been developed for estimation of lamotrigine (LAM) with 100 μL of human plasma using flucanozole as an internal standard (IS). The API‐4000 LC‐MS/MS was operated under the multiple reaction‐monitoring mode using electrospray ionization. A simple liquid–liquid extraction process was used to extract LAM and IS from human plasma. The total run time was 2.0 min and the elution of LAM and IS occurred at 1.25 and 1.45 min; this was achieved with a mobile phase consisting of 0.1% formic acid–methanol (20:40:40, v/v) at a flow rate of 0.50 mL/min on a Discovery CN (50 × 4.6 mm, 5 µm) column. The developed method was validated in human plasma with a lower limit of quantitation of 0.1 ng/mL for LAM. A linear response function was established for the range of concentrations 0.1–1500 ng/mL (r > 0.998) for LAM. The intra‐ and inter‐day precision values for LAM met the acceptance as per Food and Drug Administration guidelines. LAM was stable in the set of stability studies, viz. bench‐top, autosampler and freeze–thaw cycles. The developed assay method was applied to an oral bioequivalence study in humans. Copyright © 2011 John Wiley & Sons, Ltd.     

Development and validation of a reliable and rapid LC‐MS/MS method for simultaneous quantification of sacubitril and valsartan in rat plasma and its application to a pharmacokinetic study

A selective, sensitive and rapid liquid chromatographic method with electrospray ionization tandem mass spectrometric detection has been developed and validated for simultaneous quantification of sacubitril and valsartan in rat plasma using telmisartan as internal standard (IS). The analytes were extracted by deprotenization of 50 μL of plasma sample using 200 μL of acetonitrile. In a short chromatographic run of 1.50 min run time, separation was achieved on a Hypersil Gold C₁₈ column using a mobile phase composed of 0.1% formic acid in Milli‐Q water–0.1% formic acid in acetonitrile in gradient elution mode. The quantification of target compounds was performed in a positive electrospray ionization mode and multiple reaction monitoring. Response was a linear function of concentration in the ranges of 0.5–20,000 ng/mL for both analytes, with r² > 0.9997. The intra‐ and inter‐day precision and accuracy results were <15% and acceptable as per US Food and Drug Administration guidelines. Stability of compounds were established in a battery of stability studies, i.e. bench‐top, autosampler and long‐term storage stability as well as freeze–thaw cycles. The validated method can be used as a routine method to support pharmacokinetic studies. Copyright © 2016 John Wiley & Sons, Ltd.     

Development and validation of an LC‐MS/MS method for simultaneous quantification of levodopa and MD01 in rat plasma and its application to a pharmacokinetic study of mucuna pruriens extract

Mucuna pruriens, an ancient Indian herbal medicine containing levodopa, is widely used for Parkinson's disease. In order to simultaneously determine levodopa and 1,1‐dimethyl‐3‐carboxy‐6,7‐dihydroxy‐1,2,3,4‐tetrahydroisoquinoline (MD01) in rat plasma, an improved LC‐MS/MS method was developed and validated for a pharmacokinetic study in rats orally administered levodopa or Mucuna pruriens extract (MPE). Elimination of matrix effect and improvement of extraction recovery were achieved through systematic optimization of reversed‐phase and hydrophilic interaction chromatographic conditions together with sample clean‐up procedures. A satisfactory chromatographic performance was obtained with a Thermo Aquasil C₁₈ column (50 × 2.1 mm, 3 µm) using acetonitrile and water containing 0.2% formic acid as mobile phases. Futhermore, sodium metabisulfite and formic acid were used as stabilizers in neat solutions as well as rat plasma. The method was validated in a dynamic range of 20.0–10,000 ng/mL for levodopa and MD01; the intra‐ and inter‐day precision and accuracy were acceptable. The method was successfully utilized to determine the levodopa level in plasma samples of rats administered levodopa or MPE. Pharmacokinetic results showed that an increase in the AUC of levodopa was observed in rats following oral administration of multiple doses of MPE. Copyright © 2016 John Wiley & Sons, Ltd.     

Development and validation of a highly sensitive LC-MS/MS method for quantitation of dexlansoprazole in human plasma: application to a human pharmacokinetic study

A highly sensitive, specific and simple LC-MS/MS method was developed for the simultaneous estimation of dexlansoprazole (DEX) with 50 μL of human plasma using omeprazole as an internal standard (IS). The API-4000 LC-MS/MS was operated under multiple reaction-monitoring mode using electrospray ionization. A simple liquid-liquid extraction process was used to extract DEX and IS from human plasma. The total run time was 2.00 min and the elution of DEX and IS occurred at 1.20 min. This was achieved with a mobile phase consisting of 0.2% ammonia-acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on an X-terra RP 18 (50 × 4.6 mm, 5 μm) column. The developed method was validated in human plasma with a lower limit of quantitation of 2 ng/mL for DEX. A linear response function was established for the range of concentrations 2.00-2500.0 ng/mL (r > 0.998) for DEX. The intra- and inter-day precision values for DEX met the acceptance criteria as per FDA guidelines. DEX was stable in the battery of stability studies, viz. bench-top, auto-sampler and freeze-thaw cycles. The developed assay method was applied to an oral bioequivalence study in humans.     

Development of an LC‐MS/MS method for quantification of kadsurenone in rat plasma and its application to a pharmacokinetic study

A sensitive and rapid LC‐MS/MS method was developed and validated for the determination of kadsurenone in rat plasma using lysionotin as the internal standard (IS). The analytes were extracted from rat plasma with acetonitrile and separated on a SB‐C₁₈ column (50 × 2.1 mm, i.d.; 1.8 µm) at 30 °C. Elution was achieved with a mobile phase consisting of methanol–water–formic acid (65:35:0.1, v/v/v) at a flow rate of 0.30 mL/min. Detection and quantification for analytes were performed by mass spectrometry in the multiple reaction monitoring mode with positive electrospray ionization m/z at 357.1 → 178.1 for kadsurenone, and m/z 345.1 → 315.1 for IS. Calibration curves were linear over a concentration range of 4.88–1464 ng/mL with a lower limit of quantification of 4.88 ng/mL. The intra‐ and inter‐day accuracies and precisions were <8.9%. The LC‐MS/MS assay was successfully applied for oral pharmacokinetic evaluation of kadsurenone using the rat as an animal model. Copyright © 2013 John Wiley & Sons, Ltd.     

Development and validation of a highly sensitive LC‐MS/MS method for quantitation of bivalirudin in human plasma: application to a human pharmacokinetic study

A sensitive, specific and simple LC‐MS/MS method was developed for the identification and quantification of bivalirudin in human plasma using diazepam as an internal standard (IS). The API‐4000 LC‐MS/MS was operated under multiple‐reaction monitoring mode using electrospray ionization. The sample preparation consisted of an easy protein precipitation sample pretreatment with methanol. Chromatographic separation was achieved on a Zorbax Eclipse plus C₁₈ 100 × 2.1 mm column with a mobile phase of water–methanol–0.1% formic acid. The analytes were detected with a triple quadrupole Quantum Access with positive ionization. Ions monitored in the multiple‐reaction monitoring mode were m/z 1091 → 650 for bivalirudin (at 2.70 min) and m/z 285 → 193 for diazepam (at 3.85 min). The developed method was validated in human plasma with a lower limit of quantitation of 20 µg/L for bivalirudin. A linear response function was established for the range of concentrations 20–10,000 µg/L (r > 0.998) for bivalirudin. The intra‐ and inter‐day precision values for bivalirudin met the acceptance criteria as per US Food and Drug Administration guidelines. Bivalirudin was stable in the battery of stability studies, viz. bench‐top, freeze–thaw cycles and long‐term stability. The developed assay method was applied to an intravenous administration study in humans. Copyright © 2013 John Wiley & Sons, Ltd.     

Development of a rapid UPLC-MS/MS method for quantification of saxagliptin in rat plasma and application to pharmacokinetic study

A novel, simple and rapid ultraperformance liquid chromatography/tandem mass spectrometry (UPLC‐MS/MS) assay was established for quantification of saxagliptin in rat plasma. Plasma samples were processed by liquid–liquid extraction with ethyl acetate and chromatographed on a C₁₈ column (2.1 × 50 mm i.d., 1.7 µm). The mobile phase consisted of methanol and 0.1% formic acid (40:60, v/v). Multiple reaction monitoring transitions were performed for detection in positive‐ion mode with an electrospray ionization source. The calibration curve was linear over the concentration range of 0.5–100 ng/mL (R² > 0.99). All accuracy values were between 90.62 and 105.60% relative error and the intra‐ and inter‐day precisions were less than 9.66% relative standard deviation. Extraction recovery was more than 81.01% and the matrix effect ranged from 90.27 to 109.15%. After validation, the method was applied to a pharmacokinetic study where healthy rats were orally given 0.5 mg/kg saxagliptin. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and validation of an LC‐MS/MS method for the determination of bullatine A in rat plasma: application to a pharmacokinetic study

Bullatine A is a diterpenoid alkaloid of Xue‐Shang‐Yi‐Zhi‐Hao (Aconitum brachypodum), which is widely used in traditional Chinese medicine for the treatment of rheumatism and pain. The plasma levels of bullatine A were measured by a rapid and sensitive LC‐MS/MS method. Samples were prepared using acetonitrile precipitation and the separation of bullatine A was achieved on a Capcell Pak MG‐C₁₈ column by isocratic elution using acetonitrile (phase A) and 0.1% formic acid (phase B, pH 4.0; A:B, 30:70, v/v) as the mobile phase at a flow rate of 0.5 mL/min. Detection was performed on a triple‐quadrupole tandem mass spectrometer by multiple‐reaction monitoring of the transitions at m/z 344.2 → 105.2 for bullatine A and m/z 256.2 → 167.1 for the internal standard. The linearity was found to be within the concentration range of 1.32–440 ng/mL with a lower limit of quantification of 1.32 ng/mL. Only 1.3 min was needed for an each analytical run. This method was successfully applied in the determination of the active component bullatine A in rat plasma after intramuscular administration of A. brachypodum injection. Copyright © 2015 John Wiley & Sons, Ltd.     

Development and validation of LC–MS/MS method for quantification of bictegravir in human plasma and its application to an intracellular uptake study

A sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for quantification of bictegravir in human plasma. A small volume of only 50 μL aliquot of plasma was precipitated with acetonitrile containing an internal standard (IS). Chromatographic separation was performed on a Kinetex EVO C₁₈ column, 50 × 3.0 mm, 5 μm using an isocratic mobile phase containing 80:20 acetonitrile–water with 0.1% formic acid. A mass spectrometer was operated in ESI positive multiple reaction monitoring mode using the m/z 450.1/289.1 for bictegravir and 420.1/277.1 for IS. The dynamic range of the method was 1–10,000 ng/mL with a correlation coefficient of ≥0.9991. The precision results of calibration standards were in the range of 0.05–4.57% and accuracies were 95.07–104.70%. The mean extraction recovery was 98.64% with a precision of 2.91%. The method was validated as per US Food and Drug Administration guidelines and was found to be accurate and precise. The method was successfully applied to in vitro cellular uptake study.     

Liquid chromatography–tandem MS/MS method for simultaneous quantification of paracetamol,chlorzoxazone and aceclofenac in human plasma: An application to a clinical pharmacokinetic study

A facile, fast and specific method based on liquid chromatography–tandem mass spectrometry (LC–MS/MS) for the simultaneous quantitation of paracetamol, chlorzoxazone and aceclofenac in human plasma was developed and validated. Sample preparation was achieved by liquid–liquid extraction. The analysis was performed on a reversed‐phase C₁₈ HPLC column (5 μm, 4.6 × 50 mm) using acetonitrile–10 mM ammonium formate pH 3.0 (65:35, v/v) as the mobile phase where atrovastatin was used as an internal standard. A very small injection volume (3 μL) was applied and the run time was 2.0 min. The detection was carried out by electrospray positive and negative ionization mass spectrometry in the multiple‐reaction monitoring mode. The developed method was capable of determining the analytes over the concentration ranges of 0.03–30.0, 0.015–15.00 and 0.15–15.00 μg/mL for paracetamol, chlorzoxazone and aceclofenac, respectively. Intraday and interday precisions (as coefficient of variation) were found to be ≤12.3% with an accuracy (as relative error) of ±5.0%. The method was successfully applied to a pharmacokinetic study of the three analytes after being orally administered to six healthy volunteers.     

Development and validation of a highly sensitive LC‐MS/MS method for simultaneous quantitation of nortriptyline and 10‐hydroxynortriptyline in human plasma: application to a human pharmacokinetic study

A highly sensitive and specific LC‐MS/MS method has been developed for simultaneous estimation of nortriptyline (NTP) and 10‐hydroxynortriptyline (OH‐NTP) in human plasma (250 µL) using carbamazepine as an internal standard (IS). LC‐MS/MS was operated under the multiple reaction‐monitoring mode using the electrospray ionization technique. A simple liquid–liquid extraction process was used to extract NTP, OH‐NTP and IS from human plasma. The total run time was 2.5 min and the elution of NTP, OH‐NTP and IS occurred at 1.44, 1.28 and 1.39 min, respectively; this was achieved with a mobile phase consisting of 20 mm ammonium acetate : acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a HyPURITY C₁₈ column. The developed method was validated in human plasma with a lower limit of quantitation of 1.09 ng/mL for both NTP and OH‐NTP. A linear response function was established for the range of concentrations 1.09–30.0 ng/mL (r > 0.998) for both NTP and OH‐NTP. The intra‐ and inter‐day precision values for NTP and OH‐NTP met the acceptance as per FDA guidelines. NTP and OH‐NTP were stable in a battery of stability studies, i.e. bench‐top, auto‐sampler and freeze–thaw cycles. The developed assay was applied to a pharmacokinetic study in humans. Copyright © 2010 John Wiley & Sons, Ltd.     

Development and validation of a quantification method for oleanolic acid and hederagenin in rat plasma: application to the pharmacokinetic study

A rapid and sensitive liquid chromatography tandem mass spectrometry (LC–MS/MS) was developed and validated for simultaneous quantification of oleanolic acid and hederagenin in rat plasma. After the two analytes were extracted with liquid–liquid extraction, chromatographic separation was performed on a C₁₈ column with acetonitrile and water (85:15, v /v) as mobile phase at a flow rate of 0.4 mL/min. Calibration curves exhibited good linearity (r > 0.995) over the ranges of 0.41–82.0 ng/mL for oleanolic acid and 0.32–64.0 ng/mL for hederagenin, respectively. The lower limit of quantifications (LLOQs) in plasma were 0.41 ng/mL for oleanolic acid and 0.32 ng/mL for hederagenin. The established LLOQs were within the concentration needed for the assay in plasma, which met the requirements to evaluate their pharmacokinetics of oleanolic acid and hederagenin. This developed assay was successfully applied in the pharmacokinetic study of oleanolic acid and hederagenin in rats after oral administration of Rhizoma Clematidis extract.