Absolute oral bioavailability of fenofibric acid and choline fenofibrate in rats determined by ultra‐performance liquid chromatography tandem mass spectrometry

Choline fenofibrate is the choline salt of fenofibric acid, which releases free fenofibric acid in the gastrointestinal tract. To estimate the absolute oral bioavailability of fenofibric acid and choline fenofibrate, a novel and sensitive UPLC–MS/MS method with liquid–liquid extraction procedure was developed for the determination of fenofibric acid in rat plasma. The separation was achieved on a Phenomenex Kinetex C₁₈ column (50 × 2.1 mm, 2.6 μm) containing 2 mm ammonium acetate–methanol with a gradient elution program. Validations of this method including specificity, sensitivity (limit of quantification, 5 ng/mL), linearity (0.005–10 μg/mL), accuracy (within ±4.3%), precision (intra‐ and inter‐day coefficient of variation <11.3%), recovery (94.9–105.2% for fenofibric acid), matrix effect, stability and dilution, were all within acceptable limits. This method successfully supported the determination of fenofibric acid and choline fenofibrate. The absolute oral bioavailability was 93.4% for choline fenofibrate and 40.0% for fenofibric acid. These results suggested that choline fenofibrate and fenofibric acid had a better in vivo pharmacokinetic behavior than that of fenofibrate. The two new orally administrated pharmaceuticals, fenofibric acid and choline fenofibrate, can be developed as alternatives to fenofibrate.     

Simultaneous determination of kaempferol,quercetin, mangiferin,gallic acid,p‐hydroxybenzoic acid and chlorpheniramine maleate in rat plasma after oral administration of Mang‐Guo‐Zhi‐Ke tablets by UHPLC‐MS/MS and its application to pharmacokinetics

Mang‐Guo‐Zhi‐Ke tablets (MGZKTs) is an effective Chinese patent medicine. It contains mango leaf extract as the main raw material and the antihistamine drug, chlorpheniramine maleate is included in the formulation. However, its pharmacokinetic effect is rarely reported. A highly sensitive, reliable and rapid high‐throughput method using ultra‐high‐performance liquid chromatography with tandem mass spectrometry (UHPLC‐MS/MS) was used to simultaneously determine kaempferol, quercetin, mangiferin, p‐hydroxybenzoic acid, gallic acid and chlorpheniramine maleate in rat plasma after oral administration of MGZKTs. The method was successfully developed and fully validated to investigate the pharmacokinetics of MGZKTs. Chloramphenicol and clarithromycin were used as internal standards (IS). A practicable protein precipitation procedure with methanol was adopted for sample preparation. The samples were separated on an Acquity UHPLC Syncronis C₁₈ column (100 × 2.1 mm, 1.7 μm) using 0.1% formic acid–acetonitrile as the mobile phase. The flow rate was set at 0.4 mL/min. The obtained calibration curves were linear in the concentration range of ~1–1000 ng/mL for plasma (r > 0.99). Method validation results met the criteria reported in the US Food and Drug Administration guidelines. Quercetin, p‐hydroxybenzoic acid and kaempferol were absorbed rapidly and reached the peak concentration between 0.16 and 0.25 h. This validated that the UHPLC‐MS/MS method was successfully applied to study the pharmacokinetic parameters of the six compounds in rat plasma after oral administration of MGZKTs. This evidence will be useful for the clinical rational use of Mang‐Guo‐Zhi‐Ke tablets.     

UPLC–Q‐TOF–MS and UPLC–MS/MS methods for metabolism profiles and pharmacokinetics of major compounds in Xuanmai Ganjie Granules

Xuanmai Ganjie Granules (XMGJ), a widely used Chinese herbal formula in the clinic, is used for treatment of sore throats and coughs. Despite the chemical constituents having been clarifying by our previous studies, both of the metabolism and pharmacokinetic studies of XMGJ are unclear. This study aimed to explore the disposition process of XMGJ in vivo. A sensitive and selective ultra‐high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry (UPLC–Q‐TOF–MS) method was developed to analyze the absorbed components and metabolites in rat plasma and urine after oral administration of XMGJ. A total of 42 absorbed components, including 16 prototype compounds and 26 metabolites, were identified or tentatively characterized in rat plasma and urine after oral administration of XMGJ. Moreover, the pharmacokinetic studies of five compounds of XMGJ were investigated using ultra‐high liquid chromatography with tandem mass spectrometry method. The results indicated that liquiritin, harpagoside, glycyrrhetic acid, liquiritigenin, formononetin and their metabolites might be the major components involved in the pharmacokinetic and metabolism process of XMGJ. This research showed a comprehensive investigation of XMGJ in vivo, which could provide a meaningful basis for further material basis and pharmacological as well as toxicological research.     

Synthesis and Properties of a pH‐Insensitive Fluorescent Nitric Oxide Cheletropic Trap (FNOCT)

The synthesis and properties of the new fluorescent nitric oxide cheletropic trap (FNOCT) 14 , designed for the trapping and quantification of nitric oxide (NO) production in chemical and biological systems, is described (Scheme 3). The dicarboxylic acid 14 and the corresponding bis[(acetyloxy)methyl] ester derivative 15 of the FNOCT contain a 2‐methoxy‐substituted phenanthrene group as fluorophoric unit. The fluorescence of the reduced NO adduct of this FNOCT (λ_exc 320 nm, λ_em 380 nm) is pH‐independent. Trapping experiments were carried out in aqueous buffer solution at pH 7.4 with nitric oxide being added as a bolus as well as being released from the NO donor compound MAHMA NONOate (= (1Z)‐1‐{methyl[6‐(methylammonio)hexyl]amino}diazen‐1‐ium‐1,2‐diolate), indicating a trapping efficiency of ca. 50%. In a biological application, nitric oxide was scavenged from a culture of lipopolysaccharide‐stimulated rat alveolar macrophages. Under the applied conditions, a production of 11.1 ± 1.5 nmol of NO per hour and per 10⁵ cells was estimated.     

Pharmacokinetic parameters of three active ingredients hederacoside C,hederacoside D,and ɑ‐hederin in Hedera helix in rats

In Hedera helix hederacoside C, hederacoside D, and ɑ‐hederin are three major bioactive saponins and play pivotal roles in the overall biological activity. In this study, a specific and sensitive ultra‐high performance liquid chromatography with tandem mass spectrometry method has been developed and validated for the quantification of three major bioactive saponins in rat plasma. Chromatographic separation was performed on a reversed‐phase Thermo Hypersil GOLD C₁₈ column (2.1 mm × 50 mm, 1.9 μm) using a gradient mobile phase system of acetonitrile‐water containing 0.1% formic acid. The assay was successfully applied to study the pharmacokinetic behavior of the three analytes in rats after oral and intravenous administration of a mixture of saponins (hederacoside C, hederacoside D, and ɑ‐hederin). Further research was performed to compare the pharmacokinetic behavior of the three analytes after the oral administration of a mixture of saponins and an extract of saponins from Hedera helix, and results showed that double peaks were evident on concentration–time profile for each of the three saponins. The difference in the pharmacokinetic characteristics of three saponins between a mixture of saponins and an extract of saponins from Hedera helix was found in rat, which would be beneficial for the preclinical research and clinical use of Hedera helix.     

Pharmacokinetic comparison of five tanshinones in normal and arthritic rats after oral administration of Huo Luo Xiao Ling Dan or its single herb extract by UPLC‐MS/MS

A fast, sensitive and reliable ultra performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method has been developed and validated for simultaneous quantitation and pharmacokinetic study of five tanshinones (tanshinone I, tanshinone IIA, tanshinone IIB, dihydrotanshinone I, cryptotanshinone), the bio‐active ingredients of Huo Luo Xiao Ling Dan (HLXLD) in rat plasma. After liquid–liquid extraction, chromatographic separation was accomplished on a Shim‐pack XR‐ODS column (75 × 3.0 mm, 2.2 µm particles) and eluted with a mobile phase consisting of acetonitrile–0.05% formic acid aqueous solution (80:20, v/v) at a flow rate of 0.4 mL/min, and the total run time was 7.0 min. The detection was performed on a triple quadrupole tandem mass spectrometry equipped with an electrospray ionization source in positive ionization and multiple reaction monitoring mode. The lower limits of quantification were 0.050–0.400 ng/mL for all the analytes. Linearity, precision and accuracy, the mean extraction recoveries and matrix effects all satisfied criteria for acceptance. This validated method was successfully applied to a comparative pharmacokinetic study of five bio‐active components in rat plasma after oral administration of HLXLD or Salvia miltiorrhiza extract in normal and arthritic rats. The results showed that there were different pharmacokinetic characteristics among different groups. Copyright © 2016 John Wiley & Sons, Ltd.     

Simultaneous determination of a novel oral Janus kinase inhibitor ASP015K and its sulfated metabolite in rat plasma using LC‐MS/MS

A sensitive and selective liquid chromatography with tandem mass spectrometry (LC‐MS/MS) was developed for determining the concentrations of novel Janus kinase inhibitor ASP015K and its sulfated metabolite M2 in rat plasma. This method involves solid‐phase extraction (SPE) from 25 μL of rat plasma. LC separation was performed on an Inertsil PH‐3 column (100 mm L ×4.6 mm I.D., 5 µm) with a mobile phase consisting of 10 mM ammonium acetate and methanol under linear gradient conditions. Analytes were introduced to the LC‐MS/MS through an electrospray ionization source and detected in positive‐ion mode using selected reaction monitoring. Standard curves were linear from 0.25 to 500 ng/mL (r ≥0.9964). This assay enabled quantification of ASP015K and M2 at a concentration as low as 0.25 ng/mL in rat plasma. Validation data demonstrated that the method is selective, sensitive and accurate. Further, we also successfully applied this method to a preclinical pharmacokinetic study in rats. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination and pharmacokinetic study of four lignans in rat plasma after oral administration of an extract of Valeriana amurensis by ultra‐high performance liquid chromatography with tandem mass spectrometry

A selective and sensitive ultra‐high performance liquid chromatography with tandem mass spectrometry method was developed and validated for the determination and pharmacokinetic study of (+)‐8‐hydroxypinoresinol‐4’‐O‐β ‐D‐glucopyranoside, prinsepiol‐4‐O‐β‐D‐glucopyranoside, (+)‐pinoresinol‐4,4’‐di‐O‐β‐D‐glucopyranoside, and (−)‐massoniresinol 3α‐O‐β‐D‐glucopyranoside in rat plasma after the oral administration of a Valeriana amurensis extract. The analytes and ethyl 4‐hydroxybenzoate (internal standard) were separated on a Waters ACQUITY UPLC HSS T3 chromatographic column. The detection was performed on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring mode using an electrospray ionization source operating in negative ionization mode. The linear ranges (ng/mL) of the standard curves were 0.39–154.00, 0.62–244.70, 0.50–198.60, and 0.34–134.50 for (+)‐8‐hydroxypinoresinol‐4’‐O‐β‐D‐glucopyranoside, prinsepiol‐4‐O‐β‐D‐glucopyranoside, (+)‐pinoresinol‐4,4’‐di‐O‐β‐D‐glucopyranoside, and (−)‐massoniresinol 3α‐O‐β‐D‐glucopyranoside, respectively. The inter‐ and intra‐day precisions were less than 11.0%, the accuracies were between −5.9 and 7.7%, and the extraction recoveries of the four analytes were > 81.2% from rat plasma. The method was successfully applied to a pharmacokinetic study of the four analytes after oral administration of a Valeriana amurensis extract to rats. The developed method has the potential for pharmacokinetic analysis and to provide additional information in the clinical application of Valeriana amurensis.     

A rapid and sensitive UHPLC–MS/MS method for the determination of celosin A in rat plasma with application to pharmacokinetic study

Celosin A (CA), a natural compound isolated from Celosia argentea L., has been shown significant hepatoprotective effect on AHNP‐induced liver injury. This study described a rapid and sensitive ultra‐high‐pressure liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) assay for determination of CA in rat plasma. Methanol‐mediated precipitation was used for sample pretreatment. Chromatographic separation was achieved on a T3 column with gradient elution using water and acetonitrile as mobile phase. Determination was obtained using an electrospray ionization source in negative selected reaction monitoring mode at the transitions of m/z 793.3 → m/z 661.2 and m/z 955.6 → m/z 793.2 for CA and IS, respectively. The assay was linear over the concentration range 0.25–2500 ng/mL (r > 0.995) with a lowest limit of quantification (LLOQ) of 0.25 ng/mL. The intra‐ and inter‐day precisions (RSD) were 1.65–9.84 and 2.46–13.49%, respectively, while accuracy (RR) ranged from 96.21 to 99.45%, respectively. The recovery ranged from 95.09 to 102.22% and the matrix effect from 98.29 to 100.13%. The analyte was stable under the tested storage conditions. The method has been successfully applied to a preclinical pharmacokinetic study in rats after a single intravenous (2 mg/kg) or oral (50 mg/kg) administration. The oral bioavailability of CA was ~1.94%; in addition, there was no difference between male and female rats. This is the first time of the use of an UHPLC–MS/MS method for determination of CA concentration in rat plasma and for evaluation of its pharmacokinetic behavior.     

A UFLC–MS/MS method for the simultaneous determination of eight bioactive constituents from red wine and dealcoholized red wine in rat plasma: Application to a comparative pharmacokinetic study

To explore whether alcohol has an effect on the pharmacokinetic behavior of phenolic acids, the main bioactive constituents in red wine, a highly sensitive and simple ultra‐fast liquid chromatography coupled with triple quadrupole mass spectrometry (UFLC–MS/MS) method was developed for simultaneous quantitation of eight phenolic acids in plasma samples. Plasma samples were extracted by liquid–liquid extraction and the chromatographic separation was achieved on a Zorbax SB‐C₁₈ column within 7.0 min. Results of the validated method revealed that all of the calibration curves displayed good linear regression (r > 0.99). The intra‐ and inter‐day precisions of the analytes were <14.0% and accuracies ranged from ?8.5 to 7.3%. The extraction recoveries of the analytes were from 71.2 to 110.2% and the matrix effects ranged from 86.2 to 105.5%. The stability of these compounds under various conditions satisfied the requirements of biological sample measurement. The method was successfully applied to a comparative pharmacokinetic study of phenolic acids in rat plasma. For gallic acid and gentisic acid, the parameters AUC_0–t and AUC_0–∞ increased remarkably (p < 0.05) after oral administration of red wine, which suggested that alcohol might enhance their absorption. This is the first report to compare the pharmacokinetic behavior of phenolic acids in red wine and dealcoholized red wine.     

LC-MS/MS determination and pharmacokinetic study of albiflorin and paeoniflorin in rat plasma after oral administration of Radix Paeoniae Alba extract and Tang-Min-Ling-Wan

A rapid, sensitive and selective liquid chromatography/tandem mass spectrometry method (LC‐MS/MS) was developed and validated for simultaneous determination of albiflorin and paeoniflorin in rat plasma using geniposide as an internal standard. Plasma samples were extracted by solid‐phase extraction. Chromatographic separation was carried out on a Zorbax SB‐C₁₈ analytical column (150 × 2.1 mm × 5 µm) with 0.1% formic acid–acetonitrile (70:30, v/v) as the mobile phase. Detection was performed by multiple reaction monitoring mode using electrospray ionization in the positive ion mode. The total run time was 3.0 min between injections. The calibration curves were linear over a range of 1–1000 ng/mL for albiflorin and 2–2000 ng/mL for paeoniflorin. The overall precision and accuracy for all concentrations of quality controls and standards were better than 15%. Mean recovery was determined to be 87.7% for albiflorin and 88.8% for paeoniflorin. The validated method was successfully applied to the pharmacokinetic study of albiflorin and paeoniflorin in rat plasma after oral administration of Radix Paeoniae Alba extract and Tang‐Min‐Ling‐Wan. The pharmacokinetic parameters showed that albiflorin and paeoniflorin from Tang‐Min‐Ling‐Wan were absorbed more rapidly with higher concentrations in plasma than that from Radix Paeoniae Alba extract. The results provided a meaningful basis for evaluating the clinical applications of traditional Chinese medicine. Copyright © 2010 John Wiley & Sons, Ltd.     

A sensitive LC–MS/MS method for simultaneous determination of cabozantinib and its metabolite cabozantinib N‐oxide in rat plasma and its application in a pharmacokinetic study

Cabozantinib (CBZ) is used for the treatment of progressive, metastatic medullary thyroid cancer. Its major oxidative metabolite is cabozantinib N‐oxide (CBN), which contains a structural alert associated with mutagenicity, yet the pharmacokinetics studies lack the simultaneous investigation of CBN and dose proportionality. In the current study a simple LC–MS/MS method was developed and validated for the simultaneous estimation and pharmacokinetic investigation of CBZ and CBN in rat plasma. The analytes were separated on a Waters Atlantics C₁₈ column (2.1 × 150 mm, 3 μm). The mass spectrometry analysis was conducted in positive ionization mode with multiple reaction monitoring. Good linearity was observed over the concentration ranges of 0.500–5000 ng/mL for CBZ and 0.525–2100 ng/mL for CBN. The extraction recoveries were constant and the intra‐ and inter‐batch precision and accuracy were acceptable for the analysis of biological samples. The method was successfully applied for the simultaneous estimation of CBZ and CBN in a pharmacokinetic study in Sprague–Dawley rats. After oral administration of CBZ (1, 5 and 12.6 mg/kg), although CBZ showed dose proportionality, the metabolite CBN showed obvious nonlinear elimination pharmacokinetics with greater than dose‐proportional increases in exposure.     

Simultaneous quantification of atractyloside and carboxyatractyloside in rat plasma by LC‐MS/MS: Application to a pharmacokinetic study after oral administration of Xanthii Fructus extract

Xanthii Fructus is extensively used as an herbal medicine. Ingestion of this herb is associated with severe hepatotoxicity and nephrotoxicity. Atractyloside and carboxyatractyloside are two dominative toxic constituents in Xanthii Fructus. However, their pharmacokinetic study is lacking. In this study, a novel high‐performance liquid chromatography‐tandem mass spectrometry method was developed to simultaneously quantify the rat plasma concentrations of atractyloside and carboxyatractyloside. After protein precipitation, the analytes were chromatographic separated on a ZORBAX Eclipse Plus column (2.1 × 150 mm id, 5 µm) under gradient elute. In the negative electrospray ionization mode, the transitions at m/z 725.3→645.4 for atractyloside, m/z 769.3→689.4 for carboxyatractyloside, and m/z 479.2→121.1 for paeoniflorin (the internal standard) were acquired by multiple reaction monitoring. This analytical method showed good linearity over 1–500 ng/mL for atractyloside and 2–500 ng/mL for carboxyatractyloside with acceptable precision and accuracy. No matrix effect, instability and carryover occurred in the analysis procedure. The extraction recoveries were greater than 85.0%. This method was applied to a preliminary pharmacokinetic study by orally administering Xanthii Fructus extract (9 g/kg) to rats, which was useful to evaluate the role of these two compounds in Xanthii Fructus‐induced toxicity.     

Simultaneous determination of ginsenosides and bufadienolides in rat plasma after the oral administration of Shexiang Baoxin Pill for pharmacokinetic study by liquid chromatography tandem mass spectrometry following solid‐phase extraction

A sensitive and reliable bioanalytical method was established for quantitati\ve and pharmacokinetic investigation of nine ginsenosides and seven bufadienolides in rat plasma after the oral administration of Shexiang Baoxin Pill by liquid chromatography–electrospray ionization tandem mass spectrometry, using tinidazole and digoxin as internal standards (ISTDs). All of the analytes and ISTDs obtained satisfactory recoveries by solid‐phase extraction using an Oasis HLB μElution Plate, which was eluted with methanol and ethyl acetate successively, and chromatographic separation was achieved on a Shim‐pack XR‐ODSIIcolumn (75 × 2.0 mm, 2.2 μm) with gradient elution using a mixture of acetonitrile–0.1% formic acid solution (v /v) as the mobile phase at a flow rate of 0.3 mL/min. Detection was carried out by a triple‐quadrupole tandem mass spectrometry with positive/negative ion switching multiple reaction monitoring mode. All analytes showed good linearity over a wide concentration range (r ² > 0.99). The lower limit of quantification was in the range 0.625–12.5 ng/mL for bufadienolides and 2–5.5 ng/mL for ginsenosides, and the mean recoveries of all analytes were in the range 78.29–99.35%. The intra‐ and inter‐day precisions (RSD) were in the range 0.08–12.38% with the accuracies between 86.09 and 99.40%. The validated method was then successfully applied to pharmacokinetic study of the above 16 compounds in rat plasma. Pharmacokinetic results indicated that the developed extraction and analytical method could be employed as a rapid, effective technique for pharmacokinetic study of multiple components, especially various polarity that are difficult to extract simultaneously.     

Simultaneous determination of eight bioactive components of Cirsium setosum flavonoids in rat plasma using triple quadrupole LC/MS and its application to a pharmacokinetic study

Cirsium setosum (Willd.) MB. has been reported to exert significant anti‐hemorrhagic, anti‐inflammation, antimicrobial, sedative and detoxicating efficacy. It has been widely used to treat gastrointestinal bleeding, uterine bleeding, infectious hepatitis and cardiovascular disease in China. Recent studies have shown that flavonoids are the main active components in C. setosum. Nevertheless, to the best of our knowledge, there is no report concerning the simultaneous determinations and pharmacokinetics of constituents in C. setosum flavonoids in rat plasma. In this study, a rapid, sensitive and selective triple quadrupole liquid chromatography–mass spectrometry method was developed to determine eight analytes from the flavonoids of C. setosum in rat plasma. In addition, the pharmacokinetic study of the eight analytes in rats after oral administration of C. setosum flavonoids was successfully completed through this method. According to the pharmacokinetic parameters of the eight analytes, rutin, naringin, quercetin, acacetin, wogonin were the long‐acting components of the C. setosum flavonoids, with long elimination time and high bioavailability. Of note, the method developed in this study fills a blank in pharmacokinetic studies of C. setosum flavonoids. Our findings provide valuable views on the understanding of the absorption mechanism of C. setosum flavonoids and their clinical efficacy.     

Method development for quantification of quizartinib in rat plasma by liquid chromatography/tandem mass spectrometry for pharmacokinetic application

Quizartinib is a highly potent inhibitor of the fms‐like tyrosine kinase receptor, which is one of the most commonly mutated genes in acute myeloid leukemia. Quizartinib has shown a significant antileukemic clinical influence among relapsed/refractory acute myeloid leukemia patients. This study aimed at developing and validating an analytical method for the measurement of quizartinib in rat plasma using liquid chromatography–tandem mass spectrometry (LC–MS/MS). The method was validated according to US Food and Drug Administration guidelines, and the results obtained in this work met the set criteria. Liquid–liquid extraction was used and chromatographic separation was achieved on a BEHTM C₁₈ column. Detection of quizartinib was achieved in multiple reaction monitoring mode using positive‐ion mode electrospray ionization. The MS/MS ion transitions at mass‐to‐charge ratios (m/z) of 561.129/114.09 and 441.16/84.03 were monitored for quizartinib and ibrutinib, respectively. The linear detection range was 2–1000 ng/mL (r > 0.998), with intra‐ and inter‐day assay precisions ≤13.07 and 13.17%, respectively. This rapid, simple and sensitive method was validated and successfully applied to the pharmacokinetic study of quizartinib in rat samples.     

Identification and quantitative investigation of the effects of intestinal microflora on the metabolism and pharmacokinetics of notoginsenoside Fc assayed by liquid chromatography with electrospray ionization tandem mass spectrometry

Notoginsenoside Fc, which is a protopanaxdiol‐type saponin isolated from the leaves of Panax notoginseng, exhibits an exceptional antiplatelet aggregatory effect. To study the modulating effect of gastrointestinal contents on the metabolic profile and pharmacokinetics, pseudo germ‐free rats were used to study the influence of the bacterial community structure on the metabolic profile. Glycosidase activities were measured using the spectrophotometric method. Biotransformations of notoginsenoside Fc in normal and pseudo germ‐free rat intestinal microflora were systematically investigated using ultra high performance liquid chromatography with tandem quadrupole/time‐of‐flight mass spectrometry. Moreover, a liquid chromatography with tandem mass spectrometry method was established for simultaneous determination of the notoginsenoside Fc prototype and its degradation products. Through an in vivo pharmacokinetic study, the pharmacokinetic characteristics were compared between normal rats and pseudo germ‐free rats. During the in vitro biotransformation, seven deglycosylated products were detected and identified after incubation in the intestinal bacteria of normal rats. In pseudo germ‐free rats, glycosidase activities were significantly decreased, and no obvious degradation occurred. In an in vivo study, the systemic exposure was significantly increased 40%, as evidenced by the area under the blood concentration–time curve from time zero to infinity value and half‐life value, which were prolonged more in the pseudo germ‐free group than in normal rats. The results demonstrate that patients who use intestinal bacteria‐metabolized herbs, such as panax notoginseng, should understand the profile of intestinal bacteria to ensure therapeutic efficacy.     

A rapid and sensitive determination of aucubin in rat plasma by liquid chromatography-tandem mass spectrometry and its pharmacokinetic application

A sensitive, accurate, rapid and robust LC‐MS‐MS method for the quantification of aucubin, a major bioactive constituent of Aucuba japonica, Eucommia ulmoides and Plantago asiatica, was established and validated in rat plasma. Plasma samples were simply precipitated by adding methanol and the supernatant was chromatographed by a Diamonsil® C₁₈(2) column with the mobile phase comprising a mixture of 10 mm ammonium acetate in methanol and that in water with the ratio of 50:50 (v/v). Quantification of aucubin was performed by mass spectrometry in the multiple‐reaction monitoring mode with positive atmospheric ionization at m/z 364 → 149 for aucubin, and m/z 380 → 165 for catalpol (IS), respectively. The retention time was 2.47 and 2.44 min for aucubin and the IS, respectively. The calibration curve (10.0–30,000 ng/mL) was linear (r² > 0.99) and the lower limit of quantification was 10.0 ng/mL in the rat plasma sample. The method showed satisfactory results such as sensitivity, specificity, precision, accuracy, recovery, freeze–thaw and long‐term stability. This simple LC‐MS method was successfully applied in a pharmacokinetic study carried out in Sprague–Dawley rats after oral administration of aucubin at a single dose of 50 mg/kg. Herein the pharmacokinetic study of aucubin is reported for the first time. Copyright © 2011 John Wiley & Sons, Ltd.     

Ultra‐performance liquid chromatography–tandem mass spectrometric assay for the simultaneous determination of brucine,strychnine and brucine N‐oxide in rat plasma: application to a pharmacokinetic study

A rapid, simple and sensitive UHPLC‐MS/MS method was developed and validated for the simultaneous determination of brucine, strychnine and brucine N‐oxide in rat plasma using huperzine A as an internal standard (IS) after protein precipitation with methanol. The analytes were separated on a Purospher® STAR RP₁₈ UHPLC column (2 µm, 2.1 × 100 mm) by gradient elution using a mobile phase composed of methanol and water (containing 0.1% formic acid) at a flow rate of 0.3 mL/min. Brucine, strychnine, brucine N‐oxide and IS were detected in positive ion multiple reaction monitoring mode by means of an electrospray ionization interface (m/z 395.2 → 324.1, m/z 335.2 → 184.1, m/z 411.2 → 394.2, m/z 243.1 → 226.1). The calibration curve was linear over the range of 1–500 ng/mL for brucine and strychnine and 0.2?50 ng/mL for brucine N‐oxide. The intra‐ and inter‐day precisions of these analytes were all within 15% and the accuracy ranged from 85 to 115%. The stability experiment indicated that the plasma samples at three concentration levels were stable under different conditions. The developed method was successfully applied for the first time to pharmacokinetic studies of brucine, strychnine and brucine N‐oxide following a single oral and intravenous administration of modified total alkaloid fraction in rats. Copyright © 2016 John Wiley & Sons, Ltd.     

Development and application of a UPLC‐MS/MS method for simultaneous determination of fenofibric acid and berberine in rat plasma: application to the drug–drug pharmacokinetic interaction study of fenofibrate combined with berberine after oral administration in rats

With the purpose of carrying out pharmacokinetic interaction studies ofnberberine (BBR) and fenofibrate (FBT), an UPLC‐MS/MS method has been developed and validated. The analytes, BBR and fenofibric acid (FBA, metabolite of FBT) and the internal standard, tetrahydropalmatine, were extracted with dichloromethane–diethyl ether (3:2, v/v) and separated on an Agilent Eclipse XDB C₁₈ column using a mobile phase composed of acetonitrile and water. With positive ion electrospray ionization, the analytes were monitored on a triple quadrupole mass spectrometer in multiple reaction monitoring mode. Linear calibration curves were obtained over the concentration ranges of 0.1–100.0 ng/mL for BBR and 10.0–50,000.0 ng/mL for FBA. For BBR and FBA, the intra‐ and inter‐day precisions were <11.5 and 11.9%, respectively. The accuracy was within 11.7% and 11.3%. The mean recoveries of BBR at three concentrations of 0.2, 20.0, 80.0 ng/mL were >85.6%, and those of FBA at three concentrations of 20.0, 2500.0, 40,000.0 ng/mL were >87.9%. Consequently, the proposed method was applied to the pharmacokinetic interaction study of FBT combined with BBR after oral administration in rats and was proved to be sensitive, specific and reliable to analyze BBR and FBA in biological samples simultaneously. Copyright © 2016 John Wiley & Sons, Ltd.