Simultaneous determination of multiple components in rat plasma and pharmacokinetic studies at a pharmacodynamic dose of Xian-Ling-Gu-Bao capsule by UPLC-MS/MS.

Xian-Ling-Gu-Bao capsule (XLGB) is an effective traditional Chinese medicine prescription (TCMP) that is used for the prevention and treatment of osteoporosis in China. A rapid, simple, efficient and stable method based on UPLC-MS/MS technology was developed for simultaneous determination of multiple components of XLGB in rat plasma. Mass spectrometric detection was performed in multiple reaction monitoring (MRM) mode with electrospray ionization (ESI). For twenty-one selected quantitative prototypes, all calibration curves showed favourable linearity (r>0.9932) in linear ranges. The lower limits of quantification (LLOQs) were 2 ng/mL for psoralen (PL), 2.5 ng/mL for asperosaponin VI (AS), 1 ng/mL for isopsoralen (IPS) and sweroside (SW), 0.5 ng/mL for magnoflorine (MA), bavachinin (BVN), tanshinone IIA (TA), timosaponin BII (TBII) and icaritin (ICT), 0.1 ng/mL for epimedin B (EB) and epimedin C (EC), 0.05 ng/mL for icariin (IC), isobavachalcone (IBC), psoralidin (PD), bavachin (BV), bavachalcone (BC), epimedin A (EA) and isobavachin (IBV), 0.02 ng/mL for neobavaisoflavone (NEO) and icariside I (ICI) and 0.01 ng/mL for icariside II (ICII). The intra-day and inter-day (low, medium, high) precision (relative standard deviation) for all analytes was less than 8.63%, and the accuracies (as relative error) were in the range of -12.45% to 8.91%. Extraction recoveries and matrix effects of analytes and IS were acceptable. All analytes were stable during the assay and storage in plasma samples. The validated method was successfully applied to the pharmacokinetics (PK) studies of the twenty-one prototypes at pharmacodynamic doses (0.3 and 1 g/kg/day). In addition, dynamic profiles of 28 metabolites (phase II conjugates: 23 glucuronide conjugates, 2 sulfate conjugates and 3 glucuronide or sulfate conjugates) were also monitored by their area/IS area-time curves. As a result, coumarins, prenylated flavonoids from Psoraleae Fructus, alkaloids and prenylated flavonol glycosides from Epimedii Herba, and iridoid glycosides, triterpenoid saponins from Dipsaci Asperoidis Radix were considered to be the key effective substances of XLGB due to their high exposure and appropriate pharmacokinetic features. This is the first report to reveal pharmacodynamic ingredients by a reversed pharmacodynamic (PD) - pharmacokinetics (PK) study.

Simultaneous high-performance liquid chromatography with tandem mass spectrometry quantification of six bioactive components in rat plasma after oral administration of Yougui pill.

Yougui pills are a classic Chinese medicine that shows significant effects on nerve regeneration and neuroprotection in modern pharmacological studies. With a complex formula, Yougui pills have faced significant challenges in the fields of bioanalysis and pharmacokinetics in animals and human studies. In the present study, a specific and accurate high-performance liquid chromatography with tandem mass spectrometry method was developed and validated for the quantitative determination of the six bioactive components in rat plasma after oral administration of Yougui pills. Chromatographic separation was performed on a C18 column with a gradient elution system. Samples were analysed using positive ion mode with multiple reaction monitoring mode. The assay showed good linearity for all six bioactive components in the dynamic range of 0.50 to 50 ng/mL with acceptable intra- and inter-batch accuracy and precision. The lower limits of quantification were 0.50 ng/mL for all six bioactive components. The method was successfully applied to rat pharmacokinetics after oral administration of Yougui pills. All six bioactive components were detected in rat plasma, including songorine, benzoylhypaconitine, benzoylmesaconitine, neoline, karacoline, and sweroside, while some other target compounds were not detected, such as rhmannioside A, loganin, and cornuside I. After oral administration of Yougui pills at a dose of 2500 mg/kg, all six bioactive components were rapidly absorbed, resulting in tmax values less than 1 h and relative lower Cmax values. The t1/2 values for songorine, benzoylhypaconitine, benzoylmesaconitine, neoline, karacoline, and sweroside were calculated to be 2.62 ± 0.67, 2.11 ± 0.45, 1.94 ± 0.35, 1.88 ± 0.31, 2.07 ± 0.44, and 1.59 ± 0.30 h, which indicated that Yougui pills should be taken in multiple oral doses over a relatively short period.

UPLC-Q-TOF/MS-based metabolic profiling comparison of four major bioactive components in normal and CKD rat plasma, urine and feces following oral administration of Cornus officinalis Sieb and Rehmannia glutinosa Libosch herb couple extract.

Cornus officinalis-Rehmannia glutinosa herb couple is widely used herb medicine in clinical practice to treat chronic kidney disease (CKD). However, the in vivo integrated metabolism of its main bioactive components in CKD rats remains unknown. In this study, UPLC-Q-TOF/MS technique combined with Metabolynx™ software, was developed and successfully applied for analysis of metabolic profiles of the bioactive components of the herb couple in normal and CKD rat biological samples. Main parent components of the herb couple extract such as loganin, morroniside and catalpol were absorbed into the blood circulation of the normal and CKD rats. Another parent component acteoside was almost completely degraded. Seventeen metabolites involved in the in vivo metabolism processes were tentatively identified. These metabolites indicated that loganin was mainly metabolized to the demethylated product, and morroniside was firstly deglycosylated to the aglycone and the latter was subsequently demethylated and acetylated. Additionally, hydrogenation and deglycosylation were the principal metabolic reactions of catalpol; while O-glucuronide and O-sulphate conjugates were observed as major metabolites for methylated caffeic acid and hydroxytyrosol released from acteoside. Compared with the normal group, the CKD rat showed lower conversion capability. Few kinds and minor amounts of the metabolites appeared in the CKD rat samples. While considerable amounts of the parent compounds were detected in the CKD plasma. This will help maintain a high blood drug concentration which might be beneficial for the treatment of CKD. The proposed method could develop an integrated template approach to analyze screening and identification of the bioactive components in plasma, urine and feces after oral administration of herb medicines. Additionally, this investigation might provide helpful chemical information for further pharmacology and active mechanism research on herb medicines.

Metabolic profiles and pharmacokinetics of picroside I in rats by liquid chromatography combined with electrospray ionization tandem mass spectrometry.

Picroside I is an iridoid glycoside derived from Picrorhiza kurroa Royle ex Benth and Picrorhiza scrophulariiflora Pennell and characterized by many biological activities. In this study, a fast, selective, and sensitive UHPLC-MS/MS method was developed and validated to determine picroside I in rat plasma. Analytes were separated by using an ACQUITY UPLC® BEH C18 (2.1 × 50 mm, 1.7 µm) column at a running time of 2 min. Selected reaction monitoring (SRM) transitions were m/z 491.1 → 147.1 for picroside I and m/z 511.1 → 235.1 for the internal standard in a negative ion mode. The established UHPLC-MS/MS method achieved good linearity for picroside I within the range of 0.1-500 ng/mL. The validated method was successfully applied for the pharmacokinetic analysis of picroside I in rats after oral administration. Fifteen metabolites of picroside I were tentatively identified through ultra-high-performance chromatography/tandem quadrupole time-of-flight mass spectrometry, and four metabolites were identified by comparing with the standards. Besides, nine of these metabolites were discovered for the first time. The proposed metabolic pathways of picroside I in vivo can be divided into four parts, namely, phase I reaction of picroside I, including hydroxylation and deoxygenation; phase II reaction of picroside I, including glucuronidation, sulfation, and methylation; phase I biotransformations of metabolites, such as reduction and hydroxylation; and phase II biotransformations of metabolites, such as glucuronidation and sulfation. These results could offer insights into the effectiveness and toxicity of picroside I.

Simultaneous determination of gentiopicroside and its two active metabolites in rat plasma by LC-MS/MS and its application in pharmacokinetic studies.

Gentiopicroside is a natural secoiridoid glycoside that may require metabolic activation to exert pharmacological effects. In this study, two active metabolites of gentiopicroside (M1 and M2) were isolated from rat urines and identified with our previous method. Most importantly, a fast, sensitive and selective ultra high-performance liquid chromatography-tandem mass spectrometry method was developed to simultaneously determine gentiopicroside and its two metabolites in rat plasma. The analytes and internal standard (swertiamarin) were separated on an ACQUITY UPLC® BEH C18 column (2.1×50mm, 1.7µm) using gradient elution by acetonitrile and 0.1% formic acid at a flow rate of 0.4mL/min. The mass spectrometry detector was operated in the multiple reaction monitoring with positive ionization mode. The method had a good linearity over the concentration range of 0.2-10,000ng/mL for gentiopicroside and 0.1-5000ng/mL for the two metabolites. The validated method was successfully applied to the pharmacokinetic study of gentiopicroside and its metabolites after single oral administration of gentiopicroside (150mg/kg) to rats (n=8). The pharmacokinetic differences between gentiopicroside and its two metabolites were identified.Results provided the evidence for in vivo metabolism-based activation of gentiopicroside.

Pharmacokinetics and comparative metabolic profiling of iridoid enriched fraction of Picrorhiza kurroa - An Ayurvedic Herb.

ETHNO-PHARMACOLOGICAL RELEVANCE: Picrosides I, II and apocynin are the main active principles present in the roots and rhizomes of Picrorhiza kurroa Royle ex. Benth (Kutki). Ethno-medicinally, the plant is used for the treatment of liver, upper respiratory tract disorders and dyspepsia, since long in Ayurveda. AIM OF THE STUDY: This study attempts to determine the pharmacokinetic profile of picrosides I, II and apocynin in rats after oral administration of iridoid enriched fraction (IRF) and to recognize the pattern of its metabolites as such in IRF and in plasma. MATERIALS AND METHODS: A simple, precise, specific and sensitive RP-HPLC method was developed for simultaneous quantification of picrosides I, II and apocynin in rat plasma and in plant extract. Acetonitrile (ACN) and water was used as a solvent system with a gradient elution for pharmacokinetic studies using HPLC-PDA (Flow rate: 1.0mL/min) and metabolic profiling through UPLC-MS (Flow rate: 0.5mL/min) in selected reaction monitoring. A comparative study was performed in order to recognize the pattern and fate of metabolites in rat plasma up to 24h after single oral administration of IRF. RESULTS: Developed method produced more than 85% recovery of the targeted metabolites in rat plasma. The content of picrosides I, II and apocynin in IRF were found 5.7%, 18.3% and 27.3% w/w, respectively. The mean plasma concentration versus time profiles of picroside I, II and apocynin resulted in peak plasma concentration (Cmax) 244.9, 104.6 and 504.2ng/mL with half-life (t1/2) 14, 8 and 6h, respectively. Other pharmacokinetic parameters such as time to reach Cmax (tmax), area under curve (AUC), absorption (ka) and elimination (ke) constant, volume of distribution (Vd) were also determined. Pattern recognition analysis showed fate of 18 metabolites in rat plasma up to 24h out of 26 present in IRF. CONCLUSION: The information gained from this study postulates the basic pharmacokinetic profiling of picroside I, II and apocynin as well as fate of other metabolites after oral administration of IRF, demonstrating scientific basis of its traditional use in Ayurveda.

Comparative pharmacokinetic analysis of extracts of crude and wine-processed Dipsacus asper in rats by a sensitive ultra performance liquid chromatography-tandem mass spectrometry approach.

The purpose of this study is to establish and validate an UPLC-MS/MS approach to determine 4-caffeoylquinic acid, chlorogenic acid, 3,5-dicaffeoylquinic acid, loganic acid, loganin, sweroside, dipsacoside B and asperosaponin VI from extracts of crude and wine-processed Dipsacus asper in biological samples and apply the approach to a comparative pharmacokinetic study. A Waters BEH C18 UPLC column was employed with acetonitrile/0.2% formic acid-water as mobile phases. The mass analysis was carried out in a triple quadrupole mass spectrometer using multiple reaction monitoring (MRM) with negative scan mode. A one-step protein precipitation by acetonitrile was performed to extract the eight analytes from plasma. Our results revealed that all of the calibration curves displayed good linear regression (r2>0.9990). The lower limits of quantification (LLOQ) were determined as 10.0, 9.6, 8.9, 9.1, 9.2, 9.8, 10.1 and 9.8ng/mL. The intra-day and inter-day precisions (RSD) of the eight compounds at high, medium and low levels were less than 4.94% and the bias of the accuracies ranged from -3.89% to 3.95%.The extraction recoveries of the eight compounds were from 90.4% to 100.2% and the matrix effects ranged from 89.3% to 100.1%. The stabilities of these compounds were investigated by analyzing six replicates of QC samples at three different concentrations following storage at 25°C for 4h, -80°C for 30days, three-freeze-thaw cycles, and 4°C for 24h. All the samples showed satisfactory precision and accuracy after various stability tests. Pharmacokinetic parameters were estimated using a non-compartment model. Compared with the crude group, the parameters of Cmax and AUC0-t of 4-caffeoylquinic acid, loganic acid, loganin and asperosaponin VI increased remarkably (p<0.05) after oral administration of the aqueous extract of wine-processed Dipsacus asper, indicating that wine-processing could enhance bioavailability of 4-caffeoylquinic acid, loganic acid, loganin and asperosaponin VI.

Characterization of picroside II metabolites in rats by ultra-high-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.

Picroside II, a bioactive compound isolated from Picrorhiza scrophulariiflora Pennell, has been reported to have hepatoprotective, neuroprotective, and antioxidant effects. However, the detailed in vivo biotransformation of this compound has been rarely reported. This study aimed to investigate the metabolic profiles of picroside II in rats by using ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry. Metabolite structures were elucidated based on accurate mass measurements of deprotonated molecules and their fragmentation patterns. Thirteen metabolites were structurally identified, and the detailed metabolic pathways were proposed. The findings revealed that after oral administration, picroside II mainly undergoes four metabolic pathways. In the first pathway, picroside II is deglycosylated to generate aglycone, which is isomerized to a dialdehyde-type intermediate. A series of metabolic reactions, including glucuronidation, subsequently occurs. In the second pathway, picroside II is subjected to ester bond hydrolysis to form vanillic acid, which is further subjected to sulfate conjugation, glycine conjugation, glucuronidation, and demethylation. In the third pathway, picroside II is directly conjugated with glucuronic acid to yield a predominant metabolite (M01) in plasma. In the fourth pathway, picroside II is directly conjugated with sulfate. These findings provide insights into the in vivo disposition of picroside II and are useful to understand the mechanism of effectiveness and toxicity of this compound as well as P. scrophulariiflora-related preparations.

In vitro - In vivo metabolism and pharmacokinetics of picroside I and II using LC-ESI-MS method.

Picroside I and II, iridoid glycosides, are the major active markers of roots and rhizomes of Picrorhiza kurroa (family: Scrophulariaceae). The rhizomes of P. kurroa have been traditionally used to treat worms, constipation, low fever, scorpion sting, asthma and ailments affecting the liver. Various Ayurvedic and herbal preparations are available in the market which contains P. kurroa e.g. Arogyavadhini vati, Tiktadi kwath, Picrolax capsules and suspension. These preparations are used without any significant pharmacokinetics data. Previously, we have reported that oral bioavailability of picroside I and II is low. Most of the iridoid glycosides are primarily metabolized by intestinal microbial flora. So, it is necessary to determine the metabolic profile of picroside I and II and check the correlation with lower bioavailability. Therefore, this study was designed to check metabolic (in vitro and in vivo) profile along with pharmacokinetic profile of picroside I and II. For this, a sensitive and selective LC-ESI-MS method was developed and validated for simultaneous determination of picroside I and II in rat plasma. Chromatographic separations were performed on C18 column. The mobile phase consisted of acetonitrile: 10 mM ammonium acetate buffer [90:10 v/v], pH 3.5. In-vitro Metabolic study was performed on rat liver microsomes and primary hepatocytes. In-vivo pharmacokinetic and metabolic profile of picroside I and II was generated after oral administration of Kutkin (mixture of picroside I and II) to Sprague-Dawley rats. Various pharmacokinetic parameters viz. Cmax, Tmax, AUC(0-t) were determined. In metabolic study, eight metabolites of picroside I and six metabolites of picroside II were identified in vitro, out of which four metabolites for each picroside I and picroside II were identified in vivo.

Simultaneous determination of loganin, morroniside, catalpol and acteoside in normal and chronic kidney disease rat plasma by UPLC-MS for investigating the pharmacokinetics of Rehmannia glutinosa and Cornus officinalis Sieb drug pair extract.

A sensitive and rapid method for determination of loganin, morroniside, catalpol and acteoside in rat plasma after oral administration of Rehmannia glutinosa Libosch and Cornus officinalis Sieb drug pair based on ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS). Chromatographic separation was achieved using an Acquity UPLC BEH C18 column (100mm×2.1mm, 1.7µm) at a flow rate of 0.4mL/min, using gradient mode containing 0.1% formic acid in water and acetonitrile were used as the mobile phase A and B. Loganin, morroniside, catalpol, acteoside and the internal standard (chloramphenicol) were detected by selected reaction monitoring in the negative ion mode with the mass transition of m/z 451.0→179.0 (morroniside), m/z 435.0→227.0 (loganin), m/z 407.1→199.1 (catalpol), m/z 623.2→161.0 (acteoside) and m/z 320.8→151.9 (chloramphenicol), respectively. All calibration curves showed good linearity (r>0.991). The precision was evaluated by intra-day and inter-day assays and the RSD% were all within 9.58%. The recovery ranged from 67.62 to 80.14%. The method was successfully applied to pharmacokinetic study of the analytes in normal and doxorubicin-induced chronic kidney disease rat plasma.

A UPLC-MS Method for Simultaneous Determination of Geniposidic Acid, Two Lignans and Phenolics in Rat Plasma and its Application to Pharmacokinetic Studies of Eucommia ulmoides Extract in Rats.

The bark of Eucommia ulmoides is a well-known Chinese herbal medicine that is used to regulate blood pressure and reduce blood sugar and fats, as well as an antioxidant and antimicrobial agent. Here we describe the development of a sensitive ultrahigh performance liquid chromatography-tandem mass spectrum method for the simultaneous determination of five major active ingredients of E. ulmoides bark extract, namely, geniposidic acid (GA), protocatechuic acid (PCA), chlorogenic acid (CA), (+)-pinoresinol di-O-ß-D-glucopyranoside (PDG) and (+)-pinoresinol 4'-O-ß-D-glucopyranoside (PG), in rat plasma. The preliminary steps in the plasma analysis were the addition of an internal standard and acidification (0.1 % formic acid), followed by protein precipitation with methanol. Separation of the active ingredients was performed on an ACQUITY UPLC® BEH C18 column (2.1 × 50 mm; internal diameter 1.7 µm) at a flow rate of 0.35 mL/min, with acetonitrile/water containing 0.1 % formic acid as the mobile phase. Detection was performed on a triple quadrupole tandem mass spectrometer via electrospray ionization source with positive and negative ionization modes. All calibration curves showed good linearity (r ≥ 0.997) over the concentration range with the low limit of quantification between 4.45 and 54.9 ng/mL. Precision was evaluated by intra- and inter-day assays, and the percentages of the relative standard deviation were all within 15 %. Extraction efficiency and matrix effect were 84.3-102.4 % and 98.1-112.2 %, respectively. The validated method was successfully applied to the pharmacokinetic study in rats after oral administration of E. ulmoides extract. The results indicate that the pharmacokinetic properties of GA differ from those of PCA, CA, PDG and PG, respectively.

[Analysis on pharmacokinetics-pharmacodynamics correlation of effective ingredients of Qing'e wan].

To study the pharmacokinetics of three active ingredients in Qing'e wan, namely geniposidic acid, psoralen and isopsoralen, in rats, in order to investigate their correlation in the anti-osteoporotic effect. The rats were taken blood from their eye sockets at different time points after being orally administered with raw and salt-processed Qing'e wan. Geniposidic acid, psoralen and isopsoralen in rats plasma were determined by means of UHPLC-MS/MS to draw the concentration-time curve. The proliferation rate of osteoblasts was taken as the pharmacodynamic index, and determined by MTT method to draw effect-time curve. In comparison between the effect-time curve and the concentration-time curve, the blood concentrations of geniposidic acid and psoralen were close to the peak when the cell proliferation rate reached its peak, indicating a good correlation between them. The peak blood concentration of isopsoralen was slightly lagging behind the peak of efficacy. According to the correlation analysis after fitting the effect-time curve and the concentration-time curve, salt-processed Qing'e wan had a better correlation than the raw one. The above experimental results showed that the effect-time curve and the concentration-time curve of geniposidic acid and psoralen had a good correlation, and the correlation of salt-processed Qing'e wan was better than the raw one.

[Effects of different preparation technologies on concentrations of puerarin and catalpol in plasma and brain of rats after oral administration].

To compare the effects of different preparation technologies on the concentrations of puerarin and catalpol in plasma and brain of rats after oral administration, in order to lay an experimental basis for developing new oral Zige preparations. The nanocrystal, self-microemulsions (tween-80 and Cremophor RH-40 as emulsifiers) and inclusion complex of HP-ß-CD containing puerarin and catalpol were prepared. The concentrations of puerarin and catalpol in plasma and brain of rats after oral administration were determined by HPLC-MS/MS method. The pharmacokinetic parameters and brain target index were compared. The results showed that preparation technologies had different influences on the concentrations of puerarin and catalpol in plasma and brain. The self-microemulsion (tween-80) could significantly increase the oral absorption of puerarin than other technologies(P<0.05), and inclusion complex could remarkably increase the oral absorption of catalpol than nanocrystal(P<0.01). For puerarin, the brain targeting index of inclusion complex was the highest (P<0.05); but for catalpol, the brain targeting index of inclusion complex and self-microemulsions were both higher than nanocrystal (P<0.05). The self-microemulsion(tween-80) had the highest AUCbrain of puerarin than other groups (P<0.01); the inclusion complex had the highest AUCbrain for catalpol, but there was no significant difference compared with self-microemulsions. In conclusion, the self-microemulsion (tween-80) technology could increase the amount of puerarin and catalpol in brain, and was expected to be used in new oral Zige preparations.

[Study on quality standard of Eucommia ulmoides based on absorbed active components in rat plasma].

The method was established for determination of geniposidic acid, chlorogenic acid, pinoresinoldiglucoside, which are three kinds of constituents of Eucommia ulmoides absorbed into the blood components. LC-MS/MS technique was applied to determine the blood components of the bloodstream after administration of E. ulmoides extract. At the same time, HPLC was used for detection of the ingredients content of the blood sample from 23 batches of E. ulmoides. The results showed that geniposidic acid, chlorogenic acid and pinoresinoldiglucoside are prototype into the blood in rats after oral administration of E. ulmoides extract, The linear range of geniposidic acid, chlorogenic acid and pinoresinoldiglucoside was good, and the average recoveries geniposidic acid, chlorogenic acid and pinoresinoldiglucoside were 98.69%, 100.8% and 98.39%, respectively. The method is simple and feasible with good reproducibility.

Comparative pharmacokinetics of catalpol and acteoside in normal and chronic kidney disease rats after oral administration of Rehmannia glutinosa extract.

In this study, a sensitive and robust ultra-performance liquid chromatography-mass spectrometry method with multiple-reaction monitoring mode was developed, validated, and applied to determine pharmacokinetics of catalpol and acteoside in normal and doxorubicin-induced chronic kidney disease rats after oral administration of Rehmannia glutinosa extract. The lower limits of quantification for catalpol and acteoside in rat plasma were 2.62 and 0.61 ng/mL, with a signal-to-noise ratio of ≥10. Precision and accuracy studies showed that catalpol and acteoside plasma concentrations were within the 10% range in all studies. The extraction recoveries of catalpol and acteoside were both >68.24% and the matrix effects ranged from 96.59 to 101.62%. The method was successfully applied to the pharmacokinetic study of catalpol and acteoside after oral administration of RG extract to normal and model rats, respectively. This study might further support the traditional use of RG to treat kidney diseases clinically.

A pre-clinical pharmacokinetic study in rats of three naturally occurring iridoid glycosides, Picroside-I, II and III, using a validated simultaneous HPLC-MS/MS assay.

A selective and sensitive high-performance liquid chromatography-electro-spray ionization tandem mass spectrometry (LC-ESI-MS/MS) method was developed for the simultaneous quantitative determination of Picroside-I, II, and III in rat plasma and tissue homogenate to aid the pre-clinical studies. The chromatographic separation was performed on a Hypersil GOLD AQ C18 column using a gradient elution program with a mobile phase consisting of 2mM ammonium acetate and acetonitrile. The detection was achieved using a triple quadrupole tandem MS in negative ionization multiple reaction monitoring (MRM) mode. One-step protein precipitation was selected for plasma and tissue sample preparation while liquid-liquid extraction failed to achieve satisfactory recoveries. The calibration curves of all three analytes in either plasma or tissue homogenate showed good linearity over the concentration range of 0.5-500ng/mL with a limit of quantitation at 0.5ng/mL. Both the intra- and inter-day accuracy and precision were within ±10%. The extraction recoveries were >70%, and the relative matrix effect ranged from 80.4% to 107.4% in all the biological samples. All the analytes were stable in matrices for at least 24h at room temperature, or 21 days in frozen. Three freeze/thaw cycles did not cause degradation. The method was successfully applied for quantification of the three iridoid glycosides in the collected plasma and various tissues following intravenous administration in rats. Picroside-I, II, and III were all eliminated rapidly with large volume of distribution. Among the three glycosides, Picroside-II showed the highest liver uptake, and only Picroside-I and II were found to get across the blood brain barrier (BBB). These results were consistent with their hepatoprotective or neuroprotective effects reported clinically. With the aid of the efficient and reliable simultaneous LC-ESI-MS/MS assay this pharmacokinetic study provided insights into their therapeutic targets of these three iridoid glycosides as well as valuable experimental basis for an expansion of their clinical indications.

Two main metabolites of gentiopicroside detected in rat plasma by LC-TOF-MS following 2,4-dinitrophenylhydrazine derivatization.

The metabolism of gentiopicroside in vivo was studied by LC/MS following 2,4-dinitrophenylhydrazine derivatization for the first time. The ionization efficiency of the major metabolites erythrocentaurin and gentiopicral were greatly enhanced by the new analytical method developed, and they were successfully detected in rat plasma after oral administration of gentiopicroside. Methyl 4-formylbenzoate was used as the internal standard to quantify erythrocentaurin and gentiopicral in rat plasma in negative mode by UPLC-TOF-MS. It was found that erythrocentaurin reached the maximum plasma concentration of 625.2±246.3 ng/mL at about 2 h and gentiopicral reached the maximum plasma concentration of 157.6±86.6 ng/mL at about 4 h after oral administration of gentiopicroside at a dose of 200 mg/kg. The metabolic pathway of gentiopicroside to erythrocentaurin and gentiopicral was proposed. The monoterpene compound gentiopicroside was found to be metabolized to dihydroisocoumarin in vivo which may be responsible for the pharmacological effect of gentiopicroside. The results may shed light on clinical efficacy of gentiopicroside and the new analytical method developed may assist in studies for the metabolism of other natural iridoids and secoiridoids in vivo.

New analytical method for the study of metabolism of swertiamarin in rats after oral administration by UPLC-TOF-MS following DNPH derivatization.

The metabolism of swertiamarin in vivo was studied by LC-MS following 2,4-dinitrophenylhydrazine derivatization. The ionization efficiency of the main metabolite erythrocentaurin was greatly enhanced by the new analytical method developed, and erythrocentaurin was successfully detected for the first time in rat plasma after oral administration of swertiamarin. Methyl 4-formylbenzoate was used as the internal standard to quantify erythrocentaurin in rat plasma in negative mode by UPLC-TOF-MS, and it was found that erythrocentaurin reached the maximum mean plasma concentration of 425.8 ± 127.6 ng/mL at about 2 h after oral administration of swertiamarin at a dose of 200 mg/kg. A metabolic pathway of swertiamarin to erythrocentaurin was proposed. Swertiamarin is first hydrolyzed by bacterial ß-glucusidase to give the aglycone, which is readily converted to erythrocentaurin. The monoterpene compound swertiamarin was found to be metabolized to dihydroisocoumarin and alkaloid compounds in vivo, which may be responsible for the pharmacological effect of swertiamarin. The results may shed light on the clinical efficacy of swertiamarin and the new analytical method may assist in studies for the metabolism of other natural iridoids and secoiridoids in vivo.

Development and validation of high liquid performance chromatography-tandem mass spectrometry method for simultaneous determination of geniposidic acid and aucubin in rat plasma for pharmacokinetic study after oral administration of Du-zhong tea extract.

A specific and sensitive high performance liquid chromatography coupled with tandem mass spectrometric (HPLC-MS/MS) method was developed and validated for the simultaneous determination of geniposidic acid and aucubin in rat plasma after oral administration of Du-zhong tea extract. The plasma samples were pretreated by protein precipitation with methanol and the chromatographic separation was performed on a Hypersil C18 column (4.6 mm×250 mm, 5 µm), using a gradient mobile phase system of water-methanol (0.05% formic acid). The detection was accomplished by multiple-reaction monitoring (MRM) scanning via electrospray ionization source operating in the negative ionization mode. The linear range was 1-1,000 ng/mL for geniposidic acid and 0.2-200 ng/mL for aucubin, respectively. The accuracy (relative error, R.E.%) were between -5.40 and 5.00%, while the intra-day and inter-day precisions were less than 7.95 and 7.87% for the two analytes, respectively. The method was fully validated for the sensitivity, selectivity, recovery, matrix effect and stability. Then this method was successfully applied to the pharmacokinetic study of geniposidic acid and aucubin after oral administration of Du-zhong tea extract to rats and the results indicated that this HPLC-MS/MS assay is a valuable method for the pharmacokinetic study of geniposidic acid and aucubin in rat plasma.

LC/MS/MS determination and pharmacokinetic studies of six compounds in rat plasma following oral administration of the single and combined extracts of Eucommia ulmoides and Dipsacus asperoides.

AIM: To establish and apply a new LC/MS/MS method for the simultaneous, quantitative determination of six ingredients, aucubin (AU), geniposide (GP), geniposidic acid (GPA), pinoresinol diglucoside (PDG), secologanin (SLG), and loganin (LG) in single and combined extracts of Eucommia ulmoides and Dipsacus asperoides. METHOD: Using the LC/MS/MS-ESI(-)-MRM mode to detect the six compounds, chromatographic separation was achieved on an Agilent Eclipse plus C18 column, and the mobile phase consisted of solvent A (CH3CN) and solvent B (H2O containing 0.01% CH3COOH V/V). RESULTS: This method was successfully applied to quantify the six compounds in rat plasma after oral administration, and showed good precision, accuracy, reproducibility, and linear regression (r(2)>0.99). CONCLUSION: The results showed that following the use of the two medicinal plants, for AU and GP, the values of Cmax markedly increased, and the values of cmax markedly decreased. It was found that the compatibility of the medicinal plants might affect their pharmacokinetic properties of their constituents.