Application of Electro-Activated Dissociation Fragmentation Technique to Identifying Glucuronidation and Oxidative Metabolism Sites of Vepdegestrant by Liquid Chromatography-High Resolution Mass Spectrometry.

Drug metabolite identification is an integrated part of drug metabolism and pharmacokinetics studies in drug discovery and development. Definitive identification of metabolic modification sides of test compounds such as screening metabolic soft spots and supporting metabolite synthesis are often required. Currently, liquid chromatography-high resolution mass spectrometry is the dominant analytical platform for metabolite identification. However, the interpretation of product ion spectra generated by commonly used collision-induced disassociation (CID) and higher-energy collisional dissociation (HCD) often fails to identify locations of metabolic modifications, especially glucuronidation. Recently, a ZenoTOF 7600 mass spectrometer equipped with electron-activated dissociation (EAD-HRMS) was introduced. The primary objective of this study was to apply EAD-HRMS to identify metabolism sites of vepdegestrant (ARV-471), a model compound that consists of multiple functional groups. ARV-471 was incubated in dog liver microsomes and 12 phase I metabolites and glucuronides were detected. EAD generated unique product ions via orthogonal fragmentation, which allowed for accurately determining the metabolism sites of ARV-471, including phenol glucuronidation, piperazine N-dealkylation, glutarimide hydrolysis, piperidine oxidation, and piperidine lactam formation. In contrast, CID and HCD spectral interpretation failed to identify modification sites of three O-glucuronides and three phase I metabolites. The results demonstrated that EAD has significant advantages over CID and HCD in definitive structural elucidation of glucuronides and phase I metabolites although the utility of EAD-HRMS in identifying various types of drug metabolites remains to be further evaluated. SIGNIFICANCE STATEMENT: Definitive identification of metabolic modification sites by liquid chromatography-high resolution mass spectrometry is highly needed in drug metabolism research, such as screening metabolic soft spots and supporting metabolite synthesis. However, commonly used collision-induced dissociation (CID) and higher-energy collisional dissociation (HCD) fragmentation techniques often fail to provide critical information for definitive structural elucidation. In this study, the electron-activated dissociation (EAD) was applied to identifying glucuronidation and oxidative metabolism sites of vepdegestrant, which generated significantly better results than CID and HCD.

Relationship between body composition and pulmonary function in the general population-a cross-sectional study in Ningxia.

Studies considering the relationship between non-obesity-related body composition and lung function are few; therefore, this study aimed to explore these correlations and effects. This cross-sectional study conducted in rural Qingtongxia City and Pingluo County, Ningxia, China, included 776 participants aged 30-75 years. Body composition and lung function were measured using direct segmental multifrequency bioelectrical impedance analysis and a digital spirometer, respectively. Their correlation was assessed using partial correlation analysis, controlling for age and smoking status, and the body composition effect on lung function was analyzed using binomial logistic regression analysis. The body components total body water content, protein content, mineral content, muscle mass, fat-free mass (FFM), skeletal muscle mass, basal metabolic volume, and chest circumference (CC) positively correlated with pulmonary function (forced vital capacity and forced expiratory volume in one second) in both sexes. Neck circumference and hip circumference positively correlated with pulmonary function in women. Additionally, lung function declines more slowly in women (odds ratio [OR] = 0.66, 95% confidence interval [CI] = 0.44-0.98, p = 0.04); CC (OR = 0.92, 95% CI = 0.86-0.98, p = 0.01) increased as a protective factor for decreased lung function. Increased waist circumference (OR = 1.04, 95% CI = 1.00-1.09, p = 0.04) was a risk factor for reduced lung function. FFM contains body composition indicators positively correlating with lung function, excluding fat-related body composition. Abdominal obesity increases the risk of decreased lung function.

Association of Body Composition with Pulmonary Function in Ningxia: The China Northwest Cohort.

Background: In recent decades, obesity has become an epidemic worldwide and is a risk factor for many chronic diseases. Lung function is also a predictor of various chronic diseases. However, research results on the association between obesity and lung function are inconsistent and few studies have evaluated the association between central obesity indicators and lung function. Therefore, this study explored the correlation between central obesity and lung function. Methods: This study is a cross-sectional study. The basic participant characteristics were collected by questionnaire. A tape measure was used to measure waist circumference (WC) and hip circumference (HC). Body fat percentage was measured using an InBody370. Lung function parameters were measured using a digital spirometer connected to a computer (Chestgraph HI-101). R (R4.0.5) software was used for data analysis. A generalized linear model was used to analyze the association between obesity and lung function. Results: This study found that body mass index (BMI) adjusted for WC was negatively correlated with forced vital capacity (FVC) (ß=-0.05 [-0.06, -0.03] in men, ß=-0.05 [-0.07, -0.04] in women) and forced expiratory volume in 1 s (FEV1)(ß=-0.02 [-0.03, -0.00] in men, ß=-0.03 [-0.04, -0.02] in women). Body fat percentage was negatively correlated with FVC (ß=-0.01 [-0.01, -0.01] in men, ß=-0.01 [-0.01, -0.00] in women). Conclusion: Central obesity and combined central and general obesity were more strongly positively correlated with lung function. WC-adjusted BMI was negatively correlated with lung function. Body fat percentage was negatively correlated with lung function.

Effects of exposure to fine particulate matter on the decline of lung function in rural areas in northwestern China.

Our aim was to clarify the main factors associated with lung function and to analyze the correlation between fine particulate matter (PM2.5) and lung function in a rural Chinese population. We analyzed data of 5195 participants in the China Northwest Natural Population Cohort: Ningxia Project who were ≥ 30 years old. They were recruited from 2018 to 2019, underwent spirometry during the physical examination, and completed a self-report questionnaire. A satellite-based spatiotemporal model was used to estimate the 2-year average PM2.5 exposure based on participants' home addresses. A generalized linear mixed model was used to test the relationship between PM2.5 concentration and lung function. Sex, age, exposure to cooking oil fumes, and occupational exposure were negatively correlated (P < 0.05) with forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). Educational status, economic level, tea consumption, and alcohol consumption were positively correlated (P < 0.05) with FVC and FEV1. The adjusted results of each model revealed that FVC and FEV1 decreased with increased exposure to PM2.5. There was a strong negative correlation between a PM2.5 concentration of 35.66 µg/m3 and FVC, FEV1, and FEV1/FVC, with unadjusted hazard ratios of - 0.06 (95% confidence interval, - 0.10 to - 0.01), - 0.13 (- 0.17 to - 0.10), and - 22.10 (- 24.62 to - 19.26), respectively. In conclusion, long-term exposure to high concentrations of ambient PM2.5 is related to reduce lung function among people in rural areas in northwestern China.

Long non-coding RNA expression in silicosis and MRAK050699 function in epithelial-mesenchymal transition.

Silicosis is a lung fibrotic disease caused by chronic silica exposure. Aberrations in long non-coding RNA (lncRNA) expression are associated with fibrotic diseases, but the role of lncRNAs in silicosis pathogenesis remains unclear. Here, we investigated the expression of lncRNAs during silicosis and the role of MRAK050699 in epithelial-mesenchymal transition (EMT). Differentially expressed lncRNAs in the lung tissues of normal and silicosis rats were compared, and their biological effects were determined using the Gene Ontology term and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. There were 1077 differentially expressed lncRNAs (378 upregulated and 699 downregulated). MRAK052509, MRAK139674, AY539881, MRAK050699, XR_6113, and BC167061 were selected to verify expression in silicosis rats using quantitative reverse transcription polymerase chain reaction. MRAK050699 was knocked down in rat alveolar type II epithelial cells, and the molecular mechanism of transforming growth factor-ß (TGF-ß)-induced EMT in these cells was studied. All selected lncRNAs were upregulated in the silicosis rats, consistent with the sequencing results. MRAK050699 knockdown inhibited EMT of RLE-6TN cells by regulating the TGF-ß/Smad3 signaling pathway. Thus, the differential expression of lncRNAs is related to silicosis development, and MRAK050699 plays an important role in EMT, suggesting a potential therapeutic target for silicosis.

Parallel Metabolomic and Transcriptomic Analysis Reveals Key Factors for Quality Improvement of Tea Plants.

As one of the most popular beverages globally, tea has enormous economic, cultural, and medicinal importance that necessitates a comprehensive metabolomics study of this species. In this study, a large-scale targeted metabolomics analysis on two types of leaf tissues of nine tea cultivars from five representative geographical origins within China was carried out using the liquid chromatography-mass spectrometry technique. RNA-seq-based transcriptomic analysis was in parallel conducted on the same samples, and gene expression and metabolic differentiation between tissues as well as between the multiple tea cultivars were investigated. The data obtained provide an accessible resource for further studies of naturally occurring metabolic variation of tea plants, which will aid in thoroughly interpreting the underlying genetic and molecular mechanisms of biosynthesis of specialized metabolites in this critical species. Candidate genes including a transcription factor (CsMYB5-like), which were highly correlated with both the content of flavonoids and the expression level of genes participating in the phenylpropanoid and flavonoid biosynthesis pathway, were identified as potential targets for quality improvement of tea.

Metabolomic evaluation of Euphorbia pekinensis induced nephrotoxicity in rats.

CONTEXT: Euphorbia pekinensis Rupr. (Euphorbiaceae) has long been used in the Orient, while its clinical use was limited due to its nephrotoxic effect. OBJECTIVE: The possible mechanism of nephrotoxicity of Euphorbia pekinensis (EPR) and its related constituents were investigated. MATERIALS AND METHODS: Petroleum ether (PE), acetic ether (AE) and n-butanol (BUT) extracted sections of EPR were separately given to Wistar rats by gavage at the dose of 3 g/kg/day for 10 weeks to determine the nephrotoxic section of EPR. Then, renal metabolic profiling of EPR after oral administration of nephrotoxic section was investigated and its related constituents were identified by LC/Q-TOF-MS method. RESULTS: The average values of creatinine (CREA) in PE, AE, BUT and control groups were 76.54 ± 9.52, 54.12 ± 10.34, 51.33 ± 5.19 and 48.23 ± 6.67 µmol/L. The average values of blood urea nitrogen (BUN) in PE, AE, BUT and control groups were 15.25 ± 3.37, 8.32 ± 0.89, 9.22 ± 1.78 and 8.47 ± 1.33 mmol/L, respectively. Only kidney section of rats in PE group showed that glomeruli had cellular or fibrocellular crescents. Renal metabolic profiling showed disturbed metabolic pathways of purine, amino acid, phospholipids and sphingolipids in EPR nephrotoxicity. A total of 25 compounds [(-)-(1S)-15-hydroxy-18-carboxycembrene is a new compound] in PE section and 10 compounds in rat serum after administration of PE section were identified. CONCLUSIONS: This is the first time that the toxic compounds of PER and action mechanism of EPR nephrotoxicity were explored to provide a new reference for studying the toxic components of Traditional Chinese Medicine (TCM).

Characterization of metabolites of larotaxel in rat by liquid chromatography coupled with Q exactive high-resolution benchtop quadrupole orbitrap mass spectrometer.

1. Liquid-chromatography (LC) high-resolution (HR) mass spectrometry (MS) analysis can record HR full scans for drug metabolism studies. Larotaxel is a taxane analog that has the potential for the treatment of various types of cancer. 2. In this study, the metabolism of larotaxel was evaluated after an intravenous dose of 8 mg/kg via the caudal vein to healthy rats and its metabolites were characterized by high performance liquid chromatography coupled with a Q Exactive high-resolution benchtop quadrupole orbitrap mass spectrometer. Rat bio-samples were separated on a Capcell Pak C18 column (2.1 i.d. × 100 mm; 2.7 µm) with mobile phase of acetonitrile and water. 3. As a result, a total of 34 metabolites were detected and identified by comparing the molecular masses, retention times and spectral patterns of the analytes with those of the parent drug. Three metabolites were confirmed by comparison with reference substances. 4. The prominent metabolites were mainly hydroxyl, dihydroxyl, trihydroxyl and 10-desacetyl analogs of larotaxel, some of which resulted from oxidation of the tert-butyl groups on the side chain and further oxidation and cyclization of the tert-butyl hydroxylated metabolites.

An analytical strategy to investigate Semen Strychni nephrotoxicity based on simultaneous HILIC-ESI-MS/MS detection of Semen Strychni alkaloids, tyrosine and tyramine in HEK 293t cell lysates.

A Previous metabolomics study has demonstrated that tyrosine metabolism might be disrupted by treating with Semen Strychni on the cell nephrotoxicity model. To investigate the relationship between Semen Strychni alkaloids (SAs) and endogenous tyrosine, tyramine under the nephrotoxicity condition, an HILIC-ESI-MS/MS based analytical strategy was applied in this study. Based on the established Semen Strychni nephrotoxicity cell model, strychnine and brucine were identified and screened as the main SAs by an HPLC-Q Exactive hybrid quadrupole Orbitrap mass system. Then, a sensitive HILIC-ESI-MS/MS method was developed to simultaneously monitor strychnine, brucine, tyrosine and tyramine in cell lysate. The analytes were separated by a Shiseido CAPCELL CORE PC (150mm×2.1mm, 2.7µm) HILIC column in an acetonitrile/0.1% formic acid gradient system. All the calibration curves were linear with regression coefficients above 0.9924. The absolute recoveries were more than 80.5% and the matrix effects were between 91.6%-107.0%. With the developed method, analytes were successfully determined in cell lysates. Decreased levels of tyrosine and tyramine were observed only in combination with increased levels of SAs, indicating that the disturbance of tyrosine metabolism might be induced by the accumulation of SAs in kidney cell after exposure of Semen Strychni. The HILIC-ESI-MS/MS based analytical strategy is a useful tool to reveal the relationships between the toxic herb components and the endogenous metabolite profiling in the toxicity investigation of herb medicines.

Nephrotoxicity evaluation of a new cembrane diterpene from Euphorbiae pekinensis Radix with HEK 293T cells and the toxicokinetics study in rats using a sensitive and reliable UFLC-MS/MS.

(-)-(1S)-15-Hydroxy-18-carboxycembrene, the first cembrane-type diterpenoid found in the family Euphorbiaceae, isolated from Euphorbiae pekinensis Radix, was identified to be nephrotoxic using HEK 293T cells. Tests on cell morphology, cell viability and biochemical markers about oxidation stress were carried out using inverted microscope, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and commercial kits respectively, which proved the diterpene time- and dose-dependently decreased cells proliferation. Besides, a sensitive and robust UFLC-MS/MS method was developed and fully validated to investigate the in vivo behavior in rats of the diterpene after oral administration of Euphorbiae pekinensis Radix extracts at a dosage of 9g/kg. The method showed a good linearity in tested range (3-1500ng/mL) with acceptable accuracy and precision. The recovery of the diterpene was more than 85% and the matrix effect was within ±20%. The toxicokinetics parameters indicate the diterpene reached Cmax quickly and slowly eliminate. The study proved the newly found diterpene was one of the nephrotoxic substances of Euphorbiae pekinensis Radix and revealed its toxicokinetics behavior.

[Investigation of Variations of Components in Euphorbia pekinensis Root and Its Processed Products Based on Plant Metabolomics].

Objective: An ultra-performance liquid chromatography coupled with mass spectrometry( UPLC-MS) based on plant metabonomics method was proposed and developed for the investigation of variations of components in Euphorbia pekinensis root after herb-processing procedure. Methods: The samples were separated on an Agilent XDB C8column( 150 mm × 4. 6 mm,5 µm) using a mobile phase composed of 0. 1% formic acid in acetonitrile and 0. 1% formic acid in water under gradient elution. Analysis was performed with electrospray ionization( ESI) interface in negative ion mode within the m / z range of 100 ~ 900. The data were subjected to principal component analysis( PCA). Results: Seven components were screened out which could be considered as potential chemical markers to discriminate Euphorbia pekinensis root from its processed products. Six of the chemical markers were identified as 3,3'-di-O-methylellagic acid-4'-O-ß-D-xylopyranoside,3,3'-di-O-methyl ellagic acid,(-)-( 1S)-15-hydroxy-18-carboxycembrene,ellagic acid,brevifolincarboxylic acid and gallic acid. Conclusion: The method has been successfully applied in distinguishing Euphorbia pekinensis root from its processed products,which predicts the potential substances contributed to the toxicity reducing effect of traditional processing procedure on the herb.

Comparative pharmacokinetics of cyclophosphamide administration alone and combination with vitamin B6 in rats.

A fast and sensitive high performance liquid chromatography coupled with mass spectrometry (LC-MS) method was developed and validated for the determination of cyclophosphamide in rat plasma with and without the combination of vitamin B6. After addition of digoxin used as the internal standard (IS), plasma samples were extracted by protein precipitation with acetonitrile (1:1, v/v), and the analytes were separated by a Kromasil C18 column (150 × 4.6 mm, 5 µm) with a mobile phase of acetonitrile-0.1% formic acid water (40:60, v/v). The detection of the analyte was monitored in positive electrospray ionization by selected ion monitoringmode. The linear range was 0.01-40 µg/mL for cyclophosphamide. The intra- and inter-day precision and accuracy were all <15%. The extraction recoveries and matrix effects of the analyte and IS were all within acceptable range. The selectivity of the method was satisfactory with no endogenous interference. The results for stabilities of cyclophosphamide and IS under various conditions were all within the acceptance criteria. The validated method was successfully applied to evaluate the drug-drug interaction of cyclophosphamide and vitamin B6 in rat plasma. The results showed no differences of pharmacokinetic behaviors between cyclophosphamide administration with and without vitamin B6.

An LC-MS method for simultaneous determination of five iridoids from Zhi-zi-chi Decoction in rat brain microdialysates and tissue homogenates: towards an in depth study for its antidepressive activity.

Zhi-zi-chi Decoction has been clinically utilized for the treatment of depression for more than thousand years. In order to investigate the possible bioactive components that could pass through the blood brain barrier (BBB) and the mechanism of antidepressant, a sensitive LC-MS method was developed to detect the ingredients (geniposide, scandoside methyl ester, gardenoside, deacetyl asperulosidic acid methyl ester and genipin-1-ß-gentiobioside) in rat brain microdialysates and tissue homogenates samples (hippocampus, hypothalamus, premotor cortex, striatum, oblongata and cerebellum). Method development and validation are described in terms of calibration curves, extraction yield, lower limit of quantification (LLOQ), precision, accuracy, intra- and inter-day variability, which are in accordance with the requirements. Microdialysis in hippocampus demonstrated that the five iridoids possessed complete pharmacokinetic process while brain tissue homogenate method testified the distribution regularity in brain. The work clarified that the five iridoids, as antidepressant ingredients, could pass through the BBB, distribute targeted and possess complete pharmacokinetics in brain. These observations, along with the large database of rat brain microdialysates and tissue homogenates data, could enable future efforts aimed to improve our understanding of the relationship between bioactive ingredients and clinical therapy of depression.

Identification and analysis of alkaloids in cortex Phellodendron amurense by high-performance liquid chromatography with electrospray ionization mass spectrometry coupled with photodiode array detection.

Alkaloids from Cortex Phellodendron amurense Rupr. were identified to determine the material basis for the bioactivity of this herb. HPLC-ESI-MS with photodiode array detection coupled to XCharge C18 column was applied to analyze the alkaloids qualitatively and quantitatively. A total of 37 alkaloids were identified and tentatively characterized from the ethanol extract by online ESI-MS(n) fragmentation and UV spectral analysis. A total of ten alkaloids, including four novel natural products, were tentatively identified for the first time in P. amurense. The fragmentation pathways for certain compounds were analyzed. The contents of a pair of isomers (columbamine and jatrorrhizine) and four main alkaloids (phellodendrine, magnoflorine, berberine, and palmatine) were simultaneously quantified using the aforementioned method. Results showed that the newly discovered and known components of P. amurense were helpful in determining the material basis for the bioactivity of the herb. The application of the XCharge C18 column is a suitable and practical method for the isolation of alkaloids in plants.

Simultaneous determination of five free and total flavonoids in rat plasma by ultra HPLC-MS/MS and its application to a comparative pharmacokinetic study in normal and hyperlipidemic rats.

A simple and rapid ultra-high performance liquid chromatography-tandem mass spectrometry (uHPLC-MS/MS) method has been developed for the simultaneous determination of five free flavonoids (amentoflavone, isorhamnetin, naringenin, kaempferol and quercetin) and their total (free and conjugated) forms, and to compare the pharmacokinetics of these active ingredients in normal and hyperlipidemic rats. The free and total forms of these flavonoids were extracted by liquid-liquid extraction with ethyl acetate. The conjugated flavonoids were deconjugated by the enzyme ß-Glucuronidase and Sulfatase. Chromatographic separation was accomplished on a ZORBAX Eclipse XDB-C8 USP L7 column using gradient elution. Detection was performed on a 4000Q uHPLC-MS/MS system from AB Sciex using negative ion mode in the multiple reaction monitoring (MRM) mode. The lower limits of quantification were 2.0-5.0ng/mL for all the analytes. Intra-day and inter-day precision were less than 15% and accuracy ranged from -9.3% to 11.0%, and the mean extraction recoveries of analytes and internal standard (IS) from rat plasma were all more than 81.7%. The validated method was successfully applied to a comparative pharmacokinetic study of five free and total analytes in rat plasma. The results indicated that the absorption of five total flavonoids in hyperlipidemia group were significantly higher than those in normal group with similar concentration-time curves.

Determination of larotaxel and its metabolites in rat plasma by liquid chromatography-tandem mass spectrometry: application for a pharmacokinetic study.

A sensitive and reliable high-performance liquid chromatography-mass spectrometry (LC-MS/MS) method was developed and validated for determination of larotaxel (LTX) and its active metabolites (M1, M2 and M3) in rat plasma. The analytes were extracted by one-step protein precipitation and separated on a Capcell pak C18 column (2.0 mm × 100 mm; 2 µm; Shiseido) using methanol-water as mobile phase at a flow rate of 0.2 mL min(-1) in gradient mode. The method was validated over the concentration range of 2.5-1250 ng mL(-1) for LTX and 1.0-500 ng mL(-1) for M1, respectively, while M2 and M3 were monitored semi-quantitatively and quantified as M1 equivalents. Intra- and inter-day accuracy and precision were within the acceptable limits of less than 15% at all concentrations. Coefficients of correlation (r) for the calibration curves were more than 0.99 for all analytes. The quantitation method was successfully applied for simultaneous estimation of LTX and its metabolites in a pharmacokinetic study after oral administration at different doses of 10, 20, and 40 mg/kg and intravenous administration at the dose 10 mg/kg to Wistar rats, respectively. The results indicated that larotaxel has linear pharmacokinetic characteristics in rats after oral administration and its absolute bioavailability in rats was 12.24%.

A new cytotoxic cembrane diterpene from the roots of Euphorbia pekinensis Rupr.

A new cembrane diterpene, named (-)-(1S)-15-hydroxy-18-carboxycembrene, was isolated from petroleum ether extract of the roots of the Euphorbia pekinensis Rupr. To our knowledge, this compound is the first cembrane-type diterpenoid to be found in the family Euphorbiaceae. The structure was elucidated as (-)-(1S)-15-hydroxy-cembra -2E, 4Z, 7E, 11E-tetraen-18-oic acid by a combination of IR, HR-ESIMS, 1D- and 2D-NMR techniques. (-)-(1S)-15-hydroxy-18-carboxycembrene showed cytotoxic activity against all five human cancer cell lines tested.

A fast, sensitive, and high-throughput method for the simultaneous quantitation of three ellagitannins from Euphorbiae pekinensis Radix in rat plasma by ultra-HPLC-MS/MS.

A fast, sensitive, and high-throughput ultra-HPLC-MS/MS method has been developed and validated for the simultaneous determination of three main active constituents of Euphorbiae pekinensis Radix in rat plasma. After addition of the internal standard, plasma samples were extracted by liquid-liquid extraction with ethyl acetate/isopropanol (1:1, v/v) and separated on a CAPCELL PAK C18 column (100 × 2.0 mm, 2 µm, Shiseido, Japan), using a gradient mobile phase system of methanol/water. The detection of the analytes was performed on a 4000Q UHPLC-MS/MS system with turbo ion spray source in the negative ion and multiple reaction-monitoring mode. The linear range was 1.0-1000 ng/mL for 3,3'-di-O-methyl ellagic acid-4'-O-ß-D-glucopyranoside (i), 1.5-1500 ng/mL for 3,3'-di-O-methyl ellagic acid-4'-O-ß-D-xylopyranoside (ii), and 5.0-5000 ng/mL for 3,3'-di-O-methyl ellagic acid (iii). The intra- and interday precision and accuracy of all the analytes were within 15%. The extraction recoveries of the three analytes and internal standard from plasma were all more than 80%. The validated method was first successfully applied to the evaluation of pharmacokinetic parameters of compounds 1, 2, and 3 in rat plasma after intragastric administration of the Euphorbiae pekinensis Radix extract.

A sensitive liquid chromatographic-mass spectrometric method for simultaneous quantification of six iridoid glycosides from Zhi-zi-chi Decoction in rat plasma and its application to a pharmacokinetic study.

A sensitive liquid chromatographic-mass spectrometric (LC-MS) method was developed and validated for simultaneous determination of geniposide, geniposidic acid, scandoside methyl ester, gardenoside, deacetyl asperulosidic acid methyl ester and genipin-1-ß-gentiobioside after oral administration of Zhi-zi-chi Decoction in rat plasma. The six iridoid glycosides were extracted from plasma samples by protein precipitation, and then separated on an Apollo C18 column (250 mm × 4.6mm, 5 µm) through the application of a gradient elution. The analytes were monitored in positive electrospray ionization by selected ion monitoring mode (SIM). The lower limits of quantitation (LLOQ) of the six analytes were all lower than 6 ng/mL. The accuracy (relative error, RE%) was between -7.0% and 9.9%, while the intra- and inter-day precisions (relative standard deviation, RSD%) were less than 6.3% and 9.8% for the six analytes, respectively. The developed method was successfully applied to a comparative pharmacokinetic study of the six iridoids in rat plasma after oral administration of Zhi-zi-chi Decoction and Gardenia jasminoides extract.