The metabolite profiling of 3,4-dicaffeoylquinic acid in Sprague–Dawley rats using ultra-high performance liquid chromatography equipped with linear ion trap-Orbitrap MS

3,4-Dicaffeoylquinic acid (3,4-DiCQA) is a dicaffeoylquinic acid that possesses antioxidant, anti-inflammatory, antibacterial, antiviral, anticancer, hypoglycemic, hypotensive, and hepatoprotective activities. This study developed a rapid and reliable method using ultra-high performance liquid chromatography equipped with linear ion trap-Orbitrap MS to identify the metabolites of 3,4-DiCQA in rat plasma, urine, feces, and tissues. The metabolic profile of 3,4-DiCQA was determined after an oral administration of 200 mg/kg to rats. A strategy of full scan-parent ions list acquisition coupled to diagnostic product ion analysis for screening and identification of target metabolites was used. A total of 67 metabolites, combined with accurate mass measurement, diagnostic ions, neutral losses, and reference standards, were observed and characterized for the first time. The results indicated that hydrolysis, methylation, hydrogenation, hydration, dehydroxylation, dehydrogenation, sulfate conjugation, and glucuronide conjugation were the major metabolic reactions of 3,4-DiCQA in vivo.     

Highly sensitive determination of new metabolite in rat plasma after oral administration of swertiamarin by liquid chromatography/time of flight mass spectrometry following picolinoyl derivatization

The metabolism of swertiamarin (STM) in vivo was studied by LC/MS following picolinoyl derivatization. Incubation of erythrocentaurin (ECR), one of the main in vitro metabolites of STM by intestinal bacteria, with liver microsome indicated that STM may be metabolized to the final metabolite 3,4‐dihydro‐5‐(hydroxymethyl) isochroman‐1‐one (HMIO) in vivo. After hydrolyzation with sulfatase, HMIO was successfully detected in rat plasma after oral administration of STM by LC/MS following picolinoyl derivatization. 4‐Methoxyphenyl methanol was used as the internal standard to quantify HMIO in rat plasma. The full metabolic pathway of STM in rats is proposed. STM is first hydrolyzed by bacterial β‐glucusidase to give aglycone, which is readily converted to ECR and nitrogen‐containing metabolite. ECR is further reduced to HMIO by both liver and intestinal bacteria and HMIO is finally converted to the new sulfate conjugate metabolite. The monoterpene compound STM was found to be metabolized to dihydroisocoumarin and alkaloid compounds in vivo, which may be responsible for the pharmacological effect of STM. The results may shed light on clinical efficacy of STM and the new analytical method developed may assist in studies of the metabolism of other natural iridoids and secoiridoids in vivo. Copyright © 2013 John Wiley & Sons, Ltd.     

GC-MS Assay For 9α, 15(S)-Dihydroxy-11-Oxo-thromba-5(Z), 13(E)-Dien-1-oic Acid

Abstract

The title compound (TXB₂?M) is a quantitative index of thromboxane A₂ synthesis in the human. We developed a method for its determination in urine based on the use of the ¹³C-labeled methyl ester derivative of the analyte as internal standard and GC-EIMS. the interassay coefficient of variation (CV) was 5.3% (N=4) and the intraassay CV ranged from 2.6 to 8.2% (N=3). the equation of the regression curve correlating the amounts added and recovered was Y=0.932X+3.99 (R=0.9947). the relative recovery of TXB₂?M from nine urine specimens was 99.8 ± 2.8% (mean ± SEM). the mean (±SD) 24-hr output in six healthy male subjects was 1371 ± 307 ng, and in six females it was 1176 ± 418 ng. Concentrations as low as 200 pg/ml of urine can easily be measured with this procedure if one uses 50 ml of urine for the analysis.     

Screening and identification of multiple constituents and their metabolites of Zhi‐zi‐chi decoction in rat urine and bile by ultra‐high‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry

Zhi‐zi‐chi decoction (ZZCD) is a classical formula widely used in Chinese clinical application. In the present study, a novel and efficient strategy has been developed for screening and identification of multiple constituents and their metabolites of ZZCD using ultra‐high‐performance liquid chromatography combined with triple time‐of‐flight mass spectrometry. The novel approach of an online data acquisition method dependent on multiple mass defect filter and dynamic background subtraction is combined with multiple data processing techniques. First, a total of 109 potential bioactive compounds were detected in ZZCD. Based on the same instrumental conditions, 100 compounds were found in rat biofluids after oral administration of ZZCD, including 61 original compounds of ZZCD as well as 39 metabolites. Conjugations with sulfate, glucuronate and amino acids were found as the predominant metabolic reaction of ZZCD. As more xenobiotics were detected in urine than those in bile were, it demonstrated that multiple components of ZZCD have undergone comprehensive renal excretion. This study reported the urinary and biliary excretion in rats after oral administration of ZZCD for the first time. The present study expands our knowledge about the constituents and metabolism of ZZCD, which could be very useful for further pharmacological and clinical studies of ZZCD.     

Characterization of isochlorogenic acid A metabolites in rats using high‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry

Isochlorogenic acid A is widely present in fruits, vegetables and herbal medicines, and is characterized by anti‐inflammatory, hepatoprotective and antiviral properties. However, little is known about its metabolic fate and pharmacokinetic properties. This study is thus designed to investigate the metabolic fate of isochlorogenic acid A. An analytical method based on high‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry (HPLC/Q‐TOF MS) was established to characterize the metabolites of isochlorogenic acid A in the plasma, urine and feces of rats. A total of 32 metabolites were identified. The metabolic pathways mainly include hydrolyzation, dehydroxylation, hydrogenation and conjugation with methyl, glucuronic acid, glycine, sulfate, glutathione and cysteine. Moreover, the pharmacokinetic profiles of all the circulating metabolites were investigated. M11 resulting from hydrolyzation, dehydroxylation and hydrogenation was the dominant circulating metabolite after the intragastric administration of isochlorogenic acid A. The results obtained will be useful for further study of elucidating potential bioactive metabolites which can provide better explanation of the pharmacological and/or toxicological effects of this compound.     

Nonlinear optical microscopy: Endogenous signals and exogenous probes

Nonlinear optical microscopy (NLOM) relies on nonlinear light–matter interactions to provide images from larger depths within biological structures compared to conventional confocal fluorescence microscopy. These nonlinear light–matter interactions include multiphoton excitation fluorescence (MPEF), second‐harmonic generation (SHG), coherent anti‐Stokes Raman scattering (CARS), and stimulated Raman scattering (SRS). This review discusses the theories of and instrumentation for various NLOM techniques, with a particular focus on endogenous signals and exogenous probes. These signals and probes expand the breadth of information that optical imaging can provide. We also discuss the application of NLOM in biomedical research, including tissue engineering, drug delivery and clinical diagnostics. Current technological limitations are also discussed.

     

Simple and rapid high-performance liquid chromatographic method for endogenous alpha-tocopherol determination in human plasma

A simple and rapid reversed-phase high-performance liquid chromatographic method was developed and validated for the determination of endogenous alpha-tocopherol in human plasma. Following addition of alpha-tocopheryl acetate as the internal standard, the plasma was deproteinized using acetonitrile and isopropanol mixture prior to HPLC analysis. Methanol was used as the mobile phase and the effluent was quantitated at 292 nm. By this developed method, the concentrations of alpha-tocopherol were linearly related to their responses in the range of 0.8-30 microg/mL. The relative standard deviations intra-day and inter-day for alpha-tocopherol in plasma were less than 10%. The percentage of bias was within +/-4%, which confirmed the accuracy of the method. The method has been successfully applied for determining endogenous alpha-tocopherol in healthy Thai male volunteers.     

Identification of metabolites of 4,4'-methylenedianiline in vascular smooth muscle cells by liquid chromatography-electrospray tandem mass spectrometry

A capillary liquid chromatography-electrospray tandem mass spectrometry (LC-ES-MS/MS) method was developed for the identification of metabolites of 4,4'-methylenedianiline (diaminodiphenyl methane, (DAPM)) derived from exposure of vascular smooth muscle cells (VSMC) to this compound. The use of precolumn concentration and column switching techniques prior to reversed-phase liquid chromatography coupled online to ES-MS enabled the separation and detection of low-level DAPM and its metabolites in the exposed cell samples. The employed LC-ES-MS method, and further LC-ES-MS/MS analysis enabled the structural assignments for two DAPM metabolites from vascular smooth muscle cells: N-acetyl methylenedianiline (N-acetyl-DAPM) and N,N'-diacetyl methylenedianiline (N,N'-diacetyl-DAPM).     

MassBank: a public repository for sharing mass spectral data for life sciences

MassBank is the first public repository of mass spectra of small chemical compounds for life sciences (<3000 Da). The database contains 605 electron‐ionization mass spectrometry(EI‐MS), 137 fast atom bombardment MS and 9276 electrospray ionization (ESI)‐MSⁿ data of 2337 authentic compounds of metabolites, 11 545 EI‐MS and 834 other‐MS data of 10 286 volatile natural and synthetic compounds, and 3045 ESI‐MS² data of 679 synthetic drugs contributed by 16 research groups (January 2010). ESI‐MS² data were analyzed under nonstandardized, independent experimental conditions. MassBank is a distributed database. Each research group provides data from its own MassBank data servers distributed on the Internet. MassBank users can access either all of the MassBank data or a subset of the data by specifying one or more experimental conditions. In a spectral search to retrieve mass spectra similar to a query mass spectrum, the similarity score is calculated by a weighted cosine correlation in which weighting exponents on peak intensity and the mass‐to‐charge ratio are optimized to the ESI‐MS² data. MassBank also provides a merged spectrum for each compound prepared by merging the analyzed ESI‐MS² data on an identical compound under different collision‐induced dissociation conditions. Data merging has significantly improved the precision of the identification of a chemical compound by 21–23% at a similarity score of 0.6. Thus, MassBank is useful for the identification of chemical compounds and the publication of experimental data. Copyright © 2010 John Wiley & Sons, Ltd.