Metabolites mass spectrometry

Quantitation of metabolites is challenging in the absence of radiolabel or authentic standards. The most commonly used methods for metabolite monitoring are detection by ultraviolet (UV) absorbance and by mass spectrometry. When UV absorbance is being used for detection, the peak response will be approximately proportional to the amount of metabolite if the chromophore is not altered, such as hydroxylation of an aliphatic side group. However, if the molecule is cleaved, altering conjugated systems, relative UV peak responses may not accurately represent the relative amounts of parent compound and each metabolite. Mass spectrometry is even less reliable than UV absorbance in the absence of authentic standards, as ionization efficiency for each detected molecule will differ. In practice, a combination of UV and mass spectrometry is most appropriate. However, unlike the substrate depletion approach, the possibility would still exist of missing metabolites if the detection method does not pick up the metabolite of interest. 

Prakash, C., Shaffer, C.L., Nedderman, A. (2007) Analytical strategies for identifying drug metabolites. Mass Spectrometry Reviews, 26, 340-369. 

Pyridinium iodide, 4,4 (l,3,4-thiadiazole-2,5-diyl)-bis(l-methyl)-reduction, 6, 564 Pyridinium ion, Af-methyl-as metabolite of pyridine, 1, 234 Pyridinium ions hydrogen bonding to water mass spectrometry, 2, 135 magnetic circular dichroism, 2, 129 NMR, 2, 121... 

The degradation of 2,6-xylenol (2,6-dimethylphenol) by bacteria produces a metabolite with elemental composition C8///0O2 as determined by high-resolution mass spectrometry Which carbon skeleton and which relative configuration are deducible from the NMR experiments 44, all obtained from one 1.5 mg sample ... 

The C NMR spectrum of the metabolite shows 16 signals instead of 8 as expected from the elemental composition determined by high-resolution mass spectrometry. Moreover, aromaticity of the 2,6-xylenol is obviously lost after metabolism because two ketonic carbonyl carbon atoms (5c = 203.1 and 214.4) and four instead of twelve carbon signals are observed in the shift range of trigonal carbon nuclei (5c = 133.1, 135.4, 135.6 and 139.4) in the C NMR spectra. To conclude, metabolism involves oxidation of the benzenoid ring. 

In gas chromatography/mass spectrometry (GC/MS), the effluent from a gas chromatograph is passed into a mass spectrometer and a mass spectrum is taken every few milliseconds. Thus gas chromatography is used to separate a mixture, and mass spectrometry used to analyze it. GC/MS is a very powerful analytical technique. One of its more visible applications involves the testing of athletes for steroids, stimulants, and other performance-enhancing drugs. These drugs are converted in the body to derivatives called metabolites, which are then excreted in the... 

In order to reduce or eliminate off-line sample preparation, multidimensional chromatographic techniques have been employed in these difficult analyses. LC-GC has been employed in numerous applications that involve the analysis of poisonous compounds or metabolites from biological matrices such as fats and tissues, while GC-GC has been employed for complex samples, such as arson propellants and for samples in which special selectivity, such as chiral recognition, is required. Other techniques include on-line sample preparation methods, such as supercritical fluid extraction (SFE)-GC and LC-GC-GC. In many of these applications, the chromatographic method is coupled to mass spectrometry or another spectrometiic detector for final confirmation of the analyte identity, as required by many courts of law. 

Gudzinowicz, B. J. and Gudzinowicz, M. J. Analysis of Drugs and Metabolites by Gas Chromatography Mass Spectrometry (Vols. 1-5). New York Marcel Dekker, 1977. 

Mizutani and coworkers57a confirmed the presence of polychloro(methylsulfonyl)biphenyls (159-170) as sulfur-containing metabolites of chlorobiphenyls (Cl-BP) in the feces of mice based on both GLC-mass spectrometry and chemical derivatization. In some cases comparison with authentic samples (161 and 162) was also made. When preparing 161 and 162,2,5-dichloro-3-(methylsulfonyl)aniline, 2,5-dichloro-l-iodo-3-(methylsulfonyl)benzene and 2,2, 5,5 -tetrachloro-3,3 -bis(methyl-sulfonyl)biphenyl were also obtained and their four peak El mass spectra reported572. Similar data were given for the corresponding 4-substituted intermediates, which were involved in the preparation of 162. Also 2,4, 5-trichloro-2 -(methylsulfonyl)-biphenyl was prepared and its four peak mass spectra given. Metabolites 163 and 164 were also identified by comparison with the authentic standards. 

Castiglioni S, Zuccato E, Crisci E, Chiabrando C, Fanelly R, Bagnati R (2006) Identification and measurement of illicit drugs and their metabolites in urban wastewater by liquid chromatography-tandem mass spectrometry. Anal Chem 78 8421-8429... 

Bijlsma L, Sancho JV, Pitarch E, Ibanez M, Hernandez F (2009) Simultaneous ultra-high-pressure liquid chromatography-tandem mass spectrometry determination of amphetamine and amphetamine-like stimulants, cocaine and its metabolites, and a cannabis metabolite in surface water and urban wastewater. J Chromatogr A 1216(15) 3078-3089... 

Hummel D, Loffler D, Fink G, Temes TA (2006) Simultaneous determination of psychoactive drugs and their metabolites in aqueous matrices by liquid chromatography mass spectrometry. Environ Sci Technol 40 7321-7328... 

The active drug and metabolites can be detected from the urine by thin-layer chromatography, gas-liquid chromatography, or gas chromatography-mass spectrometry. However, assays are available only at specialized centers. Treatment of acute intoxication with mescaline is virtually identical to the treatment outlined for LSD intoxication. DOM-induced vasospasm responds well to intra-arterial tolazohne or sodium nitroprusside. Major life-threatening complications of hallucinogenic amphetamine derivatives include hyperthermia, hypertension, convulsions, cardiovascular collapse, and self-inflicted trauma. 

Figure 5.40 Product-ion spectrum of the (M + H)+ ion (m/z 614) of Indinavir with the proposed origins of the ions observed. Reprinted by permission of Elsevier Science from Identification of in vitro metabolites of Indinavir by Intelligent Automated LC-MS/MS (INTAMS) utilizing triple-quadrupole tandem mass spectrometry , by Yu, X., Cui, D. and Davis, M. R., Journal of the American Society for Mass Spectrometry, Vol. 10, pp. 175-183, Copyright 1999 by the American Society for Mass Spectrometry.

The mass spectrometry employed electrospray ionization and each metabolite gave an [M + H]+ ion which was then used as a precursor ion for a product-ion MS-MS scan. For subsequent MS" experiments, the base peak of the previous MS-MS experiment was chosen under computer control and this allowed all analytes to be studied in a single chromatographic separation. 

Figure 5.54 Structures of Praziquantel and its metabolites, cis- and fraw5-4-hydroxy-praziquantel. Reprinted from 7. Chromatogr., B, 708, Lerch, C. and Blaschke, G., Investigation of the stereoselective metabolism of Praziquantel after incubation with rat liver microsomes by capillary electrophoresis and liquid chromatography-mass spectrometry , 267-275, Copyright (1998), with permission from Elsevier Science.

Vidal JEM, Arrebola PJ, Pemandez-Gufierrez A, et al. 1998. Determination of endosulfan and its metabolites in human urine using gas chromatography-tandem mass spectrometry. J Chromatogr 719 71-78. 

An environmental protocol has been developed to assess the significance of newly discovered hazardous substances that might enter soil, water, and the food chain. Using established laboratory procedures and C-labeled 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), gas chromatography, and mass spectrometry, we determined mobility of TCDD by soil TLC in five soils, rate and amount of plant uptake in oats and soybeans, photodecomposition rate and nature of the products, persistence in two soils at 1,10, and 100 ppm, and metabolism rate in soils. We found that TCDD is immobile in soils, not readily taken up by plants, subject to photodecomposition, persistent in soils, and slowly degraded in soils to polar metabolites. Subsequent studies revealed that the environmental contamination by TCDD is extremely small and not detectable in biological samples. 

METEOR Rule-based Metabolite prediction software Predicts the metabolic fate of chemicals Displays results as a metabolic tree. User can filter results for likely metabolites. Links directly to MetaboLynx for analysis of mass spectrometry data www.lhasalimited.org... 

Anari MR, Baillie TA. Bridging cheminformatic metabolite prediction and tandem mass spectrometry. Drug Discov Today 2005 10 711-7. 

Several methods are available for the analysis of trichloroethylene in biological media. The method of choice depends on the nature of the sample matrix cost of analysis required precision, accuracy, and detection limit and turnaround time of the method. The main analytical method used to analyze for the presence of trichloroethylene and its metabolites, trichloroethanol and TCA, in biological samples is separation by gas chromatography (GC) combined with detection by mass spectrometry (MS) or electron capture detection (ECD). Trichloroethylene and/or its metabolites have been detected in exhaled air, blood, urine, breast milk, and tissues. Details on sample preparation, analytical method, and sensitivity and accuracy of selected methods are provided in Table 6-1. 

The choice of the method of analysis depends on the question to address. Spectrophotometry is sufficient for total curcuminoid content determination in a turmeric extract. Separation techniques coupled to mass spectrometry detection and MALDl-TOF are highly sensitive techniques that are more adapted to the identification of metabolites in biological fluids such as urine or plasma. ... 

Baser H-R, MD Muller (1993) Enantioselective determination of chlordane components, metabolites, and photoconversion products in environmental samples using chiral high-resolution gas chromatography and mass spectrometry. Environ Sci Technol 27 1211-1220. 

Lin C-H, RH Lerch, EM Thurmkan, HE Garrett, ME George (2002) Determination of isoxaflutole (Balance) and its metabolites in water using solid-phase extraction followed by high-performance liquid chromatography with ultraviolet or mass spectrometry. J Agric Eood Chem 50 5816-5824. 

The biodegradation of branched-chain alkanol ethoxyethylates was carried out by the standard OECD confirmatory tests and the metabolites fractionated after solid-phase extraction. The structures of the metabolites were determined by electrospray mass spectrometry and this made it possible to derive a scheme for the partial degradation of the compounds (Di Corcia et al. 1998). 

The structure of the metabolite will often be unknown, and must be predicted from knowledge of putative degradation pathways and confirmed by chemical analysis, generally including mass spectrometry and increasingly by NMR. 

Li L et al. (2006) Liquid chromatography-tandem mass spectrometry for the identification of L-tetrahydropalmatine metabolites in Penicillium janthinellum and rats. Biomed Chromatogr 20(1) 95-100... 

Several methods can be used for the residue analysis of anilides, especially gas chro-matography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS). GC/ECD or GC/NPD for the determination of anilides has generally been used except for the unstable metabolites of naproanilide and clomeprop, which are determined by HPLC/UV, HPLC/FL or GC/ECD after derivatization. 

A multi-residue method based on SPE cleanup and gas chromatography/ion trap mass spectrometry (GC/ITMS) was developed for the determination of 120 pesticides and related metabolites in two soils with organic matter contents of 4.0-5.2%. 

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