Metabolites analysis, determination

Estimation of dose from urinary metabolite analysis From the analysis of volunteer s urine for 3,5,6-TCP, the amount of absorbed chlorpyrifos was determined for each individual volunteer. Table 5 summarizes the calculated chlorpyrifos dose based on analysis of urine samples. The average chlorpyrifos dose was estimated to be 7.07 pg/kg, 182% of the dose estimated using physical techniques. 

The conformations of the 1- and 3-nitro-BaP metabolites were determined through analysis of their NMR spectra (145-146). Both 1- and 3-nitro-BaP-trans-7,8-dihydrodiols existed predominantly in quasi-diequatorial conformations, which corresponds to the preferred conformation of the proximate carcinogen BaP-trans-7,8-dihy-drodiol (149). This suggests that these dihydrodiol metabolites may be converted into electrophilic diol epoxides and in support of this contention, the stereochemistries of 1- and 3-nitro-BaP-... 

Tributyltin oxide and its metabolites were determined in urine after conversion to chlorides with HC1, extraction with ether containing tropolone (1), conversion to hydrides with NaBFLt, extraction with hexane and GC-AAS end-analysis LOD 1 pg/L for BuSnFL and Bu2SnH2, and 2 pg/L for Bu3SnH87b. 

An analytical chemical technique that utilizes radioactive (or stable) isotopes for the quantitative analysis of the amount of substance. In the absence of a kinetic isotope effect, isotopic isomers react identically with respect to their unlabeled counterparts. The method offers the advantage that specific activity (or gram-atom excess in the case of stable isotopes) is an intensive variable. Therefore, one only needs to recover sufficient labeled metabolite to determine amount of substance and disintegrations per minute (or, gram-atom excess) to reach an accurate determination of specific activity. The technique is feasible so long as one can accurately determine the initial and final specific activities. 

Subsequently, shallow water collections of Lyngbya majuscula from Puerto Rico and the Dry Tortugas yielded additional supplies of ATX as well as a new congener termed antillatoxin B (Figure 6.10) [149]. The structure of the new metabolite was determined largely by comparison with the spectroscopic data set for ATX, and stereochemistry deduced by Marfey s analysis for L-alanine while the i-N-methyl homophenylalanine was proposed based on nuclear Overhauser effect (nOe) and bioassay results. Substitution of i-N-methyl homo-phenylalanine, an intriguing amino acid of quite rare occurrence in natural products, for i-N-methyl valine... 

In most cases, morphine and its metabolites are determined in plasma for pharmacokinetic studies, e.g., [81-82]. The methodology in these methods is essentially the same. After protein precipitation, the supernatant is subjected to an SPE cartridge. Reversed-phase LC on C,8-coltunns is applied with positive-ion ESI-MS. For forensic applicatiorrs, the typical analysis time is arotmd 15 mirr, while shorter nm times are achieved in pharmacokinetic studies. Either SIM or SRM is applied. Similar LOQ have been achieved between 0.5 and 3.8 ng/ml for morphine, 2.3 and 25 ng/ml for M3G, and 0.5 and 12 ng/ml for M6G. Either analogue IS or deuterirrm-labelled IS is used. 

Figure 55-2 Multi-analyte approach to the prenatal diagnosis of methylmalonic acidemia (cb/C complementation group) by metabolite analysis in ceil-free supernatant of amniotic fluid collected at 16 weeks of gestational age. The symbol marks internal standards. A, Determination of total homocysteine by LC-MS/MS (selected reaction monitoring, SRM, transition m/z 136 to m/z 90 and m/z 140 to m/z 94 for the d -labeled internal standard). The concentration of total homocysteine was l5.7pmol/L (0.7 to 2.0pmol/L). B, Determination of methylmalonic acid by LC-MS/MS (SRM, transition m/z 231 to m/z 119 and m/z 234 to m/z 122 for the d3-labeled internal standard). The concentration of methylmalonic acid was 8.7pmol/L, the reference interval for 16 to 19 weeks of gestational age is 0.2 to 0.7)j,mol/L. C, Determination of propionylcarnitine by LC-MS/MS (parent of m/z 85 scan, the [M+H] ion of C3 is m/z 274, m/z 277 for the interna standard). The concentration was 5.6pmol/L (i.5 to l.8pmoi/L),the C3/C4 ratio was 6.9 (0.9 to 2.6).

The structures of cytochalasins A and B were determined by Aldridge et al. (206) and Tamm and co-workers (207), independently, and structures of other metabolites were determined by correlations. The absolute configurations of many metabolites have been established by X-ray analysis. Approaches to synthesis of these complex compounds have also been reported by several groups (208), and successes in cytochalasin B and F have been reported by Stork s group (209). 

Many drugs, such as buspirone, undergo multiple oxidative biotransformation reactions. In cases such as buspirone the secondary metabolites, which are minor metabolites in vitro, are major metabolites in the circulation or excreta in humans and animals because primary metabolites are rapidly converted to secondary metabolites. To determine the formation pathways and structures of secondary or sequential metabolites, a method using metabolite incubation and HPLC MSC MS analysis was developed and demonstrated using buspirone as an example (Zhu, 2002). [ Cjbuspirone was incubated with HLM, and metabolic profiling was carried out using HPLC-MSC. The... 

Endogenous volatile metabolites are normal by products of intermediate metabolites. Analysis of these metabolites is important in the diagnosis of certain disease states. An example of headspace gas chromatography analysis applied to these metabolites is the determination of ketone bodies (Seto, 1994). Ketone bodies are present in biochemical altered states known as diabetic ketoacidosis, related to diabetics and alcoholic ketoacidosis, a consequence of chronic abuse of alcohol. Studies (Iten Meier, 2000 Pounder, et al., 1998 Thomsen, et al., 1995) indicate that alcoholic ketoacidosis could be the cause of death in alcoholics, in cases of sudden and xmexpected death, where alcohol determination was negative and that an alcoholic ketoacidosis state can be diagnosed with the determination of ketone bodies in postmortem blood samples. Ketone bodies (acetone, acetoacetate and 3-hydroxybutyrate) can be measured separately by gas chromatography headspace. Acetone are determined at a headspace temperature below 60°C to avoid decarboxilation of... 

High-performance liquid chromatography-mass spectrometry (HPLC-MS) is a powerful analytical technique widely used in recent years for the analysis of biomarkers and metabolites. Biomarker determination and quantification, whether metabolic or adducted biomolecules, are commonly used to evaluate exposure and support biomonitoring research, especially in the area of occupational exposure and health. Some of the common problems and strategies of HPLC-MS biomarker analysis involve matrix effects, the use of isotope-labeled internal standard compounds, and sample cleanup usually all of these factors must be evaluated within the development phase of an analysis procedure. Specific examples of biomarker analysis using HPLC-MS include acrylamide, aromatic compounds, and 1-bromopropane, and these examples are discussed in detail. 

The total taxane (TTAX) concentration, a sum of the concentrations for CT-2103, TXL, and TXL-metabohtes was determined from scintillation counting of the plasma or tissue sample homogenates. Extractable taxanes, including TXL and organically extractable TXL metabolites, were determined by scintillation counting of ethyl acetate extractions of the plasma, tumour, liver, and spleen samples. Plasma and tissue TXL concentrations were also determined by HPLC/radiometric analysis of the extracts. Metabolites were identified by HPLC followed by mass spectrometry on a Quattro It (Micromass, Manchester, UK) triple quadrupole mass spectrometer fitted with an electrospray orthogonal Z spray ion interface operating in the positive ion mode. ... 

There are numerons reports for the gas chromatographic determination of THC and its metabolites, ll-nor-A-9-tetrahydrocannibinol-9-carboxylic acid (THC-COOH) and ll-hydroxy-A-9-tetrahydrocannibinol (11-OH-THC) in urine and blood. THC is not normally found in urine, so it must be determined in blood at levels around 2-4 ng/mL. The TMS derivative is the most widely used derivati-zation procedure with GCMS for the determination of cannabinoids. In addition to the obvious advantages of derivatizing the THC metabolites, the acidic constituents of cannabis mnst be derivatized because they can easily decarboxylate above 80°C. Almost aU gas chromatographic procedures today use fused-silica capillary columns for this analysis. Determination of THC in blood is routinely done in forensic toxicological samples, and the detection and quantification of the two THC metabolites in mine is a routine procedure for proof of cannabis use in workplace testing. Several of the procedures used for this type of analysis are listed in Table 16.9. 

High-performance liquid chromatography (HPLC) methods have been developed in recent years to allow the rapid, sensitive, and specific analysis of thiamine and its phosphates in drugs, biological materials, and metabolites. To determine total thiamine in biological materials, samples must first be treated with Taka-diastase or acid phosphatase to hydrolyze thiamine phosphate esters to free thiamine (17,18). The complete separation of thiamine and its phosphate esters at subpico-molar level by use of HPLC was first reported by Kawasaki s group (4,17) and then continued to be developed until recent years (19,20). 

AQC is one of the best precolumn fluorescence derivatization reagents for amino compounds [29]. Currently, MS/MS detection is frequently used for the selective determination of biological substances in complex mixtures. The reagent AQC reacts with primary and secondary amines to form aminoquinoline-labeled compounds via a carbamide linkage. These derivatives are separated by reversed-phase liquid chromatography and can be monitored by electrospray ionization—mass spectrometry. The loss of the aminoquinoline tag occurs readily and can be monitored by MS/MS detection, thus, metabolite analysis of amino compounds can be carried out [35]. 

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