Basic profiles of organic acids in urine

Microbiome and Metabolomics in Liver Cancer: Scientific Technology

Primary liver cancer is a heterogeneous disease. Liver cancer metabolism includes both the reprogramming of intracellular metabolism to enable cancer cells to proliferate inappropriately and adapt to the tumor microenvironment and fluctuations in regular tissue metabolism. Currently, metabolomics and metabolite profiling in liver cirrhosis, liver cancer, and hepatocellular carcinoma (HCC) have been in the spotlight in terms of cancer diagnosis, monitoring, and therapy. Metabolomics is the global analysis of small molecules, chemicals, and metabolites. Metabolomics technologies can provide critical information about the liver cancer state. Here, we review how liver cirrhosis, liver cancer, and HCC therapies interact with metabolism at the cellular and systemic levels. An overview of liver metabolomics is provided, with a focus on currently available technologies and how they have been used in clinical and translational research. We also list scalable methods, including chemometrics, followed by pathway processing in liver cancer. We conclude that important drivers of metabolomics science and scientific technologies are novel therapeutic tools and liver cancer biomarker analysis.

The gut microbiota - a vehicle for the prevention and treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) arises principally against a background of cirrhosis and these two diseases are responsible globally for over 2 million deaths a year. There are few treatment options for liver cirrhosis and HCC, so it is vital to arrest these pathologies early in their development. To do so, we propose dietary and therapeutic solutions that involve the gut microbiota and its consequences. Integrated dietary, environmental and intrinsic signals result in a bidirectional connection between the liver and the gut with its microbiota, known as the gut-liver axis. Numerous lifestyle factors can result in dysbiosis with a change in the functional composition and metabolic activity of the microbiota. A panoply of metabolites can be produced by the microbiota, including ethanol, secondary bile acids, trimethylamine, indole, quinolone, phenazine and their derivatives and the quorum sensor acyl homoserine lactones that may contribute to HCC but have yet to be fully investigated. Gram-negative bacteria can activate the pattern recognition receptor toll-like receptor 4 (TLR4) in the liver leading to nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling, which can contribute to HCC initiation and progression. The goal in preventing HCC should be to ensure a healthy gut microbiota using probiotic supplements containing beneficial bacteria and prebiotic plant fibers such as oligosaccharides that stimulate their growth. The clinical development of TLR4 antagonists is urgently needed to counteract the pathological effects of dysbiosis on the liver and other organs. Further nutrigenomic studies are required to understand better how the diet influences the gut microbiota and its adverse effects on the liver.

Modifications of the urinary metabolome in young women after cranberry juice consumption were revealed using the UHPLC-Q-orbitrap-HRMS-based metabolomics approach

The objectives of this research were to investigate urinary metabolome modifications and discover potential intake biomarkers in young women after cranberry juice consumption. Fifteen female college students were given either cranberry juice or apple juice for three days using a cross-over design. Urine samples were collected before and after juice consumption. The metabolome in the urine was analyzed using UHPLC-Q-orbitrap-HRMS-based metabolomics followed by orthogonal partial least squares-discriminant analyses (OPLS-DA). An S-plot was used to identify discriminant metabolites. Validated OPLS-DA analyses showed that cranberry juice consumption significantly altered the urinary metabolome. Compared to the baseline urine or urine after apple juice consumption, cranberry juice consumption increased urinary excretion of both exogenous and endogenous metabolites. The tentatively identified exogenous metabolites included quinic acid, coumaric acid, 4-hydroxy-5-(hydroxyphenyl)-valeric acid-O-sulphate, 5-(dihydroxyphenyl)-γ-valerolactone sulfate, diphenol glucuronide, 3,4-dihydroxyphenyl propionic acid, 3-(hydroxyphenyl) propionic acid, 4-O-methylgallic acid, trihydroxybenzoic acid and 1,3,5-trimethoxybenzene. Modifications of endogenous metabolites after cranberry juice consumption included the increases in homocitric acid, hippuric acid, 3-hydroxy-3-carboxymethyl-adipic acid, (2)3-isopropylmalate, pimelic acid and N-acetyl-l-glutamate 5-semialdehyde. These metabolites may serve as urinary biomarkers of cranberry juice consumption and contribute to the bioactivities of cranberries against urinary tract infection.

Characteristics of Colon-Derived Uremic Solutes

BACKGROUND AND OBJECTIVES

Colon microbial metabolism produces solutes that are normally excreted in the urine and accumulate in the plasma when the kidneys fail. This study sought to further identify and characterize human colon-derived uremic solutes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Colon-derived solutes normally excreted in the urine were identified by comparing urine from controls (n=17) and patients with total colectomies (n=12), using an established metabolomic platform. Colon-derived solutes that accumulate in kidney failure were then identified by comparing the plasma of the control patients with that of patients on dialysis (n=14).

RESULTS

Ninety-one urinary solutes were classified as colon-derived on the basis of the finding of a urine excretion rate at least four-fold higher in control patients than in patients with total colectomies. Forty-six were solutes with known chemical structure, 35 of which had not previously been identified as colon-derived. Sixty of the colon-derived solutes accumulated in the plasma of patients with ESKD to a degree greater than urea and were therefore classified as uremic. The estimated urinary clearance for 27 out of the 32 colon-derived solutes for which clearance could be calculated exceeded that of creatinine, consistent with tubular secretion. Sulfatase treatment revealed that 42 out of the 91 colon-derived solutes detected were likely conjugates.

CONCLUSIONS

Metabolomic analysis identified numerous colon-derived solutes that are normally excreted in human urine. Clearance by tubular secretion limits plasma levels of many colon-derived solutes.

Urinary organic acids quantitated in a healthy north Indian pediatric population

Human urine gives evidence of the metabolism in the body and contains numerous organic acids and other compounds at a variety of concentration. The concentration of organic acids in urine varies from population to population due to genotype, food habits and other epigenetic and environmental influences. Knowledge of the reference values for urinary organic acids in a healthy pediatric population is very important for critical evaluation. This study was designed to quantify 16 organic acids in a healthy north Indian pediatric population. Early morning urine samples from healthy pediatric subjects of age 1 day to 16 years who did not have symptoms of any disease were analyzed for organic acid content. The children were not on any supplemental vitamins or drugs and were on a free and unrestricted diet. The creatinine concentration of each sample was determined before organic acid analysis. Organic acids were extracted from urine with ethyl acetate, extracted residue was air dried, converted into trimethylsilyl derivatives and analysed by gas chromatography mass spectrometry. Here we reported the age wise mean values and standard deviations for each compound, adjusted for creatinine content (mmol/mol of creatinine). We found the concentration of most of the metabolites are higher in our population in comparison to other populations. Such data may help to provide a basis for diagnosing metabolic abnormalities in patients in a specific ethnicity.

The human urine metabolome

Urine has long been a "favored" biofluid among metabolomics researchers. It is sterile, easy-to-obtain in large volumes, largely free from interfering proteins or lipids and chemically complex. However, this chemical complexity has also made urine a particularly difficult substrate to fully understand. As a biological waste material, urine typically contains metabolic breakdown products from a wide range of foods, drinks, drugs, environmental contaminants, endogenous waste metabolites and bacterial by-products. Many of these compounds are poorly characterized and poorly understood. In an effort to improve our understanding of this biofluid we have undertaken a comprehensive, quantitative, metabolome-wide characterization of human urine. This involved both computer-aided literature mining and comprehensive, quantitative experimental assessment/validation. The experimental portion employed NMR spectroscopy, gas chromatography mass spectrometry (GC-MS), direct flow injection mass spectrometry (DFI/LC-MS/MS), inductively coupled plasma mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC) experiments performed on multiple human urine samples. This multi-platform metabolomic analysis allowed us to identify 445 and quantify 378 unique urine metabolites or metabolite species. The different analytical platforms were able to identify (quantify) a total of: 209 (209) by NMR, 179 (85) by GC-MS, 127 (127) by DFI/LC-MS/MS, 40 (40) by ICP-MS and 10 (10) by HPLC. Our use of multiple metabolomics platforms and technologies allowed us to identify several previously unknown urine metabolites and to substantially enhance the level of metabolome coverage. It also allowed us to critically assess the relative strengths and weaknesses of different platforms or technologies. The literature review led to the identification and annotation of another 2206 urinary compounds and was used to help guide the subsequent experimental studies. An online database containing the complete set of 2651 confirmed human urine metabolite species, their structures (3079 in total), concentrations, related literature references and links to their known disease associations are freely available at http://www.urinemetabolome.ca.

A method for comprehensive analysis of urinary acylglycines by using ultra-performance liquid chromatography quadrupole linear ion trap mass spectrometry

Acylglycines are an important class of metabolites that have been used in the diagnosis of several inborn errors of metabolism (IEM). However, current analytical methods detect only a few acylglycines. There is a need to profile these metabolites in a comprehensive manner for studying their functions and improving their diagnostic values for different IEM and potentially other diseases. We describe a sensitive method that combines the chromatographic resolving power of ultra-performance liquid chromatography (UPLC) to separate closely related metabolites including isomers with tandem mass spectrometry (MS/MS). Acylglycines were extracted from urine using an anion exchange solid-phase extraction (SPE) cartridge. After UPLC separation, the acylglycines were detected on a hybrid triple quadrupole linear ion trap mass spectrometer. A set of standards were used for the development of an optimal MS acquisition method. Several acquisition modes using information derived from collision-induced dissociation breakdown curves were used to detect acylglycines. Using this method, 18 acylglycines were detected in the urine of healthy individuals and confirmed using standards, while 47 additional acylglycines were detected and tentatively identified, based on their retention and fragmentation pattern. Among the 65 acylglycines detected, only 18 of them have been previously reported in biofluids of healthy individuals. These results will be deposited in a public human metabolome database. This example illustrates that by developing a method tailored to the analysis of a class of metabolites sharing similar structural moieties, we can potentially identify many more new metabolites, thereby expanding the overall metabolome coverage.

An analytical method for the measurement of acid metabolites of tryptophan-NAD pathway and related acids in urine

An analytical method has been developed for the measurements of five urinary acids namely, quinolinic acid, picolinic acid, nicotinic acid, 2-pyridylacetic acid and 3-pyridylacetic acid. The high performance liquid chromatograph-electrospray ionization mass spectrometry was operated in positive polarity under selected ion monitoring mode, with a column flow rate of 0.2 ml/min and an injection volume of 20 microl. The method used isotope-labelled picolinic acid (PA-d(4)) and nicotinic acid (NA-d(4)) as internal standards for the quantification. The sample preparation involved parallel use of two different types of mixed-mode solid phase extraction cartridges (Strata-X-AW for the extraction of quinolinic acid, and Strata-X-C for the remaining acids). Quantitative analysis of five target acids in several human and rat urine samples showed that the levels of acids were relatively uniform among rats while larger variations were observed for human samples.

Comparative metabolite profiling of carboxylic acids in rat urine by CE-ESI MS/MS through positively pre-charged and (2)H-coded derivatization

A new approach to the selective comparative metabolite profiling of carboxylic acids in rat urine was established using CE-MS and a method for positively pre-charged and (2)H-coded derivatization. Novel derivatizing reagents, N-alkyl-4-aminomethyl-pyridinum iodide (alkyl = butyl, butyl-d9 or hexyl), containing quaternary amine and stable-isotope atoms (deuterium), were introduced for the derivatization of carboxylic acids. CE separation in positive polarity showed high reproducibility (0.99-1.32% RSD of migration time) and eliminated problems with capillary coating known in CE-MS anion analyses. Essentially complete ionization and increased hydrophobicity after the derivatization also enhanced MS detection sensitivity (e.g. formic acid was detected at 0.5 pg). Simultaneous derivatization of one sample using two structurally similar reagents, N-butyl-4-aminomethyl-pyridinum iodide (BAMP) and N-hexyl-4-aminomethyl-pyridinum iodide, provided additional information for recognizing a carboxylic acid in an unknown sample. Moreover, characteristic fragmentation acquired by online CE-MS/MS allowed for identification and categorization of carboxylic acids. Applying this method on rat urine, we found 59 ions matching the characteristic patterns of carboxylic acids. From these 59, 32 ions were positively identified and confirmed with standards. For comparative analysis, 24 standard carboxylic acids were derivatized by chemically identical but isotopically distinct BAMP and N-butyl-d9-4-aminomethyl-pyridinium iodide, and their derivatization limits and linearity ranges were determined. Comparative analysis was also performed on two individual urine samples derivatized with BAMP and N-butyl-d9-4-aminomethyl-pyridinium iodide. The metabolite profiling variation between these two samples was clearly visualized.

Biosynthesis, degradation and pharmacological importance of the fatty acid amides

The identification of two biologically active fatty acid amides, N-arachidonoylethanolamine (anandamide) and oleamide, has generated a great deal of excitement and stimulated considerable research. However, anandamide and oleamide are merely the best-known and best-understood members of a much larger family of biologically occurring fatty acid amides. In this review, we will outline which fatty acid amides have been isolated from mammalian sources, detail what is known about how these molecules are made and degraded in vivo, and highlight their potential for the development of novel therapeutics.

Structural characterization of metabolites of salvianolic acid B from Salvia miltiorrhiza in normal and antibiotic-treated rats by liquid chromatography–mass spectrometry

This study was conducted to compare the in vivo metabolites of salvianolic acid B (Sal B) between normal rats and antibiotic-treated rats and to clarify the role of intestinal bacteria on the absorption, metabolism and excretion of Sal B. A valid method using LC-MS(n) analysis was established for identification of rat biliary and fecal metabolites. And isolation of normal rat urinary metabolites by repeated column chromatography was applied in this study. Four biliary metabolites and five fecal metabolites in normal rats were identified on the basis of their MS(n) fragmentation patterns. Meanwhile, two normal rat urinary metabolites were firstly identified on the basis of their NMR and MS data. In contrast, no metabolites were detected in antibiotic-treated rat urine and bile, while the prototype of Sal B was found in antibiotic-treated rat feces. The differences of in vivo metabolites between normal rats and antibiotic-treated rats were proposed for the first time. Furthermore, it was indicated that the intestinal bacteria showed an important role on the absorption, metabolism and excretion of Sal B. This investigation provided scientific evidence to infer the active principles responsible for the pharmacological effects of Sal B.

Determination of methylmalonic acid and glutaric acid in urine by aqueous-phase derivatization followed by headspace solid-phase microextraction and gas chromatography-mass spectrometry

In this work, a novel technique of aqueous-phase derivatization followed by headspace solid-phase microextraction and gas chromatography-mass spectrometry was developed for the determination of organic acids in urine. The analytical procedure involves derivatization of organic acids to their ethyl esters with diethyl sulfate, headspace sampling, and GC/MS analysis. The proposed method was applied to the determination of methylmalonic acid and glutaric acid in urine. The experimental parameters and method validation were studied. Optimal conditions were obtained: PDMS fiber, extraction temperature 55 degrees C, extraction time 30 min, and 60 microL of diethyl sulfate as derivatization reagent with 2 mg of the ion pairing agent tetrabutylammonium hydrogensulfate. The method was linear over three orders of magnitude, and detection limits were 21 nM for methylmalonic acid and 34 nM for glutaric acid, respectively. Consequently, in-situ derivatization/HS-SPME/GC/MS is an alternative and powerful method for determination of organic acids as biomarkers in biological fluids.

Structure--activity relationships of the estrogenic sesquiterpene ester ferutinin. Modification of the terpenoid core

Esterification of p-hydroxybenzoic acid, a very weak estrogenic compound, with the daucane alcohol jaeschkeanadiol (1b) leads to a spectacular magnification of the estrogenic activity. To identify the structural elements responsible for this effect, the terpenoid core of jaeschkeanadiol p-hydroxybenzoate (ferutinin, 1a) was modified, capitalizing on the presence of two functionalities, the monoacylated, hydrogen-bonded 1,3-diol system and the double bond. The hydrogen bonding, while possibly useful, was not critical for activity, while hydrogenation and cyclopropanation of the double bond were tolerated. Conversely, oxidative modifications of the double bond that placed a hydroxyl on the alpha-face of the molecule proved detrimental. Taken together, these observations identified the substitution at C-8/C-9 as critical for activity.

Sequential ethoxycarbonylation, methoximation and tert-butyldimethylsilylation for simultaneous determination of amino acids and carboxylic acids by dual-column gas chromatography

Amino acids (AAs) in alkaline solution were first ethoxycarbonylated with subsequent methoximation of keto acids (KAs). After acidification and solid-phase extraction, tert-butyldimethylsilylation was performed for direct analysis by gas chromatography (GC) on dual-columns with different polarities, which provided simultaneous separation of multiple amino acids, carboxylic acids (CAs) and keto acids, facilitating accurate peak confirmation based on matching with retention index sets characteristic of each analyte. The present method was linear (r2 > or = 0.9955) with good precision (0.1-9.4%) and accuracy (-8.6 to 9.9%), allowing simultaneous screening for diagnostic amino acids along with carboxylic acids and keto acids in urine from a phenylketonuria patient.

Toxicokinetics of amphetamines: metabolism and toxicokinetic data of designer drugs, amphetamine, methamphetamine, and their N-alkyl derivatives

This paper reviews the toxicokinetics of amphetamines. The designer drugs MDA (methylenedioxy-amphetamine, R,S-1-(3;,4;-methylenedioxyphenyl)2-propanamine), MDMA (R,S-methylenedioxymethamphetamine), and MDE (R,S-methylenedioxyethylamphetamine), as well as BDB (benzodioxolylbutanamine; R,S-1-(1;,3;-benzodioxol-5;-yl)-2-butanamine or R,S-1-(3;,4;-methylenedioxyphenyl)-2-butanamine) and MBDB (R,S-N-methyl-benzodioxolylbutanamine), were taken into consideration, as were the following N-alkylated amphetamine derivatives: amphetaminil, benzphetamine, clobenzorex, dimethylamphetamine, ethylamphetamine, famprofazone, fencamine, fenethylline, fenproporex, furfenorex, mefenorex, mesocarb, methamphetamine, prenylamine, and selegiline. English-language publications from 1995 to 2000 were reviewed. Papers describing identification of metabolites or cytochrome P450 isoenzyme-dependent metabolism and papers containing pharmacokinetic/toxicokinetic data were considered and summarized. The implications of toxicokinetics for toxicologic assessment or for interpretation in forensic cases are discussed.

Toxicokinetics and analytical toxicology of amphetamine-derived designer drugs ('Ecstasy')

The phase I and II metabolites of the designer drugs methylenedioxyamphetamine (MDA), R,S-methylenedioxymethamphetamine (MDMA), R,S-methylenedioxyethylamphetamine (MDE), R, S-benzodioxazolylbutanamine (BDB) and R, S-N-methyl-benzodioxazolylbutanamine (MBDB) were identified by gas chromatography-mass spectrometry (GC-MS) or liquid chromotography-mass spectrometry (LC-MS) in urine and liver microsomes of humans and rats. Two overlapping pathways could be postulated: (1) demethylenation followed by catechol-O-methyl-transferase (COMT) catalyzed methylation and/or glucuronidation/sulfatation; (2) N-dealkylation, deamination and only for MDA, MDMA, MDE oxidation to the corresponding benzoic acid derivatives conjugated with glycine. Demethylenation was mainly catalyzed by CYP2D1/6 or CYP3A2/4, but also by CYP independent mechanisms. In humans, MDMA and MBDB could also be demethylenated by CYP1A2. N-demethylation was mainly catalyzed by CYP1A2, N-deethylation by CYP3A2/4. Based on these studies, GC-MS procedures were developed for the toxicological analysis in urine and plasma. Finally, toxicokinetic parameters are reviewed.

Simultaneous determination of polycarboxylic acids by capillary electrophoresis with a copper electrode

The simultaneous determination of polycarboxylic acids including oxalic acid, citric acid, malonic acid, malic acid, tartaric acid, aspartic acid and glutamic acid was achieved by capillary electrophoresis with a copper disk electrode (d = 200 microm). In the system. 0.2 mmol/l cetylpridinium bromide (CPB) was used as an electroosmotic flow (EOF) modifier to reverse the direction of EOF. The effects of the solution pH and CPB concentration on separation were evaluated to achieve the optimum separation conditions. At the working potential of +0.14 V (vs. saturated calomel electrode), the calibration curves for all polycarboxylic acids studied were linear with 2 approximately 3-orders of magnitude and all the detection limits (S/N = 3) were below 15 fmol except malonic acid. Furthermore, the oxalic and citric acids in urine were successfully separated and determined with high sensitivity.

Profiling of organic acids by capillary gas chromatography-mass spectrometry after direct methylation in urine using trimethyloxonium tetrafluoroborate

Trimethyloxonium tetrafluoroborate (TMO) is applied as derivatising reagent to transform urinary organic acids into their methyl esters. The method is suggested as an alternative to the use of diazomethane which is carcinogenic and explosive. In contrast to other methods avoiding diazomethane, such as derivatizations with acetyl chloride-methanol and boron trifluoride-methanol, which require an organic reaction medium and therefore an extraction of the organic acids from the urine, TMO efficiently reacts with the acids in an aqueous solution and can therefore be directly applied to native urine. The use of TMO simplifies and improves the sample preparation in the profile analysis of urinary organic acids by capillary GC-MS and hereby increases the speed of analysis. The method gives reproducible results which are comparable with the data obtained using conventional solid-phase extraction with strong anion-exchange cartridges prior to derivatisation.

Chromatographic separations of aromatic carboxylic acids

The purpose of this review is to present methods of chromatographic analysis of aromatic carboxylic acids. The separation, identification and quantitative analysis of aromatic carboxylic acids are necessary because of their importance as non-steroid antiphlogistic drugs, semi-products of biosynthesis of aromatic amino-acids in plants (phenolic acids), metabolites of numerous toxic substances, drugs and catecholamines. HPLC separation of ionic samples tends to be more complicated than separation of non-ionic compounds. The review describes the dependence of the retention of ionic solutes on pH and solvent composition as well as on the ionic strength of a mobile phase. The application of the ion-suppressing RP-HPLC method using organic modifiers (aqueous buffer solutions) as eluents in aromatic carboxylic acid analysis is also presented. In more difficult cases of analysis the addition of an ion-pairing reagent, such as the quaternary alkylammonium ion, is necessary to obtain satisfactory separations. Hypotheses of ion-pair formation in reversed-phase systems as well as the influence of various agents on the separation of ionic solutes in IP-RP systems are explained. Examples of the application of ion-pair liquid chromatography to the analysis of aromatic carboxylic acids have also been reviewed. The principles and application of ion-exchange chromatography to the purification, isolation and less frequently, to chromatographic analysis are discussed. Polar adsorbents and polar bonded stationary phases are also widely used in carboxylic acid separation in normal-phase systems, mainly by TLC, often coupled with densitometry. The review also shows examples of separation of chiral benzoic acids and their derivatives in LC systems. The possibilities of application of gas chromatography preceded by derivatisation or pyrolysis of acidic compounds and applications of GC-MS and Py-GC-MS coupled methods in identification and quantitation of aromatic carboxylic acids is also reviewed.

Urinary organic acid screening by solid-phase microextraction of the methyl esters

We developed a new sample preparation method for profiling organic acids in urine by GC or GC-MS. The method includes derivatisation of the organic acids directly in the aqueous urine using trimethyloxonium tetrafluoroborate as a methylating agent, extraction of the organic acid methyl esters from the urine by solid-phase microextraction, using a polyacrylate fiber with a thickness of 85 microm and transfer of the methyl esters into the GC or the GC-MS instrument. Desorption of the analytes takes place in the heated injection port. The proposed sample preparation is very simple. There is no need for any evaporation step and for the use of an organic solvent. The risk of contamination and the loss of analytes are minimized. The total sample preparation time prior to GC or GC-MS analysis is about 40 min, and therefore more rapid than other sample preparation procedures. The urinary organic acids are well separated by GC and 29 substances are identified by GC-MS.

Gas chromatographic profiling analysis of urinary organic acids from nonsmokers and smokers

A rapid profiling and screening procedure is described for the comparative analysis of urinary organic acids among the groups of nonsmokers and smokers. The procedure involves solid-phase extraction of organic acids using Chromosorb P in normal-phase partition mode, with subsequent single-step conversion to tert.-butyldimethylsilyl derivatives, followed by direct gas chromatographic (GC) analysis on dual-capillary columns. A total of forty-two organic acids were positively identified by retention index (I) matching in urine samples (0.25 ml) from eleven nonsmokers and fifteen smokers studied. When the GC profiles were simplified to their corresponding organic acid I spectra in bar graphical form, characteristic patterns were obtained for each individual as well as for each average of nonsmoking and smoking groups. When stepwise discriminant analysis was performed on GC data after omitting hippuric acid, seven acids were selected as the variables most discriminating between smokers and nonsmokers. The star symbol plots drawn based on these discriminants were characteristic of each individual and group average, enabling to distinguish smokers from nonsmokers. And canonical plot produced by canonical discriminant analysis using the same variables as the data vectors displayed two separate clusters representing each group.

Determination of p-hydroxymandelic acid enantiomers in urine by high-performance liquid chromatography with electrochemical detection

High-performance liquid chromatography (HPLC) with electrochemical detection using a chiral ligand-exchange column was developed for the enantioselective determination of p-hydroxymandelic acid (HMA), a metabolite of synephrine, with high sensitivity. A good linear relationship between current ratio and amount was noted for 0.5-500 pmol HMA, with a correlation coefficient of 0.999 for each HMA enantiomer. The relative standard deviation (R.S.D.) was 1.6% at 100 pmol d-HMA and 2.2% at 100 pmol l-HMA. The detection limit of each HMA enantiomer was 0.5 pmol (signal to noise ratio, S/N = 3). By this method, HMA in Citrus unshiu and in urine following the ingestion of C. unshiu was determined. Although no HMA was found in c. unshiu, d- and l-HMA were present in urine after the ingestion of C. unshiu. The time courses of HMA and conjugated synephrine enantiomers excreted in urine following the ingestion of C. unshiu for 24 h could be monitored. This method should prove applicable to the study of synephrine metabolism.

Rapid gas chromatographic profiling and screening of biologically active amines

An efficient method is described for the simultaneous determination of 57 amines including volatile aliphatic amines, nonvolatile polyamines and catecholamines present in aqueous samples. The method is based on two-phase isobutyloxycarbonylation (isoBOC) with a pH shift. In 1.0 M phosphate buffer at pH 7.5, phenolic hydroxyl groups were allowed to react with isobutyl chloroformate in the dichloromethane phase, and subsequently pH of the aqueous phase was increased to 12.0 for the reaction of basic amino functions. The resulting N(O)-isoBOC amines were recovered by solid-phase extraction using Chromosorb P in normal phase partition mode, with subsequent tert.- butyldimethylsilylation of the remaining hydroxyl groups for gas chromatographic analysis. Using this combined procedure, linear responses were obtained in the concentration range of 0.2-12 ppm, with correlation coefficients varying from 0.945 to 0.999 for most of the amines studied except for 5-methoxytryptamine (0.864). Temperature-programmed retention index (I) sets as measured on DB-5 and DB-17 dual-capillary columns of different polarity were characteristic of each amine and thus, useful in the screening for amines by computer I matching. When applied to saliva samples, the present method allowed rapid screening for each spiked amine and unspiked polyamines such as 1,3-diaminopropane, putrescine, cadaverine and spermidine.

On the metabolism and the toxicological analysis of methylenedioxyphenylalkylamine designer drugs by gas chromatography-mass spectrometry

Designer drugs of the methylenedioxyphenylalkylamine type are increasingly abused. Studies on their metabolism in humans are necessary to develop a reliable gas chromatography--mass spectrometry (GC-MS) screening procedure. Such a method must allow their detection in urine for drug testing in clinical and forensic toxicology. Studies on racemic methylenedioxyamphetamine (MDA), methylenedioxymetamphetamine (MDMA), methylenedioxyethylamphetamine (MDE), benzodioxazolylbutanamine (BDB), and N-methylbenzodioxazolylbutanamine (MBDB) are presented. The metabolites were identified by GC-MS after enzymatic hydrolysis, isolation (pH 4.5 and 8-9), and derivatization (acetylation followed by methylation). The drugs undergo two overlapping metabolic pathways: O-dealkylation of the methylenedioxy group to dihydroxy derivatives followed by methylation of one of the hydroxy groups and successive degradation of the side chain to N-dealkyl and deaminooxo metabolites. MDA, MDMA, and MDE are subsequently metabolized to glycine conjugates of the corresponding 3,4-disubstituted benzoic acids. The hydroxy metabolites are excreted in a conjugated form. Based on these results, a GC-MS procedure was developed for simultaneous screening and identification of these designer drugs and/or their metabolites in urine after acid hydrolysis, isolation at pH 8-9, and acetylation. With use of mass chromatography with the most characteristic fragment ions m/z 58, 72, 86, 150, 162, 164, 176, and 178, the presence of the designer drugs was indicated and the peak underlying spectra could be identified by computerized comparison with reference spectra recorded during the presented studies. The procedure was suitable to detect an abuse of or an intoxication with the studied designer drugs (detection limit 5-50 ng/ml).

Simultaneous determination of oxalic and citric acids in urine by high-performance liquid chromatography

A simple method for the simultaneous determination of oxalic and citric acids had been developed using reversed-phase HPLC. An aqueous solution containing potassium dihydrogen phosphate (0.25%) and tetrabutylammonium hydrogen sulphate (2.5 mmol) at pH 2.0 was used as mobile phase. Under these conditions both the components were well resolved and detected at 210 nm. The recovery for oxalic and citric acids was 97% and 102%, respectively. The method presented here was applied to urine specimens of a large number of urolithic patients and control subjects. Because of the simplicity of the method its application provides better means of monitoring the concentration of oxalic and citric acids in the formation of renal calculi.

Synthesis and preclinical evaluation of technetium-99m-labeled hippurate analogues

We have synthesized seven 99mTc-labeled hippurate analogues: 99mTc-hippurate. 99mTc-alpha-hydroxyhippurate, 99mTc-m-hydroxyhippurate. 99mTc-o-hydroxyhippurate [99m-salicylglycine (99mTc-SG)], 99mTc-p-hydroxyhippurate, 99mTc-salicylglycylglycine and 99mTc-salicylglycylglycylglycine. All of the 99mTc-hippurates were cleared rapidly from the rat blood and accumulated in the kidney. Of them 99mTc-SG has the desirable biological properties of two diagnostic agents. 99mTc-mercaptoacetyltriglycine (99mTc-MAG3) and 99mTc-dimercaptosuccinate (99mTc-DMSA). A fraction of 99mTc-SG showed a transit time in the kidney and was excreted rapidly into the urine, being similar to 99mTc-MAG3. The binding ratio to the plasma proteins was 96.0% (91.1% in the albumin), being higher than that of 99mTc-DMSA, at 30 min. The lipophilicity revealed far less pH-dependent changes in a range of pH 4.0 to 7.4. 99mTc-SG distributed about 91% in the renal cortex, being similar to that of 99mTc-DMSA. From the present studies, the biological properties of 99mTc-SG suggest that it is a promising agent for measuring renal plasma flow and renal morphology.

Organic acidurias and related abnormalities

Organic acid analysis is a powerful technique in the diagnosis of inborn errors of metabolism. Since the development of the technique over twenty-five years ago, it has evolved into a sophisticated and powerful method and is an essential tool in the diagnosis of the organic acidurias. The chemistry and biochemistry of organic acids, as well as sample preparation, instrumentation, and many aspects of the more commonly used methods for the analysis of these compounds, are reviewed. The biochemical and clinical characteristics of each of the primary organic acidurias are described. In addition, the various noninherited causes of secondary organic acidurias that lead to the excretion of abnormal organic acids are also described, and ways of differentiating primary from secondary causes are discussed.

Organic acid profiling by direct treatment of deproteinized plasma with ethyl chloroformate

Carboxylic acids in plasma or serum can be conveniently determined by capillary gas chromatography (GC) following treatment with ethyl chloroformate (ECF). The mixed organic solvent used for plasma deproteinization is also suitable as medium for the subsequent reaction step. Thus, isolation of the compounds of interest is not necessary. Before treatment of the supernatant with ECF, the neutral lipids and amino acids are removed easily by hexane extraction and cation-exchange chromatography. Ketocarboxylic acids do not require a preliminary oximation. Capillary columns with a length of 15 m and a polar silicone phase proved to be ideal for the separation of mixtures of derivatized keto-, hydroxy-, mono- and dicarboxylic acids. The run time is less than 30 min.

trans,trans-Muconic acid, a reliable biological indicator for the detection of individual benzene exposure down to the ppm level

trans,trans-Muconic acid (2,4-hexadienedioic acid) (t,t-MA) is a minor benzene metabolite which can be used as a biological indicator for benzene exposure. The purpose of the study was to evaluate the limits of use of t,t-MA for detection and quantification of occupational exposures to benzene, particularly on an individual scale, phenol being used as the metabolite of reference. A simple and sensitive method previously described by the authors was carried out to analyse t,t-MA in 105 end-of-shift urinary samples from 23 workers exposed to benzene used as an extraction solvent for "concretes" recovery in the perfume industry. Good correlations were found between atmospheric benzene and both metabolites (uncorrected or corrected for creatinine) or between the metabolites themselves, with correlation coefficients from 0.81 to 0.91 (P < 0.0001). Correlation- coefficients were not improved after correction for creatinine. The overall individual benzene exposure range, median, and arithmetic mean were respectively 0.1-75, 4.5, and 9.0 ppm with corresponding t,t-MA excretion of 0.1-47.9, 5.2 and 8.9 mg/l (uncorrected) and phenol excretion of 1.4-298, 30.9, and 42.2 mg/l (uncorrected). In the control group (145 determinations for t,t-MA and 76 for phenol from 79 individuals) the range, median, and arithmetic mean were respectively < 0.04-0.66, 0.08, and 0.13 mg/l (uncorrected t,t-MA) and 1.5-42.0, 9.85 and 11.3 mg/l (uncorrected phenol). t,t-MA was far more specific than phenol and could be easily and practically used to estimate with a given probability the upper or lower corresponding benzene concentrations down to around the ppm level.(ABSTRACT TRUNCATED AT 250 WORDS)