Determination of creatinine-related urinary uracil excretion in children by high-performance liquid chromatography

Excretion rates of uracil and thymine in children (n = 140) and circadian rhythms of urinary uracil excretion (n = 9) were investigated by reversed-phase high-performance liquid chromatography with ultraviolet detection. Excretion values were related to urinary creatinine determined by Jaffé's method. Creatinine-related uracil excretion was not dependent on age or sex. The values seemed to be distributed according to a Gaussian graph in both school children and those in hospital. The intra-individual range was 1.32-23.70 mg uracil per g creatinine over a four-day period in one subject. Uracil excretion seems to be somewhat lower during the night.     

Measurement of urinary pyrimidine bases and nucleosides by high-performance liquid chromatography

A rapid procedure for the isolation, separation, identification and measurement of urinary pyrimidine bases and nucleosides by high-performance liquid chromatography (HPLC) is presented. The initial isolation of these compounds from urine was accomplished with small disposable ion-exchange columns. HPLC was performed on a silica gel column with a mobile phase composed of methylene chloride, methanol and 1 M aqueous ammonium formate buffer. Peaks were recorded at both 254 nm and 280 nm and the response ratio was used in combination with the elution volume for compound identification. The minimum detectable amount (signal-to-noise ratio = 2) ranged from 0.2 ng for uracil to 2.2 ng for cytidine. Linearity and recovery for thymine, uracil, uridine, pseudouridine, orotic acid and orotidine added to urine was demonstrated over almost a 10(3) concentration range. The potential application of this method for the study of inborn errors in the urea cycle is discussed.     

Identification of Escherichia coli by detection of hydroquinone and uracil in the urine system

For rapid identification of Escherichia coli, changes of urinary metabolites incubated with E. coli were investigated by gas chromatography--mass spectrometry. Hydroquinone and uracil were detected and the normal urinary constituent 4-deoxythreonic acid was found to diminish in urine incubated with E. coli. Hydroquinone could not be detected in urine incubated with Klebsiella pneumoniae, Serratia marcescens or Pseudomonas aeruginosa. Although uracil was detected in normal urine, urine incubated with E. coli showed an increased uracil level. Urine incubated with K. pneumoniae, S. marcescens or P. aeruginosa evidenced no such change. A decrease of 4-deoxythreonic acid was noted in urine incubated with S. marcescens or P. aeruginosa. In 7.0 X 10(7) cells of E. coli, 0.33-2.36 micrograms of hydroquinone and 13.4-42.0 micrograms of uracil were detected after 3 h of incubation at 38 degrees C, and production was not changed after 4, 5 or 8 h of incubation. These results suggest that the detection of hydroquinone and uracil in urine is useful for rapid identification of E. coli.     

Determination of furosemide in urine samples by direct injection in a micellar liquid chromatographic system

A sensitive, selective and efficient micellar liquid chromatographic (MLC) procedure was developed for the determination of furosemide (4-chloro-N-furfuryl-5-sulfamoylanthranilic acid) in urine samples by direct injection and UV detection. The procedure makes use of a C18 reversed-phase column and a micellar mobile phase of 0.05 mol l(-1) sodium dodecyl sulfate-6% v/v propanol and phosphate buffer at pH 3 to resolve furosemide from its photochemical degradation products. The importance of protecting the standards and urine samples to be analysed from light in the assay of furosemide, avoiding its degradation, was verified. The limit of quantification was 0.15 microg ml(-1) and the relative standard deviation of the inter-day assay was 0.8-0.04% in the 6-82 microg ml(-1) range. Detection of urinary excretion of furosemide was followed up to 12 h after ingestion of the drug by a healthy volunteer. No potential interference from the major metabolite (furosemide acylglucuronide) and its hydrolytic product (4-chloro-5-sulfamoylanthranilic acid) was observed. Commonly administered drugs also did not interfere. The proposed MLC procedure permits the rapid and reproducible measurement of low levels of furosemide in a small amount of urine.     

Automated high-performance liquid chromatographic determination of 5-S-cysteinyl-3,4-dihydroxyphenylalanine in urine

An automated high-performance liquid chromatographic (HPLC) method has been developed for measurement of 5-S-cysteinyl-DOPA in urine (DOPA = 3,4-dihydroxyphenylalanine). The urinary sample was injected into an HPLC boronate column. With a mobile phase of 0.1 M phosphate buffer containing 0.2 mM disodium ethylenediaminetetraacetate (Na2EDTA) (pH 6.0) mixed with methanol (9:1), 5-S-cysteinyl-DOPA was adsorbed while most other compounds were washed away. By column switching, the column flow was reversed and 5-S-cysteinyl-DOPA was desorbed by a mobile phase of 0.1 M formic acid and 0.2 mM Na2EDTA at pH 3.0 and chromatographed on a reversed-phase column. The precision, as estimated from repeated analysis of an urinary sample and from duplicate analysis of a number of samples, ranged from 1.4 to 5.2% (coefficient of variation), and the analytical recovery was 93 +/- 4.1%. The method is suitable for use in the clinical laboratory.     

Synthesis of 5-Phenylamino derivatives of orotic acid

The possibility of nucleophilic substitution of bromine in 5-bromoorotic acid by aromatic amines was studied. 5-Phenylamino derivatives of uracil and 5-phenylamino derivatives of orotic acid were synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 273–275, February, 1973.Deceased.     

Depopulation of Highly Excited Singlet States of DNA Model Compounds: Quantum Yields of 193 and 245 nm Photoproducts of Pyrimidine Monomers and Dinucleoside Monophosphates

Abstract— Formation of uracil and orotic acid photodimers, uridine and 5'-UMP photohydrates, TpT photodimers and (6-4)photoproducts, dCpT photohydrates and (6-4)photo-products and UpU, CpC and CpU photohydrates were studied in neutral deoxygenated aqueous solution at room temperature upon irradiation at either 193 or 254 nm. The photoproducts were identified and quantified and the contribution from photoionization to substrate decomposition, using λ_irr= 193 nm, was separated. The ratio of the quantum yields of respective stable products,η=φ¹⁹³/φ²⁵⁴ is indicative of the yield of internal conversion from the second to the first excited singlet state, S₂→ S₁. For the observed photodimers η decreases from 0.94 for uracil to 0.7 for TpT and further to 0.55 for orotic acid. For the (6-4)photoproducts of TpT and dCpT T| = 0.5-0.8 and for the photohydrates in the cases of UpU, CpC, CpU and dCpT TJ ranges from 0.55 to 1.     

Blocking-Deblocking of the NH-Functionality of Uracil and its Derivatives

We have been interested in various 5,6-dihydrouracils and 5,6-dihydroorotic acid derivatives as possible inhibitors of dihydrouracil dehydrogenase, dihydroorotase, and dihydroorotate dehydrogenase.² The known methods for the synthesis of 5,6-dihydrouracils and 5,6-dihydroorotic acid derivatives are either a low yield cyclization process³ or a catalytic hydrogenation⁴ procedure which frequently led to the elimination of desired functionality⁵. In order to obviate these difficulties, we have recently developed⁶ a mild non-catalytic method for the reduction of 5,6-double bond of uracil and orotic acid derivatives. By using lithium tri-sec-butyl borohydride^7–8 we have been able to reduce N₁, N₃-dialkyl uracil and orotic acid derivatives to the corresponding 5,6-dihydrouracil and orotic acid derivatives as shown in scheme (1).     

THE IMPORTANCE OF COMPLEX FORMATION IN THE SENSITIZATION OF Eu(III) EMISSION BY OROTIC ACID

Abstract— Orotic acid (I) and 3-methylorotic acid (II) are the only orotic acid derivitives which efficiently sensitire emission from Eu(III) in D₂O solution. This emission is only weakly sensitized by I-methylorotic acid (III), 1,3-dimethylorotic acid (IV), the methyl and isopropyl esters of orotic acid (V) 6-acetyluracil (VI) and not sensitized at all by the bases uracil. thymine and their nucleosides. Substituent groups on either the carboxyl group or the N-l position of the ring thus prevent efficient energy transfer from the excited orotic acid to Eu(III). These structural requirements for efficient energy transfer are the same as the structural requirements for formation of a stable. bidentate. ground state complex between Eu(III) and orotic acid (VII) (Sarpotdar and Burr, 1978).
We, therefore, propose that sensitization of Eu(III) emission by orotic acid at pH 5 is an example of energy transfer within the bidentate complex of Eu(III) and orotic acid. We also propose that the complexed orotic acid is itself excited by eollisional energy transfer from free triplet excited orotic acid (since the concentration of complex measured to be present. 5–7%, is too low to account for the efficiency of the sensitization). We also propose that emission from the excited complexed Eu(III) can be either from the complexed ion or from free Eu(III)* resulting from dissociation of the complex during the lifetime of the excited ion.
The efficiency of Eu(III) sensitized emission is shown to depend on the concentrations of Eu(III). orotic acid and pH with relationships kinetically consistent with the above hypothesis.     

Rapid bioanalysis of vancomycin in serum and urine by high-performance liquid chromatography tandem mass spectrometry using on-line sample extraction and parallel analytical columns

A novel high-performance liquid chromatography tandem mass spectrometry (LC/MS/MS) method is described for the determination of vancomycin in serum and urine. After the addition of internal standard (teicoplanin), serum and urine samples were directly injected onto an HPLC system consisting of an extraction column and dual analytical columns. The columns are plumbed through two switching valves. A six-port valve directs extraction column effluent either to waste or to an analytical column. A ten-port valve simultaneously permits equilibration of one analytical column while the other is used for sample analysis. Thus, off-line analytical column equilibration time does not require mass spectrometer time, freeing the detector for increased sample throughput. The on-line sample extraction step takes 15 seconds followed by gradient chromatography taking another 90 seconds. Having minimal sample pretreatment the method is both simple and fast. This system has been used to successfully develop a validated positive-ion electrospray bioanalytical method for the quantitation of vancomycin. Detection of vancomycin was accurate and precise, with a limit of detection of 1 ng/mL in serum and urine. The calibration curves for vancomycin in rat, dog and primate were linear in a concentration range of 0.001-10 microg/mL for serum and urine. This method has been successfully applied to determine the concentration of vancomycin in rat, dog and primate serum and urine samples from pharmacokinetic and urinary excretion studies.     

Rapid determination of orotic acid in urine by a fast liquid chromatography/tandem mass spectrometric method

Quantification of orotic acid (uracil-6-carboxylic acid) in urine is an important tool to diagnose some inherited diseases, such as urea cycle disorder (OTCD) and hereditary orotic aciduria. New rapid analytical methods are necessary to provide high-throughput orotic acid analyses. A new analytical method has been developed for the rapid analysis of orotic acid in urine by liquid chromatography coupled with ion spray tandem mass spectrometry (LC/MS/MS). After a sample dilution 1:20, the analysis was performed in the selected reaction monitoring mode in which orotic acid was detected through the transition m/z 155 to 111. The retention time was 3.9 min in a 4.5-min analysis. Daily calibration between 0.5-5.0 micromol/L of orotic acid, corresponding to 10-100 micromol/L in urine before the 1:20 dilution, offered consistent linearity and reproducibility. Interassay coefficient of variance (c.v.) was 4.97% at a mean concentration of 10.99 micromol/L. The sensitivity and specificity of tandem mass spectrometry permitted a high volume of analyses of orotic acid. The sample preparation is simple, inexpensive and not time demanding.     

Orotic acid: a milk constituent Enzymatic determination by means of a new microcalorimetric method

The presence of orotic acid (a precursor of nucleic acid) in milk is very important in order to ensure its nutritional value and good conservation. In the literature, chromatographic, spectrophotometric and polarographic methods are reviewed. The reported values have a very wide interval range (19-664 mg l(-1)) and a low precision. The new method proposed in this article employs an enzymatic reaction. It has been improved on standards and then tested on milk samples. The same samples were also tested by means of a known spectrophotometric method. The new analytical method for orotic acid determination is reliable; the results are more accurate and more precise if compared with the usual methods, and it shows the same sensibility. The calorimetric analysis is faster and easier, owing to the fact that no sample treatments are required.     

Determination of cadmium in urine by extraction and flameless atomic-absorption spectrophotometry Comparison of urine from smokers and non-smokers of different sex and age

A method is presented for determining cadmium in urine by nameless atomic-absorption spectrophotometry after extraction. The sample is dried, ashed in the presence of nitric acid, and then the residue is dissolved in hydrochloric acid. Cadmium is extracted as its tetrahexylammonium iodide complex into methyl isobutyl ketone. The organic phase is analysed for cadmium by atomic-absorption spectrophotometry with electrothermal atomization. The median urinary excretion of cadmium for smokers aged 50-64 has been found to be 0.7 and 0.75 mug l . for males and females respectively, the values for non-smokers being 0.25 and 0.4mug l .     

Determination of orotic acid, uric acid, and creatinine in milk by liquid chromatography

A simultaneous determination of orotic acid, uric acid, and creatinine in milk is described. Following deproteinization, the sample was analyzed by reversed-phase liquid chromatography, using a highly aqueous cationic ion-pair eluent and photodiode array UV detection. In view of their potential dietary significance, the validated method was applied to survey the influence of species, season, and lactation on their contribution to the nonprotein nitrogen pool in milk. Mature bovine milk contained orotic acid, uric acid, and creatinine in the range of 30-70, 9-24, and 6-12 microg/mL, respectively. Although uric acid and creatinine were present in all milks, orotic acid was essentially absent in nonruminant milks. In contrast to urate and creatinine, expression of orotic acid in bovine milk was strongly dependent on stage of early lactation. The co-existence in mammalian milks of related nucleoside and nucleotide components was also determined.     

Improvements in automated analysis of catecholamine and related metabolites in biological samples by column-switching high-performance liquid chromatography

Previously two fully automated methods based on column switching and high-performance liquid chromatography have been described, one for plasma and urinary catecholamines and the other for catecholamine urinary metabolites. Improvements in these methods, after 3 years of routine application, are now reported. The sample processing scheme was changed in order to eliminate memory effects and, in the procedure for plasma catecholamines, a pre-analytical deproteinization step was added which enhances the analytical column lifetime. The applied voltages for the electrochemical detector have been optimized, resulting in an automated method, suitable for the simultaneous determination of vanillylmandelic acid, 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindoleacetic acid. The sensitivity of the methods allows the detection of 2-3 ng/l of plasma catecholamines and 0.01-0.06 mg/l of urinary metabolites. Also, it is possible to switch from one method to the other in only 30 min. The normal values obtained from 200 healthy people are reported, together with a list of 57 potential interfering substances tested.     

Simultaneous determination of imidazoleacetic acid and N tau- and N pi-methylimidazoleacetic acids in human urine by high-performance liquid chromatography with fluorescence detection

A sensitive method for the simultaneous determination of urinary imidazoleacetic acid and N tau- and N pi-methylimidazoleacetic acids which employs high-performance liquid chromatography with fluorescence detection is described. The compounds were converted into the corresponding fluorescent esters by reaction with 4-bromomethyl-7-methoxycoumarin. These derivatives are separated by liquid chromatography on a Radial-Pak silica column. The detection limits for imidazoleacetic acid and N tau-and N pi-methylimidazoleacetic acids in urine are 15, 10 and 20 pmol/ml, respectively. The 24-h urinary excretion of imidazoleacetic acid and N tau-and N N pi-methylimidazoleacetic acids by healthy persons was 5.7-39.9, 4.3-24.6 and 1.5-19.3 nmol/mg of creatinine, respectively.     

Direct determination of folate monoglutamates in plasma by high-performance liquid chromatography using an automatic precolumn-switching system as sample clean-up procedure

A simple and rapid technique for the simultaneous isolation and analysis of folate monoglutamates (folic acid, 7,8-dihydrofolic acid, 5,6,7,8-tetrahydrofolic acid and 5-formyl-, 5-methyl- and 10-formyl-5,6,7,8-tetrahydrofolic acids) was developed using reversed-phase high-performance liquid chromatography with an automatic precolumn-switching system. The plasma or the dissolved diet samples were directly injected onto a short precolumn flushed with 50 mM phosphate buffer. The folate vitamers absorbed on the precolumn were backflushed onto the analytical column with a 25 mM phosphate buffer containing 5% methanol and then detected by UV absorption at 280 nm. A linear response was found between the injected sample amounts and the integrated areas for all vitamers analysed. The detection limit was 1-10 pmol and the precision ranged from 1.6 to 10%, depending on the metabolite studied. The recovery rates of folates in plasma were 90-95%. Decomposition of the unstable folates was avoided. Our method was applied to the analysis of mouse plasma and animal diets.     

Ion-exclusion chromatography determination of organic acid in uridine 5'-monophosphate fermentation broth

Simultaneous determination of organic acids using ion-exclusion liquid chromatography and ultraviolet detection is described. The chromatographic conditions are optimized when an Aminex HPX-87H column (300 × 7.8 mm) is employed, with a solution of 3 mmol/L sulfuric acid as eluent, a flow rate of 0.4 mL/min and a column temperature of 60°C. Eight organic acids (including orotic acid, α-ketoglutaric acid, citric acid, pyruvic acid, malic acid, succinic acid, lactic acid and acetic acid) and one nucleotide are successfully quantified. The calibration curves for these analytes are linear, with correlation coefficients exceeding 0.999. The average recovery of organic acids is in the range of 97.6% ～ 103.1%, and the relative standard deviation is in the range of 0.037% ～ 0.38%. The method is subsequently applied to obtain organic acid profiles of uridine 5'-monophosphate culture broth fermented from orotic acid by Saccharomyces cerevisiae. These data demonstrate the quantitative accuracy for nucleotide fermentation mixtures, and suggest that the method may also be applicable to other biological samples.     

Rapid procedure for chromatographic isolation of DOPA, DOPAC, epinephrine, norepinephrine and dopamine from a single urinary sample at endogenous levels

A three-step procedure has been investigated to extract 3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylacetic acid (DOPAC), epinephrine (E), norepinephrine (NE) and dopamine (DA) from a single urinary sample with the object of obtaining extracts pure enough for specific fluorimetric assay. The procedure described in this paper results from the combination of urine purification on an aluminum oxide column, separation by ion-exchange chromatography of the DOPA-DOPAC fraction from catecholamines, and ether isolation of DOPAC from DOPA. The whole procedure is rapid and easily performed in one work day. Extraction recoveries were 72.4 +- 3.5%, 76 +- 2%, 85.7 +- 3.3%, 85.6 +- 1.4% and 92.4 +- 5.5% for DOPA, DOPAC, E, NE and DA respectively (n=6). The lowest amounts of the five catechols that could be detected in urinary samples by a combination of this extraction procedure and the methods of assay used in our laboratory were 15 ng for DOPA, 40 ng for NE, 20 ng for E, 152 ng for DA and 2.95 micrograms for DOPAC. Urinary volumes convenient for accurate estimation of each compound were 20 ml for healthy human subjects. For pathological or pharmacological purposes, 5 ml of human urine were sufficient. The daily excretion of DOPA, DOPAC, E, NE and DA found by this procedure agrees with data obtained by other authors in healthy subjects. In pathological samples, our three-step procedure led to lower amounts than methods using alumina purification only. The discrepancies between the two methods are discussed in terms of development of internal standards, relative specificity of fluorimetric assays, values of blank eluates, and the possibility of interference from unknown abnormal body metabolites or pharmacological drugs not eliminated by a single-step alumina purification.     

High-performance liquid chromatographic analysis of 5-ethylpyrimidines and 5-methylpyrimidines in plasma

A high-performance liquid chromatographic (HPLC) method employing a C18 reversed-phase column, a mobile phase of sodium acetate and methanol, and an ultraviolet detector was developed for the analysis of 5-ethylpyrimidines and 5-methylpyrimidines in plasma. Samples were prepared for HPLC by sequential cation-exchange and anion-exchange column chromatography. Linear standard curves were obtained for samples containing 0.05-50 micrograms/ml 5-ethyl-2'-deoxyuridine and 5-ethyluracil, 0.05-10 micrograms ml 5-(1-hydroxyethyl)uracil, and 0.1-50 micrograms/ml thymidine, thymine and 5-hydroxymethyluracil. Applicability of the method to determination of the kinetics of 5-ethyl-2'-deoxyuridine elimination by the isolated perfused rat liver was demonstrated; clearance of the drug was 1.29 ml/min.