Simple column liquid chromatographic assay for serum neopterin

Pteridine determination in human serum with special emphasis on HPLC methods with fluorimetric detection

Conjugated and unconjugated pteridines and their derivatives are important cofactors in cellular metabolism. Hence, the amount of unconjugated pteridines in biological fluids has been found to be modified as a result of several disorders. It is necessary to note that while for the control of pteridines in urine samples there are numerous reference data, the literature referred to for the analysis of these analytes in serum/plasma is scarce. In biological fluids, pteridines can exist in different oxidation states, and these compounds can be classified into two groups according to: (a) oxidized or aromatic pteridines and (b) reduced pteridines. Oxidized pteridines yield a strong fluorescence signal, whereas reduced pteridines present a low quantum yield of fluorescence. In order to enable the analysis of the reduced forms, several preoxidation procedures to generate aromatic rings have been established. Also, stabilization of the reduced forms by the addition of reducing agents has been widely reported. The objective of this paper is to show possibilities and different approaches in the analysis of pteridines in serum samples. We have mainly focused on the description of the current situation in the application of high-performance chromatography methods with fluorimetric detection.

Spectral characterization of a pteridine derivative from cyanide-utilizing bacterium Bacillus subtilis - JN989651

Soil and water samples were collected from various regions of SIPCOT and nearby Vanappadi Lake, Ranipet, Tamilnadu, India. Based on their colony morphology and their stability during subculturing, 72 bacteria were isolated, of which 14 isolates were actinomycetes. Preliminary selection was carried out to exploit the ability of the microorganisms to utilize sodium cyanate as nitrogen source. Those organisms that were able to utilize cyanate were subjected to secondary screening viz., utilization of sodium cyanide as the nitrogen source. The oxygenolytic cleavage of cyanide is dependent on cyanide monooxygenase which obligately requires pterin cofactor for its activity. Based on this, the organisms capable of utilizing sodium cyanide were tested for the presence of pterin. Thin layer chromatography (TLC) of the cell extracts using n-butanol: 5 N glacial acetic acid (4:1) revealed that 10 out of 12 organisms that were able to utilize cyanide had the pterin-related blue fluorescent compound in the cell extract. The cell extracts of these 10 organisms were subjected to high performance thin layer chromatography (HPTLC) for further confirmation using a pterin standard. Based on the incubation period, cell biomass yield, peak height and area, strain VPW3 was selected and was identified as Bacillus subtilis. The Rf value of the cell extract was 0.73 which was consistent with the 0.74 Rf value of the pterin standard when scanned at 254 nm. The compound was extracted and purified by preparative High Performance Liquid Chromatography (HPLC). Characterization of the compound was performed by ultraviolet spectrum, fluorescence spectrum, Electrospray Ionization-Mass Spectrometry (ESI-MS), and Nuclear Magnetic Resonance spectroscopy (NMR). The compound is proposed to be 6-propionyl pterin (2-amino-6-propionyl-3H-pteridin-4-one).

Urinary neopterin quantification by reverse-phase high-performance liquid chromatography with ultraviolet detection

Neopterin plays an important role in the malignant disease diagnostics. However, the methods employed in neopterin determination are generally difficult and/or time consuming. The aim of this work was to standardize a practical method to quantify neopterin using high-performance liquid chromatography-ultraviolet (HPLC-UV) and quantify it in patients with systemic lupus erythematosus (SLE). Urine was collected from healthy subjects (n= 49), patients with inactive (n= 15), active (n= 28), and highly active SLE (n= 6). The HPLC was performed using two coupled reverse-phase columns eluted with 150 mM sodium phosphate, pH 4.0, under a flow rate of 0.8 ml/min, with UV detector set at 353 nm and 100-fold diluted urines. The inter- and intra-assay studies presented an imprecision of 12.5% and 12.9% for quality controls of 3.94 and 1.1 micromol/ml, respectively. Recovery from 79.5% to 82% was observed throughout the assay's linear range. Subjects with active (874.2 +/- 165.38 micromol/mol creatinin) and highly active SLE (1753.8 +/- 453.9 micromol/mol creatinin) showed three- and sixfold increased neopterin levels, respectively, compared to subjects with inactive SLE (314.3 +/- 121.3 micromol/mol creatinin) and healthy subjects (294.6 +/- 178.6 micromol/mol creatinin) (P< 0.05). Briefly, the proposed method was precise, specific, and reproducible, not invasive and allows the urinary neopterin quantification only with UV detection.

High-performance liquid chromatographic methods for the quantification of tetrahydrobiopterin biosynthetic enzymes

Tetrahydrobiopterin is a cofactor in hydroxylation reactions, including phenylalanine 4-monooxygenase, tyrosine 3-monooxygenase, tryptophan 5-monooxygenase, alkyl glycol ether monooxygenase and nitric oxide synthase. Determination of its biosynthesis is carried out to diagnose inherited diseases leading to partial defects in tetrahydrobiopterin synthesis. In addition, tetrahydrobiopterin synthesis is induced by proinflammatory cytokines, and intracellular levels of tetrahydro-biopterin in many cases limit the activity of tetrahydrobiopterin-dependent reactions, such as nitric oxide synthase in intact cells. Biosynthesis of tetrahydrobiopterin from guanosine 5'-triphosphate (GTP) requires the action of three enzymes, GTP-cyclohydrolase I (E.C. 3.5.4.16), 6-pyruvoyl tetrahydropterin synthase (EC, 4.6.1.10) and sepiapterin reductase (E.C. 1.1.1.153). Methods for quantification of biopterin and related pteridines in biological matrices by HPLC and application of these for determining the activity of the three tetrahydrobiopterin biosynthetic enzymes are reviewed in this article.

Assay of neopterin in serum by means of two-dimensional high-performance liquid chromatography with automated column switching using three retention mechanisms

An automated two-dimensional HPLC method for the determination of neopterin in serum is described. Neopterin is separated from proteins on a short octadecylsilica column by size exclusion and from the majority of the other serum components by adsorption. The fraction containing neopterin is transferred by column switching to a solvent-generated cation-exchange column using dodecylsulfonic acid as surface activator. Parameters influencing the separation performance and sensitivity of the fluorescence detection are discussed. The efficiency of the cleaning of the first column was optimized. The method was validated. It achieves a precision of 1% (R.S.D.) and a detection limit of about 0.3 nmol/l. The accuracy is nearly 100%. The method allows a high sample throughput, requiring 15 min per sample.

Abnormal alpha-aminoadipic acid excretion in a newborn with a defect in platelet aggregation and antenatal cerebral haemorrhage

alpha-Aminoadipic acid (alpha AA) is an intermediate in lysine metabolism. We report a new case with alpha AA excess in urine and plasma, without alpha-ketoadipic acid, in a full-term male child born to unrelated parents; he presented at 24h of life with seizures that failed to respond to phenobarbital, clonazepam, and Vigabatrin and death occurred on the 38th day of life. Brain imaging suggested antenatal haemorrhage. Small quantities of alpha AA were also detected in the blood and urine of both parents and a healthy brother, all three of whom exhibited the same defect in platelet aggregation as the deceased child. Both parents had decreased levels of plasma neopterin, a finding that might be related to the immunodeficiency described in other cases.

High-performance liquid chromatographic measurement of cerebrospinal fluid tetrahydrobiopterin, neopterin, homovanillic acid and 5-hydroxindoleacetic acid in neurological diseases

Cerebrospinal fluid (CSF) samples from patients with a variety of neurological disorders were assayed to determine the concentrations of tetrahydrobiopterin (BH4), the active cofactor of hydroxylases. Dihydroneopterin (NH2) and neopterin (N), which are linked with BH4 synthesis and are inflammatory biochemical markers, were also measured simultaneously in a number of patients. 5-Hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA), the main products of serotonin and dopamine breakdown, were analyzed in parallel whenever possible. As BH4 and NH2 are difficult to analyze owing to their instability, CSF samples were collected under special conditions to preserve the reduced BH4 and NH2. Liquid chromatographic assays and detection of the various substances measured also required particular precautions. BH4 concentrations were elevated in patients with neurological disorders such as syphilis and lupus-like disease and especially in an AIDS patient with neurological complications with an increased N/BH4 ratio.