Determination Of Catechols Research Articles

Norepinephrine and its metabolites are involved in the synthesis of neuromelanin derived from the locus coeruleus.

In order to elucidate the chemical structure of black to brown pigments, neuromelanins (NMs), in the substantia nigra (SN) and the locus coeruleus (LC) in the central nervous system of humans and other mammalian species during aging, chemical degradative methods are powerful tools. HPLC analysis after hydroiodic acid hydrolysis detected aminohydroxyphenylethylamines, aminohydroxyphenylacetic acids, and aminohydroxyethylbenzenes, which confirmed that SN‐NM and LC‐NM contain melanin derived not only from dopamine and norepinephrine (NE) but also from several other catecholic metabolites, such as 3,4‐dihydroxyphenylalanine, 3,4‐dihydroxyphenylacetic acid, 3,4‐dihydroxymandelic acid, 3,4‐dihydroxyphenylethanol, and 3,4‐dihydroxyphenylethylene glycol, in addition to the corresponding Cys‐derivatives in varying degrees. However, hydroiodic acid hydrolysis showed that LC‐NM produced the same degradation products as were detected in SN‐NM. Thus, we needed to develop a new chemical detection method to validate the existence of NE in LC‐NM. In the present study, we report that HCl hydrolysis of LC‐NM in the presence of thioglycolic acid yields new products arising from substitution of the hydroxyl group by thioglycolic acid at the benzyl position of NE and cysteinyl‐NE. This is the first chemical evidence showing that NE and cysteinyl‐NE are incorporated into LC‐NM. Using the chemical degradation methods for the determination of catechols in neuromelanin (NM), we have shown that dopamine (DA), 3,4‐dihydroxyphenylacetic acid (DOPAC), 3,4‐dihydroxyphenylethanol (DOPE), and 3,4‐dihydroxyphenylalanine (DOPA) are mainly responsible for the structure of NM from substantia nigra (SN), while norepinephrine (NE), 3,4‐dihydroxymandelic acid (DOMA), and 3,4‐dihydroxyphenylethylene glycol (DOPEG) are additionally responsible for the structure of NM from locus coeruleus (LC).

New possibilities of micellar electrokinetic chromatography and microemulsion electrokinetic chromatography in the determination of catechols and catecholamines in natural samples

New possibilities were revealed and evaluative characteristics were obtained for different versions of capillary electrophoresis with UV detection, namely, micellar electrokinetic chromatography with normal and reversed polarity and microemulsion electrokinetic chromatography, used for determining catechols and catecholamines in green and black tea and in urine.

Possibilities and limitations of different modes of capillary electrophoresis for the quantitative determination of catechols and caffeine in black and green tea

Methods of capillary electrophoresis (capillary zone electrophoresis, micellar electrokinetic chromatography, and microemulsion electrokinetic chromatography) were compared in determining polyphenolic antioxidants and alkaloids in black and green tea. It was shown that reverse-flow micellar electrokinetic chromatography (RF-MEKC, pH < 2.5) using reversed pola rity is most preferable for the rapid simultaneous determination of catechols and caffeine. The detection limit was 1 mg/L.

Simultaneous determination of 5-hydroxyindoles and catechols from urine using polymer monolith microextraction coupled to high-performance liquid chromatography with fluorescence detection

To make analytes amenable for fluorescence (FL) detection, polymer monolith microextraction (PMME) coupled to high-performance liquid chromatography with FL detection was developed for the simultaneous determination of catechols and 5-hydroxyindoleamines (5-HIAs) from urine samples. In this method, a two-step pre-column derivatization method was employed to derivatize the analytes and a poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolithic capillary column was used as the extraction medium for PMME. The conditions for the derivatization and subsequent extraction of 5-HIAs and catechols derivatives were optimized. Using our optimum conditions, the detection limit of the target analytes were 0.11–21 nM. Reproducibility of the method was obtained with intra-day and inter-day relative standard deviations less than 12% and a recovery of higher than 82%. In this study, we show how our proposed method can be used as a rapid sensitive technique for the determination of catechols and 5-HIAs from urine samples.

Enzymatic Biosensors Based on Carbon Nanotubes Paste Electrodes

AbstractThe performance of enzymatic biosensors based on the immobilization of different enzymes within a carbon nanotubes paste electrode (CNTPE) prepared by dispersion of multi‐wall carbon nanotubes (MWNT) and mineral oil is reported in this work. The strong electrocatalytic activity of carbon nanotubes towards the reduction of hydrogen peroxide and quinones and the oxidation of NADH have allowed an effective low‐potential amperometric determination of lactate, phenols, catechols and ethanol, in connection with the incorporation of lactate oxidase, polyphenol oxidase and alcohol dehydrogenase/NAD+, respectively, within the composite matrix. Compared to the analogous enzymatic CPEs, a great enhancement in the response is observed at the enzymatic CNTPEs. Therefore, highly sensitive lactate, phenols, catechols and alcohols biosensors without using any metal or redox mediator can be obtained with this new composite material.

Simultaneous determination of 5-hydroxyindoles and catechols by high-performance liquid chromatography with fluorescence detection following derivatization with benzylamine and 1,2-diphenylethylenediamine

A highly selective and sensitive method for the simultaneous determination of 5-hydroxyindoles and catechols (serotonin, norepinephrine, dopamine and related compounds) by high-performance liquid chromatography with fluorescence detection is described. The method is based on the two-step precolumn derivatization of 5-hydroxyindoles and catechols with benzylamine (BA) and 1,2-diphenylethylenediamine (DPE), respectively, resulting in highly fluorescent and stable benzoxazole derivatives. The first derivatization with BA proceeds at room temperature (ca. 23 °C) for 2 min in a mixture of 0.3 M 3-cyclohexylamino-1-propanesulfonic acid buffer (pH 10.0) and methanol in the presence of potassium hexacyanoferrate(III). The subsequent second derivatization with DPE is carried out at 50 °C for 20 min in the presence of glycine. The resulting fluorescent derivatives of five 5-hydroxyindoles and seven catechols are separated on a reversed-phase column (150×1.5 mm I.D., packed with C 18 silica, 5 μm) with isocratic elution using a mixture of acetonitrile–15 m M acetate buffer (pH 4.5) (34:66, v/v) containing 1 m M octanesulfonic acid sodium salt, and are detected spectrofluorimetrically at 480 nm with excitation at 345 nm. The detection limits (signal-to-noise ratio of 3) of the related compounds are 80 amol to 86 fmol for a 20-μl injection.

Microchip capillary electrophoresis/electrochemistry.

Microfabricated fluidic devices have generated considerable interest over the past ten years due to the fact that sample preparation, injection, separation, derivatization, and detection can be integrated into one miniaturized device. This review reports progress in the development of microfabricated analytical systems based on microchip capillary electrophoresis (CE) with electrochemical (EC) detection. Electrochemical detection has several advantages for use with microchip electrophoresis systems, for example, ease of miniaturization, sensitivity, and selectivity. In this review, the basic components necessary for microchip CEEC are described, including several examples of different detector configurations. Lastly, details of the application of this technique to the determination of catechols and phenols, amino acids, peptides, carbohydrates, nitroaromatics, polymerase chain reaction (PCR) products, organophosphates, and hydrazines are described.

The Determination of Catechols in the Presence of Ascorbic Acid and Uric Acid by Flow Injection Analysis Employing a Potentiometric Dibenzo-18-crown-6 Electrode Detector

Abstract A polished platinum disc was modified by electropolymerization of dibenzo-18-crown-6 (DB-18-C-6) onto the surface. This DB-18-C-6 electrode has been used as a detector for catechol and catecholamines in a potentiometric-flow injection mode. The potentiometric-flow injection response of the DB-18-C-6 modified electrode exhibited a linear response for catechol and catecholamine concentrations from 10-2—10-6 M achieving detection limits as low as 0.5 × 10-6M. An interference study was carried out with ascorbic acid and uric acid which are serious interferents using amperometric detectors. No significant interference was observed for the presence of either of these two or mixture of these two common interferents until they were in greater than a 10-fold excess. 1 Present address: Department of Chemistry, College of Sciences, University of Cairo, Giza, Egypt 2 Present address: Teledyne, 16830 Chestnut Street, City of Industry, CA 91749—1580 3 Present address: College of Medicine, Univ. of Florida, Gai...

Determination of several catechols on bare and polymer coated glassy carbon electrode

AbstractGlassy carbon electrodes were coated with a copolymer of styrene and maleic acid anhydride. The voltammetric behavior of catechol, ascorbic acid, dopamine, and DOPAC was examined at both bare and coated electrode using cyclic voltammetry and modified differential pulse voltammetry. Electrochemical pretreatment increased peak current of catechol and its derivatives; the polymer coating caused significant decrease of peak currents and shift of peak potentials. The signal of ascorbic acid is greatly suppressed, while that of DOPAC disappears even after polymer coating.

Laccase-based biosensor for determination of polyphenols: determination of catechols in tea

A new method of amperometric determination of phenolic compounds using an enzyme electrode is proposed. The latter represents the combination of the oxygen electrode and immobilized laccase. Analytical systems of flow injection and batch types were considered. A method of immobilization was developed that provided an increase in the stability of the enzyme. Optimal conditions for biosensor operation were found. The time needed for analysis in the flow injection mode was below 100 s. A column with immobilized enzyme could be used for up to 500 determinations of phenolic compounds without decrease of the enzyme activity. The practial validity of the method was demonstrated by tannin analysis in tea of different brands.

Simultaneous determination of endogenous catechols and exogenous 2- and 6-fluorinated catechols in tissue and plasma using liquid chromatography with electrochemical detection

Simultaneous determination of endogenous catechols and exogenous 2- and 6-fluorinated catechols in tissue and plasma using liquid chromatography with electrochemical detection

Simultaneous determination of catechols in thalamic slices with liquid chromatography/electrochemistry

A method was developed for the simultaneous determination of dopamine (DA), epinephrine (E), norepinephrine (NE), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3-methoxy-4-hydroxyphenylglycol (MHPG), as well as L-3,4-dihydroxyphenylalanine (L-DOPA) with liquid chromatography (LC) using electrochemical (EC) detection. With a ODS column and a mobile phase consisting of a sodium acetate-citrate with heptasulfonic acid, this method was applied on simultaneous determination of chatechols released from thalamic slices of ddY mouse. The pretreatment of the bathing medium required only centrifugation, and the supernatant was injected directly into the LCEC system. The high potassium stimulation of catecholaminergically innervated thalamic slices led to increase in the levels of DA, NE, DOPAC and MHPG, especially of NE, but not that of L-DOPA itself. In the present study, we designed to make simultaneous determination of catechols released from thalamic slices for estimation of the physiological status of catecholaminergic neuronal activity.

Determination of indoles and catechols in rat brain and pineal using liquid chromatography with fluorometric and amperometric detection

Tryptophan, serotonin, 5-hydroxyindoleacetic acid, and homovanillic acid were determined in rat brain by the direct injection of a centrifuged tissue homogenate into a liquid chromatographic—fluorometric/amperometric system. The above indoles, along with melatonin, were also determined in single rat pineal glands. The utility of the system in determining several additional catechols and indoles in brain was examined.

Determination of dopa, dopamine, dopac, epinephrine, norepinephrine, alpha-monofluoromethyldopa and alpha-difluoromethyldopa in various tissues of mice and rats using reversed-phase ion-pair liquid chromatography with electrochemical detection.

A method for the determination of catecholic amino acids and amines by reversed-phase ion-pair high-performance liquid chromatography with electrochemical detection has been developed. B using octanesulfonic acid for ion pairing and by optimising ionic strength, pH and methanol concentration of the mobile phase, separation was achieved of 3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylacetic acid (DOPAC), norepinephrine (NE), epinephrine (EPI), and dopamine (DA). Alpha-Difluoromethyldopa (DFMD) and alpha-monofluoromethyldopa (MFMD), two potent enzyme-activated irreversible inhibitors of aromatic amino acid decarboxylase were also separated from the natural catechols. Concentrations of catechols and inhibitors were measured in brains, hearts and kidneys of mice treated with small repeated doses of MFMD. The method has also been applied to the determination of catechols in other organs such as prostates and seminal vesicles of rats and in smaller tissues like mesenteric arteries. A semi-automated procedure making use of an automatic sample processor and a digital integrator permitted the analysis of as many as sixty samples per day.

Catechols in primary and metastatic human malignant melanoma cells in monolayer culture

Dopa and 5-S-cysteinyldopa were determined in permanent cell lines obtained from two primary and two metastatic human malignant melanoma and also in one clone of one of the primary melanoma cell lines. The cell lines differed considerably with regard to catechol content and secretion into the media. The clone also differed from the original cell line. Results in the exponential growth phase differed from those in the plateau phase and change of medium affected catechol content. Determination of catechols in cultured melanoma cells can be used for characterization of cell lines that cannot be separated by optical or ultrastructural morphological methods.

Microanalysis of catechols as lead salts by infrared spectroscopy

A method is described for qualitative determination of various catechols in the microgram range based on the infrared spectra of their lead salts. Neutral Pb(OAc) 2 precipitated catechols as their lead salts from aqueous and from ether solutions. From 5 ml aqueous solution, 25 μg catechol was easily recovered and identified by IR as lead catecholate. The salts could be reconverted to free catechols by treatment with (NH 4) 2S, H 2S, or H 2SO 4 and this solution analyzed directly by gas chromatography. Two muconic acids were also precipitated by Pb(OAc) 2 and characterized by their IR spectra.

Spectrophotometric determination of catechols with 4-aminoantipyrine

Abstract : Phenols, oxidized with hydrogen peroxide or potassium ferricyanide in alkaline medium, give a color reaction with 4-aminopyrazoles. This reaction with 4-aminoantipyrine (Emerson's reagent) is the basis of a sensitive and specific analytical method for phenols. We have observed that when atmospheric oxygen acts as the oxidant, only catechols respond to the test. This permits the determination of catechols in the presence of other phenols. (ARUTHOR)

Studies in detoxication. 51. The determination of catechols in urine, and the formation of catechols in rabbits receiving halogenobenzenes and other compounds; dihydroxylation in vivo.

Research Article| August 01 1953 Studies in detoxication. 51. The determination of catechols in urine, and the formation of catechols in rabbits receiving halogenobenzenes and other compounds. Dihydroxylation in vivo W. M. Azouz; W. M. Azouz 1Department of Biochemistry, St Mary's Hospital Medical School, London, W. 2 Search for other works by this author on: This Site PubMed Google Scholar D. V. Parke; D. V. Parke 1Department of Biochemistry, St Mary's Hospital Medical School, London, W. 2 Search for other works by this author on: This Site PubMed Google Scholar R. T. Williams R. T. Williams 1Department of Biochemistry, St Mary's Hospital Medical School, London, W. 2 Search for other works by this author on: This Site PubMed Google Scholar Biochem J (1953) 55 (1): 146–151. https://doi.org/10.1042/bj0550146 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share MailTo Twitter LinkedIn Cite Icon Cite Get Permissions Citation W. M. Azouz, D. V. Parke, R. T. Williams; Studies in detoxication. 51. The determination of catechols in urine, and the formation of catechols in rabbits receiving halogenobenzenes and other compounds. Dihydroxylation in vivo. Biochem J 1 August 1953; 55 (1): 146–151. doi: https://doi.org/10.1042/bj0550146 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Journal Search Advanced Search This content is only available as a PDF. © 1953 CAMBRIDGE UNIVERSITY PRESS1953 Article PDF first page preview Close Modal You do not currently have access to this content.