Simultaneous Determination Of Melatonin Research Articles

Caffeic Acid Based Polyurethane Membrane Modified Screen-Printed Electrodes and Their Application for the Simultaneous Determination of Melatonin and Serotonin

Caffeic acid (CA) based polyurethane (PU) films were synthesized and characterized for the simultaneous determination of melatonin (MT) and serotonin (5-HT). The CA based PUs were synthesized using a polyol mixture of 4,4’-diisocyanodiphenylmethane (MPI), polyethylene glycol-200 (PEG), and CA. The PEG–CA monomer units in the polyol were varied in molar ratios of 99:1, 97:3, 95:5, and 90:10. The synthesized PUs were characterized by FTIR spectroscopy and thermal analysis. These CA based PU films were coated onto screen-printed carbon electrodes (SPCEs) with varying thicknesses and used for the simultaneous determination of MT and 5-HT. Electrochemical responses of MT and 5-HT were evaluated using differential pulse voltammetry. The limit of detection and correlation coefficient for MT were 280 µM and 0.9797, respectively, while for 5-HT, the detection was 150 µM with a correlation coefficient of 0.9690. The precision, expressed as the relative standard deviation was 2.633% for MT and 4.668% for 5-HT. These findings suggest that CA based PU-modified electrodes hold potential in medical and biomedical applications.

A Bio-Analytic Nanoplatform Based on AU Post-Functionalized Cefeo3 for the Simultaneous Determination of Melatonin and Ascorbic Acid Through Photoelectrochemical Technology

A Bio-Analytic Nanoplatform Based on AU Post-Functionalized Cefeo3 for the Simultaneous Determination of Melatonin and Ascorbic Acid Through Photoelectrochemical Technology

Simultaneous determination of melatonin and 6-hydroxymelatonin in human overnight urine by LC-MS/MS

For the quantification of the pineal hormone melatonin and its metabolite, 6-hydroxymelatonin, in human overnight urine, a single accurate method by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed. Urine samples were deconjugated using β-glucuronidase/arylsulfatase from Helix pomatia before solid phase extraction (SPE) purification. Chromatographic separation was performed using a reverse phase C18 column with a 7-minute gradient elution. Water was used as matrix to prepare the calibration standards, and deuterated analogues of melatonin and 6-hydroxymelatonin were used as internal standards. This newly developed method was validated in terms of linearity, accuracy, repeatability, intermediate precision, recovery, matrix effect, and stability according to the guidelines of the European Medicines Agency. The method was successfully applied to the analysis of overnight urine samples from 12 healthy volunteers, showing significant correlations of urinary melatonin and 6-hydroxymelatonin excretion rates with age. The urinary 6-hydroxymelatonin to melatonin ratio was also established and will be assessed in further studies as a potential endogenous metric of CYP1A2 activity.

Simultaneous determination of melatonin and trans-resveratrol in wine by dispersive liquid–liquid microextraction followed by HPLC-FLD

The discovery of melatonin (Mel) in wines triggered a new interest in the paradigm of health benefits and wine consumption, usually ascribed to trans-resveratrol (trans-RSV). In this context, a dispersive liquid–liquid microextraction for the analysis of Mel and trans-RSV in wines by LC-FLD was developed. A 26-1 factorial design was used to identify the significant variables (p < 0.05) and Central Composite Design was used to achieve the optimal conditions: 300 µL of chloroform (extracting solvent), 1500 µL of acetonitrile (disperser solvent) and 1500 mg of NaCl (ionic strength). Excellent linearity (R2 > 0.9999), repeatability (<3.55%), and accuracy (<7.18%) were obtained using a blank matrix and recoveries (>91.9%) using wines. The method was successfully applied to the analyses of Mel (0.63–7.44 ng mL−1) and trans-RSV (169–2616 ng mL−1) in different wine varieties. Comparison with literature point the overall advantages of the new method.

Melatonin and Hyaluronic Acid Mixture as a Possible Therapeutic Agent in Dental Medicine

The present work reports an efficient procedure for a simultaneous determination of melatonin (MEL) and hyaluronic acid (HA) mixture applying first derivative UV-Vis spectrophotometry. At selected wavelength (205 nm), the linearity range for each component of the mixture was established. The linear regression correlation coefficients for the direct UV-Vis spectra (RHA2 = 0.9627) and their first derivate (RHA2 = 0.9986) put in evidence a better fit for the derivative procedure. Through such simple analysis method, it was possible to emphasize that each component of MEL-HA mixture preserves its identity and characteristic properties. Consequently, the association of MEL and HA biomolecules could be used for obtaining a complex therapeutic agent with extensive applications in dental medicine.

Nanomolar simultaneous determination of tryptophan and melatonin by a new ionic liquid carbon paste electrode modified with SnO2-Co3O4@rGO nanocomposite

This work describes the development of a new sensor for simultaneous determination of tryptophan and melatonin. The proposed sensor was an ionic liquid carbon paste electrode modified with reduced graphene oxides decorated with SnO2-Co3O4 nanoparticles. The voltammetric oxidation of the analytes by the proposed sensor confirmed that the electrooxidation process undergoes a two-electron/one-proton reaction for melatonin and a two-electron/two-proton reaction for tryptophan in diffusion-controlled processes. Moreover, based on the excellent electrochemical properties of the modified electrode, a sensitive voltammetric method was used for individual and simultaneous determination of melatonin and tryptophan in the aqueous solutions. Under the optimized experimental conditions, a linear response obtained in the range of 0.02 to 6.00μmolL−1 with detection limits of 4.1 and 3.2nmolL−1 for melatonin and tryptophan, respectively. The prepared sensor possessed accurate and rapid response toward melatonin and tryptophan with a good sensitivity, selectivity, stability, and repeatability. Finally, the applicability of the proposed sensor was verified by evaluation of melatonin and tryptophan in various real samples including human serum and tablet samples.

Solid phase extraction/cyclodextrin-modified micellar electrokinetic chromatography for the analysis of melatonin and related indole compounds in plants

The identification of melatonin in plants has inspired new investigations to understand its biological function. In this work, a robust, reliable, low-cost, quick and simple method based on solid phase extraction followed by micellar electrokinetic chromatography for the extraction, preconcentration and simultaneous determination of melatonin, tryptophan, serotonin and indole-3-acetic acid in plant material is proposed. Extraction of indole compounds from plant tissues was enhanced by ultrasound and solid phase extraction, which was carried out with C8 SPE cartridges. The use of a dual pseudostationary phase system, involving a mixture of SDS anionic micelles and β-cyclodextrin, enabled to reach adequate selectivity. A BGE of 10mM sodium tetraborate (pH9.2), containing 20mM β-CD, 20mM SDS, and 10% (v/v) of acetonitrile, allowed baseline separation in less than 10min. The proposed methodology provided limits of detection (LODs) down to low ppb levels. Under the optimal conditions, a successful application on Arabidopsis tissue, green, and linden tea leaves confirmed the validity of this method for food analysis and as a tool to contribute to the elucidation of the biological role of melatonin in plants.

Determination of melatonin and its precursors and metabolites using capillary electrophoresis with UV and fluorometric detection

A micellar electrokinetic chromatography method has been developed for simultaneous determination of melatonin and its precursors and metabolites. A 20 mM borate buffer pH 9.5 with 50 mM SDS served as the electrolyte. Tryptophan, 5-methoxyindoleacetic acid, 6-hydroxymelatonin, melatonin, serotonin, and 5-methoxytryptamine were baseline separated in less than 13 min. The limits of detection for UV detection and fluorometric detection based on native fluorescence of analytes were at the sub-ppm level. The proposed method with UV detection was applied to melatonin content control in pharmaceutical tablets with a precision expressed as RSD (n = 7) = 1.6%. For biological samples extraction with chloroform and ethyl acetate was examined. With ethyl acetate and chloroform recoveries of 87.2% and 82.1% melatonin, respectively, were obtained from plasma samples. The recovery of melatonin from spiked urine samples was 80.0% for ethyl acetate and 82.5% for chloroform. Fluorometric detection provides about two-fold improvement over UV in the detection of melatonin and minor improvements for three other analytes, but is much poorer than UV for tryptophan and 6-hydroxymelatonin in applied conditions.

Simultaneous spectrofluorimetric and spectrophotometric determination of melatonin and pyridoxine in pharmaceutical preparations by multivariate calibration methods

Partial least-squares (PLS) calibration and principal component regression (PCR) methods were utilized for the simultaneous spectrofluorimetric and spectrophotometric determination of pyridoxine (PY) and melatonin (MT). Since emission and adsorption spectra of these drugs overlap, PY and MT cannot be directly determined by fluorimetric nor by spectrophotometric methods. Full-spectrum multivariate calibration PLS and PCR methods were developed for both fluorimetry and spectrophotometry. The conditions were optimized for fluorimetric as well as for spectrophotometric determination of both drugs. The simultaneous determination of PY and MT was carried out in mixtures by recording the emission fluorescence spectrum between 324 and 500 nm ( λ ex 285 nm) for fluorimetry, and by recording the absorption spectrum between 250 and 350 nm for spectrophotometry ( λ max(PY) 310 nm, λ max(MT) 278 nm). The experimental calibration matrixes were designed orthogonally. At the optimum conditions, dynamic ranges were 0.04–1.3 and 0.1–4 μg ml –1 for fluorimetry and 1–22 and 1–24 μg ml –1 for spectrophotometry for MT and PY, respectively. The calibration concentrations were prepared in the dynamic ranges. The parameters of the chemometrics procedure for the simultaneous determination of MT and PY were optimized, and the proposed methods were validated with prediction set. Finally the procedures were successfully applied to simultaneous spectrofluorimetric and spectrophotometric determination of PY and MT in synthetic mixtures and in a pharmaceutical formulation.

Simultaneous determination of melatonin and pyridoxine in tablets by gas chromatography-mass spectrometry.

A gas chromatographic-mass spectrometric (GC-MS) method for the qualitative and quantitative determination of melatonin plus pyridoxine commercial tablets is described. Melatonin and pyridoxine were simultaneously determined by GC-MS after extraction from ground tablets with methanol and derivatization with N-methyl-N-N-trimethlylsilyltrifluoroacetamide (MSTFA). The mass chromatograms were generated using 232 m/z ion for melatonin and 280 m/z ion for pyridoxine, respectively. Splitless injection offers good reproducibility with a standard deviation of 2%. The developed method was applied to analyze the melatonin and pyridoxine content from two different tablet formulations. Also, recovery, detection and quantification limits are reported.

Simultaneous determination of serotonin, N-acetylserotonin and melatonin in the pineal gland of the juvenile golden hamster by high-performance liquid chromatography with electrochemical detection

A simple and simultaneous determination of melatonin and its precursors, serotonin (5-HT) and N-acetylserotonin, was achieved by reversed-phase high-performance liquid chromatography with electrochemical detection. The addition of an ion-paring agent, sodium 1-octanesulfonate, to the chromatographic mobile phase caused an increase of the retention time of 5-HT, and resulted in the successful simultaneous resolution of these three indoleamines. This method was used to quantitate these indoleamines in the pineal gland of juvenile golden hamsters.

Variation of melatonin and serotonin content in rat pineal gland with sex and oestrous phase difference determined by high-performance liquid chromatography with fluorimetric detection

Simultaneous determination of melatonin and serotonin in rat pineal gland is described using reversed-phase high-performance liquid chromatography with fluorimetric detection. These indoles were analysed isocratically within 15 min. In this work, veratric acid (3,4-dimethoxybenzoic acid), which has fluorescence characteristics (λ ex = 290 nm, λ em = 350 nm) around the wavelength of native fluorescence of melatonin (λ ex = 285 nm, λ em = 345 nm), was used as an internal standard. This method was applied to the determination of melatonin and serotonin in male and female rat pineal gland. No significant differences between the two groups were observed in the pineal melatonin and serotonin contents. The pineal melatonin and serotonin contents were compared with the oestrous and the dioestrous phases of female rats. They were not widely different from each other.