Liquid chromatographic determination of diclofenac in human synovial fluid

Identification of new inhibitors of NS5 from dengue virus using saturation transfer difference (STD-NMR) and molecular docking studies

The rapid spread of dengue virus has now emerged as a major health problem worldwide, particularly in tropical and sub-tropical regions. Nearly half of the human population is at risk of getting infection. Among the proteomes of dengue virus, nonstructural protein NS5 is conserved across the genus Flavivirus. NS5 comprises methyltransferase enzyme (MTase) domain, which helps in viral RNA capping, and RNA-dependent RNA polymerase (RdRp) domain, which is important for the virus replication. Negative modulation of NS5 decreases its activity and associated functions. Despite recent advances, there is still an immense need for effective approaches toward drug discovery against dengue virus. Drug repurposing is an approach to identify the new therapeutic indications of already approved drugs, for the treatment of both common and rare diseases, and can potentially lower the cost, and time required for drug discovery and development. In this study, we evaluated 75 compounds (grouped into 15 mixtures), including 13 natural compounds and 62 drugs, by using biophysical methods, for their ability to interact with NS5 protein, which were further validated by molecular docking and simulation studies. Our current study led to the identification of 12 ligands, including both 9 US-FDA approved drugs and 3 natural products that need to be further studied as potential antiviral agents against dengue virus.

Diclofenac Concentrations in Post-Mortem Specimens-Distribution, Case Reports, and Validated Method (UHPLC-QqQ-MS/MS) for Its Determination

The aim of the research was to establish a sensitive method for the quantification of diclofenac in postmortem samples. The developed method was applied in six cases: three fetuses in which the use of abortion pills by their mothers was suspected, one case of duodenal ulcer perforation, one case of traffic accident with fatal outcome, and one acute renal failure in which the distribution of diclofenac was examined. The analyses were performed using liquid-liquid extraction of postmortem samples and the quantification of diclofenac via ultra-high performance liquid chromatography, coupled with triple quadrupole tandem mass spectrometry. Gradient elution using a C18 column was applied. Electrospray ionization measurement in positive multiple reaction monitoring mode was used. Diclofenac-d4 was used as an internal standard. The validation parameters were as follows: lower limit of quantification: 0.5 ng/mL, linearity of calibration curve: 0.5-500 ng/mL, intra- and interday accuracies and precisions: not greater than 15%; recovery values: 72.0-102.2%, and matrix effect: 2.2-28.0%. The developed method enabled the determination of diclofenac in human postmortem biological fluids (blood, urine, vitreous humor, bile, and stomach content), tissues (placenta, kidney, liver, and heart), and in exhumated fetus bones, with high recovery, sensitivity, precision, and accuracy.

Application of ultra-sensitive GC-QqQ-MS/MS (MRM) method for the determination of diclofenac in whole blood samples without derivatization

Diclofenac is one of the most frequently prescribed nonsteroidal anti-inflammatory drugs (NSAID) worldwide. Although it is considered a relatively safe drug, it exhibits high toxicity to some animal populations (e.g., raptors). An ultra-sensitive gas chromatography method, coupled with tandem mass spectrometry (GC-QqQ-MS/MS) with an electron impact (EI) ionization source for diclofenac determination in whole blood samples without a derivatization procedure, was developed and fully validated. Diclofenac-d₄ was used as an internal standard. The determination of analytes was performed in the multiple-reaction monitoring (MRM) mode. The method was linear in the range from 0.1 to 200 ng/mL, with a coefficient of determination of 0.999 (R²). The lower limit of quantification was 0.1 ng/mL, and the detection limit was 0.05 ng/mL. The blood samples (200 µL) were prepared by liquid-liquid extraction (pH3) with ethyl acetate. The intra- and interday accuracies and precisions did not exceed 15%. Recovery and matrix effect values were in the range of 92.2-105.9% and -7.8 to 5.9%, respectively. The developed method was applied in authentic blood samples. A simple and precise GC-QqQ-MS/MS method can be potentially applied for routine clinical, toxicological and environmental analysis.

A Box-Behnken Optimized Methodology for the Quantification of Diclofenac using a Carbon Paste-Multiwalled Carbon Nanotubes Electrode

Background:

Diclofenac is a widely used nonsteroidal anti-inflammatory drug. Recent studies have shown that frequent consumption of this drug in high concentrations can cause heart diseases, so strict control of diclofenac’s quantity in commercial drugs is necessary. This paper presents the development of an optimized voltammetric methodology for the quantification of diclofenac, which offers some advantages over other electrochemical and accepted methods.

Objective:

Optimize with a Box-Behnken design the differential pulse voltammetry parameters towards the quantification of diclofenac in pharmaceutical samples.

Methods:

Diclofenac behavior in the working electrode was evaluated by cyclic voltammetry, in order to stablish the best conditions for diclofenac’s quantification. A Box-Behnken design was then used to optimize the differential pulse voltammetry parameters and stablish the analytical behavior of the proposed methodology. Commercial tablets were prepared for analysis according to the Pharmacopeia, the DPV optimized methodology was used to quantify diclofenac in the samples, and the results were statistically compared with those obtained with the official methodology.

Results:

After optimization, the analytical parameters found were: correlation coefficient of 0.998, detection limit of 0.001 µM, quantification limit of 0.0033 µM and sensitivity of 0.299 µA.µM-1. The statistical analysis showed there were no significant differences between the results obtained with the proposed methodology and those obtained with the official methodology.

Conclusion:

The statistical analysis showed that the proposed methodology is as reliable as the official spectrophotometric one for the quantification of diclofenac in commercial drugs, with very competitive analytical parameters, and even better to others found with more complex electrodes.

Differential pulse voltammetric determination of diclofenac in pharmaceutical preparations and human serum

<p>This article describes a differential pulse voltammetric (DPV) method for the determination of diclofenac in pharmaceutical preparations and human serum. The proposed method was based on electro-oxidation of diclofenac at platinum electrode in 0.1 M TBAClO₄/acetonitrile solution. The well-defined two oxidation peaks were observed at 0.87 and 1.27 V, respectively. Calibration curves that obtained by using current values measured for second peak were linear over the concentration range of 1.5-17.5 μg mL^-1and 2-20 μg mL^-1 in supporting electrolyte and serum, respectively. Precision and accuracy were also checked in all media. Intra- and inter-day precision values for diclofenac were less than 3.87, and accuracy (relative error) was better than 4.12%. The method developed in this study is accurate, precise and can be easily applied to Diclomec, Dicloflam and Voltaren tablets as pharmaceutical preparation. In addition, the proposed technique was successfully applied to spiked human serum samples. No electro-active interferences from the endogenous substances were found in human serum.</p>

Determination of diclofenac in pharmaceutical preparations by voltammetry and gas chromatography methods

Rapid, sensitive and specific methods were developed for the determination of diclofenac in pharmaceutical preparations by linear sweep voltammetry (LSV) and gas chromatography (GC) with mass spectrometry (MS) detection. The linearity was established over the concentration range of 5–35 μg/mL for LSV and 0.25–5 μg/mL for GC–MS method. The intra- and inter-day relative standard deviation (RSD) was less than 4.39% and 4.62% for LSV and GC–MS, respectively. Limits of quantification (LOQ) were determined as 4.8 and 0.15 μg/mL for LSV and GC–MS, respectively. No interference was found from tablet excipients at the selected assay conditions. The methods were applied for the quality control of commercial diclofenac dosage forms to quantify the drug and to check the formulation content uniformity.

Determination of diclofenac on a dysprosium nanowire- modified carbon paste electrode accomplished in a flow injection system by advanced filtering

A new detection technique called Fast Fourier Transform Square-Wave Voltammetry (FFT SWV) is based on measurements of electrode admittance as a function of potential. The response of the detector (microelectrode), which is generated by a redox processes, is fast, which makes the method suitable for most applications involving flowing electrolytes. The carbon paste electrode was modified by nanostructures to improve sensitivity. Synthesized dysprosium nanowires provide a more effective nanotube-like surface [1-4] so they are good candidates for use as a modifier for electrochemical reactions. The redox properties of diclofenac were used for its determination in human serum and urine samples. The support electrolyte that provided a more defined and intense peak current for diclofenac determination was a 0.05 mol L(-1) acetate buffer pH = 4.0. The drug presented an irreversible oxidation peak at 850 mV vs. Ag/AgCl on a modified nanowire carbon paste electrode which produced high current and reduced the oxidation potential by about 100 mV. Furthermore, the signal-to-noise ratio was significantly increased by application of a discrete Fast Fourier Transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. To obtain the much sensivity the effective parameters such as frequency, amplitude and pH was optimized. As a result, C(DL) of 2.0 × 10(-9) M and an LOQ of 5.0 × 10(-9) M were found for the determination for diclofenac. A good recovery was obtained for assay spiked urine samples and a good quantification of diclofenac was achieved in a commercial formulation.

ssDNA aptamers that recognize diclofenac and 2-anilinophenylacetic acid

A series of 56 ssDNA aptamer variants that bind to diclofenac (DCF) were selected from an initial pool of 2.4x10(14) ssDNA molecules by Flu-Mag SELEX process. Sequence analysis of these aptamer variants showed three major groups based on sequence similarity in their random N40 sequences. Out of these, four aptamers designated as D10/DA24, D22, D16, and D3 showed high affinity to DCF with K(d) values 100.64, 166.34, 148.73, and 42.7 nM, respectively. Secondary structures of these aptamers showed highly distinct features with typical stem and loop structures. Specificity tests with these four aptamer variants showed that D3 aptamer had higher specificity to DCF followed by 2-anilinophenylacetic acid (2APA), a structural analog of DCF. Whereas aptamers D16 and D22 showed higher specificity to 2APA compared to DCF as target used during selection process. Further, the D10/DA24 aptamer showed high affinity but no specificity to DCF. The DCF aptamers selected can be potential candidates for drug-delivery systems, specific detection of DCF and its derivatives in pharmaceutical preparations and contaminants.

High-performance liquid chromatography analysis of anti-inflammatory pharmaceuticals with ultraviolet and electrospray-mass spectrometry detection in suspected counterfeit homeopathic medicinal products

A simple high-performance liquid chromatography (HPLC) method with both ultraviolet (UV) and electrospray ionisation mass spectrometry (ESI-MS) detection has been developed for the determination of seven pharmaceuticals in counterfeit homeopathic preparations. Naproxen, Ketoprofen, Ibuprofen, Diclofenac, Piroxicam, Nimesulide and Paracetamol were separated by reversed phase chromatography with acetonitrile-water (0.1% acetic acid) mobile phase, and detected by UV at 245 nm and by ESI-MS in negative ionisation mode with the exception of Paracetamol which was detected in positive ionisation mode. Benzoic acid was used as internal standard (IS). This method was successfully applied to the analysis of homeopathic preparations like mother tinctures, solutions, tablets, granules, creams, and suppositories. Linearity was studied with UV detection in the 50-400 microg mL(-1) range and with ESI-MS in the 0.1-50 microg mL(-1) range. Good correlation coefficients were found in both UV and ESI-MS. Detection limits ranged from 0.18 to 41.5 ng in UV and from 0.035 to 1.00 ng in ESI-MS.

Liquid chromatographic analysis of certain commercial formulations for non-opioid analgesics

A simple and sensitive method for separation and quantitative determination of non-opioid analgesics from pharmaceutical preparations has been developed and validated. Commercial formulations of three non-opioid analgesics, viz. paracetamol, ibuprofen and diclofenac, were chosen for present studies. These were extracted, isolated, purified and recrystallized and were characterized by melting point, lambda(max) and IR. Quantitative determination was carried out using HPLC and TLC supplemented with UV spectrophotometry.

Indirect Fluorometric Determination of Diclofenac Sodium

A simple and easy method of analysis for diclofenac sodium is reported. A spectrofluorometric method for the microdetermination of diclofenac sodium has been developed through its reaction with cerium(IV) in an acidic solution and measurement of the fluorescence of the Ce(III) ions produced. Under the optimum experimental conditions for the oxidation reaction, 1.0 M H2SO4 with 90 min of heating time (100 degrees C), the range of application is 124.3-600 ng mL(-1) and the limit of detection is 72.7 ng mL(-1). The proposed method was applied to the determination of diclofenac sodium in pharmaceutical tablets. The results of the analysis show a good agreement with those obtained by the official USP 27 HPLC method.

Determinations of fluoroquinolones and nonsteroidal anti-inflammatory drugs in urine by extractive spectrophotometry and photoinduced spectrofluorimetry using multivariate calibration

Multivariate calibration methods are chemometric tools that may be applied to the analysis of spectroscopic data with multichannel detection. Two procedures, based on spectrophotometric and fluorimetric signals, are reported for the simultaneous determination of two fluoroquinolones (ciprofloxacin and ofloxacin) and two nonsteroidal anti-inflammatory drugs (diclofenac and mefenamic acid) using first- and second-order multivariate calibration methods. In the spectrophotometric method, an extractive procedure into chloroform using trioctylmethylammonium chloride-adogen as counter ion was optimized, with the object of extracting the analytes from urine samples and eliminating matrix interferences. After separation, the absorption spectrum of the organic phase was used as the analytical signal in a partial least squares method. A photoinduced spectrofluorimetric (PIF) method using excitation-emission fluorescence matrices, is proposed, to apply three-way chemometric calibration, with the aim of analyzing ofloxacin, ciprofloxacin, and diclofenac in urine samples without the previous extractive sample-cleaning step. For both procedures, recoveries around 100% were found for all the analytes. However, the PIF three-way chemometric method provides the most sensitive and selective procedure as the urine interferences are modulated using the three-way chemometric technique.