A BRIEF REVIEW OF ANALYTICAL METHODS FOR THE ESTIMATION OF TTR KINETIC STABILIZERS IN PHARMACEUTICAL FORMULATIONS AND BIOLOGICAL MATRICES

Transthyretin kinetic stabilizers are used as first-line drug therapy for transthyretin amyloid polyneuropathy mostly in patients unsuitable for liver transplantation. The two drugs prescribed in clinical practice are Tafamidis and Diflunisal. The European Medicines Agency approved Tafamidis for this prescription in 2011 and 2019 American Food and Drug Association also registered it for the same use. Diflunisal is a non-steroidal anti-inflammatory drug but its structural similarities to Tafamidis determine its “off-label” use for such clinical conditions. This review article represents the various analytical methods available in published literature for the determination of Tafamidis and Diflunisal in bulk drugs, pharmaceutical formulations, and biological matrices. Detailed information about all developed quantitative methods consisting of spectrophotometry, spectrofluorimetry, high-performance liquid chromatography with ultraviolet, fluorescence or diode array detection, liquid chromatography-tandem mass spectrometry, and voltammetry is provided and can be effectively used in the development of new analytical procedures and routine drug manufacturing or clinical practice

HPLC DETERMINATION OF SILDENAFIL IN TABLETS

Objective: The popularity of Sildenafil, the widespread distribution of various products and dietary supplements with added synthetic drugs, requires reliable analysis methods. This research study aimed to develop a simple isocratic HPLC method for the determination of Sildenafil in tablet dosage forms from the local market. Methods: Separation was carried out at 30 °C, using column LiChrosorb® RP-18 (150 x 4.0 mm, 5 μm) with mobile phase consisting of acetonitrile: methanol: 0.5% triethylamine (15: 26: 59 v/v/v). The detector was set at 290 nm. The flow rate was 1.0 ml/min and the injection volume was 20 μl. Results: Linear correlation was obtained within the range 6.25–50.0 μg/ml with correlation coefficient (R2) 0.9998. The achieved limits of detection and quantitation were 0.7 and 2.2 μg/ml, respectively. Conclusion: The developed method can be applied for the quality control of Sildenafil preparations

HPLC Determination of Amoxicillin, Tinidazole and Omeprazole in a Model Mixture

The present study examines the possibilities for the simultaneous determination of amoxicillin, tinidazole, and omeprazole in a model mixture by high-performance liquid chromatography. Chromatographic separation was performed in isocratic mode on a LiChrospher® 100 RP-18 column. The mobile phase consists of acetonitrile and phosphate buffer (0.001 M, pH 7.6) in a ratio of 40:60 v/v. The analysis was performed at a flow rate of 1.0 ml/min and a wavelength of 280 nm. The method was validated in terms of selectivity, linearity, precision and accuracy, limit of detection, and limit of quantification. The resulting correlation coefficients R2 are higher than 0.999, and the relative standard deviation does not exceed 2%

Spectrophotometric Determination of Drugs by Means of Schiff Base Formation: A Review

Molecules that do not ordinarily absorb radiation in the visible region of the spectrum can be made to do so by introducing chromogens that facilitate electronic transitions. The most commonly derivatized functional groups are aromatic nitro- (preliminary reduction required) and aromatic amino- groups.An amino compound that lacks chromophore can be assayed spectrophotometrically using a suitable carbonyl reagent. Certain amines condense with various aldehydes in strongly acidic media, giving them the ability to give color. Among many, the following aldehydes are widely used: 4-dimethylaminobenzaldehyde, vanillin, p-dimethylaminocinnamaldehyde, salicylaldehyde, etc. The reaction with aromatic amines produces Schiff bases.In this review, we have summarized and discussed the important analytical chromogenic reagents regularly used in drug analysis by visible spectrophotometric methods

HPLC ASSAY OF MODEL TABLET FORMULATIONS CONTAINING METRONIDAZOLE AND CIPROFLOXACIN

Objective: This paper describes development and validation of a high-performance liquid chromatographic analytical procedure for simultaneously determination of metronidazole and ciprofloxacin in a model tablet formulations.Methods: The separation was achieved with a LiChrosorb® RP-18 (250 x 4.6 mm) column, at 33 °C temperature with isocratic mode and a mobile phase containing triethylamine: o-phosphoric acid and аcetonitrile (0.02:80:20 v/v/v). The flow rate was 1.0 ml/min and the eluent was monitored at 290 nm.Results: The selected chromatographic conditions were found to separate effectively metronidazole and ciprofloxacin with a retention time of 3.46 min and 6.68 min, respectively. The method was validated for analytical parameters specificity, linearity, precision, accuracy, LOD and LOQ. The calibration curves were linear in the concentration range of 12.5-100.0 µg/ml for metronidazole and ciprofloxacin. The recovery for metronidazole and ciprofloxacin was 100.1 % and 100.2 %, respectively.Conclusion: The analytical procedure was applied to quality control of model tablet formulations. It was established that the developed analytical procedure was successfully used for routine analysis of metronidazole and ciprofloxacin in model tablet dosage forms without any interference from included excipients.Keywords: Metronidazole, Ciprofloxacin, RP-HPLC, Validation, Model tablet formulations, Quality contro

Development and validation of analytical procedure for analysis of Amoxiciline, Metronidazole and Omeprazole, used as anti- Helicobacter pylori agents alone and in mixture

Background: The contemporary treatment of ulcerogenic diseases and gastroesophageal reflux disease is related usually to application of a combination of imidazole-based antibacterial, antibiotic and proton pump inhibitor. In the current study, the three most common representatives Amoxicilline (AMO), Metronidazole (MET) and Omeprazole (OME), respectively, are subjected to analysis through classical analytical procedure, providing high level accuracy, sensitivity and good separation abilities. As such a UV/VIS method was applied as a well known identification and quantitation technique for analyses in various samples. Furthermore, this technique is known to be a good detection method in combination with chromatographic systems. Purpose: A simple, specific, accurate and precise reverse phase-high performance liquid chromatographic method has been developed for the simultaneous determination of Amoxicillin Trihydrate (AMO), Metronidazole (MET) and Omeprazole (OME) in synthetic mixture. Materials and methods: Some important parameters like pH of the mobile phase, concentration of the acid or buffer solution, percentage and type of the organic modifier, etc. were tested for a good chromatographic separation. The sample was analyzed using a mobile phase of Acetonitrile: Phosphate buffer (pH=7.6±0.1) (40:60 v/v). The flow rate was 1.0 mL/ min with detection at 280 nm. Results: The retention time for AMO, MET and OME was found to be 1.67, 2.86 and 5.99 min respectively, and the recoveries in the synthetic mixture were between 98 and 102%. The validated method was linear over the concentration range of 25 to 200 μg/mL for AMO, 12.5 to 100 μg/mL for MET and 5–40 µg/mL for OME, with a correlation coefficient > 0.999. Conclusion: The developed method has been validated in accordance with the International Conference on Harmonization (ICH) guidelines and showed excellent linearity, accuracy, precision, specificity, robustness, as well as system suitability results within the acceptance criteria

Simultaneous HPLC determination of remdesivir and dexamethasone in the presence of metformin, sitagliptin, and glimepiride in a synthetic mixture and spiked human plasma

The COVID-19 pandemic has raised many questions regarding the control and therapy of type 2 diabetes and the higher risk of severe disease progression. One of the therapeutic regimens used in moderate and severe cases of COVID-19, endorsed by the World Health Organization, involves the administration of an antiviral medicinal product and a corticosteroid. The present study describes the development of a liquid chromatographic method for the simultaneous separation and quantification of Remdesivir and Dexamethasone in the presence of Metformin, Sitagliptin, and Glimepiride in a synthetic mixture. The developed method also allows determination of Remdesivir, Dexamethasone, and Glimepiride in spiked plasma samples, using Sitagliptin as internal standard. A mixture of acetonitrile and potassium dihydrogen phosphate buffer (pH 3) in a ratio of 45:55 v/v was used as а mobile phase on a C18 column. The recovery percentages from plasma ranged from 85.1 to 108.5%. The developed method can serve in routine quality control and clinical laboratory practice

Exploring the Chemical Composition of Bulgarian Lavender Absolute (Lavandula Angustifolia Mill.) by GC/MS and GC-FID

Lavender (L. angustifolia Mill.) is an important essential oil-bearing and medicinal plant with high commercial value. Lavender scent components can be derived not only as an essential oil but also as lavender concrete or absolute. The development of reliable analytical methods for origin assessment and quality assurance is of significant fundamental importance and high practical interest. Therefore, a comprehensive chemical profiling of seven industrial samples of Bulgarian lavender absolute (L. angustifolia Mill.) was performed by means of gas chromatography–mass spectrometry (GC/MS) and gas chromatography with flame ionization detection (GC-FID). As a result, 111 individual compounds were identified by GC/MS, and their quantitative content was simultaneously determined by GC-FID, representing 94.28–97.43% of the total contents of the lavender absolute. According to our results, the main constituents of lavender absolute (LA) are representatives of the terpene compounds (with the dominating presence of oxygenated monoterpenes, 52.83–80.55%), followed by sesquiterpenes (7.80–15.21%) and triterpenoids (as minor components). Coumarins in various amounts (1.79–14.73%) and aliphatic compounds (hydrocarbons, ketones, esters, etc.) are found, as well. The acyclic monoterpene linalool is the main terpene alcohol and, together with its ester linalyl acetate, are the two main constituents in the LAs. Linalool was found in concentrations of 27.33–38.24% in the LA1-LA6 samples and 20.74% in the LA7 samples. The amount of linalyl acetate was in the range of 26.58 to 37.39% in the LA1–LA6 samples, while, surprisingly, it was not observed in LA7. This study shows that the chemical profile of the studied LAs is close to the lavender essential oil (LO), fulfilling most of the requirements of the International Standard ISO 3515:2002

Antimicrobial activity, mechanism of action, and methods for stabilisation of defensins as new therapeutic agents

Bioactive compounds, such as antimicrobial peptides (AMPs), have increasingly been used recently to counteract the rapidly increasing incidence of bacterial resistance to usual antibiotics and chemotherapeutics. In humans, endogenous AMPs are part of the immune system and act against pathogens. Defensins compose a class of AMPs that have activity against gram-positive and -negative bacteria, viruses, and fungi. For some, antitumour activity has also been reported. Such characteristics indicate that they represent a potential new class of therapeutic agents against microorganisms, including multidrug resistant pathogens. However, pH and enzymatic degradation and variable tissue distribution of these compounds limit their clinical application. New technologies and different methods have been developed to overcome these limitations and increase their half-life, such as cyclization, lipidation, design of peptidomimetics, synthesis of hybrid peptides, and use of nanocarriers. The objective of this review was to analyse current applications of defensins as antimicrobial agents and their mechanism of action. Moreover, new technologies and methods for stabilizing defensins are discussed