Simple spectrophotometric method for determination of paroxetine in tablets using 1,2-naphthoquinone-4-sulphonate as a chromogenic reagent

Evaluation of 4-fluoro-7-nitrobenzofurazan as a dual-function chromogenic and fluorogenic probe for tulathromycin and its innovative utility for development of two eco-friendly and high-through microwell assays for analysis of pharmaceutical formulations

Tulathromycin is a triamilide antibacterial drug which has been approved for use in the European Union and the United States for the treatment and prevention of bovine respiratory diseases. The aim of this study was the development of two innovative microwell spectrometric (photometric and fluorometric) assays for determination of tulathromycin in its pharmaceutical formulations. To achieve this goal, 4-fluoro-7-nitrobenzofurazan was investigated as a dual-function chromogenic and fluorogenic probe for tulathromycin. The reaction between tulathromycin and 4-fluoro-7-nitrobenzofurazan proceeded smoothly in an alkaline medium, resulting in the formation of a colored and fluorescent product. The product displayed a maximum light absorption at 475 nm and emitted fluorescence at 545 nm when excited at 475 nm. Extensive investigations were conducted to optimize the factors affecting the tulathromycin /4-fluoro-7-nitrobenzofurazan reaction, and the optimal conditions were established. Using these optimized conditions, both microwell-based photometric and fluorometric assays were developed. The calibration curves relating the absorbance and fluorescence intensities of the reaction product with the corresponding tulathromycin concentrations were generated. The absorbance-concentration relationship was found to be linear within a tulathromycin concentration range of 10-400 µg mL-1, with a limit of quantitation of 6.2 µg mL-1. On the other hand, the fluorescence-concentration relationship was linear within a concentration range of 0.04-1.2 µg mL-1, with a limit of quantitation of 0.06 µg mL-1. Rigorous validations of both assays' procedures were performed, and both assays were successfully employed for the analysis of tulathromycin-containing pharmaceutical formulations (injections) with satisfactory accuracy and precision. The ecologically friendly assessment of both assays demonstrated their compliance with the principles of green analytical chemistry approaches. Moreover, the proposed microwell-based assays enabled the simultaneous analysis of multiple samples using small volumes, enabling high-throughput analysis. In conclusion, this study represents the first evaluation of 4-fluoro-7-nitrobenzofurazan as a probe with dual functionality for the microwell-based photometric and fluorometric analysis of tulathromycin. The developed assays serve as valuable analytical tools for ensuring the quality of tulathromycin 's pharmaceutical formulations.

A dual-function chromogenic and fluorogenic benzofurazan probe for plazomicin and its innovative utility for development of two microwell assays with high throughput for analysis of drug substance and pharmaceutical formulations

Plazomicin (PLZ) is a novel aminoglycoside which has been recently approved by The US Food and Drug Administration for the treatment of complicated urinary tract infections including acute pyelonephritis, caused by certain Enterobacteriaceae, in adult patients with limited or no options for alternative treatment. This study focuses on the development of microwell-based photometric and fluorometric assays for the quantitative determination of PLZ in its bulk drug substance and commercial pharmaceutical formulations (Zemedri® injections). Both assays utilize the dual-function chromogenic and fluorogenic properties of the 4-fluoro-7-nitrobenzofurazan (NBD-F) probe. The reaction between PLZ and NBD-F, conducted in a borate buffer at pH 8, resulted in the formation of a colored and fluorescent reaction product. The product exhibited maximum light absorption at 473 nm and emitted fluorescence at 541 nm when excited at 473 nm. Factors influencing the reaction between PLZ and NBD-F were thoroughly investigated, and optimal conditions were determined. Under the optimized reaction conditions, calibration curves were generated to establish the relationship between absorbance and fluorescence intensities of the reaction product with the corresponding PLZ concentrations. The absorbance-concentration relation was linear in a PLZ concentration range of 20-800 μg mL-1 with a limit of quantitation of 25 μg mL-1, while the fluorescence-concentration relation was linear in the concentration range of 0.05-1.5 μg mL-1 with a limit of quantitation of 0.08 μg mL-1. Both assays underwent validation and were successfully applied to the quantitation of PLZ in its bulk drug substance and pharmaceutical formulations (injections) with satisfactory accuracy and precision. The eco-friendliness/greenness assessment of the assays demonstrated that both assays comply with the requirements of green analytical chemistry approaches. Furthermore, the proposed microwell assay plates allowed for the simultaneous handling of numerous samples with micro-volumes, enabling high-throughput analysis. In conclusion, this study represents the first evaluation of NBD-F as a dual-function probe for the microwell-based photometric and fluorometric determination of PLZ. The developed assays serve as valuable analytical tools for the quality control of PLZ's bulk drug substance and pharmaceutical formulations.

Enlightening the Path to Protein Engineering: Chemoselective Turn-On Probes for High-Throughput Screening of Enzymatic Activity

Many successful stories in enzyme engineering are based on the creation of randomized diversity in large mutant libraries, containing millions to billions of enzyme variants. Methods that enabled their evaluation with high throughput are dominated by spectroscopic techniques due to their high speed and sensitivity. A large proportion of studies relies on fluorogenic substrates that mimic the chemical properties of the target or coupled enzymatic assays with an optical read-out that assesses the desired catalytic efficiency indirectly. The most reliable hits, however, are achieved by screening for conversions of the starting material to the desired product. For this purpose, functional group assays offer a general approach to achieve a fast, optical read-out. They use the chemoselectivity, differences in electronic and steric properties of various functional groups, to reduce the number of false-positive results and the analytical noise stemming from enzymatic background activities. This review summarizes the developments and use of functional group probes for chemoselective derivatizations, with a clear focus on screening for enzymatic activity in protein engineering.

A novel 96-microwell-based high-throughput spectrophotometric assay for pharmaceutical quality control of crizotinib, a novel potent drug for the treatment of non-small cell lung cancer

<p>This study describes the development and validation of a novel 96-microwell-based high throughput spectrophotometric assay for pharmaceutical quality control of crizotinib (CZT), a novel drug for the treatment of non-small cell lung cancer. We examined the reaction between CZT and 1,2-naphthoquinone-4-sulphonate, a chromogenic reagent. A red-colored product showing a maximum absorption peak (λ_max) at 490 nm was produced in an alkaline medium (pH 9). We examined stoichiometry of the reaction and postulated the reaction mechanism. To our knowledge, this is the first study to describe a color-developing reaction for the proposed assay. The reaction was performed in a 96-microwell plate, and the absorbance of the colored product was measured using an absorbance reader at 490 nm. Under optimized reaction conditions, Beer's law, which shows a correlation between absorbance and CZT concentration, was obeyed in the range of 4-50 µg/well with an appropriate correlation coefficient (0.999). The limits of detection and quantification were 1.73 and 5.23 µg/well, respectively. The assay showed high precision and accuracy. The proposed assay was applied successfully for the determination of CZT in capsules. Thus, the assay proposed in this study is practical and valuable for routine application in pharmaceutical quality control laboratories.</p>

Novel spectrophotometric method for determination of cinacalcet hydrochloride in its tablets via derivatization with 1,2-naphthoquinone-4-sulphonate

This study represents the first report on the development of a novel spectrophotometric method for determination of cinacalcet hydrochloride (CIN) in its tablet dosage forms. Studies were carried out to investigate the reaction between CIN and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 8.5), an orange red-colored product exhibiting maximum absorption peak (λ_max) at 490 nm was produced. The stoichiometry and kinetic of the reaction were investigated and the reaction mechanism was postulated. This color-developing reaction was employed in the development of a simple and rapid visible-spectrophotometric method for determination of CIN in its tablets. Under the optimized reaction conditions, Beer's law correlating the absorbance with CIN concentration was obeyed in the range of 3 - 100 μg/ml with good correlation coefficient (0.9993). The molar absorptivity (ε) was 4.2 × 10⁵ l/mol/cm. The limits of detection and quantification were 1.9 and 5.7 μg/ml, respectively. The precision of the method was satisfactory; the values of relative standard deviations (RSD) did not exceed 2%. No interference was observed from the excipients that are present in the tablets. The proposed method was applied successfully for the determination of CIN in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.80 - 102.23 ± 1.27 - 1.62%. The results were compared favorably with those of a reference pre-validated method. The method is practical and valuable in terms of its routine application in quality control laboratories.

Spectrophotometric Determination of the Antidepressants Sertraline and Paroxetine HCl using 2,4-Dinitrofluorobenzene

A simple and sensitive spectrophotometric method was developed for the determination of each of sertraline (SER) and paroxetine HCl (PXT) in dosage forms. The method is based upon reaction of PXT and SER with 2,4-dinitrofluorobenzene (DNFB) to form colored products. The absorbance of the products were measured at 375and 390 nm for SER and PXT respectively. The absorbance concentration plots were rectilinear over the concentration rang of 1-10 and 2-20 μg/mL with lower detection limits (LOD) of 0.11 and 0.28 μg/mL and quantification limits (LOQ) of 0.32 and 0.85 μg/mL for SER and PXT, respectively. The developed method was successfully applied for the determination of SER and PXT in dosage forms. The common excipients and additives did not interfere in their determinations. There was no significant difference between the results obtained by the proposed and the reference methods regarding Student t-test and the variance ratio F-test respectively. A proposal of the reaction pathway was postulated.