Environmentally benign first derivative synchronous spectrofluorimetry for the analysis of two binary mixtures containing duloxetine with avanafil or tadalafil in spiked plasma samples

Antidepressants can cause sexual dysfunction side effects, necessitating the co-administration of phosphodiesterase type 5 inhibitors. The simultaneous determination of these drugs in biological fluids is critical for therapeutic drug monitoring. For the first time, two binary mixtures containing duloxetine with either avanafil or tadalafil were estimated utilizing simple green spectrofluorimetric methods without the need for a previous separation step. The study was based on first derivative synchronous spectrofluorimetry in ethanol using a change in wavelength difference (∆λ) of 20 and 25 nm for the first and second combinations, respectively. Duloxetine and avanafil were estimated at 297.7 and 331 nm in their binary mixture, while duloxetine and tadalafil were determined at 290.3 and 297.7 nm, respectively. The linearity was achieved over the ranges of 0.1-1.5 μg mL-1 for both duloxetine and avanafil and 0.01-0.40 μg mL-1 for tadalafil, with limits of detection of 0.013, 0.022, and 0.004 μg mL-1 for duloxetine, avanafil, and tadalafil, respectively. Successful application of the developed approaches was accomplished for the estimation of the two mixtures in dosage forms as well as human plasma with excellent percentage recoveries (96-103.75% in plasma), which supports their suitability for use in quality control laboratories and pharmacokinetic studies. Moreover, the adopted approaches' greenness was evidenced by applying three tools.

Self-ratiometric fluorescence approach based on plant extract-assisted synthesized silver nanoparticles for the determination of vanillin

The current study designed and applied a novel self-ratiometric fluorescent nanosensor composed of green-synthesized silver nanoparticles (Ag-NPs) to determine vanillin in adult and infant foods and human plasma. A straightforward microwave-assisted approach is proposed for synthesizing Ag-NPs in less than 1 min using a reducing agent, tailed pepper seed extract. The synthesized Ag-NPs had a strong fluorescence with an intense emission band at 360 nm and a shoulder peak at 430 nm when excited at 265 nm. Upon interaction with vanillin, the fluorescence peak of Ag-NPs at 360 nm decreases in a concentration-dependent manner while being shifted to a longer wavelength, 385 nm. Meanwhile, the shoulder fluorescence peak at 430 nm is only slightly affected by vanillin addition. Thus, a new Ag-NP self-ratiometric probe was designed and validated for vanillin determination using the peak at 385 nm and the shoulder peak at 430 as two built-in reference peaks. The optimized system accurately measured vanillin with a detection limit of 9.0 ng/mL and a linear range of 0.05-8.0 μg/mL without needing pre-derivatization or high-cost instrumentation. The method successfully measured vanillin in adult and infant milk formula, biscuits, and human plasma samples with high percentage recoveries (95.3-104.6%) and excellent precision (relative SD; ≤3.85%).

Sensitive determination of naftazone using carbon quantum dots nanoprobe by fluorimetry and smartphone-based techniques

A simple, fast, and direct mix-and-read spectrofluorimetric method has been developed for the sensitive determination of naftazone (NFZ) utilizing graphene quantum dots (GQDs) as a greener and highly luminescent nanosensor. NFZ effectively quenches the strong fluorescence of GQDs at λex/λem of 350/440 nm via the inner filter effect mechanism. The nanosensor exhibits excellent linearity for NFZ over the concentration range of 0.46 to 186 μM with a limit of detection of 0.04 μM. The proposed method was validated for the successful determination of NFZ in tablets and on manufacturing equipment surfaces with good % recoveries of 98.4-101.6 and 96.3 - 102.2%, respectively. Furthermore, an integrated smartphone-based reader has been implemented and successfully applied for the determination of NFZ. The smartphone-based reader consists of a 365 nm UV torch as an excitation source, a smartphone for recording images, and smartphone-powered image analysis software for signal interpretation, together with a paper-based analytical device (PAD) utilizing filter paper as a substrate and correction fluid as a barrier for creation of detection zones. This smart platform showed excellent sensitivity with a limit of detection down to 0.12 nmol/zone, and it could be used for in-site determination of NFZ, especially for the limited resources laboratories.

Utility and greenness appraisal of nuclear magnetic resonance for sustainable simultaneous determination of three 1,4-benzodiazepines and their main impurity 2-amino-5-chlorobenzophenone

A robust, stability-indicating, and eco-friendly proton nuclear magnetic resonance (1H-qNMR) method was developed for the concurrent determination of three 1,4-benzodiazepines (BDZs), namely diazepam (DZP), alprazolam (ALP), and chlordiazepoxide (CDP) and their common impurity, synthesis precursor, and degradation product; 2-amino-5-chlorobenzophenone (ACB). In the present method, a novel approach was developed for composing a green and cost-efficient solvent system as an alternative to the common NMR organic solvents utilizing 0.3 M sodium dodecyl sulfate prepared in deuterated water. The conducted method is characterized by simplicity with no need for sample pretreatment or labeling. Phloroglucinol was used as an internal standard. The chosen signals for the determinations of ALP, CDP, DZP and ACB were at 2.35 ppm (singlet), 2.84 ppm (singlet), 3.11 ppm (singlet), and 6.90 ppm (doublet of doublet), respectively. The proposed method possessed linearity over the concentration range of 0.25-15.0 mg ml-1 for DZP, ALP, CDP and of 0.5-25.0 mg ml-1 for ACB with LOD values of 0.06, 0.03, 0.07 and 0.16 mg ml-1 respectively, and LOQ values of 0.18, 0.09, 0.21 and 0.49 mg ml-1, respectively. Accuracy of the method was evidenced by excellent recovery% (99.57-99.90%) and small standard deviation (≥ 1.10) for the three analyzed drugs. Intra- and inter-day precision were determined with coefficient of variation ranging from 0.12 to 1.14 and from 0.72 to 1.67, respectively. For the studied compounds, appraisal of the method greenness was achieved via four approaches: Analytical Eco-Scale, Green Analytical Procedure Index (GAPI), Analytical greenness metric (AGREE), and RGB Additive Color Model. The results proved that the proposed method has the privilege of being a green analytical method.

Perception of the interaction behavior between pepsin and the antimicrobial drug secnidazole with combined experimental spectroscopy and computer-aided techniques

Drug-pepsin interaction possibly affects pepsin activity, leads to undesirable shift of its functionality, and likely induces adverse effects in the gastrointestinal tract. The present study aims at exploring the interaction of pepsin with the antiprotozoal/antibacterial drug secnidazole adopting a combination of experimental spectroscopy and computational techniques. For this purpose, different spectroscopic methods including fluorescence, synchronous fluorescence, UV-Visible absorption, and infrared spectroscopy were adopted and coordinated with in silico analysis via molecular docking. The employed synchronized approaches evidenced that; pepsin interacted with secnidazole via static mechanism at stomach pH inferring some consequent conformational changes in the structure of pepsin. Thermodynamic study of drug-pepsin interaction demonstrated that the interaction is spontaneous via van der Waals and hydrogen bonding interaction and the orientation of ligand within pepsin cavity was illustrated by molecular docking. The synchronous fluorescence study proved that tyrosine amino acid residues were involved in the interaction more than tryptophan amino acid residues. Eventually, the combined experimental and molecular docking approaches suggest that secnidazole interacts with pepsin and alter its structure, that finding correlates to gastrointestinal side effects related to secnidazole oral administration.

Facile Conversion of the Quinone-Semicarbazone Chromophore of Naftazone into a Fluorescent Quinol-Semicarbazide: Kinetic Study and Analysis of Naftazone in Pharmaceuticals and Human Serum

Naftazone is a quinone-semi carbazone drug that possesses a strong orange color, and hence it was usually analyzed colorimetrically or by HPLC-UV. However, these methods are not sensitive enough to determine naftazone in biological samples. Naftazone lacks intrinsic fluorescence and does not possess easily derivatizable functional groups. In this contribution, we introduced the first spectrofluorimetric method for naftazone assay through reduction-elicited fluorogenic derivatization through the reduction of its quinone-semicarbazone moiety to the corresponding quinol-semicarbazide derivative by potassium borohydride as a reduction probe. The solvent-dependent fluorescence of the reaction product was studied in various protic and aprotic solvents. Eventually, the fluorescence of the reduced naftazone was measured in 2-propanol at λ_emission of 350 nm after excitation at λ_ecxitation of 295 nm. The relative fluorescence intensity was linearly correlated to the drug concentration (r = 0.9995) from 10.0 to 500 ng/mL with high sensitivity, where the lower detection limit was 2.9 ng/mL. Hence, the method was effectively applied for naftazone tablets quality control with a mean %recovery of 100.3 ± 1.5, and the results agreed with those of the comparison HPLC-UV method. Furthermore, a new salting-out assisted liquid-liquid extraction (SALLE) method was established for naftazone extraction from human serum, followed by its determination using the developed reduction-based fluorogenic method. The developed SALLE method showed excellent recovery for naftazone from human serum (92.3-106.5%) with good precision (RSD ≤ 6.8%). Additionally, the reaction of naftazone with potassium borohydride was kinetically monitored, and it was found to follow pseudo-first-order kinetics with an activation energy of 43.8 kcal/mol. The developed method's greenness was approved using three green analytical chemistry metrics.

Pentabromobenzyl-RP versus triazole-HILIC columns for separation of the polar basic analytes famotidine and famotidone: LC method development combined with in silico tools to follow the potential consequences of famotidine gastric instability

The competence of hydrophilic interaction (HILIC) and reversed phase liquid chromatography (RPLC) modes, employing two new stationary phases: triazole- and pentabromobenzyl-bonded silica (PBr), respectively, was inspected for separation of two polar basic analytes: famotidine (FAM) and its acidic degradant famotidone (FON). Comparison of the chromatographic efficiency, greenness, and economy aspects showed that the RPLC is superior to the HILIC. Hence, the RPLC method was adopted and validated adhering to the FDA guidelines showing excellent linearity for FAM (1.0-20.0 μg/mL) with a detection limit of 0.14 μg/mL. The method was applied to study the behavior of FAM in simulated gastric juice (SGJ), where it exhibited rapid degradation yielding FON. This degradation pathway is a probable major reason for the poor bioavailability of FAM. The kinetic study of the gastric degradation of FAM in SGJ demonstrated pseudo-first order reaction with a rate constant of 8.1 × 10^-3 min^-1. Moreover, FAM degradation has been proven to be pH-dependent and catalyzed by the gastric juice components. Hence, in situ buffered dosage form is recommended to overcome or decrease this problem. Molecular docking study shows that FON is missing a crucial stabilizing interaction with the key amino acid Asp98 causing a reduced activity at hH₂R receptor relative to FAM. Moreover, ADMET properties prediction revealed some differences in the toxicity, pharmacokinetics, metabolism, and solubility profiles of FAM and FON.

Green conventional and first-order derivative fluorimetry methods for determination of trimebutine and its degradation product (eudesmic acid). Emphasis on the solvent and pH effects on their emission spectral properties

In this report, the fluorescence properties of the antimuscarinic drug trimebutine maleate (TRB) were fully studied and characterized. TRB exhibited intrinsic fluorescence that is greatly dependent on the local environmental factors including the solvent nature and the pH. Yet, its fluorescence was not significantly influenced by the existence of some surface active agents and polymer. The outcomes of this investigation verified that TRB fluorescence emission is intense in ethanol: 1.0 M aqueous acetic acid (9:1, v/v) with emission maxima at 357 nm and excitation maxima at 270 nm. Whereas, going towards higher pH causes fluorescence quenching. These conditions permitted ultrasensitive fluorimetric determination of TRB over the concentration range of 2.00-1500.0 ng/mL with a lower detection limit of 0.40ng/mL Application for the determination of TRB in tablets, ampoule and suspension was successfully achieved with %recoveries ranged between 98.21-100.17%. Furthermore, a first order derivative fluorimetric method was validated for resolving and simultaneous determination of TRB and its degradation product and impurity, eudesmic acid (EUA) making use of the pH-mediated fluorescence spectral shift of EUA. An ethanolic solution containing acetate buffer (pH 5.3) was used for this goal with excitation at 255 nm and measurement of the first order derivative peak amplitudes at respective zero-crossing points of 375 and 351 nm over the corresponding concentration ranges of 20.00-500.00 and 10.00-300.00 ng/mL for TRB and EUA, respectively. The two methods were assessed regarding greenness and eco-friendship by the National Environmental Methods Index and analytical eco-scale score approaches which confirmed their excellent greenness and safety.

Development and Validation of a Micellar High-Performance Liquid Chromatographic Method for Determination of Risedronate in Raw Material and in a Pharmaceutical Formulation: Application to Stability Studies

A micellar HPLC method was developed for analysis of the antiosteoporosis drug risedronate. The analysis was carried out using a 250 4.6 mm id, 5 m particle size C18 Waters Symmetry column. The mobile phase consisted of 0.02 M sodium dodecyl sulfate + 0.3 triethylamine + 10 n-propanol, prepared in 0.02 M orthophosphoric acid. The pH of the mobile phase was adjusted to pH 6.0, and it was pumped at a flow rate of 0.7 mL/min with UV detection at 262 nm. The method showed good linearity in the range of 280 g/mL, with an LOD of 0.40 g/mL (1.31 106 M) and an LOQ of 1.21 g/mL. The suggested method was successfully applied for the analysis of risedronate in raw material and a tablet formulation, with average recoveries of 99.91 1.30 and 101.52 0.30, respectively. The stability-indicating capability of the proposed method was proved using forced degradation. By changing the pH of the mobile phase to 4.0, the oxidative degradation product could be separated from risedronate.

Estimation of nizatidine gastric nitrosatability and product toxicity via an integrated approach combining HILIC, in silico toxicology, and molecular docking

The liability of the H₂-receptor antagonist nizatidine (NZ) to nitrosation in simulated gastric juice (SGJ) and under WHO-suggested conditions was investigated for the first time. For monitoring the nitrosatability of NZ, a hydrophilic interaction liquid chromatography (HILIC) method was optimized and validated according to FDA guidance. A Cosmosil HILIC® column and a mobile phase composed of acetonitrile: 0.04 M acetate buffer pH 6.0 (92:8, v/v) were used for the separation of NZ and its N-nitroso derivative (NZ-NO) within 6 min with LODs of 0.02 and 0.1 μg/mL, respectively. NZ was found highly susceptible to nitrosation in SGJ reaching 100% nitrosation in 10 min, while only 18% nitrosation was observed after 160 min under the WHO-suggested conditions. The chemical structure of NZ-NO was clarified by ESI⁺/MS. In silico toxicology study confirmed the mutagenicity and toxicity of NZ-NO. Experiments evidenced that ascorbic acid strongly suppresses the nitrosation of NZ suggesting their co-administration for protection from potential risks. In addition, the impacts of the HILIC method on safety, health, and environment were favorably evaluated by three green analytical chemistry metrics and it was proved that, unlike the popular impression, HILIC methods could be green to the environment.

Development and validation of a micellar high-performance liquid chromatographic method for determination of risedronate in raw material and in a pharmaceutical formulation: application to stability studies

A micellar HPLC method was developed for analysis of the antiosteoporosis drug risedronate. The analysis was carried out using a 250 x 4.6 mm id, 5 microm particle size C18 Waters Symmetry column. The mobile phase consisted of 0.02 M sodium dodecyl sulfate + 0.3% triethylamine + 10% n-propanol, prepared in 0.02 M orthophosphoric acid. The pH of the mobile phase was adjusted to pH 6.0, and it was pumped at a flow rate of 0.7 mL/min with UV detection at 262 nm. The method showed good linearity in the range of 2-80 microg/mL, with an LOD of 0.40 microg/mL (1.31 x 10(-6) M) and an LOQ of 1.21 microg/mL. The suggested method was successfully applied for the analysis of risedronate in raw material and a tablet formulation, with average recoveries of 99.91 +/- 1.30 and 101.52 +/- 0.30%, respectively. The stability-indicating capability of the proposed method was proved using forced degradation. By changing the pH of the mobile phase to 4.0, the oxidative degradation product could be separated from risedronate.