Spectrofluorimetric methods for the determination of gemifloxacin in tablets and spiked plasma samples

Luminescent and time-resolved determination of gemifloxacin mesylate in pharmaceutical formulations and spiked blood plasma samples using a lanthanide complex as a probe

A novel luminescence-based analytical methodology was established employing a europium(III) complex with 3-allyl-2-hydroxybenzohydrazide (HAZ) as the coordinating ligand for the quantification of gemifloxacin mesylate (GMF) in pharmaceutical preparations and human plasma samples spiked with the compound. The stoichiometry of the europium complex with HAZ was determined via the Job plot and exhibited a metal-to-ligand ratio of 1 : 2. The analytical procedure relies on a rapid and significant enhancement of luminescence by the Eu(AZ)2 complex when it interacts with gemifloxacin mesylate, which allowed for the rapid detection of 96 samples within approximately 2 minutes. The thermodynamic parameters of the complexation of GMF with Eu(AZ)2 were evaluated and showed that the complexation of GMF was spontaneous with a negative ΔG. The binding constant K was 4.27 × 105 L mol-1 and DFT calculations supported GMF binding and the formation of Eu(AZ)2-GMF without further ligand exchange. The calibration graph for the luminescence quantitation of GMF was linear over a wide concentration range of 0.11-16 μg mL-1 (2.26 × 10-7 to 3.30 × 10-5 mol L-1), with a limit of quantification (LOQ) of 110 ng mL-1 (230 nmol L-1) and a detection limit (LOD) of 40 ng mL-1 (82 nmol L-1). The proposed method showed good accuracy with an average recovery of 99% with relative standard deviations of less than 5% in spiking experiments, even in complex pharmaceutical dosage forms such as tablets and in human blood plasma. Herein, the ability of the suppression of the luminescence background by using the long lag times of the lanthanide probe in a time-resolved detection scheme provided reliable and precise results, which suggests its potential for use in further real or patient samples.

Ultra-Sensitive Fluorimetric Method for the First Estimation of Vonoprazan in Real Human Plasma and Content Uniformity Test

Vonoprazan (VON) has been approved recently via US-FDA in 2015 as the first in class of potassium competitive acid blocker group. VON is used for management of GIT ulcer, reflux esophagitis and for eradication of Helicobacter pylori. So, the first spectrofluorimetric method was developed for estimation of VON in real human plasma and content uniformity test. The fluorimetric methodology based on reaction of secondary amine group in VON with benzofurazan (0.05% w/v NBD-Cl) reagent as nucleophilic substitution reaction in alkaline medium (0.1 M borate buffer pH 8.2) to produce highly fluorescent product measure at 530 nm after excitation at 465 nm. The linear calibration range was found 15 to 200 ng mL^-1 with lower limit of quantitation (LOQ) equal to 8.57 ng mL^-1. The method was successfully applied for estimation of VON in pharmacokinetic (PK) and content uniformity studies. The maximum plasma concentration was found to be (C_max) 71.03 ng mL^-1 after maximum time (t_max) equal to 1.5 ± 0.15 h. The presented strategy also applied to ensure concentration of drug in each tablet using content uniformity test with high percent of recovery 100.05 ± 0.66. The proposed method was established for clinical laboratories and therapeutic drug monitoring studies.

Utility of 4-chloro-7-nitrobenzofurazan for spectrofluorimetric and spectrophotometric determinations of the anti-hirsutism agent (α-difluoromethylornithine) in pharmaceutical cream samples

α-Difluoromethylornithine is an effective medication for the treatment of African Trypanosomiasis and widely distributed for the treatment of hirsutism. This work provides an adequate analytical protocol for the spectrophotometric and the spectrofluorimetric determination of α-difluoromethylornithine through its interaction with 4-chloro-7-nitrobenzofurazan (NBD-chloride) reagent. After optimization of the reaction conditions (NBD-chloride volume, buffer volume, the best diluting solvent, heating time and temperature and pH of the medium) the reaction product was measured spectrophotometrically at λ_max = 478 nm and spectrofluorimetrically at λ_emission = 540 nm after λ_excitation = 475 nm. The proposed methods were linear over the ranges 5-30 μg ml^-1 and 0.4-2 μg ml^-1 for the spectrophotometric method and the spectrofluorimetric method, respectively. Moreover, the proposed work offers an adequate sensitive and selective determination for α-difluoromethylornithine where the detection limits were 0.90 μg ml^-1 and 0.071 μg ml^-1 for the spectrophotometric method and the spectrofluorimetric method, respectively. Furthermore, both methods were successfully applied for the quantification of α-difluoromethylornithine in the pharmaceutical cream samples with acceptable recovery results.

Application of different spectrofluorimetric methods for determination of lesinurad and allopurinol in pharmaceutical preparation and human plasma

Lesinurad and allopurinol combination is newly FDA approved for treatment of patients suffering from hyperuricemia associated with uncontrolled gout. In the present work, two different highly sensitive, selective and accurate fluorescence spectroscopic methods were developed for quantitative analysis of lesinurad and allopurinol in their pharmaceutical dosage form without any tedious operation procedure. Lesinurad was quantitatively analyzed based on its unique native fluorescence nature. Lesinurad fluorescence emission was quantitatively determined at 343 nm after excitation at 288 nm without any interference from allopurinol. Allopurinol, has free terminal secondary amino group, reacted with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBDCl) through nucleophilic substitution mechanism forming highly fluorescent dark yellow fluorophore. Allopurinol was quantitavely analyzed based on measurement the emission fluorescence intensity of the fluorescent dark yellow fluorophore at 535 nm after excitation at 465 nm. Different parameters which affect the described methods of the studied drugs were carefully checked and optimized. Calibration graphs were found to be linear over the concentration range of 0.25-4.0 μg/mL for lesinurad and 0.2-20 μg/mL for allopurinol. The proposed methods were successfully applied for the quantitative analysis of the two drugs in Duzallo® pharmaceutical dosage form and spiked human plasma.

Potentiometric Carbon Quantum Dots-Based Screen-Printed Arrays for Nano-Tracing Gemifloxacin as a Model Fluoroquinolone Implicated in Antimicrobial Resistance

Antimicrobial resistance (AMR) is a neglected issue that poses a serious global threat to public health, causing long-term negative consequences at both humanitarian and economic levels. Herein, we report an unprecedented economic fabrication method of seven potentiometric screen-printed sensors for the ultra-trace determination of gemifloxacin (GEMI) as a model of the fluoroquinolones antibiotics deeply involved in the growing AMR problem. Sensors were constructed by depositing homemade carbon ink on a recycled X-ray sheet, patterned using stencils printed with an office printer in simple, cost-effective steps requiring no sophisticated equipment. Four sensors were modified using carbon quantum dots (CQDs) synthesized from dextrose through a single-step method. Sensors exhibited a linear response in the concentration ranges 10−5–10−2 M (sensors 1, 3 and 4), 10−6–10−3 M (sensor 2) and 10−6–10−2 M (sensors 5, 6 and 7). LOD allowed tracing of the target drug at a nano-molar level down to 210 nM. GEMI was successfully determined in pharmaceutical formulations and different water samples without any pretreatment steps with satisfactory recovery (96.93–105.28% with SD values < 3). All sensors revealed a long lifetime of up to several months and are considered promising tools for monitoring water quality and efficiency of water treatment measures.

Validated Microwell-Based Spectrofluorimetric Method for Quantification of Ravidasvir (New Anti-Chronic Hepatitis C Virus-GT4) in Rat Plasma and Its Application to Pharmacokinetic Study

Background

Ravidasvir (RAV) has been regarded as a potent new NS5A inhibitor with a magnificent safety and tolerability in the management of genotype 4 hepatitis C virus (HCV) patients. Suitable analytical techniques are needed for the measurement of RAV in different biological matrices.

Methods

We have developed a fast, sensitive and economical 96-microwell-based spectrofluorimetric technique combined with one-step protein precipitation extraction strategy for the measurement of RAV in rat plasma.

Results

Under the optimum conditions, the direct relationship in rat plasma was accomplished between the RAV concentrations and the fluorescence (FL) intensity in a scope of 2.5–200 ng/mL with 0.9998 and 0.9999 for the quantification and correlation coefficients, respectively. The lower limit of detection (LLOD) was 0.840 ng/mL and this demonstrates the high sensitivity of the proposed assay. The accuracy (RE%) ranged from 95.34% to 102.29%, and the precision (RSD%) was less than 3.59%. The recovery was ranged from 93.12% to 96.26%. The stability of RAV in rat plasma was carried out and established its good stability in the range of room conventional temperature and at long-term stability (−80°C, 30 days). The developed technique was validated as stated by the United States Food and Drug Administration (US-FDA) guidelines for bioanalytical technique verification.

Conclusion

The approved technique was effectively applied for a pharmacokinetic (PK) study after single oral gavage administration of RAV at a dose of 35 mg/kg and it could be presumed that the proposed assay can be applied to clinical trials.

A Validated Reverse Phase-Ultra-Performance Liquid Chromatography Method for the Determination of Gemifloxacin Mesylate in Bulk and its Pharmaceutical Preparation

Objectives

Gemifloxacin Mesylate is a fourth generation fluoroquinolone antibacterial agent. A simple, accurate, and precise reversed phase (RP)-ultra performance liquid chromatography (UPLC) method was developed and validated for short time analysis of Gemifloxacin Mesylate in its bulk and pharmaceutical preparation.

Materials and Methods

The optimum separation was achieved at 0.5±0.03 min using an Acclaim^TM RSLC 120 C18 column 2.2 μm (2.1×100 mm) at 30°C by isocratic mobile phase at pH 3.0 composed of acetonitrile:phosphate buffer (25 mM) in a ratio of 75:25 (v/v). The column effluents were monitored at 276 nm using a photodiode array detector at a flow rate of 0.5 mL/min. The method was validated according to International Conference on Harmonization guidelines.

Results

The linearity of the calibration curve ranged from 0.5 μg/mL to 10 μg/mL and the square of the regression coefficient (r²) was 0.9991. The % relative standard deviation (RSD) of inter-day precision ranged from 0.081% to 1.233%, while for intra-day it ranged from 0.364% to 1.018%. The method was accurate with % recovery ranging from 93.71% to 100.29% and % RSD ranging from 1.054 to 2.722. The limit of detection and the limit of quantification were 0.066 and 0.2 μg/mL, respectively.

Conclusion

The validated method proved its ability for the assay of Gemifloxacin Mesylate in its bulk and dosage form in a short time (less than 1 min). To the best of our knowledge, this is the first RP-UPLC method for the determination of Gemifloxacin Mesylate.

Supramolecular interaction of gemifloxacin and hydroxyl propyl β-cyclodextrin spectroscopic characterization, molecular modeling and analytical application

The solid inclusion complex of gemifloxacin (GFX) and hydroxyl propyl β-cyclodextrin (HPβ-CD) was prepared and examined by UV-visible, FTIR, NMR, electrospray ionization mass spectrometry (ESI-MS) and fluorescence spectroscopy. The formation of inclusion complex has been confirmed on the basis of changes of spectroscopic properties. Further the interaction between GFX and HPβ-CD was studied using molecular modeling approaches. The results showed that HPβCD reacted with GFX to form a 1:1 host-guest inclusion complex. Based on the enhancement of the fluorescence intensity of GFX produced through complex formation, a simple, accurate, rapid and highly sensitive spectrofluorometric method for the determination of GFX in pharmaceutical formulation was developed. The linear relationships between the intensity and GFX concentration was obtained in the concentration range of 20-140 ng/mL with good correlation coefficients (0.9997). The limit of detection (LOD) was found to be 4 ng/mL. The proposed method was successfully applied to the analysis of GFX in pharmaceutical preparation.

Spectrophotometric determination of gemifloxacin mesylate, moxifloxacin hydrochloride, and enrofloxacin in pharmaceutical formulations using Acid dyes

SIMPLE, RAPID, AND EXTRACTIVE SPECTROPHOTOMETRIC METHODS WERE DEVELOPED FOR THE DETERMINATION OF SOME FLUOROQUINOLONES ANTIBIOTICS: gemifloxacin mesylate (GMF), moxifloxacin hydrochloride (MXF), and enrofloxacin (ENF) in pure forms and pharmaceutical formulations. These methods are based on the formation of ion-pair complexes between the basic drugs and acid dyes, namely, bromocresol green (BCG), bromocresol purple (BCP), bromophenol blue (BPB), bromothymol blue (BTB), and methyl orange (MO) in acidic buffer solutions. The formed complexes were extracted with chloroform and measured at 420, 408, 416, 415, and 422 nm for BCG, BCP, BPB, BTB, and MO, respectively, for GMF; at 410, 415, 416, and 420 nm for BCP, BTB, BPB, and MO, respectively, for MXF; and at 419 and 414 nm for BCG and BTB, respectively, in case of ENF. The analytical parameters and their effects are investigated. Beer's law was obeyed in the ranges 1.0-30, 1.0-20, and 2.0-24  μ g mL(-1) for GMF, MXF, and ENF, respectively. The proposed methods have been applied successfully for the analysis of the studied drugs in pure forms and pharmaceutical formulations. Statistical comparison of the results with the reference methods showed excellent agreement and indicated no significant difference in accuracy and precision.

Two validated spectrofluorometric methods for determination of gemifloxacin mesylate in tablets and human plasma

Two new, sensitive, and selective spectrofluorometric methods were developed for the determination of gemifloxacin mesylate (GFX) in tablets and spiked human plasma. Method A was based on measurement of the enhanced fluorescence spectral behaviour of GFX in a sodium dodecyl sulphate (SDS) micellar system. In aqueous solution of acetate buffer pH 5.5, the fluorescence intensity of GFX was greatly enhanced about tenfold in the presence of SDS. The fluorescence intensity was measured at 402 nm after excitation at 274 nm. Method B was based on Hantzsch condensation reaction between the primary amino group of GFX with acetylacetone and formaldehyde in acetate buffer of pH 3.5 yielding a highly yellow fluorescent derivative. The reaction of GFX with acetylacetone-formaldehyde system solution resulted in bathochromic shift of both emission (476 nm) and excitation (420 nm) wavelengths. The fluorescence intensity was directly proportional to the concentration over the range 10–1000 ng/ml and 100–2000 ng/ml for method A and B, respectively. The proposed methods were applied successfully for determination of GFX in its tablets and spiked plasma. Therefore, these methods can be considered of real interest for reliable and practical quality control analysis of GFX.

High Throughput Quantitative Bioanalytical LC/MS/MS Determination of Gemifloxacin in Human Urine

A highly specific, sensitive, and rapid method, to quantify gemifloxacin in human urine using HPLC coupled to the triple quadrupole mass spectrometer system, was developed and validated. Gemifloxacin and ofloxacin (internal standard) were rapidly extracted from urine samples without any tedious pretreatment procedure. Urine samples were filtered through a Millex-GP, 0.22 μm syringe filter. Optimal chromatographic separation of the analytes was achieved on Zorbax SB-C18(30 mm × 2 mm i.d., 3.5 μm maintained at ambient temperature). The mobile phase consisted of 0.1% formic acid (pH 3.2) and acetonitrile (80 : 20) and a flow rate of 0.2 mL min−1for 4 min. The analytes were monitored by electrospray ionization in positive ion multiple reaction monitoring mode. The method provided a linear response (r=0.9998) from a quantitation range of 5 ng mL−1to at least 500 ng mL−1. The mean extraction recovery % of gemifloxacin from spiked human urine was 101.33 ± 2.58%. The reproducibility of the method was reliable with the intra- and inter-day precision of <2% and accuracy within 2%. The established method was reliably applied for the determination of gemifloxacin in volunteers’ urine samples with the mean recoveries of gemifloxacin from Factive tablets 320 mg > 97.0%.

Anodic Voltammetric determination of gemifloxacin using screen-printed carbon electrode

The electrochemical oxidation behavior and voltammetric assay of gemifloxacin were investigated using differential-pulse and cyclic voltammetry on a screen-printed carbon electrode. The effects of pH, scan rates, and concentration of the drug on the anodic peak current were studied. Voltammograms of gemifloxacin in Tris–HCl buffer (pH 7.0) exhibited a well-defined single oxidation peak. A differential-pulse voltammetric procedure for the quantitation of gemifloxacin has been developed and suitably validated with respect to linearity, limits of detection and quantification, accuracy, precision, specificity, and robustness. The calibration was linear from 0.5 to 10.0 μM, and the limits of detection and quantification were 0.15 and 5.0 μM. Recoveries ranging from 96.26% to 103.64% were obtained. The method was successfully applied to the determination of gemifloxacin in pharmaceutical tablets without any pre-treatment. Excipients present in the tablets did not interfere in the assay.

Development and validation of a spectrofluorimetric method for the determination of erlotinib in spiked human plasma

A rapid and sensitive spectrofluorimetric method was developed and validated for the determination of erlotinib (ETB), a potent anticancer drug, in spiked human plasma without any derivatization. The described method was validated and the analytical parameters of linearity, accuracy, precision (intra- and inter-day), limit of detection (LOD), and limit of quantification (LOQ) were evaluated. The relation between the fluorescence intensity and concentration was found to be linear (r(2) 0.9998) over the range 125 to 1000 ng/mL with the detection limit of 15 ng/mL. A simple liquid-liquid extraction method was followed in order to extract the drug from spiked plasma. The mean absolute recoveries of ETB were 85.59 % (±0.57), 86.91 % (±1.77) and 89.31 % (±3.01) at spiked plasma ETB concentration of 5000, 3750 and 2500 ng/mL, respectively. The spectrofluorimetric method presented here is a rapid, simple, specific, and reproducible method and can be used to characterize the plasma pharmacokinetics of ETB.