Simple Isocratic HPLC Method for Determination of Enantiomeric Impurity in Besifloxacin Hydrochloride

Exploring the Role of Sodium Dodecyl Sulfate Surfactant in Enhancing the Fluorescence Properties of Besifloxacin Fluoroquinolone; Application to Eye Formulations and Artificial Aqueous Humor

An ultrasensitive, selective, rapid, and cost-effective spectrofluorimetric approach is established and validated to quantify the ophthalmic fluoroquinolone antibiotic, besifloxacin (BN), in its ophthalmic preparations and artificial aqueous humor. Unlike previously reported methods that require costly fluorogenic derivatization reagents, lengthy analytical procedures, or expensive instrumentation, the proposed approach offers a simple and highly sensitive alternative method for detecting BN. The suggested method relies on using 2.0% w/v sodium dodecyl sulfate (SDS) as a micellar system in an acetate buffer solution (pH 3.6) to boost the fluorescence intensity of BN at λem of 446 nm. The fluorescence intensity of BN was remarkably amplified by around 2.6 folds compared to the BN in acetate buffer without SDS surfactant. The linearity range of the developed method was 5.0-100 ng/mL with detection and quantitation limits of 0.64 and 1.93 ng/mL, respectively. Moreover, the proposed micellar system has been effectively used for the assay of the BN in eye drops and artificial aqueous humor and the achieved percentage recoveries for artificial aqueous humor samples were in the range of 98.82 ± 1.89-103.08 ± 1.60%.

Hantzsch Reaction-Based Fluorimetric Approach for Sensitive Determination of Besifloxacin in Pharmaceutical Eye Drops and Aqueous Humor

An innovative and sensitive analytical tool (fluorimetric spectroscopy) for quantifying besifloxacin (BFC) in eye drops and aqueous humor is introduced. The method presented here utilizes a well-known derivatization reaction called Hantzsch reaction to activate BFC's fluorescence. All the factors affecting the sensitivity of the developed approach were optimized to boost the method's sensitivity. After optimizations, this reaction enables the fluorimetric determination (at 485 nm) of BFC in eye drops and spiked aqueous humor without any obstructions from the naturally present biointerferents. The dynamic range for BFC determination in the pure state is 0.15-1.0 (μg/mL), with detection and quantification limits of 0.02 and 0.05 (μg/mL), respectively. The approach exhibits favorable recovery rates in spiked aqueous humor (95.5% ± 1.15%-100.3% ± 0.50%).

A novel, sensitive, and widely accessible besifloxacin quantification method by HPLC-fluorescence: Application to an ocular pharmacokinetic study

Besifloxacin has been embraced for the treatment of ocular bacterial infections. While LC-MS/MS has been used in investigating BSF pharmacokinetics, those costly instruments are not universally available and have complicated requirements for operation and maintenance. Additionally, pharmacokinetics of besifloxacin in dose-intense regimens are still unknown. Herein, a new quantification method was developed employing the widely accessible HPLC with fluorescence detection and applied to an ocular pharmacokinetic study with an intense regimen. Biosamples were pre-treated using protein precipitation. Chromatographic separation was achieved on a C18 column using mobile phase of 0.1% trifluoroacetic acid and acetonitrile. To address the weak fluorescence issue of besifloxacin, effects of detection parameters, elution pattern, pH of mobile phase, and reconstitution solvents were investigated. The method was fully validated per US-FDA guidelines and demonstrated precision (<13%), accuracy (91-112%), lower limit of quantification (5 ng/mL), linearity over clinically relevant concentrations (R² > 0.999), matrix-effects (93-105%), recoveries (95-106%), and excellent selectivity. The method showed agreement with agar disk diffusion assays for in vitro screening and comparable in vivo performance to LC-MS/MS (Deming Regression, y = 1.010x + 0.123, r = 0.997; Bland-Altman analysis, mean difference was -6.3%; n = 21). Pharmacokinetic parameters suggested superior surface-retentive properties of besifloxacin. Maximum concentrations were 1412 ± 1910 and 0.15 ± 0.12 μg/mL; area under the curve was 1,637 and 1.08 µg·h/g; and half-life was 4.9 and 4.1 h; and pharmacokinetic-to-pharmacodynamic ratios were ≥ 409 and ≤ 17.8 against ocular pathogens in tears and aqueous humor, respectively. This readily available method is sensitive for biosamples and practical for routine use, facilitating besifloxacin therapy development.

Enantiomeric separation of vilanterol trifenatate by chiral liquid chromatography

Vilanterol trifenatate is a novel chiral long-acting β2-agonist developed. Vilanterol combined with inhaled corticosteroids can treat COPD and asthma. A simple liquid chromatographic method is developed for the quantitative determination of R-vilanterol and S-vilanterol (impurity S). HPLC separation was achieved on Chiralpak ID (250 × 4.6 mm; particle size 5 μm) column using hexane-ethanol-ethanolamine (75:25:0.1, v/v/v) as mobile phase at a flow rate of 1.0 mL/min. The resolution is greater than 3.3. Ethanolamine in the mobile phase is vital to enhance chromatographic efficiency and resolution between the isomers. The method was validated with respect to accuracy, specificity, precision, LOD, LOQ, linearity, and robustness as ICH guidelines.

Study of degradation behavior of besifloxacin, characterization of its degradation products by LC-ESI-QTOF-MS and their in silico toxicity prediction

Knowledge and understanding of the stability profile of a drug is important as it affects its safety and efficacy. In the present work, besifloxacin, a new, fourth-generation fluoroquinolone antibiotic, was subjected to different forced-degradation conditions as per International Conference on Harmonization (ICH) guidelines such as hydrolysis (acid, base and neutral), oxidation, thermal and photolysis. The drug degraded under acidic, basic, oxidative and photolytic conditions while it was found to be stable under dry heat and neutral hydrolytic conditions. In total, five degradation products (DPs) were formed under different conditions-DP1 and DP2 (photolysis), DP3 (oxidation), DP4 (acidic), DP3 and DP5 (basic). The chromatographic separation of besifloxacin and its degradation products was achieved on a Sunfire C18 (250 mm × 4.6 mm, 5 μm) column with 0.1% aqueous formic acid-acetonitrile as a mobile phase. The gradient RP-HPLC method was developed and validated as per ICH guidelines. The degradation products were characterized with the help of LC-ESI-QTOF mass spectrometric studies and the most likely degradation pathway of the drug was proposed. In silico toxicity assessment of the drug and its degradation products was carried out, which indicated that DP3 and DP4 carry a mutagenicity alert.