Development of a UPLC-MS/MS method for the determination of lomefloxacin in rabbit aqueous humor and its application to a pharmacokinetic study

Luteolin ameliorates cornea stromal collagen degradation and inflammatory damage in rats with corneal alkali burn

Corneal alkali burn (AB) is a blindness-causing ocular trauma commonly seen in clinics. An excessive inflammatory reaction and stromal collagen degradation contribute to corneal pathological damage. Luteolin (LUT) has been studied for its anti-inflammatory effects. In this study, the effect of LUT on cornea stromal collagen degradation and inflammatory damage in rats with corneal alkali burn was investigated. After corneal alkali burn, rats were randomly assigned to the AB group and AB + LUT group and received an injection of saline and LUT (200 mg/kg) once daily. Subsequently, corneal opacity, epithelial defects, inflammation and neovascularization (NV) were observed and recorded on Days 1, 2, 3, 7 and 14 post-injury. The concentration of LUT in ocular surface tissues and anterior chamber, as well as the levels of collagen degradation, inflammatory cytokines, matrix metalloproteinases (MMPs) and their activity in the cornea were detected. Human corneal fibroblasts (HCFs) were co-cultured with interleukin (IL)-1β and LUT. Cell proliferation and apoptosis were assessed by CCK-8 assay and flow cytometry respectively. Measurement of hydroxyproline (HYP) in culture supernatants was used to quantify the amount of collagen degradation. Plasmin activity was also assessed. ELISA or real-time PCR was used to detect the production of matrix metalloproteinases (MMPs), IL-8, IL-6 and monocyte chemotactic protein (MCP)-1. Furthermore, the immunoblot method was used to assess the phosphorylation of mitogen-activated protein kinases (MAPKs), transforming growth factor-β-activated kinase (TAK)-1, activator protein-1 (AP-1) and inhibitory protein IκB-α. At last, immunofluorescence staining helped to develop nuclear factor (NF)-κB. LUT was detectable in ocular tissues and anterior chamber after intraperitoneal injection. An intraperitoneal injection of LUT ameliorated alkali burn-elicited corneal opacity, corneal epithelial defects, collagen degradation, NV, and the infiltration of inflammatory cells. The mRNA expressions of IL-1β, IL-6, MCP-1, vascular endothelial growth factor (VEGF)-A, MMPs in corneal tissue were downregulated by LUT intervention. And its administration reduced the protein levels of IL-1β, collagenases, and MMP activity. Furthermore, in vitro study showed that LUT inhibited IL-1β-induced type I collagen degradation and the release of inflammatory cytokines and chemokines by corneal stromal fibroblasts. LUT also inhibited the IL-1β-induced activation of TAK-1, mitogen-activated protein kinase (MAPK), c-Jun, and NF-κB signaling pathways in these cells. Our results demonstrate that LUT inhibited alkali burn-stimulated collagen breakdown and corneal inflammation, most likely by attenuating the IL-1β signaling pathway. LUT may therefore prove to be of clinical value for treating corneal alkali burns.

A novel spectrofluorimetric method for determination of lomefloxacin adopting on zinc(II) chelation strategy: Application in human plasma

A new sensitive and instantaneous spectrofluorimetric method for efficient determination of lomefloxacin (LMX) in its pure, dosage form and human plasma was designed. The developed method depends on formation of a metal-chelation compound of LMX as a ligand with zinc(II) in a buffer of acetate (pH 5.5). The following parameters; type of metal, concentration of metal, pH, type of buffer and diluting solvent were optimized. After carefully investigation; 0.2 mM zinc, 2.0 ml acetate buffer (pH 5.5) and water as diluting solvent were set as optimum reaction conditions. Under these conditions, a large increase in the intensity of the fluorescence of LMX was attained at 450 after excitation at 284 nm. The limits of detection and quantification were 5.8 and 1.9 ng ml^-1 , respectively, with linearity range of 10.0 to 500.0 ng ml^-1 . The binding mode of LMX and zinc(II) ion (Zn²⁺ ) was found to be 2:1, respectively, and confirmed by Job's plot method. Furthermore, it extended to the analysis of LMX in the spiked plasma of humans with percentage recovery (98.70 ± 0.97 to 100.30 ± 1.69%, n = 3).

Validated Liquid Chromatography-Tandem Mass Spectroscopic Method for Simultaneous Determination of Certain Drugs Used in Cataract Surgery in Rabbit Aqueous Humor

A sensitive, selective, accurate and precise ultra-high performance liquid chromatography-Tandem mass spectrometry (MS/MS) method was developed and validated for the simultaneous determination of drugs used as eye drops in cataract surgery in aqueous humor. Cataract surgery requires a powerful mydriatic eye drops combination such as cyclopentolate hydrochloride and phenylephrine hydrochloride to dilate the pupil and facilitate eye lens replacement and also requires strong fluoroquinolone antibiotic such as lomefloxacin hydrochloride. The method was performed with positive ion electrospray ionization and the analytes were quantified and monitored on a triple quadrupole mass spectrometer using multiple reaction monitoring scanning mode. Liquid-liquid extraction was used for the purification and preconcentration of analytes from rabbit aqueous humor matrix. Chromatographic elution was performed using an Phenomenex Luna® C18 (150 mm × 2.1 mm, 1.6 μm) column and moxifloxacin hydrochloride as internal standard with a mobile phase consisting of methanol:water:formic acid (70:29:1, by volume) at flow rate of 0.2 mL/min. Satisfactory results regarding linearity, recovery, stability, accuracy and precision of the analytes were obtained. Full validation of the procedure was performed according to the US Food and Drug Administration guidance for industry: bioanalytical method validation and European Medicines Agency (EMA) guideline on bioanalytical method validation.

Screening and optimization of samarium-assisted complexation for the determination of norfloxacin, levofloxacin and lomefloxacin in their corresponding dosage forms employing spectrofluorimetry

Multivariate strategy was applied for setting a fluorescent technique for the determination of three fluoroquinolones: norfloxacin (NOR), levofloxacin (LEV) and lomefloxacin (LOM) in their pure powder and dosage forms. Based on their known interaction with lanthanides, and augmented fluorescence intensity obtained by antenna effect at λ_ex/λ_em = 314/553, 312/553 and 310/556 for NOR, LEV and LOM, respectively, the current research was scrutinized. Four continuous factors were selected for study in the screening step by means of Plackett-Burman Design, where temperature factor was excluded for being non-significant and the other factors as volume of metal ion solution, pH and reaction time were evaluated through Central Composite Design. 3-D surfaces demonstrations and 2-D contour plots designated the factors interactions followed by optimization plots, which defined the best blend for factors conjunction. pH factor was the chief motor force affecting the response as the number of coordinated ligands formed depends on the pH, whereas 1:2 complex is the main species at higher pH values followed by the volume of metal ion solution and ended by little effect of the reaction time. Model verification was monitored, which showed the model superiority for the three fluoroquinolones, where all target points tested were in good agreement with the predicted ones. The linear range for the tested drugs were found to be 0.090-1.280 μg/mL for NOR, 0.068-1.448 μg/mL for LEV and 0.077-1.552 μg/mL in case of LOM, thus approving the suitability of this method for Quality Control testing. Furthermore, applying these conditions to test the fluoroquinolones in their pharmaceuticals was done as well as intra and inter-day effects as to confirm the validity of this technique for routine analysis. Recovery % and RSD were found to be 99.958 ± 0.797, 99.887 ± 0.935 and 100.427 ± 0.698 for NOR, LEV and LOM respectively in their pure powder. While it was calculated to be 100.200 ± 0.785, 100.530 ± 0.396 and 100.620 ± 0.896 for NOR, LEV and LOM in their corresponding dosage forms. This excellent precision and accuracy obtained in results impulse it to be one of the most appropriate methods for further analysis.

Pharmacokinetic study of sirolimus ophthalmic formulations by consecutive sampling and liquid chromatography-tandem mass spectrometry

Sirolimus is regarded as one of the most effective immunosuppressants receiving extensive attention over the years, for which the ocular application needs further development in clinical keratoplasty. In order to study the transcorneal absorption effect of ophthalmic administration, there was a need to study the pharmacokinetics of drugs in aqueous humor. In this work, a validated and reliable HPLC-ESI-MS/MS method was established to study the pharmacokinetics of sirolimus nanoformulations in rabbit aqueous humor. The analysis conditions were as follows. Ascomycin was chosen as internal standard. After a simple precipitation extraction procedure, the aqueous humor samples were separated on a XBridge C18 column (4.6 mm × 150 mm, 3.5 μm, Waters Co., USA) with a mobile phase comprised of water (0.1% formic acid and 5 mM ammonium formate) and methanol (0.1% formic acid) at the ratio of 10:90 (v/v). The mass analysis was achieved by positive ionization with multiple reaction monitoring (MRM) mode. The highest response ion pairs m/z at 931.5→864.5 were chosen for sirolimus. The validated results showed that the calibration range was 0.3-100.6 ng/mL with r = 0.9997 (n = 6). The R.S.D. values of the intra- and inter-day precision were less than 11% and the average accuracy values were between 94.73%-100.20%. Besides, for reducing the consumption of rabbits and the variation of the data, we designed a consecutive sampling method in pharmacokinetic study, with only seven rabbits consumed for each formulation. In conclusion, the developed analysis method was more reliable and practical than previously reported experiments. Meanwhile, the validated method was successfully applied to study the pharmacokinetics of sirolimus micelle and sirolimus nanosuspension after ophthalmic administration.