Insight on novel oxindole conjugates adopting different anti-inflammatory investigations and quantitative evaluation.

Background: A dual COX/5-LOX strategy was adopted to develop new oxindole derivatives with superior anti-inflammatory activity. Methods: Three series of oxindoles - esters 4a-p, 6a-l and imines 7a-o - were synthesized and evaluated for their anti-inflammatory and analgesic activities. Molecular docking and predicted pharmacokinetic parameters were done for the most active compounds. A new LC-MS/MS method was developed and validated for the quantification of 4h in rat plasma. Results: Compounds 4h, 6d, 6f, 6j and 7m revealed % edema inhibition up to 100.00%; also, 4l and 7j showed 100.00% writhing protection. Compound 4h showed dual inhibitory activity with IC50 = 0.0533 and 0.4195 µM for COX-2 and 5-LOX, respectively. Molecular docking rationalized the obtained biological activity. The pharmacokinetic parameters of 4h from rat plasma were obtained.

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Exploring new imines as anti-inflammatory COX and 5-LOX inhibitors with an improved pharmacokinetic profile.

Background: Dual COX/5-LOX inhibition is a bright strategy for developing new potent and safe anti-inflammatory agents. Methods: New imines were synthesized and evaluated for their anti-inflammatory activity. The most active compounds were further investigated for their safety profile. Their molecular docking and physicochemical parameters were assessed. A new LC-MS/MS method was developed for the quantification of compound 4d in rat plasma. Results: Synthesized compounds were found to have anti-inflammatory activity (77-88% edema inhibition). In addition, 4d, 5m and 7d showed analgesic activity (92.50, 95.71 and 96.28% protection, respectively). 4d showed dual COX-2/5-LOX activity. Molecular docking expected the binding pattern of compounds in COX-1, COX-2 and 5-LOX active sites. The in vivo pharmacokinetic parameters of compound 4d were also obtained.

Indirect synchronous fluorescence spectroscopy and direct high-performance thin-layer chromatographic methods for enantioseperation of zopiclone and determination of chiral-switching eszopiclone: Evaluation of thermodynamic quantities of chromatographic separation.

Economic and enantioselective synchronous fluorescence spectroscopy and high-performance thin-layer chromatography methods have been developed and validated as per ICH guidelines for the separation of zopiclone enantiomers using L-(+)-tartaric acid as a chiral selector, followed by determination of the chiral-switching eszopiclone. Synchronous fluorescence spectroscopy was successfully applied for chiral recognition of R & S enantiomers of zopiclone at ∆λ = 110 nm based on creating of diastereomeric complexes with 0.06M tartaric acid in an aqueous medium containing 0.2M disodium hydrogen orthophosphate. Synchronous fluorescence intensities of eszopiclone were recorded at 296 nm in concentration range 0.2- to 4-µg/mL eszopiclone. High-performance thin-layer chromatography method depends on resolution of zopiclone enantiomers on achiral HPTLC silica-gel plates using acetonitrile:methanol:water (8:2:0.25, v/v/v) containing L-(+)-tartaric acid as a chiral mobile-phase additive followed by densitometric measurements at 304 nm in concentration range of 1 to 10 µg/band of eszopiclone. The effect of chiral-selector concentration, pH, and temperature on the resolution have been studied and optimized for the proposed methods. The cited procedures were successfully applied to determine eszopiclone in commercial tablets of pure and racemic forms. Enantiomeric excess was evaluated using optical purity test and integrated peak area to describe the enantiomeric ratio. Thermodynamics of chromatographic separation, enthalpy, and entropy were evaluated using the Van't Hoff equation. The proposed methods were found to be selective for identification and determination of the eutomer in drug substances and products.

Roflumilast analogs with improved metabolic stability, plasma protein binding, and pharmacokinetic profile.

With the aim of studying their in vitro and in vivo pharmacokinetics, new chromatographic methods were developed for the determination of three new roflumilast synthetic analogs (I-III) as PDE-4B inhibitors in rat liver S9 fraction, phosphate buffered saline, pH 7.4, and human and rat plasma. The developed high performance liquid chromatography-ultra violet (HPLC-UV) methods were performed on a Zorbax Eclipse C8 column and UV detection was carried out at 215 nm. The three compounds were tested for their metabolic stability and were found to be metabolically more stable than roflumilast especially the 2-mercaptobenzothiazol-6-yl analog (III) which displayed an in vitro half-life time (247.55 minutes) higher than that of roflumilast (12.29 minutes) and a low in vitro clearance of 5.67 mL/min./kg. Possible phase I metabolites were investigated using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) showing hydroxylation of the unsubstituted benzothiazol-2-yl (I) and benzothiazole-6-yl (II) analogs and a cleaved benzothiazole metabolite of the 2-mercaptobenzothiazol-6-yl analog (III). Plasma protein binding affinity was tested using equilibrium membrane dialysis method showing a very high percentage (more than 95%) of plasma protein binding of compounds I and II where compound III exhibited lower percentage (53.71%) demonstrating its accessibility for tissue distribution. Also, a UPLC-MS/MS method was developed using an Acquity UPLC BEH shield RP C18 column to be applied to an in vivo pharmacokinetic study in rats following a subcutaneous dose (1 mg/kg). Compounds I-III showed improved in vivo pharmacokinetic parameters especially compound III which displayed a half-life 3-fold greater than roflumilast (21 hours) and a Cmax value of 113.958 ng/mL. Accordingly, this new chemical entity should be subjected to further investigation as it can be a good drug candidate for treating chronic obstructive pulmonary disease.

Synthesis and molecular docking of new roflumilast analogues as preferential-selective potent PDE-4B inhibitors with improved pharmacokinetic profile.

In the present work, we designed and synthesized new roflumilast analogues with preferential-selective PDE-4B inhibition activity and improved pharmacokinetic properties. The unsubstituted benzo[d]thiazol-2-yl and -6-yl benzamide derivatives (4a and 6a) showed both good potency and preferential selectivity for PDE-4B. More remarkably, 6c revealed 6 times preferential PDE-4B/4D selectivity with a significant increase of in vitro cAMP and good % inhibition of TNF-α concentration. In addition, the in vitro pharmacokinetics of 6c showed good metabolic stability with in vitro CLint (5.67 mL/min/kg) and moderate % plasma protein binding (53.71%). This was reflected onto increased in vivo exposure with a half-life greater than roflumilast by 3 folds (21 h) and a Cmax value of 113.958 ng/mL. Molecular docking attributed its good activity to its key binding interactions in PDE-4B active site with additional hydrogen bonding with amino acids lining the metal pocket. Summing up, 6c can be considered as suitable candidate for further investigation for the treatment of COPD.

Simultaneous determination of amlodipine besylate and atorvastatin calcium in binary mixture by spectrofluorimetry and HPLC coupled with fluorescence detection.

Caduet tablets are novel prescription drug that combines amlodipine besylate (AM) with atorvastatin calcium (AT). A spectrofluorimetric and an HPLC-fluorescence detection methods were developed for simultaneous determination of both drugs in tablets. In the spectrofluorimetric method, native fluorescence of AM and AT were measured in methanol at 442 and 369 nm upon excitation at 361 and 274 nm, respectively. The emission spectrum of each drug reveals zero value at the emission wavelength of the other drug, thus allowing their simultaneous determination without interference. In the HPLC method, separation of AM and AT was achieved within 8 minutes on a C18 column using acetonitrile:phosphate buffer (0.015 M, pH 3) (45:55, v/v) as the mobile phase. Fluorescence detection was carried out using excitation wavelengths 361 and 274 nm and emission wavelengths 442 and 378 nm for AM and AT, respectively. Excellent linearity was observed. Careful validation proved advantages of the new methods: high sensitivity, accuracy, selectivity and suitability for quality control laboratories.