Potential and performance of anisotropic 19F NMR for the enantiomeric analysis of fluorinated chiral active pharmaceutical ingredients.

Controlling the enantiomeric purity of chiral drugs is of paramount importance in pharmaceutical chemistry. Isotropic 1H NMR spectroscopy involving chiral agents is a widely used method for discriminating enantiomers and quantifying their relative proportions. However, the relatively weak spectral separation of enantiomers (1H Δδiso(R, S)) in frequency units at low and moderate magnetic fields, as well as the lack of versatility of a majority of those agents with respect to different chemical functions, may limit the general use of this approach. In this article, we investigate the analytical potential of 19F NMR in anisotropic chiral media for the enantiomeric analysis of fluorinated active pharmaceutical ingredients (API) via two residual anisotropic NMR interactions: the chemical shift anisotropy (19F-RCSA) and dipolar coupling ((19F-19F)-RDC). Lyotropic chiral liquid crystals (CLC) based on poly-γ-benzyl-L-glutamate (PBLG) show an interesting versatility and adaptability to enantiodiscrimination as illustrated for two chiral drugs, Flurbiprofen® (FLU) and Efavirenz® (EFA), which have very different chemical functions. The approach has been tested on a routine 300 MHz NMR spectrometer equipped with a standard probe (5 mm BBFO probe) in a high-throughput context (i.e., ≈10 s of NMR experiments) while the performance for enantiomeric excess (ee) measurement is evaluated in terms of trueness and precision. The limits of detection (LOD) determined were 0.17 and 0.16 µmol ml-1 for FLU and EFA, respectively, allow working in dilute conditions even with such a short experimental duration. The enantiodiscrimination capabilities are also discussed with respect to experimental features such as CLC composition and temperature.

Direct distinction of ibuprofen and flurbiprofen enantiomers by ion mobility mass spectrometry of their ternary complexes with metal cations and cyclodextrins in the gas phase.

Enantiomeric drugs are widely used and play important roles in pharmaceuticals. Ion mobility spectrometry coupled with mass spectrometry technology provides a unique method for distinguishing the enantiomeric drugs, enantiomeric identification, and quantitation in the gas phase. In this study, enantiomeric molecules of ibuprofen and flurbiprofen were clearly recognized by forming host-guest complex ions using trapped ion mobility time-of-flight mass spectrometry. Ternary complex ions can be produced easily by electrospray ionization of the mixed solutions of ibuprofen, cyclodextrins, and CaCl2 , LiCl, or NaCl, as well as flurbiprofen, cyclodextrins, and CaCl2 . The relative contents of different chiral ibuprofens in a mixed solution were also quantitatively measured. This new method is a simple, effective, and a convenient enantioselective analysis method.

Applicability of capillary electrophoresis-frontal analysis for displacement studies: Effect of several drugs on l-tryptophan and lidocaine binding to human serum albumin.

The effective concentration of a drug in the blood, i.e. the concentration of a free drug in the blood, is influenced by the strength of drug binding onto plasma proteins. Besides its efficacy, these interactions subsequently influence the liberation, absorption, distribution, metabolism, excretion, and toxicological properties of the drug. It is important to not only determine the binding strength and stoichiometry, but also the binding site of a drug on the plasma protein molecule, because the co-administration of drugs with the same binding site can affect the above-mentioned concentration and as a result the pharmacological behavior of the drugs and lead to side effects caused by the change in free drug concentration, its toxicity. In this study, the binding characteristics of six drugs with human serum albumin, the most abundant protein in human plasma, were determined by capillary electrophoresis-frontal analysis, and the obtained values of binding parameters were compared with the literature data. The effect of several drugs and site markers on the binding of l-tryptophan and lidocaine to human serum albumin was investigated in subsequent displacement studies which thus demonstrated the usability of capillary electrophoresis as an automated high-throughput screening method for drug-protein binding studies.

Simultaneous enantiomeric analysis of non-steroidal anti-inflammatory drugs in environment by chiral LC-MS/MS: A pilot study in Beijing, China.

A simple, sensitive and quick method for direct simultaneous chiral analysis of frequently used non-steroidal anti-inflammatory drugs (NSAIDs) (ibuprofen, naproxen and flurbiprofen) in river water by HPLC-MS/MS was established and validated. Chromatographic parameters including the mobile phase composition, pH values, temperature and flow rates were optimized to obtain both satisfactory sensitivity and enantiomeric resolution (Rs≥ 1.0), which suggested the composition and pH values of mobile phase played crucial influence on enantioseparations. The method demonstrated its superiority compared with previous studies regarding to the low MQLs (1.1-37.1 ng/L) and short runtime (< 20 min), enabling quantitative enantiomeric determination of trace level of emerging contaminants in water. The environmental monitoring of receiving water (34 sites along rivers) in Beijing revealed ibuprofen was the most abundant, with mean concentration of 114.9 ng/L and detection frequency of 91%, naproxen was also detectable at all sites from < MQL-43.2 ng/L, both presenting an excess of the S-(+)-enantiomer. Therefore to better understand the ecological risk posed from the trace organic contaminants on the aquatic organisms, chiral pollutants need analyzed at the enantiomeric levels. This is the first to profile the enantiospecific occurrence of NSAIDs in surface water in Beijing, China. It could provide useful information on environmental behaviors of chiral pollutants and facilitate more accurate environmental risk assessment.

Validation of an analytical method to quantify the permeation and penetration of flurbiprofen into human pharynx tissue.

The aim of this investigation was to develop receiver and extraction fluids, and subsequently validate an analytical method to quantify the permeation and penetration of flurbiprofen into human pharynx tissue using a Franz diffusion cell. The solubility and stability of flurbiprofen in a suitable receiver fluid, and a suitable extraction method and fluid to recover and quantitate flurbiprofen from human pharynx tissue, were investigated using high-performance liquid chromatography (HPLC). The potential interference of human pharynx tissue in the receiver fluid was also investigated. The HPLC analytical method was successfully validated according to current guidelines. The final receiver fluid demonstrated sufficient solubility and stability, and the extraction method and fluid resulted in >95% recovery of flurbiprofen following exposure to human pharynx tissue. The lower limit of quantitation of flurbiprofen was 0.045 µg/mL in both the receiver and extraction fluids. There was no interference of the human pharynx tissue with the HPLC method. This investigation validated an analytical method for quantitating flurbiprofen, and determined a suitable receiver fluid and extraction method and fluid, which can be used to investigate the permeation and penetration of flurbiprofen through human pharynx tissue using the Franz diffusion cell method.

Development of fast dissolving tablets of flurbiprofen by sublimation method and its in vitro evaluation

Flurbiprofen belongs to Biopharmaceutical Classification System (BCS) class II drugs which are poorly soluble in water. The objective of present research work was to prepare fast dissolving tablets of Flurbiprofen using varying concentrations of three different sublimating agents to improve the dissolution rate. Seven formulations were prepared containing different concentrations of camphor, ammonium bicarbonate and thymol as sublimating agent along with primogel as a superdisintegrant. Tablets were manufactured by direct compression method. The prepared tablets were evaluated for pre-compression and post-compression parameters result, For all formulations result was within official limits. FTIR studies revealed that there were no interactions between the drug and the excipients used. From in vitro drug release studies it was concluded that the formulations F6 and F7 containing 10% and 15% of thymol showed fast drug release of 100.00% and 100.84% respectively in 30 minutes. Formulations containing camphor (F2 & F3) and ammonium bicarbonate (F4 & F5) as sublimating agents showed a drug release of less than 80%, while the control formulation F1 having no sublimating agent showed 49.14% of drug release in 30 minutes. Thus thymol can successfully be used to formulate fast dissolving tablets of flurbiprofen by sublimation method with much better dissolution profile

Solubility and dissolution enhancement of flurbiprofen by solid dispersion using hydrophilic carriers

ABSTRACT The intent of the current work is to study the effect of polyethylene glycol 8000 and polyethylene glycol 10000 as hydrophilic carriers on dissolution behaviour of flurbiprofen. In the present study, solvent evaporation method was used to prepare flurbiprofen solid dispersions and evaluated for physico-chemical properties, drug-carrier compatibility studies and dissolution behaviour of drug. Solubility studies showed more solubility in higher pH values and formulations SD4 and SD8 were selected to prepare the fast dissolving tablets. FTIR and DSC study showed no interaction and drug was dispersed molecularly in hydrophilic carrier. XRD studies revealed that there was change in the crystallinity of the drug. The results of In vitro studies showed SD8 formulation confer significant improvement (p<0.05) in drug release, Q20 was 99.08±1.35% compared to conventional and marketed tablets (47.31±0.74% and 56.86±1.91%). The mean dissolution time (MDT) was reduced to 8.79 min compared to conventional and marketed tablets (25.76 and 22.22 min.) indicating faster drug release. The DE (% dissolution efficiency) was increased by 2.5 folds (61.63%) compared to conventional tablets (23.71%). From the results, it is evident that polyethylene glycol solid dispersions in less carrier ratio may enhance the solubility and there by improve the dissolution rate of flurbiprofen.

Investigation of the parameters affecting the release of flurbiprofen from chitosan microspheres

ABSTRACT Flurbiprofen (FLB), a NSAID, widely used for preventing pain generally for arthritis or dental problems. In this study, FLB loaded chitosan microspheres were prepared by ionotropic gelation method. In this method, microspheres were formed by dropping chitosan solutions containing FLB into sodium alginate solutions including sodium tripolyphosphate (TPP). A variety of formulation parameters like drug:polymer ratio, drug concentration, polymer's molecular weight, polymer concentration, pH and the concentration of TPP solutions, drying method and stirring time were analyzed. The dissolution studies were performed in a shaking water bath in pH 7.4 phosphate buffer saline (PBS) at 37 °C. Laser diffractometer was used for particle size analysis, and scanning electron microscope (SEM) was used for morphological properties. Drug loading and loading efficiency were calculated by using UV spectrophotometer. The particles obtained were spherical with 0.7-1.3 mm size range, and the loading efficiency was approximately 21-79%. The dissolution studies conducted revealed that drug:polimer ratio and the polymer type and concentration affected the drug release from microspheres. It was observed that increasing the polymer concentration, polymer's molecular weight and TPP concentration decreased the FLB release from microspheres, which was according to Higuchi kinetics.

Enantioselective simultaneous analysis of selected pharmaceuticals in environmental samples by ultrahigh performance supercritical fluid based chromatography tandem mass spectrometry.

In order to assess the true impact of each single enantiomer of pharmacologically active compounds (PACs) in the environment, highly efficient, fast and sensitive analytical methods are needed. For the first time this paper focuses on the use of ultrahigh performance supercritical fluid based chromatography coupled to a triple quadrupole mass spectrometer to develop multi-residue enantioselective methods for chiral PACs in environmental matrices. This technique exploits the advantages of supercritical fluid chromatography, ultrahigh performance liquid chromatography and mass spectrometry. Two coated modified 2.5 µm-polysaccharide-based chiral stationary phases were investigated: an amylose tris-3,5-dimethylphenylcarbamate column and a cellulose tris-3-chloro-4-methylphenylcarbamate column. The effect of different chromatographic variables on chiral recognition is highlighted. This novel approach resulted in the baseline resolution of 13 enantiomers PACs (aminorex, carprofen, chloramphenicol, 3-N-dechloroethylifosfamide, flurbiprofen, 2-hydroxyibuprofen, ifosfamide, imazalil, naproxen, ofloxacin, omeprazole, praziquantel and tetramisole) and partial resolution of 2 enantiomers PACs (ibuprofen and indoprofen) under fast-gradient conditions (<10 min analysis time). The overall performance of the methods was satisfactory. The applicability of the methods was tested on influent and effluent wastewater samples. To the best of our knowledge, this is the first feasibility study on the simultaneous separation of chemically diverse chiral PACs in environmental matrices using ultrahigh performance supercritical fluid based chromatography coupled with tandem mass spectrometry.

Stability-Indicating HPTLC Method for Simultaneous Estimation of Flurbiprofen and Chloramphenicol in Ophthalmic Solution.

A specific, accurate and reproducible stability-indicating high performance thin layer chromatography (HPTLC) method was developed for the estimation of flurbiprofen and chloramphenicol in the presence of their degradation products. Degradation studies of both the drugs were carried out in acidic, alkaline, neutral, oxidative, photolytic and thermal stress conditions. Separation was performed on thin layer chromatography plate precoated with silica gel 60 F254 using ethyl acetate : n-hexane : methanol : tri-ethyl amine (5 : 4 : 2 : 0.5, v/v/v/v). Spots at retention factor 0.29 and 0.62 were recognized as flurbiprofen and chloramphenicol, respectively, and were quantified through densitometric measurements at wavelength 267 nm. Method was found to be linear over the concentration range 12-60 ng/spot with correlation coefficient of 0.9997 for flurbiprofen and 200-1,000 ng/spot with correlation coefficient of 0.9977 for chloramphenicol. The proposed method was applied to the estimation of flurbiprofen and chloramphenicol in commercial ophthalmic formulation. The developed HPTLC method can be applied for routine analysis of flurbiprofen and chloramphenicol in the presence of their degradation products in their individual as well as combined pharmaceutical formulations.

Peak distortions arising from large-volume injections in supercritical fluid chromatography.

Preparative separations in supercritical fluid chromatography (SFC) involve the injection of large volumes of the solute. In SFC, the mobile phase is typically high pressure CO2+modifier and the solute to be injected is usually dissolved in the modifier. Two-types of injection methods, modifier-stream and mixed-stream, are common in commercial preparative SFC systems. In modifier-stream injection, the injection is made in the modifier stream which is later mixed with the CO2 stream, while in the mixed-stream injection, the injection is made in a mixed CO2+modifier stream. In this work a systematic experimental and modelling study of the two techniques is reported using single-enantiomers of flurbiprofen on Chiralpak AD-H with CO2+methanol as the mobile phase. While modifier-stream injection shows non-distorted peaks, mixed-stream injection results in severe peak-distortion. By comparing the modelling and experimental results, it is shown that the modifier "plug" introduced in the mixed-stream injection is the primary cause of the peak distortions. The experimental results also point to the possible existence of viscous fingering which contributes to further peak distortion.

Evaluation of amino acid ester-based ionic liquids as buffer additives in CE for the separation of 2-arylpropionic acids nonsteroidal anti-inflammatory drugs.

The aim of the present study is the CE performance evaluation for the separation of 2-arylpropionic acid nonsteroidal anti-inflammatory drugs. In particular, the separation of indoprofen, carprofen, ketoprofen, ibuprofen, and flurbiprofen was obtained by supporting the BGE either with SDS or an amino acid ester-based ionic liquid (AAIL). The performance of these additives was evaluated by comparing migration times, efficiencies and %RSD values. The addition of the AAIL into the BGE provided baseline separation within 10 min, while in the case of SDS, the analytes eluted within 23 min. The optimum conditions involve a BGE of 100 mM Tris/10 mM sodium tetraboratedecahydrate (pH 8) and 40 mM l-alanine tert butyl ester lactate or 10 mM SDS and a temperature of 35°C for AAIL and 20°C for SDS. The run-to-run reproducibility was evaluated by computing the %RSD values of the EOF and the analyte peaks. When the AAIL was used, an excellent reproducibility was obtained, since all %RSD values were below 1.3%. On the contrary, the addition of SDS resulted in much higher RSD values (2.1-11.7%). The efficiency values of all analyte peaks were above 102 000 for l-AlaC4 Lac, in comparison to SDS, which provided efficiency values between 47000 and 76000. Finally, in an attempt to study the synergistic effect of SDS and AAIL, both additives were added into the BGE at concentrations of 10 and 40 mM, respectively. The results were similar to the ones obtained when SDS was used as the sole additive.

Separation efficiency of dual-selector systems in capillary electrophoresis.

We introduce an easy but highly descriptive model of separation efficiency of dual-selector systems in capillary electrophoresis. The model expresses effective mobilities of analytes in dual-selector mixtures as a function of mixture composition and total concentration. The effective mobility follows the pattern familiar from single-selector systems, while complexation constant and mobility of the complex are replaced by the same but "overall" parameters and a total concentration of the mixture takes the role of a selector concentration. The overall parameters can be either calculated from the individual ones (an arbitrary mixture) or measured directly (a particular mixture). We inspected two model dual-selector systems consisting of heptakis(2,6-di-O-methyl)-ß-CD and ß-CD and of heptakis(2,6-di-O-methyl)-ß-CD and 6-O-α-maltosyl-ß-CD, and ibuprofen and flurbiprofen as model analytes (pH 8.2, non-enantioselective separation). Adopting any optimization strategy typically used in single-selector systems and finding an optimal mixture composition and total concentration is perhaps the prime benefit of the model. We demonstrate this approach on the selectivity parameter and show that the model is precise enough to be used in analytical practice. It also results that an electromigration order (reversal) of analytes can exhibit a rather curious dependency on the mixture composition and concentration. Last, the model can be used for better understanding of separation principles in dual-selector systems in general.

Formulation and in vitro evaluation of mucoadhesive controlled release matrix tablets of flurbiprofen using response surface methodology

The objective of the current study was to formulate mucoadhesive controlled release matrix tablets of flurbiprofen and to optimize its drug release profile and bioadhesion using response surface methodology. Tablets were prepared via a direct compression technique and evaluated for in vitro dissolution parameters and bioadhesive strength. A central composite design for two factors at five levels each was employed for the study. Carbopol 934 and sodium carboxymethylcellulose were taken as independent variables. Fourier transform infrared (FTIR) spectroscopy studies were performed to observe the stability of the drug during direct compression and to check for a drug-polymer interaction. Various kinetic models were applied to evaluate drug release from the polymers. Contour and response surface plots were also drawn to portray the relationship between the independent and response variables. Mucoadhesive tablets of flurbiprofen exhibited non-Fickian drug release kinetics extending towards zero-order, with some formulations (F3, F8, and F9) reaching super case II transport, as the value of the release rate exponent (n) varied between 0.584 and 1.104. Polynomial mathematical models, generated for various response variables, were found to be statistically significant (P<0.05). The study also helped to find the drug's optimum formulation with excellent bioadhesive strength. Suitable combinations of two polymers provided adequate release profile, while carbopol 934 produced more bioadhesion.

O objetivo do presente estudo foi formular comprimidos mucoadesivos de flurbiprofeno, de liberação controlada, e otimizar o perfil da liberação do fármaco e a bioadesão, utilizando a metodologia de superfície de resposta. Prepararam-se os comprimidos via técnica de compressão direta, que foram avaliados in vitro quanto aos parâmetros de dissolução e da força bioadesiva. Planejamento com componente central para dois fatores em cinco níveis cada foi empregado para esse estudo. Carbopol 934 e carboximetilcelulose sódica foram tomados como variáveis independentes. Efetuaram-se estudos de espectroscopia por transformada de Fourier (FTIR) para observar a estabilidade do fármaco durante a compressão direta e para avaliar a interação a fármaco-polímero. Aplicaram-se vários métodos cinéticos para avaliar a liberação do fármaco dos polímeros. Gráficos de superfície de contorno e de resposta foram efetuados para retratar a relação entre as variáveis dependentes e a resposta. Os comprimidos mucoadesivos de flurbiprofeno apresentaram cinética de liberação não-fickiana, estendendo para ordem zero, para algumas formulações (F3, F8 e F9), alcançando transporte super caso II, à medida que o valor do expoente (n) de taxa de liberação variou entre 0,584 e 1,104. Modelos matemáticos polinomiais, gerados por diversas variáveis de resposta, foram estatisticamente, significativos (P<0,05). O estudo também auxiliou a encontrar a formulação ótima do fármaco, com excelente força de bioadesão. Combinações adequadas dos dois polímeros resultaram em perfis de liberação adequado, sendo que o Carbopol 934 produziu mais adesão.

Sensing chiral drugs by using CdSe/ZnS nanoparticles capped with N-acetyl-L-cysteine methyl ester.

Chiral quantum dots (QDs), differing in their core or shell size and, consequently, in their optical properties, were synthesized by the treatment of commercially available amine-capped quantum dots with methyl ester N-acetyl-L-cysteine (CysP). Interestingly, their colloidal methanol solutions remain stable for several months. Their NMR and IR spectra were in accordance with CysP binding to the QD surface through two anchoring groups; its thiolate (strongly bound) and the carbonyl group of its ester (weaker bound) group, whereas their circular dichroism (CD) spectra showed a new broad redshifted band, suggesting that the attachment to the QD surface modified the conformational equilibrium towards conformer(s) with optical activity in this region. These QDs were sufficiently fluorescent to perform studies of the chiral recognition of drugs, in particular the aryl propionic acids (APAs) ketoprofen (KP), naproxen (NP), flurbiprofen (FP), and ibuprofen (IP). We used different drug concentration ranges, depending on the QD solubility. All the assayed drugs quenched the QD emission in a concentration-dependent mode. Quenching fluorescence assays with the chiral QDs (CS@CysP) showed their extraordinary capacity for the chiral recognition of KP, NP, and FP, and particularly in the case of KP and FP, a remarkable positive allosteric effect was detected for the R enantiomer. By using a drug/CS@CysP molar ratio of 5000:1 and 2500:1, the changes of intensity and the sign of the CD spectrum of the drug evidenced the dissociation of the drug carboxylic group in the presence of the QD.

Enantioseparations in nonaqueous capillary electrophoresis using charged cyclodextrins.

The enantioseparation of acidic and basic compounds can be successfully achieved in nonaqueous capillary electrophoresis using single-isomer charged ß-cyclodextrin (ß-CD) derivatives of opposite charge to that of the analytes. This chapter describes how to separate the enantiomers of three basic substances selected as model compounds, i.e., alprenolol, bupranolol, and terbutaline, using the negatively charged heptakis(2,3-di-O-acetyl-6-O-sulfo)-ß-CD. The enantiomers of three acidic drugs (tiaprofenic acid, suprofen, and flurbiprofen) are resolved using a monosubstituted amino ß-CD derivative, namely, 6-monodeoxy-6-mono(3-hydroxy)propylamino-ß-CD.

Chiral separation of flurbiprofen enantiomers by preparative and simulated moving bed chromatography.

This study presents the chiral resolution of flurbiprofen enantiomers by preparative liquid chromatography using the simulated moving bed (SMB) technology. Flurbiprofen enantiomers are widely used as nonsteroidal anti-inflammatory drugs, and although demonstrate different therapeutic actions, they are still marketed as a racemic mixture. The results presented here clearly show the importance of the selection of the proper solvent composition for the preparative separation of flurbiprofen enantiomers. Chiral SMB separation is carried out using a laboratory-scale unit (the FlexSMB-LSRE®) with six columns, packed with the Chiralpak AD® stationary phase (20 µm). Results presented include the experimental measurement of equilibrium and kinetic data for two very different solvent compositions, a traditional high hydrocarbon content [10%ethanol/90%n-hexane/0.01% trifluoroacetic acid (TFA)] and a strong polar organic composition (100%ethanol/0.01%TFA). Experimental data, obtained using the two mobile phase compositions, are used to predict and optimize the SMB operation. After selecting 10%ethanol/90%n-hexane/0.01%TFA as the most appropriate solvent composition, three feed concentrations of racemic flurbiprofen were considered. Using 40 g/l of racemic flurbiprofen feed solution, the purities for both outlet streams were above 99.4%, the productivity was 13.1 g(feed) /(L(bed) h), and a solvent consumption of 0.41 L(solvent) /g(feed) was achieved.

Enantiorecognition of profens by capillary electrophoresis using a novel chiral selector eremomycin.

The evaluation of a macrocyclic glycopeptide antibiotic, eremomycin, as a chiral selector in capillary electrophoresis (CE) has been performed. The stability of eremomycin in solution and capillary electrolyte, as well as its optical and electrophoretic properties have been discussed. The effect of experimental parameters influencing the enantioseparation of several profens has been studied. Excellent enantioseparation of profens has been achieved and migration order has been validated. Comparison of enantioseparations of profens in CE by using eremomycin-mediated electrolytes and in HPLC with eremomycin immobilized on silica has revealed similar trends for both methods.

Macrocyclic antibiotics as chiral selectors in the design of enantioselective, potentiometric membrane electrodes for the determination of S-flurbiprofen.

Construction of three novel enantioselective, potentiometric membrane electrodes based on carbon paste impregnated with different macrocyclic antibiotics vancomycin and teicoplanin as chiral selectors are described. The solutions for the construction of electrodes were prepared in phosphate buffer pH 4 for the vancomycin-based electrode (VCM), pH 6 and pH 6/40% acetonitrile solutions for teicoplanin-based electrodes, TCP I and II, respectively. The proposed electrodes were applied in the assay of S-flurbiprofen raw material and its pharmaceutical formulation by use of direct potentiometry, VCM electrode exhibiting the best enantioselectivity. The surfaces of the electrodes are easily renewable by simply polishing on an alumina paper.