0000000000005256
AUTHOR
Rosa María Villanueva-camañas
Potential of human serum albumin as chiral selector of basic drugs in affinity electrokinetic chromatography-partial filling technique
The enantiomeric resolution of compounds using HSA by means of affinity EKC (AEKC)-partial filling technique is the result of a delicate balance between different experimental variables such as protein concentration, running pH (background electrophoretic buffer (BGE), protein, and compound solutions), and plug length. In this paper, the possibility of using HSA as chiral selector for enantioseparation of 28 basic drugs using this methodology is studied. The effect of the physicochemical parameters, the structural properties of compounds, and compound-HSA protein binding percentages over their chiral resolution with HSA is outlined. Based on the results obtained, a decision tree is proposed…
Biopartitioning micellar separation methods: modelling drug absorption
The search for new pharmacologically active compounds in drug discovery programmes often neglects biopharmaceutical properties as drug absorption. As a result, poor biopharmaceutical characteristics constitute a major reason for the low success rate for candidates in clinical development. Since the cost of drug development is many times larger than the cost of drug discovery, predictive methodologies aiding the selection of bioavailable drug candidates are of profound significance. This paper has been focussed on recent developments and applications of chromatographic systems, particularly those systems based on amphiphilic structures, in the frame of alternative approaches for estimating t…
SENSITIZED LANTHANIDE FLUORESCENCE DETECTION OF STEROIDAL HORMONES
Several steroidal hormones with an α,β-unsaturated carbonyl group sensitized the fluorescence of terbium(III) ions: medroxyprogesterone, medroxyprogesterone acetate, methyltestosterone, nandrolone, nandrolone decanoate, progesterone, testosterone, testosterone enanthate, and testosterone propionate, but other steroids which have this chromophore did not give any signal: clostebol acetate, dehydrotestosterone, dydrogesterone, methandienone, and methenolone enanthate. Sensitized fluorescence was used to detect the steroids when eluted with micellar mobile phases of sodium dodecyl sulphate (SDS)-acetonitrile and SDS-pentanol containing 0.01 M Tb(III), with 245 nm and 545 nm as excitation and e…
Opioid analgetics retention–pharmacologic activity models using biopartitioning micellar chromatography
Opioids are drugs used in medicine for pain control. In this paper, retention-pharmacokinetics and retention-pharmacodynamics relationships of opioids are proposed and statistically validated. These models are based on the compound retention in the biopartitioning micellar chromatography system (BMC), a new methodology which has successfully been used to develop QRAR models for many other families of compounds. The obtained results are compared to the traditional QSAR models using lipophilicity data. The adequacy of QRAR models is due to the fact that the characteristics of the compounds such as the hydrophobicity, electronic charge and steric effects determine both their retention in BMC a…
Retention-structure relationship studies for some steroidal hormones in micellar liquid chromatography
The retention behavior in a C18 column of fourteen steroidal hormones (clostebol acetate, dehydrotestosterone, dydrogesterone, medroxyprogesterone, medroxyprogesterone acetate, methandienone, methyltestosterone, nandrolone, nandrolone decanoate, progesterone, testosterone, testosterone enanthate, testosterone propionate and, stanozolol) with pure micellar mobile phases prepared from sodium dodecyl sulfate (SDS), and hybrid mobile phases comprising SDS-acetonitrile and SDS-pentanol, was correlated with their octanol-water partition coefficients. Similar correlations were found with retention data obtained by other authors in gas chromatography, conventional reversed-phase liquid chromatograp…
Characterization of antihistamine–human serum protein interactions by capillary electrophoresis
An important topic in the drug discovery and development process is the role of drug binding to plasma proteins. In this paper the characterization of the interaction between antihistamines (cationic drugs) towards human serum albumin (HSA) and alpha(1)-acid glycoprotein (AGP) under physiological conditions by capillary electrophoresis-frontal analysis is presented. Furthermore, the binding of these drugs to all plasma proteins is evaluated by using ultrafiltration and capillary electrophoresis. Antihistamines present a wide-ranging behaviour with respect to their affinities towards plasma proteins. Orphenadrine, phenindamine, tripelenamine and tripolidine principally bind to HSA; carbinoxa…
Reliability of the retention factor estimations in liquid chromatography.
The retention factor is one of the most universally used parameters in chromatography. However, large differences in the experimental retention factor values are observed when the same compound is injected in a given stationary/mobile phase system under intermediate precision conditions. Conventional protocols for estimating retention factors have problems that mainly arise from difficulties in the hold-up time measurements and the omission of the existence of extra-column times by practicing chromatographers. In the present paper, three different approaches for estimating retention factors are tested: (i) classical retention factor estimations based on the gross hold-up time, (ii) based on…
Efficiency of antidepressant drugs as monoamine reuptake inhibitors: analysis of the hydrophobicity influence using biopartitioning micellar chromatographic data.
The reuptake blockade of biogenic amines by antidepressants is related not only to their therapeutics effects, but also to their side effects and potential drug-drug interactions. As an alternative to classical quantitative structure-activity relationships studies, in this work we propose different quantitative retention-activity relationships (QRAR) models that are able to describe the monoamine reuptake inhibition by antidepressants. The retention of compounds is measured using a biopartitioning micellar chromatography (BMC) system that can simulate the same hydrophobic, electronic and steric molecular interactions as those that condition drug activity. Since all the compounds considered …
DETERMINATION OF PENTOBARBITAL IN BIOLOGICAL SAMPLES BY MICELLAR LIQUID CHROMATOGRAPHY
A liquid chromatographic procedure for the determination of pentobarbital in urine and plasma samples is described. The proposed system uses a Spherisorb octadecyl-silane ODS-2 C18 analytical column, a guard column of similar characteristics, and a 0.02 M CTAB-15% 1-propanol at pH 7.5 mobile phase. The UV detector was set at 250 nm. Pentobarbital was isolated from urine and plasma samples by using a single solid phase extraction procedure with LMS cartridges. Mephobarbital was used as internal standard. Limits of detection were 0.53 μg/mL and 0.60 μg/mL in urine and plasma samples respectively. In both cases the coefficients of variation were lower than 6.5%, and the recoveries ranged betwe…
Chromatographic retention–activity relationships for prediction of the toxicity pH-dependence of phenols
Abstract An investigation of the use of the chromatographic retention (log k ) as an in vitro approach for modeling the pH-dependence of the toxicity to Guppy of phenols is developed. A data set of 19 phenols with available experimental toxicity–pH data was used. The importance of the mechanism of toxic action (MOA) of phenols was studied. log k data at three pH values were used for the phenols classification and two groups or ‘MODEs’ were identified. For one ‘MODE’ a quantitative retention–activity relationship (QRAR) model was calculated. Finally, the model was used to assess the toxicity to Guppy of phenols at different pH values. The results of this investigation suggest that chromato…
Development of predictive retention-activity relationship models of non-steroidal anti-inflammatory drugs by micellar liquid chromatography: comparison with immobilized artificial membrane columns.
The predictive and interpretative capability of quantitative chromatographic retention-biological activity models is supported by the fact that under adequate experimental conditions the solute partitioning into chromatographic system can emulate the solute partitioning into lipid bilayers of biological membranes, which is the basis for drug and metabolite uptake, passive transport across membranes and bioaccumulation. The use of micellar solutions of Brij35 as mobile phases in reversed-phase liquid chromatography has proven to be valid to predict some biological activities of different kinds of drugs. In this study, quantitative retention-activity relationship (QRAR) models to describe som…
Biopartitioning micellar chromatoraphy to predict blood to lung, blood to liver, blood to fat and blood to skin partition coefficients of drugs
[EN] Biopartitioning micellar chromatography (BMC), a mode of micellar liquid chromatography that uses micellar mobile phases of Brij35 in adequate experimental conditions, has demonstrated to be useful in mimicking the drug partitioning process into biological systems. In this paper, the usefulness of BMC for predicting the partition coefficients from blood to lung, blood to liver. blood to fat and blood to skin is demonstrated. PLS2 and multiple linear regression (MLR) models based on BMC retention data are proposed and compared with other ones reported in bibliography. The proposed models present better or similar descriptive and predictive capability. (C) 2008 Elsevier B.V. All rights r…
Quantitative retention–structure and retention–activity relationships of barbiturates by micellar liquid chromatography
Abstract Studies on the structural requirements of chromatographic surfaces to emulate in vitro the partitioning process in biomembranes are of great interest. The use of micellar mobile phases in RPLC modifies the hydrophobicity of the stationary phase and provides hydrophobic and electrostatic sites of interaction as a consequence of the adsorption of surfactant monomers to the chromatographic surface. Modified stationary phases in MLC could be structurally similar to biomembranes, but thorough studies are necessary to confirm this. In this paper we focus our attention on barbiturates. The influence of the nature and concentration of the surfactant (Brij 35, SDS and CTAB) and the mobile p…
Development of predictive retention-activity relationship models of antipsychotic drugs by micellar liquid chromatography
The predictive and interpretative capability of quantitative chromatographic retention-biological activity models is supported by the fact that in adequate experimental conditions the solute partitioning into the chromatographic system can emulate the solute partitioning into lipid bilayers of biological membranes, which is the basis of drug and metabolite uptake, passive transport across membranes and bioaocumulation. The use of micellar solutions of Brij35 as mobile phases in reversed liquid chromatography has proven to be valid in predicting some biological activities of different kinds of drugs. In this paper, the correlations between the logarithm of capacity factors and pharmacokineti…
Determination of amobarbital and secobarbital in plasma samples using micellar liquid chromatography
A new liquid chromatographic procedure for the determination of amobarbital and secobarbital in plasma samples is proposed. The method uses a Spherisorb octadecylsilane ODS-2 C18 analytical column, a guard column of similar characteristics and 0.04 M CTAB solution buffered at pH 7.5 containing 3% 1-propanol as micellar mobile phase. The UV detection was carried out at 250 nm. Butabarbital was used as internal standard. Plasma samples preparation only required adequate dilution with the mobile phase before injection into the chromatographic system. The limits of detection were 0.2 and 0.4 mg/L for amobarbital and secobarbital, respectively. The proposed method allows the determination of amo…
Evaluation of enantioselective binding of basic drugs to plasma by ACE.
The present paper deals with the evaluation of the stereoselective binding of antihistamines (brompheniramine, chlorpheniramine, hydroxyzine, orphenadrine and phenindamine), phenothiazines (promethazine and trimeprazine) and a local anesthetic (bupivacaine) to human plasma proteins. Since all of them are drugs highly bound to proteins, a methodology to determine the bound fraction of each drug enantiomer was proposed. This methodology includes the incubation of samples containing plasma and racemic drug, ultrafiltration of the mixture and the chiral separation of enantiomers in the bound drug fraction using affinity EKC (AEKC)-partial filling technique and HSA as chiral selector. The result…
Chromatographic multivariate quality control of pharmaceuticals giving strongly overlapped peaks based on the chromatogram profile
In the present paper, the simultaneous quantification of two analytes showing strongly overlapped chromatographic peaks (alpha = 1.02), under the assumption that both available equipment and training of the laboratory staff are basic, is studied. A pharmaceutical preparation (Mutabase) containing two drugs of similar physicochemical properties (amitriptyline and perphenazine) is selected as case of study. The assays are carried out under realistic working conditions (i.e. routine testing laboratories). Uncertainty considerations are introduced in the study. A partial least squares model is directly applied to the chromatographic data (with no previous signal transformation) to perform quali…
Analysis of pharmaceutical preparations containing local anesthetics by micellar liquid chromatography and spectrophotometric detection
An HPLC procedure for the determination of six local anesthetics, bupivacaine, lidocaine, mepivacaine, procaine, propanocaine and tetracaine, in pharmaceutical silane ODS-2 C18 analytical column and spectrophotometric detection at 230 nm were used. The chromatographic tographic behaviour of local anesthetics with different micellar eluents of sodium dodecyl sulphate (SDS) is described. Selection of the adequate composition of the micellar mobile phase (SDS and 1-propanol concentrations) for the analysis of pharmaceuticals was studied. Adequate retention was achieved with an eluent containing 0.15 M SDS +10% 1-propanol at pH 3. Application of the proposed method to the analysis of eight phar…
Description of the retention behaviour of solutes in micellar liquid chromatography with organic modifiers: Comparison of two methods
Two methods for the description of the retention behaviour of solutes in micellar liquid chromatography are compared. One of them divides the parameter space into triangular subspaces, fitting a different equation in each subspace. The second method makes use of a unique equation, valid in the whole parameter space. In both cases, equations of the type log k=f (μ, ϕ), and 1/k=f (μ, ϕ), (μ and ϕ are the concentration of surfactant and alcohol, respectively), were used to describe the retention. The use of the hyperbolic function, 1/k=c0+c1μ+c3μϕ, to describe the whole parameter space yielded the best prediction. When a small portion of the parameter space was modelled, a simpler hyperbolic f…
Chromatographic evaluation of the toxicity in fish of pesticides
Abstract Ecotoxicity assessment is essential before placing new chemical substances on the market. An investigation of the use of the chromatographic retention (log k) in biopartitioning micellar chromatography (BMC) as an in vitro approach to evaluate the toxicity in fish of pesticides (acute toxicity levels as pLC50) is proposed. A heterogeneous data set of 85 pesticides from six chemical families with available experimental fish toxicity data (ECOTOX database from U.S. Environmental Protection Agency (EPA)) was used. For pesticides exhibiting non-polar narcosis mechanism in fish (non-specific toxicity), more reliable models and precise pLC50 estimations are obtained from log k (quantitat…
Quantitative retention- and migration-toxicity relationships of phenoxy acid herbicides in micellar liquid chromatography and micellar electrokinetic chromatography
Abstract The need to obtain a tool for estimation of toxicity parameters for chemicals supports, the postulation of predictive models as an alternative to conventional classical assays. The use of micellar solutions of Brij35 as mobile phases in reversed phase liquid chromatography has proven to be valid in predicting some biological activities of different kinds of drugs. In this paper, the correlations between retention of phenoxy acids using different concentrations of Brij35 as micellar mobile phase in micellar liquid chromatography (MLC) and migration in micellar electrokinetic chromatography (MEKC) with several toxicity parameters are studied. Adequate correlations retention- and migr…
Chromatographic estimation of the soil-sorption coefficients of organic compounds
Abstract Soil-sorption coefficient ( K OC ) assessment is essential before placing a new chemical substance on the market. Since experimental K OC measurements are tedious, time-consuming and costly, alternative approaches to estimating K OC from other descriptors have been proposed. We review the use of chromatographic retention (log k ) values, obtained in different types of chromatographic systems, as descriptors to establish predictive log K OC -log k models. We highlighted critical aspects of such models and performed a comparative study using data in the literature. We compare two strategies to deal with the large variability of experimental log K OC data. We contrast the results of t…
Resolution of mixtures of steroidal hormones with micellar eluents of sodium dodecyl sulphate and acetonitrile or pentanol
An optimization strategy was applied to explore the capability of hybrid micellar eluents of sodium dodecyl sulphate (SDS), using acetonitrile or pentanol as modifiers, to resolve mixtures of eleven steroids showing a wide range of hydrophobicity (clostebol acetate, dehydrotestosterone, dydrogesterone, medroxyprogesterone, medroxyprogesterone acetate, methandienone, methyltestosterone, progesterone, testosterone, testosterone enanthate and testosterone propionate). The accurate prediction of the retention behaviour of the steroids, with relative errors in the 0.8–1.7% and 0.4–2.9% ranges for SDS-acetonitrile and SDS-pentanol eluents, respectively, demonstrated the reliability of the methodo…
Determination of phenolic antioxidants in vegetal and animal fats without previous extraction by dilution with n-propanol and micellar liquid chromatography
Abstract A simple and rapid HPLC method for the determination of phenolic antioxidants (propyl and octyl gallates, tert -butylhydroquinone and 3- tert -butyl-4-hydroxyanisole) in sunflower, corn and olive oils, margarine, lard and butter oil is described. The samples are diluted with n -propanol, filtered and injected; solutions containing 30% (w/w) sample can be injected. The analytes are separated with a C18 column and a micellar mobile phase containing 0.1 M SDS, 2.5% n -propanol and 10 mM phosphate of pH 3, and detected at 290 nm. Calibration curves are linear ( r > 0.9999) and the limits of detection range from 0.2 to 1.3 ng, which correspond to antioxidant concentrations well below t…
Development of Predictive Retention-Activity Relationship Models of Barbiturates by Micellar Liquid Chromatography
The need to get a tool for biological parameters estimation of new compounds for clinical applications, supports the postulation of predictive models as an alternative to conventional classical assays being no necessary the use of experimentation in animals. Our main aim in this work is to determine correlations between the logarithm of capacity factors and preclinical pharmacology and therapeutic efficacy parameters of barbiturates. The predictive and interpretative capability of quantitative chromatographic retention-biological activity models is supported by the fact that in adequate experimental conditions the solute partitioning into chromatographic system can emulate the solute partit…
Development of predictive retention-activity models of butyrophenones by biopartitioning micellar chromatography
The predictive and interpretative capability of quantitative chromatographic retention-biological activity models is supported by the fact that in adequate experimental conditions the solute partitioning into the chromatographic system can emulate the solute partitioning into lipid bilayers of biological membranes, which is the basis of drug and metabolite uptake, passive transport across membranes and bioaccumulation. The use of retention data obtained in biopartitioning micellar chromatography (BMC) has been demonstrated to be helpful in describing the biological behaviour of different kinds of drugs. In this chromatographic system, polioxyethylene 23 lauryl ether Brij35 micellar mobile p…
Comparison between sodium dodecylsulphate and cetyltrimethylammonium bromide as mobile phases in the micellar liquid chromatography determination of non-steroidal anti-inflammatory drugs in pharmaceuticals.
The retention behaviour of non-steroidal anti-inflammatory drugs (NSAIDs) using micellar mobile phases of sodium dodecylsulphate (SDS) is studied and compared with that observed with micellar mobile phases of cetyltrimethylammonium bromide (CTAB). A liquid chromatographic procedure for the determination of acemetacin, diclofenac, indomethacin, ketoprofen, naproxen and tolmetin in pharmaceutical preparations is described. The proposed system uses a Kromasil C18 analytical column and a solution of 0.15 M SDS at pH 3 with 10% 1-propanol as mobile phase. Under these conditions, the studied NSAIDs elute between 6 and 10 min at a 1 mL min(-1) flow rate. Limits of detection (LOD) are lower than 0.…
Enantiomeric quality control of antihistamines in pharmaceuticals by affinity electrokinetic chromatography with human serum albumin as chiral selector
The present paper deals with the enantiomeric separation of six antihistaminic enantiomers by affinity electrokinetic chromatography (AEKC)-partial filling technique using human serum albumin (HSA) as chiral selector. A multivariate optimization approach of the most critical experimental variables in enantioresolution, running pH, HSA concentration and HSA plug length (SPL) was carried out since there are interactions between variables that could not be considered in an univariate optimization. The estimated and experimental resolution values obtained for antihistaminic enantiomers varied from 1.13 (for orphenadrine) to 2.15 (for brompheniramine). The optimum experimental conditions for ena…
Biopartitioning micellar chromatography: An alternative high-throughput method for assessing the ecotoxicity of anilines and phenols
An investigation of the use of the chromatographic retention (log k) as an in vitro approach for modelling the toxicity to Fathead Minnows of anilines and phenols is developed. A data set of 65 compounds with available experimental toxicity data was used. Log k data at three pH values were used for the compounds classification and two groups or 'MODEs' were identified. For one 'MODE' a quantitative retention-activity relationship (QRAR) model was calculated. Finally, it was used to estimate the toxicity to Fathead minnows of anilines and phenols for which experimental data are not available. These estimations were compared to those obtained from another toxicity (to Tetrahymena pyriformis) …
Estimation of the effect of the acidosis and alkalosis on the anesthetic potency of local anesthetics by biopartitioning micellar chromatography and micellar electrokinetic chromatography.
Local anesthetics are hydrophobic compounds and weak bases with protonation constants ranged between 7.5 and 8.8. These drugs block reversibly nerve conduction near their site of application or injection and thus produce temporary loss of feeling or sensation in a limited area of the body. The efficacy of anesthetic blockade of local anesthetics depends on the charged/uncharged form ratio and the hydrophobicity of the compounds. In addition their toxicological effects have been reported to be highly dependent on the physiological pH. Biopartitioning micellar chromatography (BMC) and micellar electrokinetic chromatography (MEKC), that use micellar solutions as mobile phases, have proven to b…
Determination of phenobarbital in plasma by micellar liquid chromatography
A new liquid chromatographic procedure for the determination of phenobarbital in plasma samples is described. The proposed system uses a Spherisorb octadecyl-silane ODS-2 C(18) analytical column, a guard column of similar characteristics, and a 0.03 M CTAB-3% 1-propanol at pH 7 mobile phase. The UV detector was set at 250 nm. Butabarbital was used as internal standard. Sample preparation only required the addition to the plasma samples of a 0.1 M SDS solution at pH 3 and centrifugation before injection into the chromatographic system. The limit of detection was 0.83 microg/mL of phenobarbital in plasma samples. The coefficients of variation were lower than 7. 5%.
Modelling bioconcentration of pesticides in fish using biopartitioning micellar chromatography.
Ecotoxicity assessment is essential before placing new chemical substances on the market. An investigation of the use of the chromatographic retention (log k) in biopartitioning micellar chromatography (BMC) as an in vitro approach to evaluate the bioconcentration factor (BCF) of pesticides in fish is proposed. A heterogeneous set of 85 pesticides from six chemical families was used. For pesticides exhibiting bioconcentration in fish (experimental log BCF > 2), a quantitative retention-activity relationships (QRAR) model is able to perform precise log BCF estimations of new pesticides. Considering the present data, the results based on log k seem to be more reliable than those from availabl…
Determination of Anticonvulsant Drugs in Pharmaceutical Preparations by Micellar Liquid Chromatography
A micellar liquid chromatographic method for quality control of pharmaceutical preparations (capsules, pills, tablets, injections, drops, and suppositories) containing the anticonvulsant drugs acetazolamide, carbamacepine, chlordiazepoxide, diazepam, ethosuximide, phenytoin, phenobarbital, and zopiclone has been developed. This methodology involves the use of micellar solutions of cetyltrimethylammonium bromide (CTAB) as mobile phases and UV detection. The proposed approach is rapid and reproducible. Sample preparation only requires dissolution with micellar solvent and adequate dilution with the mobile phase before injection into the chromatographic system.
Characterization of basic drug–human serum protein interactions by capillary electrophoresis
Drug-protein interactions are determining factors in the therapeutic, pharmacodynamic and toxicological drug properties. The affinity of drugs towards plasmatic proteins is apparently well established in bibliography. Albumin (HSA) especially binds neutral and negatively charged compounds; alpha(1)-acid glycoprotein (AGP) binds many cationic drugs, lipoproteins bind to nonionic and lipophilic drugs and some anionic drugs while globulins interact inappreciably with the majority of drugs. In this paper, the characterization of the interaction between cationic drugs, beta-blockers and phenotiazines towards HSA, AGP, and both HSA + AGP mixtures of proteins under physiological conditions by CE-f…
Emerging approaches to estimate retention factors in high performance liquid chromatography.
The retention factor is one of the most universally used parameters in chromatography. The errors associated with the conventional ways to determine the retention factor of compounds in liquid chromatography are studied and compared with those corresponding to new approaches. The later avoid the use of extra-column time and hold-up time values, which have proven to be tedious and ambiguous. Simulations and real data, used to examine the accuracy of four different approaches (two classic and two new), suggest that the new approaches could be considered more satisfactory than the classic ones.
Biopartitioning micellar chromatography to predict skin permeability
Dermal absorption of chemicals is an area of increasing interest to the pharmaceutical and cosmetic industries, as well as in dermal exposure and risk assessment processes. In this paper the capability of biopartitioning micellar chromatography (BMC) as an in vitro technique to describe compound percutaneous absorption is evaluated. A multivariate study (principal component analysis, partial least squares) is performed in order to evaluate the importance of some physicochemical variables on the skin permeability constant values. From these results, a quantitative retention-activity relationship model for predicting the skin permeability constants that uses the BMC retention data and melting…
Fast enantiomeric separation of propranolol by affinity capillary electrophoresis using human serum albumin as chiral selector: application to quality control of pharmaceuticals
Abstract In the last years, capillary electrophoresis (CE) has gained considerable interest in pharmaceutical laboratories for controlling the chiral purity of drugs. This paper describes a simple and fast method for resolution of propranolol enantiomers by affinity capillary electrophoresis (ACE) using human serum albumin (HSA) as chiral selector. The effect of several experimental variables such as HSA concentration, temperature, chiral selector plug length and addition of organic modifiers, on the separation is evaluated. Complete enantioresolution of R- and S-propranolol was achieved in less than 5 min when the capillary was completely filled with 100 μM HSA solution and the electrophor…
Quality control of pharmaceuticals containing non-steroidal anti-inflammatory drugs by micellar liquid chromatography
A liquid chromatographic procedure is described for the determination of acemetacin, diclofenac, indomethacin, ketoprofen, nabumetone, naproxen, piketoprofen, and tolmentin in pharmaceutical preparations. The compounds were separated on a Kromasil C18 analytical column, with a guard column of similar characteristics; the mobile phase was 0.06 M cetyltrimethylammonium bromide, at pH 7, containing 10% 1-butanol. At a flow rate of 1 mL min−1 the elution time of the most retained compound was 23 min. Limits of detection were between 0.01 μ g mL−1 for diclofenac and 0.2 μ g mL−1 for naproxen. The proposed method enables the determination of non-steroidal anti-inflammatory drugs in pharmaceutical…
Microseparation techniques for the study of the enantioselectivity of drug-plasma protein binding.
Stereoselectivity in protein binding can have a significant effect on the pharmacokinetic and pharmacodynamic properties of chiral drugs. The investigation of enantioselectivity of drugs in their binding with human plasma proteins and the identification of the molecular mechanisms involved in the stereodiscrimination by the proteins represent a great challenge for clinical pharmacology. In this review, the separation techniques used for enantioselective protein binding experiments are described and compared. An overview of studies on enantiomer–protein interactions, enantiomer–enantiomer interactions as well as chiral drug–drug interactions, including allosteric effects, is presented. The c…
High-throughput capillary electrophoresis frontal analysis method for the study of drug interactions with human serum albumin at near-physiological conditions.
The application of the short-end capillary injection to capillary electrophoresis frontal analysis (CE-FA) to study the interaction between basic, neutral and acid drugs towards human serum albumin (HSA) at near-physiological conditions is presented. The compounds selected display a wide range of binding affinities and the results obtained were in good agreement with those reported in the literature. An equation for the estimation of the number of primary binding sites and their corresponding affinity constants is developed isolating the experimentally measured variables in just one axis. The proposed CE-FA method to screen drug interactions with HSA under physiological conditions is simple…
Evaluation of the pH effect of formulations on the skin permeability of drugs by biopartitioning micellar chromatography☆
Dermal absorption of chemicals is an area of increasing interest for the pharmaceutical and cosmetic industries, as well as in dermal exposure and risk assessment processes. Biopartitioning micellar chromatography (BMC) is a mode of reversed phase micellar chromatography that has proved to be useful in the description and prediction of several pharmacological properties of xenobiotics including oral drug absorption, ocular and skin drug permeability. The present paper deals with the application of biopartitionig micellar chromatography to evaluate the pH effect on the skin permeability of twelve non-steroidal anti-inflammatory drugs and lidocaine. For this purpose the BMC retention of the w…
Evaluation of enantioselective binding of fluoxetine to human serum albumin by ultrafiltration and CE - Experimental design and quality considerations
Several pharmacokinetic processes are affected by enantioselectivity (ES). At the level of distribution, protein binding (PB) is one of the most important. The enantioselective binding of fluoxetine (FLX) to HSA has been evaluated in this work by ultrafiltration of FLX–HSA mixtures and chiral analysis of unbound fractions by EKC-CD. PB, affinity constants (K) and ES were obtained for both enantiomers of FLX. In order to improve the consistency of the estimations, the evaluation of affinity constants of each enantiomer was performed using two designs, one keeping constant the total concentration of protein and varying the total concentration of the enantiomers, and the other in the opposite …
Enantioseparation of nuarimol by affinity electrokinetic chromatography-partial filling technique using human serum albumin as chiral selector
The present paper deals with the enantiomeric separation of nuarimol enantiomers by affinity EKC-partial filling technique using HSA as chiral selector. Firstly, a study of nuarimol interactions with HSA by CE-frontal analysis was performed. The binding parameters obtained for the first site of interaction were n(1) = 0.84; K(1) = 9.7 +/- 0.3x10(3 )M(-1) and the protein binding percentage of nuarimol at physiological concentration of HSA was 75.2 +/- 0.2%. Due to the moderate affinity of nuarimol towards HSA the possibility of using this protein as chiral selector for the separation of nuarimol using the partial filling technique was evaluated. A multivariate optimization approach of the mo…
Chiral separation of bupivacaine enantiomers by capillary electrophoresis partial-filling technique with human serum albumin as chiral selector
Abstract Capillary electrophoresis (CE) is a powerful technique for enantiomer separations due to its intrinsic high separation efficiencies, speed of analysis, low reagent consumption and small sample requirements. However, some chiral selectors present strong background UV absorption providing high detection limits. The present paper deals with the application of the partial-filling technique to the separation of bupivacaine enantiomers by capillary electrophoresis using human serum albumin (HSA) as chiral selector. In this procedure the cationic surfactant cetyltrimethylammonium bromide (CTAB) was used as a dinamic capillary coating in order to reduce the electro-osmotic flow and detect …
QRAR models for central nervous system drugs using biopartitioning micellar chromatography.
The capability of biopartitioning Micellar Chromatography, BMC, to describe and estimate pharmacokinetic and pharmacodynamic parameters of central nervous system drugs is reviewed in this article. BMC is a mode of micellar liquid chromatography, MLC, that uses micellar mobile phases of Brij35 (polyoxyethilene(23) lauryl ether) prepared in physiological conditions (pH, ionic strength). The retention of a drug in this system depends on its hydrophobic, electronic and steric properties, which also determine its biological activity. The results of BMC studies suggest that this in vitro approach is an attractive useful tool to be implemented into the lead optimization step of drug development sc…
Development and validation of a procedure for estimating the hydrophobicity of structurally unrelated compounds by micellar liquid chromatography
Reversed-phase liquid chromatography has been used most often to estimate values of log P, but despite years of study, there is no universally accepted method of performing these estimations. The main problem has to do with the fact that the hydrophobic parameter, log k w , depends on the hydrogen bond acceptor-donor character of the compounds. The use of micellar mobile phases to perform these estimations is evaluated here, and the influence of the nature of the surfactant (anionic, cationic, and nonionic) on the log k-log P relationships is studied. The use of a nonionic surfactant, such as Brij35, to prepare the mobile phases provided adequate results regardeless of the hydrogen bond acc…
Direct injection of edible oils as microemulsions in a micellar mobile phase applied to the liquid chromatographic determination of synthetic antioxidants
Abstract A simple and quick procedure for analysis of hydrophobic samples by direct injection in a liquid chromatograph, without previous extraction, has been developed. The sample is solved in a water/sodium dodecyl sulphate/n-pentanol microemulsion without destroying the microemulsion structure, and injected. A micellar mobile phase containing 0.1 M SDS, 2.5% n-propanol and 10 mM phosphate of pH 3 is used. The procedure is applied to the determination of synthetic antioxidants (propyl gallate, tert-butylhydroquinone, 2,4,5-trihydroxybutyrophenone, nordihydroguaiaretic acid, octyl gallate, 3-tert-butyl-4-hydroxyanisole and dodecyl gallate) in sunflower, corn and olive oils. Linear calibrat…
Quantitative Retention−Structure and Retention−Activity Relationship Studies of Local Anesthetics by Micellar Liquid Chromatography
The retention of compounds in micellar liquid chromatography (MLC) is governed by hydrophobic and electrostatic forces. For ionic compounds, both interactions should be considered. The present report offers a novel retention model that includes the hydrophobicity of compounds and the molar fraction of the charged form of compounds and compares it with other previously reported models. High correlations between the logarithm of capacity factors and these structural parameters were obtained for local anesthetics with different degrees of ionization using a nonionic surfactant solution as mobile phase. Modeling the retention of compounds as a function of physicochemical parameters and experime…
Rapid in vitro test to predict ocular tissue permeability based on biopartitioning micellar chromatography.
The drug permeability prediction across the ocular tissues is important in the development of new drugs and drug delivery strategies. Physicochemical characteristics of drugs, mainly acid-base character, hydrophobicity and the molecular size determine both their transport across the eye tissue barriers and their retention in biopartitioning micellar chromatography (BMC). An in vitro model able to describe and predict the whole cornea drug permeability is proposed. The model uses the retention of drugs in BMC and molecular weight (MW) as predictive variables. The relationships between drug retention data in BMC and their bibliographic permeability values in stroma, epithelium-plus-stroma and…
Determination of Parabens in Cosmetics without Previous Extraction by Micellar Liquid Chromatography
A simple and rapid micellar liquid chromatography method for the determination of p-hydroxybenzoic acid esters (methyl-, ethyl-, n-propyl-, and n-butylparaben) in cosmetics (bath foam, milk lotion, hand cream, cream base, and shampoo) is described. The samples are solved with n-propanol, further diluted with more n-propanol or with an aqueous sodium dodecyl sulphate (SDS) micellar solution, and injected. Separations are performed with a micellar mobile phase containing 0.1M SDS, 2.5% n-propanol, 10mM phosphate (pH 3), and with an octadecyl silica column (C 18 ). Calibrations are linear (correlation coefficient r > 0.999) and the limits of detection range from 0.03 to 0.3 ng paraben. The det…
Determination of synthetic antioxidants in dairy products and dietetic supplements by micellar liquid chromatography with direct sample injection
A simple and rapid HPLC method for the determination of synthetic antioxidants (propyl gallate, tert-butylhydroquinone, 2,4,5-trihydroxybutyrophenone, nordihydroguaiaretic acid, octyl gallate, 3-tert-butyl-4-hydroxyanisole and dodecyl gallate) in powdered and liquid milk, cream of milk and dietetic supplements is described. The samples are diluted or solved in a micellar solution, filtered and directly injected. The retention behavior of the antioxidants on a C18 column, with micellar mobile phases containing SDS (0.05–0.15 M), n-propanol (1–9%, v/v) and 10 mM phosphate at pH 3, has been studied by using mathematical models. Retention is predicted with errors below 3%. To optimize the mobil…
Evaluation of enantioselective binding of antihistamines to human serum albumin by ACE.
The drug binding to plasma and tissue proteins is a fundamental factor in determining the overall pharmacological activity of a drug. HSA, together with alpha(1)-acid glycoprotein, are the most important plasma proteins, which act as drug carriers, with implications on the pharmacokinetic of drugs. Among plasma proteins, HSA possesses the highest enantioselectivity. In this paper, a new methodology for the study of enantiodifferentiation of chiral drugs with HSA is developed and applied to evaluate the possible enantioselective binding of four antihistamines: brompheniramine, chlorpheniramine, hydroxyzine and orphenadrine to HSA. This study includes the determination of affinity constants o…
Permeability and toxicological profile estimation of organochlorine compounds by biopartitioning micellar chromatography
This paper points out the usefulness of biopartitioning micellar chromatography (BMC) as a high-throughput primary screening tool providing key information about the oral absorption, skin permeability (Kp), brain–blood distribution coefficient (BB) and ecotoxicological parameters such as median lethal concentration (LC50) and bioconcentration factors of 15 organochloride compounds. The retention data of compounds in BMC conditions were interpolated in previously developed quantitative–retention activity relationships by our research group. Results show that the compounds studied readily cross the intestinal barrier (oral absorption >ercnt;) and the blood–brain barrier (log BB >p;0.4). In ad…
Biopartitioning micellar chromatography to pedict mutagenicity of aromatic amines
[EN] Mutagenicity is a toxicity endpoint associated with the chronic exposure to chemicals. Aromatic amines have considerable industrial and environmental importance due to their widespread use in industry and their mutagenic capacity. Biopartitioning micellar chromatography (BMC), a mode of micellar liquid chromatography that uses micellar mobile phases of Brij35 in adequate experimental conditions, has demonstrated to be useful in mimicking the drug partitioning process into biological systems. In this paper, the usefulness of BMC for predicting mutagenicity of aromatic amines is demonstrated. A multiple linear regression (MLR) model based on BMC retention data is proposed and compared wi…
Liquid chromatographic procedure for the evaluation of β-blockers in pharmaceuticals using hybrid micellar mobile phases
Abstract A reversed-phase chromatographic procedure with a micellar eluent is proposed for the determination of several β-blockers (acebutolol, atenolol, carteolol, celiprolol, labetalol, metoprolol, nadolol, oxprenolol, propranolol, and timolol) in pharmaceutical formulations (tablets, capsules, and ophthalamic solutions). A study is shown on the chromatographic behaviour of these drugs with mobile phases containing sodium dodecyl sulphate (0.075–0.15 M ) and propanol (0–15%, v/v), at different pH values (3–7). The excellent correlation between log of the octanol-water partition coefficient and log of capacity factor, for the ten drugs in mobile phases of SDS and propanol, suggested that t…
Biopartitioning micellar chromatography to predict ecotoxicity
Abstract The knowledge of chemical toxicity is necessary for risk assessment and ranking of chemicals according their hazard potential. The use of biopartitioning micellar chromatography has proven to be valid in predicting several biological activities of different kinds of compounds. In this paper, the relationships between retention of 66 organic pollutants and several ecotoxicity parameters are studied. Adequate correlations retention-ecotoxicity (LC 50 in fish and daphnia, EC 50 in green algae and daphnia, values of chronic toxicity in fish and green algae and bioconcentration factor in fish) of organic pollutants are obtained. These models are compared with the corresponding obtained …
Evaluation of enantioselective binding of propanocaine to human serum albumin by ultrafiltration and electrokinetic chromatography under intermediate precision conditions.
Abstract Stereoselectivity in protein binding can have a significant effect on the pharmacokinetic and pharmacodynamic properties of chiral drugs. In this paper, the enantioselective binding of propanocaine (PRO) enantiomers to human serum albumin (HSA), the most relevant plasmatic protein in view of stereoselectivity, has been evaluated by incubation and ultrafiltration of racemic PRO–HSA mixtures and chiral analysis of the bound and unbound fractions by electrokinetic chromatography using HSA as chiral selector. Experimental conditions for the separation of PRO enantiomers using HSA as chiral selector and electrokinetic chromatography have been optimised. Affinity constants and protein bi…
Chiral separation of oxprenolol by affinity electrokinetic chromatography-partial filling technique using human serum albumin as chiral selector
The intrinsic characteristics of capillary electrophoresis have made this technique a powerful tool in the chiral separation field. The present paper deals with the enantiomeric separation of oxprenolol enantiomers by affinity electrokinetic chromatography-partial filling technique using human serum albumin (HSA) as chiral selector. Several experimental conditions and variables affecting the separation such as pH, HSA concentration and plug length, background electrolyte concentration, temperature and voltage were studied. Baseline separation of oxprenolol enantiomers was obtained in less than 8 min under the following selected conditions: electrophoretic buffer composed of 50 mM Tris-(hydr…
Retention pharmacokinetic and pharmacodynamic parameter relationships of antihistamine drugs using biopartitioning micellar chromatography
Abstract Antihistamines are drugs which act by competitive inhibition of the H1 or H2 histamine receptors. Little has been known about their clinical pharmacokinetics and biological responses until the last few years. In this paper, we propose quantitative retention–activity relationship, QRAR, models based on the retention data of antihistamines in a biopartitioning micellar chromatography (BMC) system using a Brij35 mobile phase for describing pharmacokinetic parameters such as half-life and volume of distribution, or the pharmacodynamic parameters, therapeutic plasma levels, lethal doses and drug-receptor dissociation constant. The predictive ability of these models is statistically vali…
Chromatographic quantitation of the hydrophobicity of ionic compounds by the use of micellar mobile phases
Abstract Many biologically active compounds of interest in structure–activity relationships are ionic at physiological pH. However, ionic organic compounds are only weakly or not retained in conventional RPLC which impedes the chromatographic estimation of their hydrophobicity and the development of quantitative retention–activity relationship studies. The use of micellar mobile phases allows the retention of ionic compounds. Hydrophobic and electrostatic forces govern the retention of ionic compounds in micellar liquid chromatography. In this paper three different retention models log k–log P for ionic compounds are tested (P=partition coefficient). The retention model (log k=a log P+bα+c)…
Comparison between micellar liquid chromatography and capillary zone electrophoresis for the determination of hydrophobic basic drugs in pharmaceutical preparations
[EN] The determination of highly hydrophobic basic compounds by means of conventional reversed-phase liquid chromatographic methods has several drawbacks. Owing to the characteristics of micellar liquid chromatography (MLC) and capillary electrophoresis (CE), these techniques could be advantageous alternatives to reversed-phase chromatographic methods for the determination of these kinds of compounds. The objective of this study was to develop and compare MLC and CE methods for the determination of antipsychotic basic drugs (amitryptiline, haloperidol, perphenazine and thioridazine) in pharmaceutical preparations. The chromatographic determination of the analytes was performed on a Kromasil…
Analysis of pharmaceutical preparations containing antihistamine drugs by micellar liquid chromatography
Rapid chromatographic procedures for analytical quality control of pharmaceutical preparations containing antihistamine drugs, alone or together with other kind of compounds are proposed. The method uses C18 stationary phases and micellar mobile phases of cetyltrimethylammonium bromide (CTAB) with either 1-propanol or 1-butanol as organic modifier. The proposed procedures allow the determination of the antihistamines: brompheniramine, chlorcyclizine, chlorpheniramine, diphenhydramine, doxylamine, flunarizine, hydroxyzine, promethazine, terfenadine, tripelennamine and triprolidine, in addition to caffeine, dextromethorphan, guaifenesin, paracetamol and pyridoxine in different pharmaceutical …
Determination of procaine and tetracaine in plasma samples by micellar liquid chromatography and direct injection of sample
A liquid chromatographic procedure is proposed for the determination of procaine and tetracaine in plasma samples with direct injection. The method uses a Spherisorb octadecylsilane ODS-2 C18 analytical column and a micellar mobile phase containing 0.15 M sodium dodecyl sulphate, 0.5% triethylamine at pH 2.5 and 10% propanol. The UV detection was carried out at 300 nm. Plasma sample preparation required only adequate dilution with the mobile phase before injection into the chromatographic system. The proposed method allows the determination of procaine and tetracaine in plasma at therapeutic levels.
DETERMINATION OF STEROIDAL HORMONES IN URINE SAMPLES BY MICELLAR LIQUID CHROMATOGRAPHY FOLLOWING SOLID-PHASE EXTRACTION
Steroidal hormones were determined in spiked urine samples using micellar mobile phases of sodium dodecyl sulphate (SDS)-pentanol, solid-phase extraction (SPE), and detection in the UV region. In the optimized procedure, a 10 mL aliquot of urine sample is loaded into a C18 cartridge and washed with 2 mL of 50:50 (v/v) methanol-water, followed by 200 μL of 70:30 (v/v) methanol-water. The retained steroids are eluted with 2 mL of methanol and the eluate evaporated to dryness under nitrogen at 50°C. The residue is redissolved with 200 μL of the micellar mobile phase used in the chromatographic separation and injected into the chromatograph. The performance of the procedure was checked for 13 s…
Multivariate optimization approach for chiral resolution of drugs using human serum albumin in affinity electrokinetic chromatography-partial filling technique.
The enantiomeric resolution of chiral compounds using HSA by means of affinity EKC (AEKC)-partial filling technique is the result of a delicate balance between different experimental variables such as protein concentration, running pH (background electrophoretic buffer, protein and compound solutions) and protein solution plug length. In this paper multivariate optimization approaches for chiral separation of four basic drugs (alprenolol, oxprenolol, promethazine and propranolol) using HSA as chiral selector in AEKC-partial filling technique are studied. The experimental conditions to achieve maximum resolution are optimized using the Box-Behnken experimental design. Partial least squares a…
Determination of barbiturates in urine by micellar liquid chromatography and direct injection of sample.
Abstract A liquid chromatographic procedure for the determination of six barbiturates (barbital, diallyl barbituric acid, phenobarbital, butabarbital, amobarbital and pentobarbital) in urine samples is described. The proposed system uses a Spherisorb octadecyl-silane ODS-2 C 18 analytical column and a guard column of similar characteristics. The UV detector was set at 240 nm. A study to select adequate composition of the micellar mobile phase for the separation of these compounds in urine samples is performed. Maximum resolution was achieved with a 0.07 M sodium dodecylsulphate-0.3% propanol at pH 7.4 eluent. Limits of detection at 240 nm were ranged between 0.13 μg ml −1 for diallyl barbit…
On the measurement of consistent long-term retention factor values in micellar liquid chromatography
Abstract In the field of the quantitative structure–retention and retention–activity relationships (QRAR and QSRR) is crucial to obtain consistent retention factors (k). For this purpose, two unbiased approaches to estimate k are used: (i) the IUPAC approach (based on the extra-column time correction) and (ii) the ‘2-references’ approach (based on the k estimation respect to two prefixed reference k values). Three reference chemicals were selected attending to their retention time, chemical stability and non-ionic character. Consistent retention factor values for these references were estimated for C18 chromatographic columns and Brij35 solutions as mobile phases after statistical analysis.…
Quantitative structure-retention relationships for ionic and non-ionic compounds in biopartitioning micellar chromatography
Quantitative structure–retention relationships, QSRRs, represent a powerful tool in chromatography. The objectives of QSRR studies are to predict the chromatographic retention behaviour of solutes based on their structural properties, to elucidate retention mechanisms, to optimize the separation of complex mixtures or to prepare experimental designs. In this paper, using the retention factors of 151 structurally unrelated solutes that cover a wide range of hydrophobicity, molecular size, hydrogen bonding properties and ionization degrees obtained in biopartitioning micellar chromatography (BMC) at different Brij35 micellar concentrations, several multivariate QSRR models are tested. It is d…
An LD50model for predicting psychotropic drug toxicity using biopartitioning micellar chromatography
The LD50 determination is the main way to measure the acute toxicity of all types of substances. At the present time, however, there is increasing opposition to the use of living animals in research and testing activities from animal rights groups as well as some scientists. Nevertheless, the need to have a tool for estimating the potential toxicity of new compounds for human consumption has encouraged the development of alternative methods. Under adequate conditions, the partitioning in micellar liquid chromatography can describe the drug biopartitioning. We have named this chromatographic system biopartitioning micellar chromatography (BMC). In this paper, an LD50 QRAR model developed for…
Enantioseparation of phenotiazines by affinity electrokinetic chromatography using human serum albumin as chiral selector
Nowadays, there is a special interest within the pharmaceutical laboratories to develop single enantiomer formulations and consequently a need for analytical methods to determine the enantiomeric purity of drugs. The present paper deals with the enantiomeric separation of promethazine and trimeprazine enantiomers by affinity electrokinetic chromatography (AEKC)-partial filling technique using human serum albumin (HSA) as chiral selector. A multivariate optimization of the most critical experimental variables in enantioresolution, running pH, HSA concentration and plug length, is carried out to obtain enantioresolution of promethazine and trimeprazine. The estimated maximum and optimum resol…
Screening of acetylcholinesterase inhibitors by CE after enzymatic reaction at capillary inlet.
In this study the development of a procedure based on capillary electrophoresis after enzymatic reaction at capillary inlet methodology for the screening and in vitro evaluation of the biological activity of acetylcholinesterase (AChE) inhibitors is presented. The progress of the enzymatic reaction of the hydrolysis of acetylthiocholine at pH 8 in the presence of AChE and the inhibitor studied is determined by measuring at 230 nm the peak area of the reaction product thiocholine (TCh). In the method employed the capillary was first filled with 30 mM borate-phosphate buffer (pH 8.0) and subsequently, plugs of: (i) water, (ii) AChE solution, (iii) substrate solution with or without inhibitor,…
Role of hydrophobicity on the monoamine receptor binding affinities of central nervous system drugs: a quantitative retention-activity relationships analysis using biopartitioning micellar chromatography.
Abstract Biological action and activity reflect an aspect of the fundamental physicochemical properties of the bioactive compounds. As an alternative to classical QSAR studies, in this work different quantitative retention–activity relationships (QRAR) models are proposed, which are able to describe the role of hydrophobicity on the binding affinity to different brain monoamine receptors (H 1 -histamine, α 1 -noradrenergic and 5-HT 2 -serotonergic) of different families of psychotherapeutic drugs. The retention of compounds is measured in a biopartitioning micellar chromatography (BMC) system using Brij-35 mobile phases. The adequacy of the QRAR models developed is due to the fact that both…
Retention-activity relationship studies of benzodiazepines by micellar liquid chromatography
Solute partitioning into lipid bilayers of biological membranes is the basis for drug and metabolite uptake, passive transport across membranes and bioaccumulation. In order to emulate in vitro the partitioning process in the biomembranes, different approaches have been proposed. The use of micellar solutions as mobile phases in reversed-phase liquid chromatography (micellar liquid chromatography, MLC) has proven to be valid in the prediction of the biological activities of local anesthetics, catecholamines and barbiturates. In this paper we focus our attention on benzodiazepines. The retention of benzodiazepines using different concentrations of Brij35 as micellar mobile phase in modified …