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PubMed1998

Cyclodextrin aided separation of peptides and proteins by capillary zone electrophoresis.

Carboxymethylated-beta-cyclodextrin (CMBCD) in the electrophoretic medium (aqueous 50 mM sodium phosphate, pH 2.5) enhanced the separation using raw fused-silica capillaries in CZE of the four standard proteins: alpha-chymotrypsinogen A, cytochrome c, lysozyme and ribonuclease A. Furthermore, with 20 mM CMBCD in the electrophoretic medium, the cis-trans isomers of angiotensin could be separated at room temperature, whereas the separation of the conformers required subambient temperatures as low as -20 degrees C without CMBCD in the electrophoretic medium [50 mM sodium phosphate (pH 2.5), containing 10% (v/v) methanol]. Addition of heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DMBCD) had no effect on the separation of the above proteins and peptides. The results suggest that in microcolumn separation techniques, certain cyclodextrin additives can be useful selectivity enhancers.

Amino Acid Sequence↗

PubMed1999

Interaction of some steroid drugs with beta-cyclodextrin polymer.

The interaction of 15 steroidal drugs with a water-soluble beta-cyclodextrin polymer was studied by reversed-phase thin-layer chromatography in the absence and in the presence of 0.1 M sodium chloride. The relative strength of interaction was calculated and the relationship between the hydrophobicity parameters of the drugs and the strength of the drug-beta-cyclodextrin polymer was elucidated by principal component analysis. Drugs readily formed inclusion complexes with the cyclodextrin derivatives; the strength of the interaction was higher in the presence of sodium chloride. It was assumed that the formation of inclusion complexes may influence the behaviour of the drugs resulting in modified biological efficacy.

Chemical Phenomena↗

PubMed1999

Metachromatic activity of beta-cyclodextrin sulfates as heparin mimics.

Heparin is a versatile biologically active substance which has been reported to have an inhibitory effect on angiogenesis if administered together with hydrocortisone. Since very little is known about the mechanism of this activity, beta-cyclodextrin sulfates were prepared to mimic heparin. The sulfate groups were introduced into beta-cyclodextrin regioselectively using protecting groups. The obtained polyanions were tested for their complex binding properties by mixing them with cationic dyes and measuring the metachromatic response which proved to be a very useful tool to evaluate the biological activity of these compounds. The results reveal that the activity depends largely upon the charge density at the surface of the beta-cyclodextrin sulfates: a large number of sulfate groups or anionic groups relatively close to each other display high activity, whereas molecules with fewer sulfate groups or with them more distant from each other exhibit smaller activities.

Cyclodextrins↗

PubMed1999

Release of testosterone from an osmotic pump tablet utilizing (SBE)7m-beta-cyclodextrin as both a solubilizing and an osmotic pump agent.

A controlled porosity osmotic pump system for poorly water soluble drugs has been developed using sulfobutyl ether-beta-cyclodextrin sodium salt, (SBE)7m-beta-CD, which can act as both a solubilizing and an osmotic agent. The release of testosterone, a poorly water soluble drug (0.039 mg/ml at 37 degrees C), was evaluated using a new model device. The effect of (SBE)7m-beta-CD as the solubilizing and osmotic pump agent was compared with hydroxypropyl-beta-cyclodextrin (HP-beta-CD), a neutral cyclodextrin, and a sugar mixture (osmotic agent only). Testosterone release from the device was significantly faster with (SBE)7m-beta-CD than with HP-beta-CD or the sugar mixture. The solubility of testosterone in the device increased to 76.7 mg/ml through complexation with (SBE)7m-beta-CD in the imbibed water. It appears that testosterone release from the device in the presence of (SBE)7m-beta-CD was mainly due to osmotic pumping while for HP-beta-CD the major contribution appears to be due to diffusion. In the case of the sugar mixture, testosterone was poorly released, presumably due to the absence of a solubilizer. Therefore, it was concluded that (SBE)7m-beta-CD provides novel properties for the development of controlled- porosity osmotic pump tablets for poor solubility drugs.

Algorithms↗

PubMed2000

Chromatographic separation of chlorthalidone enantiomers using beta-cyclodextrins as chiral additives.

Different beta-cyclodextrins have been tested as chiral additives in the mobile phase for the chromatographic analysis of chlorthalidone enantiomers in a C18 LiChrospher (125 x 4 mm I.D.) column. The effect on enantioresolution of different parameters was studied: composition of the mobile phase (percentage of organic solvent, type of buffer and pH), mobile phase flow-rate, and type and concentration of beta-cyclodextrin. A 25:75 mixture of methanol and 0.1 M phosphate buffer, pH 4, containing 2% triethylamine (v/v), and 12.5 mM beta-cyclodextrin, at a flow-rate of 0.8 ml/min, was found to be the best option for the resolution of chlorthalidone enantiomers. Under such conditions, linear calibration curves were obtained in the 0.5-20-microg/ml interval using UV detection at 230 nm. The limit of detection for both isomers was 50 ng/ml. The utility of the described assay has been tested by analyzing chlorthalidone in different pharmaceutical preparations. Examples of application to biological samples are also given.

Chlorthalidone↗

PubMed2002

Utilization of supercritical carbon dioxide for complex formation of ibuprofen and methyl-beta-cyclodextrin.

The dissolution rate of a drug into the biological environment can be enhanced by forming complexes with cyclodextrins and their derivatives. In this study, ibuprofen-methyl-beta-cyclodextrin complexes were prepared successfully by passing ibuprofen-laden CO(2) through a methyl-beta-cyclodextrin packed bed. The maximum drug loading obtained in this work was 10.8 wt.%, which was comparable to that of a 1:1 complex (13.6 wt.% of ibuprofen). The complex exhibited instantaneous dissolution profiles in water solution. The enhanced dissolution rate was attributed to the amorphous character and improved wettability of the product.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2003

Non-surfactant nanospheres of progesterone inclusion complexes with amphiphilic beta-cyclodextrins.

Amphiphilic beta-cyclodextrins were formulated as nanospheres and characterised by particle size, zeta potential and TEM following freeze-fracture. The nanospheres were loaded with progesterone with different loading techniques involving the spontaneous formation of nanospheres from pre-formed inclusion complexes of amphiphilic beta-cyclodextrins modified on the primary or secondary face with progesterone. Inclusion complexes were characterised with various techniques including Differential Scanning Calorimetry (DSC), Fast Atom Bombardment Mass Spectrometry (FAB MS) and 1H NMR spectroscopy; and progesterone was believed to be partially included in the CD cavity. Loading properties of conventionally-loaded nanospheres were compared with those prepared directly from pre-formed inclusion complexes and loading technique was found to enhance associated drug percentage significantly (P<0.05). Although both amphiphilic beta-cyclodextrins (6-N-CAPRO-beta-CD and beta-CDC6) were capable of high progesterone loading, beta-CDC6 displayed slightly higher entrapment efficiency due to the possible higher affinity of progesterone to the 14 alkyl chains surrounding this molecule resulting in higher drug adsorption to particle surface. Progesterone was released within a period of 1 h from all formulations. Progesterone-loaded amphiphilic beta-CD nanospheres were proved to be a promising non-surfactant injectable delivery system providing high-quantity of water-insoluble progesterone rapidly within 1 h.

Cyclodextrins↗

PubMed1997

Optimization of a simple method for the chiral separation of phenethylamines of forensic interest based on cyclodextrin complexation capillary electrophoresis and its preliminary application to the analysis of human urine and hair.

Because of the forensic importance of the chiral analysis of amphetamine and other phenethylamines for investigating their synthetic pathways and the metabolic patterns of these compounds, a capillary electrophoresis method has been developed based on the chiral selectivity of beta-cyclodextrin. The influence of different experimental conditions, such as cyclodextrin nature and concentration, voltage, temperature and buffer concentration and pH, on analytical performance has been studied. The optimized analytical conditions are: capillary: bare fused silica, 50 microns I.D., 40 cm effective length; buffer: 150 mM phosphate pH = 2.5, 15 mM beta-cyclodextrin; voltage: 10 kV; temperature: 17.5 degrees C; detection: UV absorption at 200 nm wavelength. Under these conditions, amphetamine, methamphetamine and ephedrine have been easily separated, with baseline resolution of the respective enantiomers. Sensitivity was better than 300 ng per ml. The average precision of migration times of the three analytes was good with RSD = 0.45% and 0.58% in intra-day and day-to-day tests, respectively. Reproducibility of peak heights was also good, with RSD = 2.51% and 3.14% in intra-day and day-to-day tests, respectively. The preliminary analysis of amphetamine in human urine and hair samples, subjected to a simple work-up procedure based on liquid-liquid extraction, showed clean blank electropherograms, excellent chiral resolution and sensitivity, suitable for the analysis of real samples from amphetamine users.

Amphetamine↗

PubMed2000

1H-NMR and molecular modelling techniques for the investigation of the inclusion complex of econazole with alpha-cyclodextrin in the presence of malic acid.

Carrying on a study where the combination of alpha-cyclodextrin and malic acid was found to be the most effective in improving the solubility of econazole, an antifungal drug very poorly water soluble, in the present work 1H-NMR and nuclear overhauser effect (NOE) experiments and molecular modelling studies were performed to gain insight into the interactions in solution between such three components and the structure of the supposed multicomponent complex. Findings demonstrated that two different complexes can be simultaneously present in solution involving, respectively, the inclusion of econazole monochloro-phenyl group within the host cavity from the primary hydroxyl side of the cyclodextrin cavity, or that of the other phenyl group through the opposite side of the cavity. It was shown that also malic acid is strictly involved in the molecular assembly of the complex, particularly through interactions with primary hydroxyl groups of the cyclodextrin molecule. Molecular modelling studies allowed to elaborate possible geometric models of the multicomponent complex and to select the more energetically favourable conformations which complied better with experimental data. Results suggested the possible formation in solution of stable oligomeric aggregates constituted by the repeated concatenation of the three components.

Antifungal Agents↗

PubMed2004

Preparation and study the 1:2 inclusion complex of carvedilol with beta-cyclodextrin.

An inclusion complex of beta-cyclodextrin with carvedilol was prepared by using a convenient new method of microwave irradiation. Phase-solubility studies demonstrated the ability of beta-cyclodextrins to complex with carvedilol and increase drug solubility. The structure of inclusion complex was determined by fluorescence spectroscopy and 1H NMR, 13C NMR measurements in solution. The solid inclusion was characterised by infrared spectroscopy, differential scanning calorimetry (DSC) and element analysis. These experimental results confirmed the existence of 1:2 inclusion complex of carvedilol with beta-cyclodextrin, the formation constant of complex was determined by the fluorescence method. Molecular modeling predicted the energy-minimized structure of the complex.

Carbazoles↗

PubMed2001

Analysis of interleukin-8 release from normal human epidermal keratinocytes exposed to aliphatic hydrocarbons: delivery of hydrocarbons to cell cultures via complexation with alpha-cyclodextrin.

While inhalation exposures represent the predominant route for jet fuel toxicity, increased concern has been placed on topical exposures due to reports of severe contact dermatitis among military personnel. All three of the predominant aviation fuels currently used by the commercial and military sectors have been demonstrated experimentally to induce the production of interleukin-8 (IL-8), a proinflammatory cytokine, in normal human epidermal keratinocytes (NHEK). The objective of this study was to examine the effects of individual hydrocarbon components found in these fuels on IL-8 production by NHEK. In order to circumvent the extreme hydrophobicity of these compounds, inclusion complexes were formed between alpha-cyclodextrin/aliphatic hydrocarbons by adding 2 mM hydrocarbons to 4 mM alpha-cyclodextrin. NHEK were exposed to four aliphatic hydrocarbons (undecane, dodecane, tridecane, hexadecane) for 24 h at concentrations of 7.8-500 microM. These hydrocarbons caused a peak in IL-8 release at a concentration of 31.2 microM, with the exception of dodecane which peaked at 62.5 microM. Subtoxic concentrations of the aliphatic hydrocarbons were those < 62.5 microM. These studies demonstrate that the etiology of proinflammatory cytokine expression due to jet fuel exposure may be due in large part to the aliphatic hydrocarbon components. Furthermore, these studies provide additional evidence that hydrocarbons can be successfully delivered to cells in culture by encapsulating them in cyclodextrin inclusion complexes.

Cells, Cultured↗

PubMed2003

Physicochemical investigation of the effects of water-soluble polymers on vinpocetine complexation with beta-cyclodextrin and its sulfobutyl ether derivative in solution and solid state.

The studies reported in this work aimed to elucidate the inclusion complex formation of vinpocetine (VP), a poorly water-soluble base type drug, with beta-cyclodextrin (betaCD) and its sulfobutyl ether derivative (sulfobutyl ether beta-cyclodextrin (SBEbetaCD)), with or without water-soluble polymers (PVP and HPMC), by thoroughly investigating their interactions in solution and solid state. Phase solubility studies were carried out to evaluate the solubilizing power of both cyclodextrins (CDs), in association with water-soluble polymers, towards VP and to determine the apparent stability constants (Kc) of the complexes. SBEbetaCD showed higher solubilizing efficacy toward VP than the parent betaCD due to its greater solubility and complexing abilities, what was reflected in higher Kc values. Improvement in Kc values for ternary complexes clearly proves the benefit on the addition of water-soluble polymers to promote higher complexation efficiency. VP-CDs (1:1) binary and ternary systems were prepared by physical mixing, kneading, co-evaporation, and lyophilization methods. In the solid state, drug-carrier interactions were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and Fourier-transform infrared spectroscopy. The results of these analysis suggested the formation of new solid phases, some of them in amorphous state, allowing to the conclusion of strong evidences of binary and ternary inclusion complex formation between VP, CD and water-soluble polymers, particularly for co-evaporated and lyophilized binary and ternary products.

Chemical Phenomena↗

PubMed2003

Efficient determination and evaluation of model cyclodextrin complex binding constants by electrospray mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) is now routinely used for the detection of cyclodextrin noncovalent complexes, complementing previously established methods. Host-guest complexes formed in solution are also stable for characterization by ESI in the gas phase. This paper reports the first investigations to characterize the stability of three inclusion complexes between beta-cyclodextrin (beta-CD) and three model "guest" molecules, by determining the cyclodextrin compound complex stability constant (K(st)) with the use of mass spectrometric studies. The relative signal intensity of the complexes were monitored in the positive ion mode by mixing each "guest" molecule with an up to 50-fold molar excess of betaCD. A novel linear equation, similar to Benesi-Hildebrand, was derived allowing the determination of K(st) for 1:1 stoichiometry in all complexes. These values were compared with the K(st) obtained by spectrophotometric experiments and they were evaluated to be slightly different, indicating the validity of the described method.

Cyclodextrins↗

PubMed2002

Resonance Rayleigh scattering technology as a new method for the determination of the inclusion constant of beta-cyclodextrin.

The interaction of procaine hydrochloride and beta-cyclodextrin in aqueous solution was studied using resonance Rayleigh scattering technology. The molar ratio of the inclusion complex was 1:1 established by spectrophotometry. The resonance Rayleigh scattering technology was first applied in the determination of the beta-cyclodextrin inclusion constant. The inclusion constant of procaine hydrochloride beta-cyclodextrin complex Kf is 1.23 x 10(2) and 1.27 x 10(2) l mol(-1) for method I and 1.15 x 10(2) and 1.21 x 10(2) l mol(-1) for method II. These determination results were in correspondence with the results of the spectrophotometric and fluorescence methods. Therefore, the resonance Rayleigh scattering method can be used as a new technology for the determination of the inclusion constant.

Cyclodextrins↗

PubMed2000

Chlortetracycline staining patterns of frozen-thawed bull spermatozoa treated with beta-cyclodextrins, dibutyryl cAMP and progesterone.

Efforts to achieve complete chemical definition of media used for in vitro capacitation of bovine spermatozoa including removal of heparin purified from porcine intestinal mucosa are presented. Fluorescent staining with chlortetracycline (CTC), known to reflect changes coincident with sperm capacitation in certain species, was studied following treatments of frozen-thawed bull spermatozoa with beta-cyclodextrins, dibutyryl cAMP (dbcAMP) and progesterone in comparison with heparin. The CTC staining patterns (F, B and AR) were confirmed to correlate with known conditions that effectively prepare cryopreserved bull spermatozoa for fertilisation in vitro. In the absence of glucose, the routinely employed heparin-containing capacitating medium caused an increase in spermatozoa displaying the AR pattern. Both progesterone (100 microM) and dbcAMP (0.01-0.1 mM) were able to increase the proportion of B pattern stained sperm cells more than after exposure to control (mDM) conditions without a significant reduction in motility. Exposure to either dbcAMP or beta-cyclodextrins was accompanied by an increase in proportions of spermatozoa displaying the AR pattern over those seen in controls. Exposure to beta-cyclodextrins did not increase the proportion of B pattern stained spermatozoa. Comparison of spermatozoa from two bulls revealed differential responses of spermatozoa from different males to treatments with heparin and progesterone. In vitro fertilisation results demonstrated that previously cryopreserved bull spermatozoa could be capacitated in chemically defined conditions devoid of heparin or other biological components.

Animals↗

PubMed1996

Mechanism of enantioseparation of salsolinols, endogenous neurotoxins in human brain, with ion-pair chromatography using beta-cyclodextrin as a mobile phase additive.

A novel method for direct separation of the enantiomers of salsolinol and N-methylsalsolinol was devised. The enantiomers were completely separated with ion-pair chromatography on a reversed-phase column with beta-cyclodextrin as a chiral mobile phase additive and sodium 1-heptanesulfonate as a counterion. The mechanism for enantioseparation with this ion-pair system containing beta-cyclodextrin was discussed. The effects of beta-cyclodextrin, counterions, pH, ionic strength, and organic solvent on retention were investigated, and a retention model was proposed and proved to be consistent with the experimental data. A preliminary study of the enantiomeric composition of salsolinol and N-methylsalsolinol in banana and in human brain was made as an example of the application of this assay.

Brain Chemistry↗

PubMed1997

A persubstituted cationic beta-cyclodextrin for chiral separations.

The applications of a novel polycationic derivative of beta-cyclodextrin (beta-CD), heptakis(6-hydroxyethylamino-6-deoxy-beta-cyclodextrin) (beta-CD-EA), as a chiral host--guest additive for the enantioseparation of various classes of chiral anionic analytes are presented. The cationic beta-CD described in this paper is persubstituted with seven ethanolamine side arms at the primary rim of each cyclodextrin (CD) molecule. It is found that the electrophoretic mobility of beta-CD-EA can be adjusted to influence the chiral selectivity by changing the pH of the background electrolyte. Most of the observed CD capillary zone electrophoresis (CZE) separations of anionic drugs and herbicides were accomplished in the pH range of 4.0-7.0 with a reverse polarity configuration. At pH 5.0, enantioseparation of a mixture of three structurally related antiinflammatory agents (fenoprofen, flurbiprofen, and ibuprofen) was possible in about 30 min. However, other chiral acids, such as a series of phenoxypropionic acid herbicides and dansylated amino acids (glutamic acid and aspartic acids), were best separated at pH 6.0 or 7.0. An impressive separation of a mixture of six structurally related anionic herbicides [(+/-)-2-phenoxypropionic acid, (+/-)-2-(2-chlorophenoxy)propionic acid, (+/-)-2-(3-chlorophenoxy)propionic acid, (+/-)-2-(4-chlorophenoxy)propionic acid, (+/-)-2-(2,4-dichlorophenoxy)propionic acid, and (+/-)-2-(2,4,5-trichlorophenoxy)propionic acid] was achieved for the first time in about 15 min during a single run with 20 mM beta-CD-EA. The analytical applicability of this cationic CD molecule for chiral separations is discussed in detail.

Amino Acids↗

PubMed1999

Symmetry breaking during the formation of beta-cyclodextrin-imidazole inclusion compounds: capillary electrophoresis study.

A mathematical model was developed for the estimation of binding constants by capillary electrophoresis. The effective electrophoretic mobility in a solute mixture is dependent on the cyclodextrin concentration in the background electrolyte (BGE) as well as the stoichiometry and the binding constant of the guest-cyclodextrin complex. As well, a determination of the degree of complexation, nc (the percent of complexed guest) could be carried out. The model was applied to a series of imidazole derivatives. Thermodynamic data for the solute complexation mechanism were calculated. Different van't Hoff plot shapes of the degree of complexation were observed with different BGE pH values, indicating a change in the solute complexation mechanism. Enthalpy-entropy compensation revealed that the solute complexation mechanism was independent of the imidazole derivative molecular structure, the same at pH = 4.5, 5.0, 5.5, 6.0, and 6.5 but changed at pH = 7.0 and 7.5. Topological defects formed during a symmetry-breaking transition could be responsible for the modification of the structure of the cyclodextrin cavity and explained the nc variations in relation to pH and temperature.

Algorithms↗