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PubMed2004

Enhanced solubilization and removal of naphthalene and phenanthrene by cyclodextrins from two contaminated soils.

The development of innovative methods for cleaning contaminated soils has emerged as a significant environmental priority. Herein, are investigated the effectiveness of cyclodextrin (CD) to solubilize and to extract organic pollutants from soils. The interactions in the cyclodextrin/pollutant/soil system have been studied "step by step" using two kinds of polycyclic aromatic hydrocarbons (PAH), naphthalene (Nap) and phenanthrene (Phe), cyclodextrins and soils. Inclusion complex formation of PAH with beta-cyclodextrin (beta-CD) and hydroxypropyl-beta-cyclodextrin (HPCD) has been investigated and was proposed as a way to facilitate the pollutant removal from soil. Little effect of ionic strength was observed on CD complex formation for both compounds. The solubility of PAH in 50 g L(-1) of HPCD was enhanced 20- and 90-fold for naphthalene and phenanthrene, respectively. Batch experiments were performed to study the adsorption-desorption of two PAH on two soils and the influence of CDs over these processes. These experiments were also conducted with a mixture of two PAH. The batch desorption results indicate that removal capacity of HPCD was higher than that of beta-CD. Phenanthrene was strongly sorbed on soils, this led to low desorption rates compared to that of naphthalene, whatever the extracting agent used. When HPCD solution was used as a flushing agent, 80% of naphthalene and 64% of phenanthrene recovery from soil were observed. For both compounds, the slowest desorption rate was found for the soil that had the greatest content of organic matter. CD sorption on soils, was relatively low and depended on soil type. The soil organic matter (SOM) could favor the retention of both CD and pollutant involving the extraction rate to be decreased. A competitive hydrophobic interactions of pollutant between SOM and CD molecules, and co-sorption were expected to be the mechanism for the inhibited desorption.

Adsorption↗
PubMed2006

Competitive immobilization of multiple component chlorinated solvents by cyclodextrin derivatives.

Immobilization of chlorinated solvents with hydropropyl and methyl cyclodextrins (CDs) was observed by head-space analysis to obtain the stability constants in single and multiple component systems. In each single component system, the highest stability constant was 0.299 mM(-1) for perchloroethylene (PCE) by methyl-beta-cyclodextrin (M-beta-CD), 0.136 mM(-1) for trichloroethylene (TCE) by M-beta-CD, 0.106 mM(-1) for cis-dichloroethylene (cis-DCE) by hydropropyl-alpha-cyclodextrin, and 0.090 mM(-1) for trans-dichloroethylene (trans-DCE) by M-beta-CD. When HP-beta-CD and M-beta-CD were used, the stability constants of PCE and TCE increased and those of DCEs decreased in a multiple component system. Differences in stability constants of single and multiple component systems thus should be important parameters when cyclodextrins are applied to solubilization of multiple chlorinated solvents.

Chemical Phenomena↗
PubMed2004

Combined effect of pH and polysorbates with cyclodextrins on solubilization of naringenin.

pH control and inclusion complex formation are commonly used as solubilization techniques in formulating ionizable drugs. Naringenin is a weakly acid compound with a low water solubility. The role of both ionized and unionized species of naringenin in solution by complexation with beta-cyclodextrin, 2-hydroxypropyl-beta-cyclodextrin and methyl-beta-cyclodextrin was investigated. This combined use of ionization and complexation increases not only the solubility of the unionized naringenin, but also that of the ionized one. This study puts on evidence the role of pH, pKa and complexation constants in increasing drug total aqueous solubility, determined by the single components in solution, as ionized and unionized naringenin both in free and complexed forms. Moreover, the presence of non-ionic surfactants in the media of complexation gives a positive contribution to the improvement of the solubility of naringenin, alone or in combination with beta-cyclodextrin.

Algorithms↗
PubMed2005

Interaction of naproxen with ionic cyclodextrins in aqueous solution and in the solid state.

The possible role of the cyclodextrin charge in the interaction with an acidic drug such as naproxen (pKa 4.8) has been evaluated. Sulfobutylether-beta-cyclodextrin (SBE-betaCyd) and trimethylammonium-beta-cyclodextrin (TMA-betaCyd) were selected as, respectively, anionically and cationically charged carriers and their performance was compared with that of the parent beta-cyclodextrin (betaCyd) and of its methyl-derivative (Me betaCyd) previously found as the best partner for the drug. Interactions in solution were investigated by phase-solubility, fluorescence and circular dichroism analyses. Equimolar drug-carrier products prepared by different techniques (blending, cogrinding, sealed-heating, colyophilization) were characterized by differential scanning calorimetry and X-ray powder diffractometry and tested for drug dissolution properties. Anionic charges of SBE-betaCyd did not negatively influence interactions in unbuffered aqueous solutions (pH approximately 5) with the acidic drug. In fact, it was a very effective carrier, exhibiting solubilizing and complexing properties considerably better than the parent betaCyd and comparable to those of Me betaCyd. On the contrary, the positive charges of TMA-betaCyd did not favour interactions with the counter-ionic drug (despite the presence of about 60% ionised drug) and it was less efficacious also than native betaCyd. Therefore, the role of the Cyd charge on the complexing and solubilizing properties towards naproxen was not important whereas other factors, such as steric hindrance effects and favourable hydrophobic interactions were significant in determining the drug affinity for the Cyd inclusion. Solid state studies evidenced similar amorphizing properties of both charged Cyds towards naproxen. On the other hand, dissolution tests, in agreement with solution studies, showed that all products with SBE-betaCyd exhibited significantly better dissolution properties than the corresponding ones with TMA-betaCyd. A clear influence of the preparation method of drug-Cyd solid systems on the performance of the end product was also observed. Colyophilization was the most effective technique, followed by the cogrinding one. Colyophilized product with SBE-betaCyd allowed a 10-times increase in drug dissolution efficiency (D.E.) (with respect to the five-times increase obtained with the corresponding coground product) and a reduction of t(50%) from about 60 min (for the coground product) to less than 2 min.

Cyclodextrins↗
PubMed2004

A new method for the determination of the critical micelle concentration of Triton X-100 in the absence and presence of beta-cyclodextrin by resonance Rayleigh scattering technology.

A new method for the determination of the critical micelle concentration (CMC) of Triton X-100 in aqueous solution and beta-cyclodextrin solution by resonance Rayleigh scattering (RRS) has been developed. The method is based on the measurement of the RRS intensity of different concentration of Triton X-100 in aqueous solution and beta-cyclodextrin solution (6.0 x 10(-4) mol l(-1)). When the RRS intensities were plotted against the concentration of Triton X-100, an inflection point appeared at the Triton X-100 concentration of 5.0 x 10(-4) mol l(-1) in aqueous solution and 1.1 x 10(-3) mol l(-1) in beta-cyclodextrin solution, respectively. These values of concentration corresponded to the CMC of Triton X-100 in aqueous solution and beta-cyclodextrin solution, which also agreed closely with the results reported by surface tension and UV-Vis absorption spectrophotometry. Therefore, the present RRS method is very convenient, rapid and accurate and can be used as a new technology for the determination of CMC values of surfactants without any probe. The relationship between the RRS intensity and the concentration, aggregate state and the aggregate molecular size of Triton X-100 has been primarily discussed.

Micelles↗
PubMed2005

Spectroscopic studies of inclusion complexes of 1-naphthol-4-sulfonate with beta-cyclodextrin in aqueous solution.

The photophysical properties of 1-naphthol-4-sulfonate (1N4S) in some solvents and in aqueous beta-cyclodextrin solution have been investigated. The effect of beta-cyclodextrin on the fluorescence quantum yield and on the proton transfer is examined. Fluorescence measurements show 1:1 inclusion of 1N4S in the beta-cyclodextrin cavity with an association constant of 108M(-1). NMR studies are used to study the inclusion phenomena and to provide information on the geometry of 1N4S inside the cavity of beta-cyclodextrin.

Hydrogen-Ion Concentration↗
PubMed2006

Spectroscopic studies on the inclusion complex of 2-naphthol-6-sulfonate with beta-cyclodextrin.

The photophysical properties of 2-naphthol-6-sulfonate (2-NOH-6-S) in various solvents and in aqueous beta-cyclodextrin solution have been investigated. The fluorescence quantum yields in non-aqueous solvents are approximately 0.20+/-0.02, while in water the yield is higher. The fluorescence quantum yield in water was found to depend on the pH value of the medium and increases as the pH increase up to a pH value of 4.0 where it comes to be constant. Absorption and fluorescence measurements show 1:1 inclusion of 2-NOH-6-S in the beta-cyclodextrin cavity. The association constant of 2-NOH-6-S-beta-cyclodextrin complex based on fluorescence measurements was calculated using Benesi-Hildbrand relationship and found to be 330+/-30M(-1). (1)H NMR studies are used to confirm the inclusion and to provide information on the geometry of 2-NOH-6-S inside the cavity of beta-cyclodextrin.

Deuterium Oxide↗
PubMed2000

Phase behavior of fully hydrated DMPC-amphiphilic cyclodextrin systems.

With the aim of exploring relationships between the chemical structure and the physico-chemical properties of amphiphilic beta-cyclodextrin, a reappraisal of the obtaining of pure heptakis (2,3-di-O-hexanoyl)-beta-cyclodextrin (beta-CDC(6)) was undertaken. In this paper the chemical characterization of the newly synthesized beta-CDC(6) and its ability to form mixed structures with dimyristoylphosphatidylcholine (DMPC) are reported. Miscibility of the two amphiphiles is examined: (i) in monolayers formed at the air-water interface by analyzing the surface pressure-area isotherms; and (ii) in fully hydrated mixtures by differential scanning calorimetry (DSC) and X-ray diffraction at small and wide angles. Results demonstrate that the beta-cyclodextrin derivative is partially miscible to the phospholipid: intimate mixing occurs at beta-CDC(6) molar ratios smaller than 7-15 mol%, depending on the dimensional scale considered, while beyond these compositions phase separation is observed. At the air-water interface, the miscibility region of the two compounds shows non-ideal behavior characterized by the non-additivity of the molecular areas in the mixed monolayers. At the three-dimension level, the formation of a beta-CDC(6)/DMPC mixed lamellar phase occurs except at beta-CDC(6) molar ratios close to 5 mol% at which a highly ordered structure is depicted below the solid-to-liquid state transition of the DMPC hydrocarbon chains. At beta-CDC(6) contents higher than 7 mol%, the mixed assemblies coexist with excess amphiphilic cyclodextrin which then forms a separated hexagonal structure.

Calorimetry, Differential Scanning↗
PubMed2000

Enantiomeric separations of drugs using mixtures of charged and neutral cyclodextrins.

An overview on the use of mixtures of neutral and charged cyclodextrins as chiral additives for the enantioseparation of drugs by capillary electrophoresis is presented. These so called dual cyclodextrin systems can often provide unique selectivities. A brief theoretical background illustrating the influence of the chiral discrimination ability and the effective mobility of the two cyclodextrins on the overall selectivity of the enantiomeric separation is given. Typical examples of applications in the pharmaceutical field, based on the simultaneous use of a charged (cationic or anionic) and neutral cyclodextrins, are described.

Cyclodextrins↗
PubMed2000

Simultaneous determination of eleven ingredients in ophthalmic solutions by cyclodextrin-modified micellar electrokinetic chromatography with tetrabutylammonium salt.

Cyclodextrin-modified micellar electrokinetic chromatography was applied to determine simultaneously 11 active ingredients in ophthalmic solutions. All the ingredients were successfully separated by using the mixed carrier system containing sodium dodecyl sulfate with beta-cyclodextrin and tetrabutylammonium phosphate. The effects of the cyclodextrin type on selectivity were also examined. Excellent separation of the all ingredients was obtained by the use of dimethyl-beta-cyclodextrin. The established method was validated and confirmed to be applicable to the determination of the active ingredients in a commercial ophthalmic solution. These results suggest that capillary electrophoresis can be applied to the quantitative analysis as well as qualitative analysis in pharmaceuticals.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2001

New reversed-phase liquid chromatographic method to detect aflatoxins in food and feed with cyclodextrins as fluorescence enhancers added to the eluent.

The effect of succynil-beta-cyclodextrin (beta-CD-Su), dimethyl-beta-cyclodextrin (DIMEB) and beta-cyclodextrin (beta-CD) on the fluorescence of aflatoxins B1, B2, G1, G2 and M1 (AFB1, AFB2, AFG1, AFG2 and AFM1) was studied: beta-CD-Su promoted the largest fluorescence enhancement for AFB1 and AFM1 while DIMEB showed better results for AFG1 . On the basis of the fluorescence enhancement, a new RP-HPLC method for detecting aflatoxins B1, B2, G1, G2 and M1 was developed using cyclodextrins directly dissolved in the LC eluent. Aflatoxins B1, B2, G1 and G2 were resolved using a MICRA NPS ODS-1 column using methanol-water as mobile phase to which 6 x 10(-3) M beta-CD-Su or beta-CD were added. Chromatographic responses of AFB1 and AFG1 achieved using beta-CD dissolved in the mobile phase were enhanced, respectively, 8 and 12 times, and 10 and 15 times with beta-CD-Su. Detection limits lower than 0.3 microg/kg were achieved for all the four aflatoxins. Aflatoxin M1 was analysed using a Spherisorb S3 ODS-2 Narrow Bore column and methanol-water as mobile phase with added 2 x 10(-3) M beta-CD-Su. An area enhancement of 1.5 was detected for the toxin and the detection limit achieved under these analytical conditions was lower than 0.0005 microg/kg. Both methods were statistically validated showing a linear response for all the aflatoxins tested (R2 > or = 0.99), and applied to the analysis of spiked and naturally contaminated food samples.

Aflatoxins↗
PubMed1998

Cationic beta-cyclodextrin derivative for chiral separations.

A novel hepta-substituted beta-cyclodextrin bearing the methoxyethylamine group linked to the upper cyclodextrin rim was successfully used as a chiral selector for enantiomeric separation of non-steroidal anti-inflammatory drugs (NSAIDs) and phenoxypropionic acid herbicides (PPAHs). Separation parameters such as pH and concentration were found to have major influences on enantiomeric resolution of the NSAIDs and PPAHs. Results indicate that heptakis(6-methoxyethylamine-6-deoxy)-beta-cyclodextrin [beta-CD-OMe (VII)] performs exceptionally well for the enantiomeric resolution of NSAIDs: indoprofen and fenoprofen (Rs = 11 and 14, respectively). In addition, baseline enantiomeric separation of a mixture of six pairs of PPAHs was achieved in under 30 min. Compared to other cationic beta-cyclodextrins reported in the literature, the beta-CD-OMe (VII) showed improved selectivity for both classes of the aforementioned anionic racemates.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Enantioseparation of 3,4-dihydroxyphenylalanine and 2-hydrazino-2-methyl-3-(3,4-dihydroxyphenyl)propanoic acid by capillary electrophoresis using cyclodextrins.

The enantiomeric separations of 3,4-dihydroxyphenylalanine (dopa) and 2-hydrazino-2-methyl-3-(3,4-dihydroxyphenyl)propanoic acid (carbidopa) by capillary electrophoresis were studied using several native, neutral and anionic cyclodextrins as chiral additives and uncoated fused-silica capillaries. The effect of the type and concentration of the cyclodextrin added to 20 mM phosphate buffer (pH 2.5) on enantioseparation and migration times was studied. A high resolution value of 15.63 was obtained for dopa enantiomers with a buffer containing 20 mM single isomer, heptakis(2,3-diacetyl-6-sulfato)-beta-cyclodextrin. The enantiomers of carbidopa were separated using 20 mM carboxymethyl-beta-cyclodextrin as a chiral resolving agent. Both methods allowed the determination of 0.1% of the D-enantiomer (second migrating) in the presence of the L-enantiomer (first migrating) of dopa and carbidopa with a good precision. These methods also gave good results in terms of precision for both peak area, migration time, linearity and accuracy.

Carbidopa↗
PubMed2000

Effect of cyclodextrin-encapsulated beta-carotene on progesterone production by bovine luteal cells.

Experiments were conducted to examine the effect of cyclodextrin-encapsulated beta-carotene on basal or cholesterol (cyclodextrin-encapsulated), LH and dibutyryl cyclic AMP (dbcAMP)-stimulated progesterone production by bovine corpus luteum cells isolated from mid-luteal heifer ovaries by collagenase digestion. Cells were cultured with serum-free DMEM/Ham's F12 medium in serum pre-treated plastic culture dishes for periods of up to 11 days. Medium was replaced after 24h and thereafter every 48 h. Beta-carotene was added to cultures in a carrier molecule, dimethyl-beta-cyclodextrin, to facilitate dissolution. All treatments were started on day 3 of culture. Treatment of cells with 1 or 2 micromol/l beta-carotene resulted in sharp inhibition of progesterone production. On the contrary, treatment of cells with 0.1 micromol/l beta-carotene resulted in significant stimulation (P<0.05) of both basal and cholesterol-stimulated progesterone secretion. The effect of beta-carotene on LH or dbcAMP-stimulated progesterone production was also examined. Treatment of cells with LH or dbcAMP always resulted in stimulation of progesterone secretion (P<0.001). However, cells treated with LH plus beta-carotene or dbcAMP plus beta-carotene both produced significantly (P<0.01) less progesterone relative to those cells treated with LH or dbcAMP alone on days 7, 9 and 11 of culture. These results indicate that beta-carotene can enhance luteal steroidogenesis when present at low concentrations but is inhibitory at higher concentrations and that encapsulation of beta-carotene in cyclodextrin is an effective method of supplying it to cells in culture.

Animals↗
PubMed2000

Cyclodextrins: a versatile tool in separation science.

Cyclodextrins have been used extensively in separation science because they have been shown to discriminate between positional isomers, functional groups, homologues and enantiomers. This property makes them one of the most useful agents for a wide variety of separations. The main goal of this review is a discussion of somewhat more exotic applications of cyclodextrins to separation methods. Techniques examined in detail include gel electrophoresis, isotachophoresis, isoelectric focusing, preparative scale electrophoretic techniques, thin-layer chromatography, electrochemically modulated liquid chromatography, use of monolithic media in liquid chromatography, microdialysis, separation on hollow fibers, foam flotation enrichment, solid- and liquid-phase extractions, countercurrent chromatography, separation through liquid and composite membranes, and cyclodextrin applications in molecularly imprinted polymers. Since a lot of attention has been paid to use of cyclodextrins in capillary electrophoresis, liquid, gas and supercritical fluid chromatography, these techniques will be only briefly discussed. The second goal of this review is a discussion of a scaling-up the analytical separations to semi-preparative or preparative techniques. It was found that despite a need for large scale separations in the industry, development of these techniques has been somewhat lagging behind development of miniaturized analytical separations. It is hoped that the focus on areas outside more traditional separation applications might stimulate further research.

Chromatography↗
PubMed2001

Cyclodextrin solubilization of benzodiazepines: formulation of midazolam nasal spray.

The cyclodextrin solubilization of three benzodiazepines, i.e. alprazolam, midazolam and triazolam, was investigated. The cyclodextrin solubilization was enhanced through ring-opening of the benzodiazepine rings and ionization of the ring-open forms. Additional enhancement was obtained through interaction of a water-soluble polymer with the cyclodextrin complexes. The ring-opening was pH-dependent and completely reversible, the ring-open forms dominating at low pH but the ring-closed forms at physiologic pH. The ring-closed forms were rapidly regenerated upon elevation of pH. In freshly collected human serum in vitro at 37 degrees C, the half-life for the first-order rate constant for the ring-closing reaction was estimated to be less than 2 min for both alprazolam and midazolam. Midazolam (17 mg/ml) was solubilized in aqueous pH 4.3 nasal formulation containing 14% (w/v) sulfobutylether beta-cyclodextrin, 0.1% (w/v) hydroxypropyl methylcellulose, preservatives and buffer salts. Six healthy volunteers received 0.06 mg/kg midazolam intranasally and 2 mg intravenously, and blood samples were collected up to 360 min after the administration. Midazolam was absorbed rapidly reaching maximum serum concentrations of 54.3+/-5.0 ng/ml at 15+/-2 min. The elimination half-life of midazolam was 2.2+/-0.3 h and the absolute availability was 73+/-7%. All mean values+/-SEM.

Administration, Intranasal↗
PubMed2001

Development of a capillary electrophoresis assay for the determination of carvedilol enantiomers in serum using cyclodextrins.

A capillary electrophoresis method using cyclodextrins as the chiral selectors was developed for the determination of carvedilol enantiomers in serum. Several types of cyclodextrins were evaluated. The effect of cyclodextrin concentration on enantiomer resolution was investigated. Best results were obtained using 10 mM hydroxypropyl-beta-cyclodextrin in the run buffer. The effect of voltage on efficiency was assessed. Other electrophoretic conditions were optimized. The method was validated for carvedilol enantiomers in serum. Linearity of detection was assessed over the concentration range of 50-4000 ng/ml of each enantiomer in serum. Intra- and inter-assay variability obtained were under 8% for both enantiomers.

Buffers↗
PubMed2002

Do we know the mechanism of chiral recognition between cyclodextrins and analytes?

The resolution of chiral phenethylamine analogue compounds were studied in presence of single-isomer neutral and negatively charged cyclodextrins (CDs) by means of capillary electrophoresis (CE) and NMR spectroscopy. Whereas the native beta-CD and heptakis(2-N,N-dimethylcarbamoyl)beta-cyclodextrin were not able to separate the racemates of four ephedrine derivatives studied, heptakis(2,3-O-diacetyl)beta-cyclodextrin and especially heptakis(2,3-O-diacetyl-6-sulfo)beta-cyclodextrin could resolve all four pairs of enantiomers in one run. UV and NMR spectroscopic measurements revealed various kinds of complexes of phenethylamines with the CDs. Either defined inclusion complexes or manifold complexes which are mostly characterized by an attachment of the analyte to the outside of the CD cavity were found. No correlation between the kind of complexation and the resolution observed by means of CE could be found.

Cyclodextrins↗