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PubMed2005

Melarsoprol-cyclodextrins inclusion complexes.

Melarsoprol, a water-insoluble drug, is mainly used in the treatment of trypanosomiasis and has demonstrated an in vitro activity on myeloid and lymphoid leukemia derived cell lines. It is marketed as a very poorly tolerated non-aqueous solution (Arsobal). The aim of our work was to develop melarsoprol-cyclodextrin complexes in order to improve the tolerability and the bioavailability of melarsoprol. Phase-solubility analysis showed A(L)-type diagrams with beta-cyclodextrin (betaCD), randomly methylated beta-cyclodextrin (RAMEbetaCD) and hydroxypropyl-beta-cyclodextrin (HPbetaCD), which suggested the formation of 1:1 inclusion complexes. The solubility enhancement factor of melarsoprol (solubility in 250 mM of cyclodextrin/solubility in water) was about 7.2x10(3) with both beta-cyclodextrin derivatives. The 1:1 stoichiometry was confirmed in the aqueous solutions by the UV spectrophotometer using Job's plot method. The apparent stability constants K(1:1), calculated from mole-ratio titration plots, were 57 143+/-4 425M(-1) for RAMEbetaCD and 50 761+/-5 070 M(-1) for HPbetaCD. Data from 1H-NMR and ROESY experiments provided a clear evidence of inclusion complexation of melarsoprol with its dithiaarsane extremity inserted into the wide rim of the cyclodextrin torus. Moreover, RAMEbetaCD had a pronounced effect on the drug hydrolysis and the dissolution rate of melarsoprol. However, the cytotoxic properties of melarsoprol on K562 and U937 human leukemia cell lines was not modified by complexation.

Antineoplastic Agents↗
PubMed2005

Cationic-modified cyclodextrin nanosphere/anionic polymer as flocculation/sorption systems.

Simultaneous removal of dissolved and colloidal substances has been a challenging task. The cationic-modified beta-cyclodextrin nanospheres synthesized in this work, in conjunction with a water-soluble polyacrylamide-based anionic polymer, potentially provide a novel approach to address the problem. The cyclodextrin was rendered cationic using (2,3-epoxypropyl)trimethylammonium chloride as a reagent. The cationicity of the modified cyclodextrin and the reaction between cyclodextrin and the reagent were characterized by electrophoresis measurement, polyelectrolyte titration, and NMR. As a dual-component flocculation system, the cationic cyclodextrin/anionic polymer significantly induced clay flocculation, lowering the relative turbidity of the clay suspension over a wide pH range. Meanwhile, as a nanospherical absorbent, the modified cyclodextrins exhibited strong affinity toward aromatic compounds via inclusion complex formation in the hydrophobic cavities, which was monitored by UV spectroscopy. These systems facilitated the simultaneous removal of dissolved and colloidal substances, which was unachievable previously. In addition, the interaction between anionic polymers and the clay particles pretreated with cationic cyclodextrin was investigated in order to reveal the flocculation mechanism.

Acrylic Resins↗
PubMed2004

Cyclodextrin-enhanced solubilization of pentachlorophenol in water.

The solubilization of pentachlorophenol (PCP) by beta-cyclodextrin (beta-CD) and three of its most used derivatives, methyl-beta-cyclodextrin (MCD), hydroxypropyl-beta-cyclodextrin (HPCD) and carboxymethyl-beta-cyclodextrin (CMCD), has been investigated. The formation of soluble inclusion complexes between PCP and cyclodextrin (CDs) increases the aqueous solubility of PCP. Due to the ionizable nature of PCP, the effects of pH and ionic strength on the equilibrium complexation were evaluated. All CDs were found to form 1:1 inclusion complexes. Equilibrium constants calculated from solubility enhancement experiments revealed that the stability of the complexes was dependent on the polarity of the compound, on the ionic strength and on the cyclodextrin type. In general, weaker equilibrium constants were observed for PCP with beta-CD than with MCD or CMCD. For all CDs, the complexation or the solubilization efficiency of PCP (weak acid) depended on pH and ionic strength. Moreover, we observed that the solubility of the beta-CD/PCP complex was lower than that of the beta-CD molecule and dependent on the ionic strength of the solution. Although the equilibrium constant of PCP/CD complex was found to be higher at pH 3 than at pH 7 in water, extraction of PCP from porous media by a CD solution at neutral pH would be achievable due to the higher PCP aqueous solubility in neutral/basic media.

Cyclodextrins↗
PubMed2003

Stereoselective phosphorylation of branched cyclodextrins with inorganic cyclo-triphosphate.

The phosphorylation by inorganic sodium cyclo-triphosphate (P(3m)) having a six-membered ring was examined for cyclomaltohexaose (alpha-cyclodextrin) and branched cyclodextrins (mono-6-O-alpha-D-glucopyranosylcyclomaltohexaose, mono-6-O-alpha-D-maltosylcyclomaltohexaose, mono-6-O-alpha-D-glucopyranosylcyclomaltoheptaose, and mono-6-O-alpha-D-maltosylcyclomaltoheptaose) in aqueous solution. For all cyclomaltooligosaccharides (cyclodextrins) studied, the 2-OH group was stereoselectively phosphorylated. In the reaction of branched cyclodextrins and P(3m), only the 2-OH on the alpha-D-glucopyranosyl group of the cyclodextrin rings was phosphorylated with maximum yields of more than 27%. The phosphorylation mechanism of branched cyclodextrins with P(3m) is also discussed.

Cyclodextrins↗
PubMed2001

Rapid enantiomeric separation of polychlorinated biphenyls by electrokinetic chromatography using mixtures of neutral and charged cyclodextrin derivatives.

Electrokinetic chromatography with cyclodextrin derivatives (CD-EKC) was used to achieve the rapid enantiomeric separation of chiral polychlorinated biphenyls (PCBs). Thirteen of the 19 chiral PCBs stable at room temperature were individually separated into their two enantiomers by using 2-morpholinoethanesulfonic acid (MES) buffer (pH 6.5) containing carboxymethylated gamma-cyclodextrin (CM-gamma-CD) as pseudostationary phase mixed with beta-cyclodextrin (beta-CD) or permethylated beta-cyclodextrin (PM-beta-CD). Urea was also added to increase the solubility of PCBs and cyclodextrins in the aqueous separation buffer. Several experimental parameters such as the nature, concentration, and pH of the buffer, nature and concentration of the cyclodextrin derivatives used, and the addition of different additives were studied in order to improve the enantiomeric separation. In addition, the effect of some instrumental parameters such as separation temperature and applied voltage was also investigated. PCBs were enantiomerically separated in less than 12 min by using a 50 mM MES buffer (pH 6.5) containing 20 mM CM-gamma-CD, 10 mM beta-CD or 20 mM PM-beta-CD, and 2 M urea at a temperature of 45 degrees C and an applied voltage of 20 kV.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2003

Cyclodextrin-based liquid chromatographic enantiomeric separation of chiral dihydrofurocoumarins, an emerging class of medicinal compounds.

A set of 28 racemic dihydrofurocoumarins in which the stereogenic center is located in the furan ring have been synthesized. Currently no effective asymmetric synthesis of this class of compounds exists, although their enantiomers are produced biologically by certain plants. Their diverse medicinal properties are being investigated in several laboratories. The enantioselective separation of these dihydrofurocoumarins by three native and six derivatized cyclodextrins has been evaluated in the reversed-phase mode, the polar organic mode, and normal-phase mode. The hydroxypropyl-beta-cyclodextrin is the most effective chiral stationary phase (CSP) at separating the dihydrofurocoumarins into enantiomers, showing some enantioselectivity for 22 dihydrofurocoumarins, and baseline resolving 16 of the 28 compounds in the reversed-phase mode. The acetyl-beta-cyclodextrin and 2,3-dimethyl-beta-cyclodextrin also showed enantioselectivity for a large number (18 and 17, respectively) of dihydrofurocoumarins in the reversed-phase mode. The native cyclodextrins are ineffective and the aromatic derivatized beta-cyclodextrins are only marginally effective at separating the furocoumarin enantiomers in the reversed-phase mode. The polar organic mode and the normal-phase mode have also been evaluated with these CSPs, but no enantioseparations were observed.

Coumarins↗
PubMed1998

Interaction between cyclodextrins and aflatoxins Q1, M1 and P1. Fluorescence and chromatographic studies.

The fluorescence properties of the aflatoxins M1, Q1, P1 in solution and the effect of various cyclodextrins (alpha-, beta-, gamma-, hydroxypropyl-beta- and alpha-beta-heptakis-di-O-methyl-beta-) on their fluorescence emission were studied. Among the aflatoxins, a substantial enhancement of the fluorescence emission of aflatoxin Q1 in the presence of aqueous solutions of alpha-, beta-, hydroxypropyl-beta, and alpha-beta-heptakis-di-O-methyl-beta-cyclodextrin, was observed. On the contrary, gamma-cyclodextrin proved to be inefficient to enhance the fluorescence properties of this compound. No important fluorescence enhancement was found for aflatoxins P1 or M1 for any of the cyclodextrin derivatives tested. The complex formation constant (Kf) of these compounds with beta-cyclodextrin was chromatographically determined, and from the results obtained, we can conclude that Kf cannot be used alone to explain the fluorescence increase. Thermodynamic studies showed that delta-H and delta-S parameters, associated with the partition of aflatoxins in RP-HPLC, increased when beta-cyclodextrin was added to the eluent.

Aflatoxin M1↗
PubMed1999

Cyclodextrin inclusion: catalytic effects on the degradation of organophosphorus pesticides in neutral aqueous solution.

alpha-, beta and gamma-Cyclodextrins were found to have promotive inclusion-catalytic effects on the degradation of organophosphorus pesticides solubilized in neutral aqueous media. Pesticide degradations were especially accelerated in such systems as alpha-cyclodextrin plus diazinon and beta-cyclodextrin plus chloropyrifos. The above findings are in contrast with the inhibitive catalytic effects of cyclodextrins on pesticide degradations in alkaline media. Cyclodextrin catalytic effects found here were considerably affected by differences in the substitutional and hetero-cyclic properties of the aromatic rings of pesticides and also by the sizes of cyclodextrin cavities.

Acetone↗
PubMed1999

Cyclodextrins and carrier systems.

This paper describes two new possibilities of using cyclodextrins to increase water solubility and bioavailability of poorly water-soluble drugs intended for targeting delivery by the oral or the parenteral route. They use either amphiphilic cyclodextrin nanoparticles or polymeric nanoparticles containing cyclodextrins. Amphiphilic skirt-shaped cyclodextrins, resulting from the esterification of primary hydroxyl groups by hydrocarbon chains varying from C6 to C14, are capable of forming spontaneously nanoparticles which have been loaded with a series of steroid drugs. The drug in the amphiphilic cyclodextrin nanoparticles is molecularly dispersed and can be released very rapidly. Poly(isobutylcyanoacrylate) nanoparticles can be loaded with natural or hydroxypropyl cyclodextrins. This technique results in a significant increase in the loading capacity of nanoparticles with a series of steroids and in a very rapid release of the drug. Both methods are described as well as their potential interest for water-insoluble drugs.

Administration, Oral↗
PubMed2002

Comparative studies of the influence of cyclodextrins on the stability of the sunscreen agent, 2-ethylhexyl-p-methoxycinnamate.

The effects of beta-cyclodextrin (beta-CD) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the base-catalyzed degradation and light-induced decomposition of the sunscreen agent, trans-2-ethylhexyl-p-methoxycinnamate (trans-EHMC) were investigated. Reversed-phase liquid chromatography was used to study the interaction between natural and modified cyclodextrins, added to the mobile phase, and the sunscreen. Among the available cyclodextrins (beta-CD, HP-beta-CD, hydroxypropyl-alpha-cyclodextrin and hydroxypropyl-gamma-cyclodextrin), only HP-beta-CD and beta-CD produced a significant decrease in the chromatographic retention of trans-EHMC. The complexation of the sunscreen agent with HP-beta-CD and beta-CD was confirmed by thermal analysis and nuclear magnetic resonance spectroscopy. beta-CD depressed the decomposition of trans-EHMC in alkaline solutions more effectively than HP-beta-CD. Moreover, the irradiation-induced degradation of the sunscreen agent in emulsion vehicles was reduced by complexation with beta-CD (the extent of degradation was 26.1% for the complex compared to 35.8% for free trans-EHMC) whereas HP-beta-CD had no significant effect. Therefore, the complex of beta-CD with trans-EHMC enhances the chemical- and photo-stability of the sunscreen agent. Moreover, it limits adverse interactions of the UV filter with other formulation ingredients.

Chemistry, Pharmaceutical↗
PubMed2003

Complex formation of sericoside with hydrophilic cyclodextrins: improvement of solubility and skin penetration in topical emulsion based formulations.

The main objective of this study was to devise novel methods for improving the solubility of the anti-inflammatory triterpenoid sericoside, the main component of Terminalia sericea extract, thus enabling its incorporation into topical formulations. Sericoside was stabilized by complex formation with hydrophilic derivatives of beta- and gamma-cyclodextrins in a molar ratio of 1.0:1.1. The complex of extract and cyclodextrin was equilibrated in water at 25 degrees C for approximately 24 h. The dehydrated complexes of T. sericea extract and cyclodextrin were characterized by differential scanning calorimetry, thermogravimetry analysis and X-ray diffraction. Complex formation with beta-cyclodextrin as well as gamma-cyclodextrin derivatives was detectable using these three analytical tools; however, only complexes with gamma-cyclodextrin derivatives showed stability upon storage after incorporation into topical o/w or w/o formulations. Furthermore, a T. sericea extract/gamma-cyclodextrin complex incorporated in an o/w formulation resulted in a 2.6-fold higher percutaneous penetration of sericoside in in vitro excised pig skin as compared to pure T. sericea extract. For the first time, the virtually insoluble anti-inflammatory active sericoside was incorporated into a topical emulsion based formulation in a stable manner, resulting in efficient skin penetration.

Administration, Topical↗
PubMedDate not supplied

Molecular binding behavior of pyridine-2,6-dicarboxamide-bridged bis(beta-cyclodextrin) with oligopeptides: switchable molecular binding mode.

Bridged bis(beta-cyclodextrin) 1 with a pyridine-2,6-dicarboxamide linker was synthesized, and its inclusion complexation behavior with some aliphatic oligopeptides was investigated in aqueous buffer solution of pH 2.0 and 7.2 at 25 degrees C by means of circular dichroism, fluorescence, and 2D NMR techniques. The results show that the resulting inclusion complexes of 1 with oligopeptides adopt a cooperative "cyclodextrin-guest-cyclodextrin" sandwich binding mode in a neutral media, but a "guest-linker-cyclodextrin" coinclusion binding mode in an acidic media. These switchable binding modes consequently rationalize the binding ability of bis(beta-cyclodextrin) 1 at different pH values; that is, 1 shows the stronger association with oligopeptides in a neutral media. Because of the simultaneous contributions of hydrophobic, hydrogen bond, and electrostatic interactions, bis(beta-cyclodextrin) 1 affords length-selectivity up to 4.7 for the Gly-Gly/Gly-Gly-Gly pair at pH 2.0 and sequence-selectivity up to 4.2 for the Gly-Leu/Leu-Gly pair at pH 7.2. These phenomena are discussed from the viewpoint of the size-fit concept and the multipoint recognitions between host and guest.

Binding Sites↗
PubMed2004

Hydration of black foam films made of amphiphilic cyclodextrins.

We investigate the interfacial behavior of a new type of amphiphilic cyclic oligosaccharide obtained by grafting a phospholipid onto a methylated cyclodextrin. These compounds are able to form stable black foam films, the structure of which can be determined using X-ray reflectivity. These films consist of a highly hydrated bilayer of modified cyclodextrins which are remarkably thick due to their abundant hydration core. In the present paper, we explore the influence of cyclodextrin hydration on the film structure. The hydration rate of the films is tuned by changing the cyclodextrin methylation, by binding the modified cyclodextrins to various molecules (complex formation) and by exposing the films to IR radiation. In addition, we show that the gas permeability of these phospholipidyl-cyclodextrin films is governed by their central layer of bound water, which is an efficient barrier against gas permeation.

Color↗
PubMed2004

Methyl-beta-cyclodextrin inhibits cell growth and cell cycle arrest via a prostaglandin E(2) independent pathway.

Methyl-beta-cyclodextrin, a cyclic oligosaccharide known for its interaction with the plasma membrane induces several events in cells including cell growth and anti-tumor activity. In this study, we have investigated the possible role of cyclooxygenase 2 (COX-2) in cell growth arrest induced by methyl-beta-cyclodextrin in Raw264.7 macrophage cells. Methyl-beta-cyclodextrin inhibited cell growth and arrested the cell cycle, and this cell cycle arrest reduced the population of cells in the S phase, and concomitantly reduced cyclin A and D expressions. Methyl-beta-cyclodextrin in a dose- and time-dependent manner, also induced COX-2 expression, prostaglandin E(2) (PGE(2)) synthesis, and COX-2 promoter activity. Pretreatment of cells with NS398, a COX-2 specific inhibitor completely blocked PGE(2) synthesis induced by methyl-beta-cyclodextrin, however inhibition on cell proliferation and cell cycle arrest was not effected, suggesting non-association of COX-2 in the cell cycle arrest. These results suggest that methyl-beta-cyclodextrin induced cell growth inhibition and cell cycle arrest in Raw264.7 cells may be mediated by cyclin A and D1 expression.

Animals↗
PubMed2003

The utility of cyclodextrins in lipase-catalyzed transesterification in organic solvents: enhanced reaction rate and enantioselectivity.

The use of enzymes as valuable catalysts in organic solvents has been well documented. However, some of their features limit their application in organic synthesis, especially the frequently lower enzyme activity under nonaqueous conditions, which constitutes a major drawback in the application of enzymes in organic solvents. In addition, many enzymatic reactions are subject to substrate or product inhibition, leading to a decrease in the reaction rate and enantioselectivity. To overcome these drawbacks and to make enzymes more appealing to organic chemists, we demonstrate the use of cyclodextrins as regulators for the Pseudomonas cepacia lipase (PSL) and macrocyclic additives to enhance the reaction rate and enantioselectivity E in lipase-catalyzed enantioselective transesterification of 1-(2-furyl)ethanol in organic solvents. Both reaction rate and enantioselectivity were significantly enhanced by several orders of magnitude when using co-lyophilized lipase in the presence of cyclodextrins. The effect of cyclodextrin derivatives as well as solvents on the improvement of the reaction parameters has been studied. The observed enhancement was tentatively interpreted in terms of their ability to give a certain flexibility to the enzyme and to form a host-guest complex, thus avoiding product inhibition and leading to enhancement of the reaction rate and enantioselectivity. The effect of cyclodextrin additives on the enzyme morphology has been studied using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) of the co-lyophilized lipase with cyclodextrins. The ability of cyclodextrins to form a host-guest complex to avoid product inhibition, which leads to the observed enhancement, has been proved by NOESY, COSY, 13C and 1H NMR.

Catalysis↗
PubMed2005

Acetylenic cyclodextrins for multireceptor architectures: cups with sticky ends for the formation of extension wires and junctions.

A mono-6-O-propargyl permethylated beta-cyclodextrin, 3, has been prepared by two synthetic routes as a versatile building block for the construction of cyclodextrin dimers and trimers with a core junction which is potentially electron conducting. Glaser-Hay coupling of 3 gave beta-cyclodextrin dimer 6, and Pd(0)-catalysed coupling allowed the preparation of a cyclodextrin dimer with a 1,4-phenylene bridge, 7, and a cyclodextrin trimer based on a 1,3,5-trisubstituted benzene, 8. All compounds have been fully characterised, and in particular, detailed analysis by 2D NMR spectroscopic techniques has provided useful insight into the identities of the compounds. The detailed full characterisation of mono-3,6-anhydro-heptakis(2,3-O-methyl)-hexakis(6-O-methyl)-beta-cyclodextrin, 5, is also described. Product 5 is formed during the methylation of compound 3, and its formation was found to be sensitive to the reaction conditions. The absorption and fluorescence spectra of the phenylene-bridged dimer 7 and trimer 8 are also reported. They show different properties of the excited state based on the different electronic coupling imposed by the phenylene core.

Acetylene↗
PubMed2007

Monomeric creatine kinase aggregation and sodium dodecyl sulfate-cyclodextrin assisted refolding.

The monomeric state of creatine kinase (CK) was stably captured at the equilibrium state by employing cysteine residue modifications in the presence of a denaturant, and at a partially folded state. The partially folded monomeric CK (PF-CK) was aggregated with kinetic order, which was mainly caused by the hydrophobic surface interactions between the CK subunits. The artificial chaperone, described as a SDS-cyclodextrin, was applied to prevent aggregation as well as to refold the PF-CK: SDS treatment onto the monomeric CK can significantly block aggregation and can be successfully refolded in the solutions containing cyclodextrins and DTT. Three types of cyclodextrins such as alpha-, beta-, and gamma-cyclodextrins were applied to strip SDS from the enzyme molecule, and each kinetic course was measured. The intrinsic fluorescence changes showed that reactivation occurred and this accompanied the conformational changes. The size exclusion chromatography detected the variously trapped monomeric CKs such as the thiol residue modified PF-CK, the SDS-binding PF-CK, the cyclodextrin treated PF-CK, and the DTT treated SDS-binding PF-CK. Our study demonstrated monomer CK aggregation for the first time; we also demonstrated the complex reassociation of CK during refolding with the aid of the SDS-cyclodextrin, and these pathways followed first-order kinetics.

Animals↗
PubMed2003

Potential use of cyclodextrins to enhance the solubility of YM466 in aqueous solution.

Various solubilizing agents for YM466, a new Factor Xa inhibitor, were investigated to begin designing the aqueous formulation for subcutaneous administration. The tentative target concentration was 5 mg/mL. First, three kinds of buffer solutions (glycine-HCl, citrate, and lactate) were examined for their solubilizing effects. The dissolution rate of YM466 in lactate buffer was the fastest, as determined by visual examination at room temperature. The dissolution rate of YM466 in lactate buffer was enhanced, without degradation, by heating at 40 degrees C, and YM466 solution at a concentration of 1 mg/mL became transparent 10 min after the start of heating. The solubility of YM466 increased along with lactate concentrations ranging from 50 mM to 200 mM and reached a high of 1.3 mg/mL after increasing lactate concentration to 200 mM at 5 degrees C. The addition of cyclodextrins beta-cyclodextrin (beta-CD), 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and gamma-cyclodextrin (gamma-CD), but not alpha-cyclodextrin (alpha-CD), had remarkable impact on its solubility, and 7-8 mg/mL of YM466 was dissolved by the addition of HP-beta-CD or gamma-CD. These results demonstrated that YM466 was included in cyclodextrins and that the inclusion formations required a cavity size larger than alpha-CD. Based on the calculation from the linear portion of the phase solubility diagrams, apparent stability constants of alpha-CD, beta-CD, HP-beta-CD, and gamma-CD at 5 degrees C were estimated to be 2M(-1), 206M(-1), 143M(-1), and 276M(-1), respectively. Therefore, we found that gamma-CD has the largest inclusion capacity.

Chromatography, High Pressure Liquid↗