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CD Complex (cd + complex)
Selected AbstractsDetermination of the binding constants of modafinil enantiomers with sulfated ,-cyclodextrin chiral selector by capillary electrophoresis using three different linear plotting methodsELECTROPHORESIS, Issue 17 2010Khaldun M. Al Azzam Abstract Binding constants for the enantiomers of modafinil with the negatively charged chiral selector sulfated-,-CD (S-,-CD) using CE technique is presented. The calculations of the binding constants employing three different linearization plots (double reciprocal, X -reciprocal and Y -reciprocal) were performed from the electrophoretic mobility values of modafinil enantiomers at different concentrations of S-,-CD in the BGE. The highest inclusion affinity of the modafinil enantiomers were observed for the S -enantiomer,S-,-CD complex, in agreement with the computational calculations performed previously. Binding constants for each enantiomer,S-,-CD complex at different temperatures, as well as thermodynamic parameters for binding, were calculated. Host,guest binding constants using the double reciprocal fit showed better linearity (r2>0.99) at all temperatures studied (15,30°C) and compared with the other two fit methods. The linear van't Hoff (15,30°C) plot obtained indicated that the thermodynamic parameters of complexation were temperature dependent for the enantiomers. [source] Synthesis and Electrochemical Study of an Original Copper(II)-Capped Salen,Cyclodextrin ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2010Elise Deunf Abstract A new metallocapped cyclodextrin (CD) was synthesized by the regioselective debenzylation, induced by diisobutylaluminium hydride (DIBAL-H), of perbenzylated cyclodextrins. This reaction allowed for the efficient preparation of an unprecedented CD,salen type copper(II) complex. The electrochemical behavior of both the bound and unbound CD,salen compounds was investigated by cyclic voltammetry. Notably, it was shown that the presence of tert -butyl groups at the ortho - and para -positions of the salen aromatic rings stabilized the copper(II) phenoxyl radical species that was generated upon the one-electron oxidation of the starting compound. Importantly, this stabilization remained effective when the salen-type ligand was covalently attached to the CD. This allowed for investigations of the reactivity of the copper(II) phenoxyl radical complex towards a primary alcohol to be performed by cyclic voltammetry. This reaction can be considered as mimicking the behavior of galactose oxidase. However, under these conditions, no reactivity was observed in the presence of benzyl alcohol. This may be due to distortion, either of the initially square planar salen ligand after its grafting to the CD primary face, and/or of the CD itself. On the other hand, the electrochemical reduction of the un-grafted copper(II) salen-type ligand led to a transient anionic species that exhibited significant stability on the time-scale of the slow cyclic voltammetry measurement in the absence of the CD, but was unstable in the presence of the CD. In the latter case, it was demonstrated that the anionic species was protonated by the CD. Importantly, this protonation was not fast enough to prevent catalytic activation of iodomethane by the electro-generated copper(I)-capped salen CD complex. [source] Controlled and complete release of a model poorly water-soluble drug, prednisolone, from hydroxypropyl methylcellulose matrix tablets using (SBE)7m -,-cyclodextrin as a solubilizing agentJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2001Venkatramana M. Rao Abstract Sustained-release formulations such as hydroxypropyl methylcellulose (HPMC)-based hydrophilic matrix tablets of poorly water-soluble drugs often result in incomplete release because of the poor solubility and dissolution rate of the drug in the hydrophilic matrix. Sulfobutylether-,-cyclodextrins ((SBE)7M -,-CDs) have been known to improve the solubility of such drugs by forming inclusion complexes. The present paper deals with the modification of drug release from an HPMC-based matrix tablet of a sparingly water-soluble drug, prednisolone (PDL), using (SBE)7M -,-CD as a solubilizing agent. Tablets were prepared by direct compression of a physically mixed PDL, (SBE)7M -,-CD, and polymer. On exposure to water, an in situ PDL:(SBE)7M -,-CD complex was formed in the gel layer, and enhanced drug release relative to a control formulation was observed (lactose used as the excipient instead of (SBE)7M -,-CD ). Other possible changes due to the incorporation of (SBE)7M -,-CD in the formulation were also probed. Incorporation of (SBE)7M -,-CD lead to a higher water uptake relative to the control (lactose) formulation. For a fixed total tablet weight, polymer type, and loading, the drug release rate appeared to depend on the molar ratio of (SBE)7M -,-CD to PDL and not the absolute amount of (SBE)7M -,-CD present in the matrix tablet. This work shows that incorporation of (SBE)7M -,-CD into the matrix tablets could be considered in designing a sustained-release tablet of poorly water-soluble drugs. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:807,816, 2001 [source] Metastatic Crohn's disease: a reviewJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 9 2008I Palamaras Abstract Metastatic Crohn's disease (MCD) indicates the presence of non-caseating granuloma of the skin at sites separated from the gastrointestinal tract by normal tissue and is the least common dermatologic manifestation of CD. In adults, MCD usually appears after the initial diagnosis of CD in 70% of cases, whereas in children, it appears at the same time as CD in almost half of the cases. The most frequent skin lesions in adults are nodules, plaques with or without ulceration on the extremities and ulcers on the genitals. In children, genital swelling with or without erythema is the most frequent presentation of MCD. Simultaneous presence of perianal CD affects more females (60%) and particularly children. Associated gastrointestinal symptoms are present in one third of the cases in adults and in half of the cases in children. Treatment is often unsatisfactory. Randomised controlled trials are lacking. Various chemotherapeutic agents have been used such as oral metronidazole, topical and/or oral steroids, azathioprine, cyclosporine, sulfasalazine, tetracyclines, topical or systemic tacrolimus, infliximab alone or with methotrexate, and surgical treatment with oral zinc sulphate. MCD represents another ,great imitator'. This reviews the most relevant characteristics of this disease, in order to increase awareness and to avoid delay in diagnosis and improve management of the whole CD complex. [source] Improved efficacy and tolerability of retinoic acid in acne vulgaris: a new topical formulation with cyclodextrin complex ,JOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 4 2004RY Anadolu ABSTRACT Objectives, Retinoic acid (RA) has long been used, both topically and systemically, for disorders of keratinization, acne and related disorders. In the present study, the efficacy and tolerability of topical RA prepared as a cyclodextrin beta complex (,-CD) is investigated in 66 acne vulgaris patients. Methods, This randomized, double-blind, placebo-controlled study compares nightly topical application of RA/,-CD complex hydrogel formulation (0.025%), RA/,-CD complex in moisturizing base (0.025%), hydrogel base, moisturizer base or a commercial RA gel (0.05%) in acne vulgaris patients. Improvement of acne was assessed using a 5-point improvement scale and by measuring sebum and moisture content of the skin using an SM 810 sebumeter/corneometer. Results, After 3 months of treatment, mean scores of acne improvement on the 5-point scale were 4 with the RA/,-CD complex hydrogel formulation, 4.1 with the RA/,-CD complex in moisturizing base, 1.2 with hydrogel placebo base, 1.1 with moisturizer placebo base and 3 with the commercial RA product. All patients treated with the commercial product experienced local side-effects. One patient discontinued due to severe irritation. None of the patients treated with the RA/,-CD complex in the moisturizing base and hydrogel formulation experienced significant local irritation, although the sebum content of the skin decreased after application of the RA/,-CD preparations. This change was not significant compared to controls. The moisture content of the skin was better preserved in the group treated with the RA/,-CD complex in the moisturizing base. Conclusion, The topical RA/,-CD complex, in hydrogel and moisturizing base, was more effective than the twice concentrated commercial RA product. There were few topical side-effects with this new formulation, which increases patient compliance. Topical RA/,-CD (0.025% RA) did not significantly reduce sebum secretion but may help to preserve optimum epidermal moisture content with the proper base formulation. This is the first study in the literature reporting efficacy and tolerability of the topical RA/,-CD complex in acne vulgaris. We conclude that the topical RA/,-CD complex displays an improved efficacy and tolerability profile and is an effective treatment alternative for acne vulgaris. [source] Photo-induced polymerization of methyl methacrylate/cyclodextrin complex in aqueous solutionPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11 2008Jianping Deng Abstract Polymerization of hydroxypropyl- , -cyclodextrin (HP- , -CD) complex of methyl methacrylate (MMA) (MMA/HP- , -CD) was carried out under UV irradiation in aqueous solution with Irgacure 2959 (4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone) as a photoinitiator at room temperature. The effects of some principal factors, including UV irradiation intensity, initiator concentration, and the ratio of HP- , -CD to MMA, on the polymerization were investigated in detail. Compared to the corresponding thermal polymerization, photo-induced polymerization of the MMA/HP- , -CD complex could be accomplished at a higher speed; the polymerization conversion in photo-induced polymerization reached 94% within 30,min, while it was only 62% for the thermal polymerization of 16,hr at 70°C. The number-average molecular weight (Mn) and polymerization conversion decreased with the increase in UV intensity and initiator concentration. The resulting PMMA precipitated spontaneously from the solution during polymerization in the absence of any precipitator. About 95,wt% of the HP- , -CD remained in the solution after polymerization and the reusability of the residual HP- , -CD was experimentally demonstrated. Copyright © 2008 John Wiley & Sons, Ltd. [source] Effect of urea on analyte complexation by 2,6-dimethyl-,-CD in peptide enantioseparations by CEELECTROPHORESIS, Issue 21 2009Manuela Hammitzsch-Wiedemann Abstract The aim of the present study was the investigation of the effect of urea on analyte complexation in CD-mediated separations of peptide enantiomers by CE in the pH range of about 2,5. pH-independent complexation and mobility parameters in the absence and presence of 2,M urea were obtained by three-dimensional, non-linear curve fitting of the effective analyte mobility as a function of pH and heptakis-(2,6-di- O -methyl)-,-CD concentration. Urea led to decreased binding strength of the CD towards the protonated and neutral analyte enantiomers as well as to decreased mobilities of the free analytes. In contrast, mobilities of the fully protonated enantiomer,CD complexes as well as the pKa values of the free and complexed analytes increased. The effect of urea on separation efficiency varied with pH and CD concentration. In the case of Ala-Tyr and Ala-Phe, separations improved in the presence of urea at pH 2.2. In contrast, separations were impaired by urea at pH 3.8 and low concentrations of the CD. Decreased separation efficiency was noted for Asp-PheOMe and Glu-PheNH2 at low CD concentrations when urea was added but separations improved at higher CD concentrations over the entire pH range studied. The effect of urea on analyte complexation appeared to be primarily non-stereoselective. Furthermore, the pH-dependent reversal of the enantiomer migration order observed for Ala-Tyr and Ala-Phe can be rationalized by the complexation and mobility parameters. [source] Gas phase isomeric differentiation of oleanolic and ursolic acids associated with heptakis-(2,6-di- O -methyl)-,-cyclodextrin by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2010Zhan Yu Abstract Oleanolic acid (OA) and ursolic acid (UA) are isomeric triterpenoid compounds with similar pharmaceutical properties. Usually, modern chromatographic and electrophoretic methods are widely utilized to differentiate these two compounds. Compared with mass spectrometric (MS) methods, these modern separation methods are both time- and sample-consuming. Herein, we present a new method for structural differentiation of OA and UA by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with the association of heptakis-(2,6-di- O -methyl)-,-cyclodextrin (DM-,-CD). Exact MS and tandem MS (MS/MS) data showed that there is no perceptible difference between OA and UA, as well as their ,-cyclodextrin and ,-cyclodextrin complexes. However, there is a remarkable difference in MS/MS spectra of DM-,-CD complexes of OA and UA. The peak corresponding to the neutral loss of a formic acid and a water molecule could only be observed in the MS/MS spectrum of the complex of DM-,-CD : OA. Molecular modeling calculations were also employed to further investigate the structural differences of DM-,-CD : OA and DM-,-CD : UA complexes. Therefore, by employing DM-,-CD as a reference reagent, OA and UA could be differentiated with purely MS method. Copyright © 2010 John Wiley & Sons, Ltd. [source] Inclusion Behavior of ,-Cyclodextrin with Bipyridine Molecules: Factors Governing Host-Guest Inclusion GeometriesCHEMISTRY - AN ASIAN JOURNAL, Issue 3 2009Yan-Li Zhao Dr. Abstract Guest Effect: The differences of nitrogen atom positions and the bridge bonds linked to two pyridine rings of some bipyridine guests can significantly affect the binding abilities and inclusion geometries of ,-cyclodextrin with the guests in both the solution and solid states. The 1:1 complexation of ,-cyclodextrin (,-CD) with structurally similar bipyridine guests which lead to the formation of six inclusion complexes (1,6) of ,-CD with 4,4,-vinylenedipyridine, 2,2,-vinylenedipyridine, 1-(2-pyridyl)-2-(4-pyridyl)ethylene, 4,4,-ethylene-dipyridine, 4,4,-dithiodipyridine, and 2,2,-dithiodipyridine has been investigated comprehensively by X-ray crystallography in the solid state and by 1H,NMR spectroscopy and microcalorimetric titration in aqueous solution. The complex formation constants (KS) for the stoichiometric 1:1 host,guest inclusion complexation of ,-CD with the bipyridine derivatives were determined in aqueous solution by microcalorimetry and the host,guest inclusion geometries of the complexes were deduced from 1H ROESY NMR spectroscopy. It transpires that the guest bipyridine molecules are included in the ,-CD cavity with a range of different inclusion geometries. In the solid state, the crystal superstructures for the ,-CD complexes 1, 4, and 5 are characterized by the triclinic crystal system (space group P1) commensurate with AAAA type supramolecular aggregation. By contrast, the ,-CD complexes 2, 3, and 6 display either monoclinic (space group P21) or orthorhombic (space group C2221) crystal systems, characteristic of ABAB type supramolecular aggregation. The results demonstrate that the relative locations of the nitrogen atom positions and the bridge-bond links between the two pyridine rings in these bipyridine guests, not only lead to distinct crystal systems and space groups, but also to different binding geometries and thermodynamical parameters on complexation of the bipyridines with ,-CD. The knowledge obtained from this research improves our understanding of the molecular recognition and self-assembly processes exhibited by ,-CD, both in the solid state and in aqueous solution. [source] Using glycidyl methacrylate as cross-linking agent to prepare thermosensitive hydrogels by a novel one-step methodJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2008Jianping Deng Abstract A novel one-step approach is reported to prepare thermosensitive hydrogels simply by using hydroxypropyl-,-cyclodextrin (HP-,-CD)/glycidyl methacrylate (GMA)/N -isopropylacrylamide (NIPAM) system. From GMA and HP-,-CD, HP-,-CD/GMA inclusion complex was prepared and identified with NMR, FTIR, and UV-vis spectroscopies. GMA in the form of HP-,-CD/GMA complex was copolymerized with NIPAM in water with K2S2O8 as initiator, yielding hydrogels designated as poly(NIPAM-CD-GMA). The inclusion of CD in the hydrogels was confirmed by FTIR spectroscopy. The contents of CD and GMA placed considerable influence on the swelling ratio and temperature-sensitivity of the produced hydrogels. The hydrogels bearing CD moieties showed higher swelling ratio and temperature-sensitivity when compared with that without CD. The porous structure of the hydrogels containing CD was observed in the SEM images. Relevant mechanism of the ring-opening reaction of epoxide groups in GMA, the subsequent crosslinking reactions and the formation of hydrogels containing CD moieties were proposed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2193,2201, 2008 [source] A capped trigonal prismatic cadmium complex with tetra- and tridentate ligands: bis(triethanolamine)-,3N,O,O,;,4N,O,O,,O,,-cadmium(II) squarate monohydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2004brahim Uçar In the crystal structure of the title compound, [Cd(C6H15NO3)2](C4O4)·H2O, a supramolecular structure is observed. The asymmetric unit consists of one unit of the cationic Cd complex, one water molecule and two half-squarate anions, each sitting on a crystallographic inversion center. The different coordinations of the two triethanolamine (TEA) ligands results in an unusual example of coordination number seven for the CdII ion. Both TEA ligands coordinate to the CdII ion, forming a distorted monocapped trigonal prismatic geometry with approximate C2v symmetry. One of the TEA ligands acts as an N,O,O,-tridentate ligand, whereas the other behaves as an N,O,O,,O,,-tetradentate donor. The anions and cations are linked to one another by hydrogen bonds between hydroxy H atoms of the TEA ligands and squarate O atoms. The crystal structure is stabilized by O,H,O hydrogen bonds between the unligated water molecule and a squarate O atom, together with a weak ,,ring interaction between the ethylene group of a TEA ligand and a squarate anion. [source] Effect of water on zinc (II), cadmium (II) complexes with pyridylimidazole: Theoretical study of stability and electronic spectrumINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2006Yi Liao Abstract The geometry structures of complexes such as [Zn(PIm)2(H2O)] and [Cd(PIm)2(H2O)2] [PIm = (2-(2,-pyridyl) imidazole)] are optimized by density functional theory (DFT) B3LYP methods. On the basis of their stable structures, the stability of the coordinated water existing in the complexes is analyzed quantitatively in terms of the interaction between the central metal and the coordinated water. The interaction energy of the Zn pyridylimidazole complex increased obviously by considering the intermolecular hydrogen bond (OH,N). The theoretical calculation well explained penta- and hexa-coordinated conformation, respectively, in Zn and Cd pyridylimidazole complexes. The spectral properties of the Zn Cd complexes have been studied by time-dependent density functional theory (TD-DFT). The calculation results show that the coordinated waters in Cd complexes have little effect on their spectral properties. While the axially coordinated waters in Zn pyridylimidazole cause a red shift in the absorption wavelength and change the pattern of charge transfer as a result of the effect of polarization from intermolecular hydrogen bond. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Preparation of budesonide/,-cyclodextrin complexes in supercritical fluids with a novel SEDS methodJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2006Tarja Toropainen Abstract The aim was to investigate if solid drug/cyclodextrin complexes could be produced in a single-step process with a solution enhanced dispersion by supercritical fluids (SEDS) method. Budesonide and ,-cyclodextrin (CD) solutions (50% or 99.5% ethanol) were pumped from the same (conventional method) or separate (modified method) containers together with supercritical carbon dioxide through a coaxial nozzle into a particle formation chamber. The pressure was maintained at 100, 150 or 200 bar with a temperature of 40, 60 or 80°C. SEDS-processed powders were characterised with HPLC, DSC and XRPD for budesonide content, complexation and crystallinity. The budesonide dissolution rate was determined in 1% ,-CD aqueous solution. Solid, white budesonide/,-CD complex particles were formed using the conventional and modified SEDS processes. The complexation efficiency was dependent on the processing conditions. For example, with the conventional method (100 bar, 60°C) the yield of the powder was 65,±,12% with 0.14,±,0.02 mg budesonide/mg powder, corresponding to 1:2 drug:CD molar ratio. The dissolution rate of this complexed budesonide (93,±,2% after 15 min) was markedly higher compared to unprocessed micronised budesonide (41,±,10%) and SEDS-processed budesonide without CD (61,±,3%). As a conclusion, SEDS is a novel method to produce solid drug/CD complexes in a single-step process. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:2235,2245, 2006 [source] | |||||||||||||