Inclusion Complexation of Carbaryl and β-Cyclodextrin in Solution and in the Solid State

This study was carried out with the aim ofinvestigating the interactions between-cyclodextrin and carbaryl, a carbamatepesticide, and their effect on some physico-chemicalproperties of carbaryl, such as aqueous solubility andlipophilicity. The interactions between carbaryl and-cyclodextrin were thoroughly investigated bothin solution and in the solid state. The effect of-cyclodextrin on the aqueous solubility ofcarbaryl was evaluated by the phase solubility method.The amount of carbaryl dissolved increased linearlywith the addition of -cyclodextrin according toan A_L type plot and without precipitation of thecomplex. The apparent stability constant of thecomplex was 289 ± 21 M^-1, assuming a 1 : 1stoichiometry; this value was confirmed by a methodbased on circular dichroism measurements.Equimolar carbaryl/-cyclodextrin solid systemswere prepared by physical-mixing and freeze-drying,and fully characterised by Differential ScanningCalorimetry, X-ray powder diffractometry and FourierTransform Infra-Red analysis. The results of the solidstate study demonstrated that the freeze-drying methodyields a system with a high degree of amorphisationand yields an inclusion complex.The dissolution profile of the pesticide was affectedby the physico-chemical properties of each solidsystem, the freeze-dried form dissolving more rapidly. However, the physical association of-cyclodextrin and carbaryl enhanced the aqueoussolubility of the insecticide as well.     

Interaction between Sulfaproxyline and β-Cyclodextrin in the Solution and Solid States

The 1 : 1 inclusion complex between sulfaproxyline (SP) and -cyclodextrin (-CD) was prepared by the freeze-drying and the kneading method. Complex formation was confirmed in the solid state by X-ray diffractometry and by infrared spectroscopy. The interaction between sulfaproxyline and -cyclodextrin in solution was studied by the solubility method and 13C-NMR spectroscopy. Phase solubility studies in water revealed a AN type diagram and a stability constant of 930 ± 120 M-1 for a 1 : 1 inclusion complex was derived. Complexation was found to improve the dissolution rate of sulfaproxyline.     

Pseudorotaxanes of β-Cyclodextrin with Diamino End-functionalized Oligo-phenyl and -benzyl Compounds in Solution and in the Solid State

-Cyclodextrin forms a 1:1 host:guest inclusion complex ([2]pseudorotaxane) with 4-[2-(4-aminophenyl)ethyl]-benzenamine (1) in water as determined by 1D and 2D NMRexperiments. In the crystalline state, the structure of the complex has revealed a 2:2 stoichiometry, with two CD molecules forming head-to-head dimers byH-bonds between the secondary O3 hydroxyl groups and enclosing two molecules of the guest. The packing mode of the present complex is encountered for the first time, since it does not belong to any of the four known packing types of the dimeric CD inclusion complexes. On the other hand,N ¹,N ⁴-bis(4-aminophenyl)-1,4-benzenedimethanamine 2), which is longer than 1 by a phenylene diamine unit, has not afforded any crystals, at present, however it threads into CD in aqueous solution forming most probably [2]- and [3]pseudorotaxanes. The solution structures and the equilibria in this system are investigated.     

Structure of the β-Cyclodextrin·p-Hydroxybenzaldehyde Inclusion Complex in Aqueous Solution and in the Crystalline State

-Cyclodextrin (-CD) and p-hydroxybenzaldehyde (p-HB) were studied by ¹H-NMR in deuterated aqueous solution and the stoichiometry of the resulting complex (1:1) was determined by the continuous variation method. Inclusion of p-HB in -CD was confirmed by the observation of NMR shifts for the inside H5 protons of the -CD cavity. In the solid state X-ray analysis was carried out and revealed the detailed structure of the inclusion complex. Two -CDs cocrystallize with four p-HB and 9.45 water molecules[2(C₆H₁₀O₅)^7·4C₇H₆O_2·9.45H₂O] in the triclinic space group P1 with unit cell parameters: a = 15.262(2), b = 15.728(1), c = 16.350(1) Å, = 92.67(1)°, = 96.97(1)°, = 103.31(1)°. The anisotropic refinement of 1973 atomic parameters converged at an R-factor = 0.066 for 10157 data with F_o ² > 2 (F_o ²). The 2:4 stoichiometry for the -CD inclusion complex with p-HB in the crystalline state is different from that obtained in solution. -CD forms dimers stabilized by direct O2(m)₁O3(m)₁·O2(n)₂O3(n)₂ hydrogen bonds (intradimer) and by indirect O6(m)₁·O6(n)₂ hydrogen bonds with one or two bridging water molecules joined in between (interdimer). These dimers are stacked like coins in a roll constructing infinite channels where the p-HB molecules are included. The p-HB molecules direct their polar CHO and OH groups into the nonpolar -CD cavities and are hydrogen bonded to each other, yielding infinite, antiparallel chains. In addition, crystals of the complex were also investigated with thermogravimetry, vibrational spectroscopy (FTIR), and ¹³C CP-MAS NMR spectroscopy. The results obtained enabled us to structurally characterize the -CD inclusion complex with p-HB.     

Interaction of Hydroxy Acids with β-Cyclodextrin

The solubility of -cyclodextrin (-CD) was studied in aqueous solutions of various organic acids. The hydroxy acids, especially citric and tartaric acid were found to increase the solubility of -CD, while some other carboxylic acids reduced it. From solubility data the apparent complex association constants were calculated.     

Stability of Mefenamic Acid in the Inclusion Complex with β-Cyclodextrin in the Solid Phase

The inclusion complex of mefenamic acid with -cyclodextrin was obtained by the method of coprecipitation from diethyl ether. The product was identified by the thermogravimetric and X-ray methods. The complex stability constants were determined by the potentiometric method. The effect of -CD on the solubility and stability of mefenamic acid was analysed.     

Influence of Substituents in β-Cyclodextrin on the Interaction of Levofloxacin–β-Cyclodextrin Complexes with Liposomal Membrane

Colloid Journal - The effect of substituents (polar CH2CH(OH)CH3, hydrophobic CH3, and charged $${{\left( {{\text{C}}{{{\text{H}}}_{{\text{2}}}}} \right)}_{{\text{4}}}}{\text{SO}}_{3}^{ - }$$ ) in...     

The Interaction of β-Cyclodextrin with Benzoic Acid

The interaction of β-cyclodextrin with benzoic acid was studied by UV and IR spectroscopy, X-ray diffraction, and thermogravimetry. The introduction of the benzoic acid molecule into the internal hydrophobic β-cyclodextrin cavity and additional stabilization by weak H-bonds caused the formation of 1: 1 axial inclusion complexes of the host—guest type. The degree of crystallinity of the inclusion complex decreased compared with the initial compounds, whereas its thermal stability increased.     

Supramolecular Interaction of Primaquine with Native β-Cyclodextrin

The supramolecular host–guest inclusion complex of Primaquine (PQ) with the nano-hydrophobic cavity of beta-cyclodextrin (β-CD) was prepared by physical mixing, kneading and co-precipitation methods. The formation of an inclusion complex in PQ with β-CD in the solution phase has been confirmed by UV–visible and fluorescence spectroscopy. The stoichiometry of the inclusion complex is 1:1; the Primaquine molecule is deeply entrapped in the cavity of β-cyclodextrin, which was confirmed by analysis of spectral shifts and corresponding absorbance and fluorescence intensities. The Benesi–Hildebrand plot was used to calculate the binding constant of the inclusion complex of PQ with β-CD at room temperature. The Gibbs energy change of the inclusion complex process has been calculated. The \( {\text{p}}K_{\text{a}} \) and \( {\text{p}}K_{\text{a}}^{*} \) for the monocation and neutral equilibrium of PQ in aqueous and β-CD media are discussed. The thermal stability for the inclusion complex of PQ with β-CD has been analyzed using differential scanning calorimetry. The modification of the crystal structure to amorphous for the solid inclusion complex was confirmed by powder X-ray diffraction. The structure of the complex is proposed by docking studies using the Patch-Dock server. A cytotoxic analysis was also carried out for the pure PQ and its solid complex on the MDA MB 231 cell line and showed that the activity is good for both substances. The cytotoxicity neither improved nor decreased with the formation of the inclusion complex with β-CD.     

Interaction of Fluorinated Alcohols with the β-Cyclodextrin/Acridine Complex

Abstract

The role of hydrogen bonding vs. hydrophobic interactions are evaluated with respect to the driving forces for alcohol complexation with β-cyclodextrin (β-CD). Simultaneous information is gathered regarding these considerations in the binding of acridine to the β-CD molecule.     

Analytical Study of β-Irradiated Antibiotics in the Solid State

This paper reports results of the study on the influence of β-irradiation on the physical and chemical properties of selected salts of β-lactam antibiotics in solid state (sodium salt: ampicillin, azlocillin, benzylpenicillin, carbenicillin and piperacillin; potassium salt of benzylpenicillin, ampicillin anhydricum, ampicillin trihydricum, amoxicillin trihydricum and bacampicillin hydrochloride). The source of irradiation was a linear accelerator of electrons, and the irradiation effects were checked on the basis of the following: determination of mass, melting point and water contrent, and spectrophotometric (UV, IR) chromatographic and thermal (DTG, DSC) studies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Temperature of the Liquid–Glass Transition and Microhard State of Amorphous Substances in the Model of Delocalized Atoms

Russian Journal of Physical Chemistry A - Using the model of delocalized atoms, an explanation is offered for the linear dependence of the microhardness of inorganic glasses on their glass...     

Study on the Supramolecular Interaction of β-Cyclodextrin with Gemfibrozil by Spectrofluorimetry and Its Analytical Application

The supramolecular interaction of gemfibrozil with β-cyclodextrin （β-CD） was studied by spectrofluorimetry. The mechanism of the inclusion was discussed by spectrofluoremetry, infrared spectrum and ^1H NMR spectrum. The results showed that a 1 ： 1 （β-CD ： gemfibrozil） complex was formed with an apparent association constant of 3.844 × 10^3 L·mol^-1. Based on the enhancement of the fluorescent intensity of gemfibrozil, a spectrofluorimetric method for the determination of gemfibrozil in bulk aqueous solution in the presence of β-CD was developed. The linear range was 3.30 ng·mL^- 1 -6.00 ug·mL^-1 with the detection limit of 0.980 ng·mL^-1. There was no interference from the excipients normally used in tablet composition and the serum main compositions. The proposed method was then successfully applied to the determination of gemfibrozil in capsules and serum.     

Spectroscopic Study on Interaction of β-Cyclodextrin with Triprolidine Hydrochloride

The complexation of triprolidine hydrochloride （TRP） and β-cyclodextrin （β-CD） in deuterium oxide was investigated by 400 MHz 1^H NMR spectroscopy. The 800 MHz 2D ROESY data revealed that two 1 ：1 and one 2 ： 1 β-CD-TRP inclusion complexes were formed. Both aromatic moieties （p-tolyl and pyridyl ring） has entered into the β-CD cavity, confirming the existence of two different equilibria for 1 ： 1 inclusion complexes in which p-tolyl ring of the guest is more tightly held by the host cavity. The ROE intermolecular interactions provided the plausible structures of these 1 ： 1 and 2 ： 1 stoichiometric inclusion complexes of β-CD-triprolidine hydrochloride in solu- tion.     

Regression Analysis for the Host–Guest Interaction of β-Cyclodextrin with Mono- and 1,4-Disubstituted Benzenes

A multiple regression model was generated, which can satisfactorily estimate the association constants (K _a ) for the inclusion complexation of -cyclodextrin with mono- and 1,4-disubstituted benzenes. It was found that lnK K _a was correlated with the substituent molar refraction (R _m ), hydrophobic constant () and Hammett constant ) of the guest compounds with a correlation coefficient of 0.95. The main driving forces for -cyclodextrin complexation was concluded to consist of van der Waals forces and hydrophobic interactions, while the influence of electronic effects was small.     

Enantiomeric Separation of Drugs Using Ion Interaction Reagents in Combination with β-Cyclodextrin in HPLC

This work describes the use of β-cyclodextrin (β-CD) as a mobile phase additive in combination with ion interaction reagents (IIR) for the enantioresolution of cyclopentolate, 2,6-diketopiperazine derivative and methylphenobarbital. The effect of concentration and type of IIR and temperature on retention and enantioseparation were studied. It has been found that the addition of an IIR to β-CD solution can lead to the improvement in enantioresolution. Interestingly, the most significant enhancement of enantioresolution was achieved for cyclopentolate, most probably due to its highest basicity. Also the stability constants of the complexes formed between β-CD and model compounds in the presence of IIR were estimated. Significant increase of complexation rate of cyclopentolate with β-cyclodextrin in presence of IIRs was observed.     

Studies of the Interaction of the Salicylideneserinatecopper(II) Complex with β-Cyclodextrin: Characterization and Reactivity of the Inclusion Compound

The compound formed by the copper-Schiff base complex salicylideneserinatecopper(II), [Cu(sal-ser)(H2O)], interacting with -cyclodextrin was prepared, and characterized in the solid state by infrared, UV-visible and EPR spectroscopies, X- ray diffraction, and thermoanalytical techniques. The catalytic activity of this compound, [Cu(sal-ser)CD], in the decomposition of hydrogen peroxide, and in the dismutation of superoxide radicals was also verified, in comparison with the reactivity of the free complex, in aqueous solution. In both cases, a decreasing in the reaction rate was observed for the CD-containing compound. The results of structural characterization, in addition to the substantial differences observed in the catalytic activities of the compounds, are indicative of partial insertion of the copper complex in the cavity of the oligosaccharide.     

Study of the Supramolecular Inclusion of β-Cyclodextrin with Andrographolide

An inclusion complex of -cyclodextrin with andrographolide (Andro) was prepared by using a convenient new method of microwave irradiation. The structure of the inclusion complex was determined by UV and IR analyses as well as ¹H NMR, ¹³C NMR and two dimensional NOE spectroscopic measurements. The results indicated that the possible stoichiometry of complex formation is 1:1 (guest:host ratio) and the two isomeric 1:1 inclusion complexes are present simultaneously in solution. Thermal studies proved the thermal stability of the inclusion complex.     

Synthesis and Characterization of Polymer Brushes Containing β-Cyclodextrin Grafted to Magnetic Nanoparticles for Determination of Naproxen in Urine

β-Cyclodextrin containing polymer brushes were grafted to magnetic nanoparticles following free radical copolymerization of N,N-dimethylacrylamide and allyl glycidyl ether on the surface. The products were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, and transmission electron microscopy and employed for solid phase extraction of naproxen in human urine. The profile of the naproxen adsorbed by the nanoparticles demonstrated high accessibility of the β-cyclodextrin. Scatchard analysis indicated that the capacity of the nanoparticles was 112 µmol g^?1 at 25°C and a pH of 5. The adsorption data of naproxen were considered by Langmuir, Freundlich, Redlich–Peterson, and Temkin isotherms. Approximately 55% of naproxen was released in simulated gastric fluid in 30 min and 94% in simulated intestinal fluid in 30 h. These data have indicated the utility of the naproxen loaded- β-cyclodextrin containing polymer brushes grafted to magnetic nanoparticles for enteric drug delivery.