Preparation and study on the solid inclusion complex of ciprofloxacin with beta-cyclodextrin

The interaction of ciprofloxacin with beta-cyclodextrin (betaCD) has been studied by several analytical techniques, including 1H-NMR (nuclear magnetic resonance),13C-NMR, fluorescence spectroscopy, infrared (IR) spectroscopy, thermal analysis, and scanning electron microscope. In this paper, solid inclusion complex of ciprofloxacin with beta-CD was synthesized by the coprecipitation method. In addition, the characterization of the inclusion complex has been proved by fluorimetry, IR, differential scanning calorimetry and 1D, 2D NMR. The experimental results confirmed the existence of 1:1 inclusion complex of ciprofloxacin with beta-CD. The formation constant of complex was determined by fluorescence method and 1H-NMR. Spatial configuration of complex has been proposed on two dimensional NMR technique.     

Preparation and study on the solid inclusion complex of sparfloxacin with HP-beta-cyclodextrin

The interaction of sparfloxacin with HP-beta-cyclodextrin (HP-beta-CD) has been studied by several analytical techniques, including 1H NMR, fluorescence spectroscopy, infrared spectroscopy, thermal analysis and scanning electron microscopy. In this paper, solid inclusion complex of sparfloxacin with HP-beta-CD was synthesized by the coprecipitation method. In addition, the characterization of the inclusion complex has been proved by fluorimetry, infrared, differential scanning calorimetry and 1D, 2D NMR. The experimental results confirmed the existence of 1:1 inclusion complex of sparfloxacin with HP-beta-CD. The formation constant of complex was determined by the fluorescence method and 1H NMR. Spacial configuration of complex has been proposed on 2D NMR technique.     

Preparation and spectroscopic studies of an inclusion complex of adenine with beta-cyclodextrin in solution and in the solid state

The interaction between adenine and beta-CD has been investigated in solution and in the solid state by several analytical techniques, primarily by 1H-NMR, 2D ROESY and fluorescence spectra, and secondarily by other important techniques, for example, Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The association constant and 1:1 nature of the complex between adenine and beta-CD in solution were determined by fluorescence spectroscopy. A spatial configuration for the complex in solution is proposed from analysis of the 1H-NMR and 2D ROESY data. The Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) data are consistent with the formation of an inclusion complex. In addition, a solid inclusion complex of adenine with beta-CD was synthesized by the coprecipitation method.     

Preparation and study on the solid inclusion complex of cloxacillin sodium with beta-cyclodextrin

The interaction of cloxacillin sodium with beta-cyclodextrin (beta-CD) has been studied by several analytical techniques, including (1)H NMR, fluorescence spectroscopy, infrared spectroscopy. In this paper, solid inclusion complex of cloxacillin sodium with beta-CD was synthesized by the coprecipitation method. In addition, the characterization of the inclusion complex has been proved by fluorimetry, infrared spectroscopy and 1D, 2D NMR. The experimental results confirmed the existence of 1:1 inclusion complex of cloxacillin sodium with beta-CD. The formation constant of complex was determined by fluorescence method and (1)H NMR. Spacial configuration of complex has been proposed on 2D NMR technique.     

Preparation and study on the novel solid inclusion complex of ciprofloxacin with HP-beta-cyclodextrin

The interaction of ciprofloxacin with HP-beta-cyclodextrin (HP-beta-CD) has been studied by several analytical techniques, including 1H nuclear magnetic resonance (NMR), 13C NMR, fluorescence spectra, infrared spectroscopy, thermal analyzer and scanning electron microscope. In this paper, solid inclusion complex of ciprofloxacin with HP-beta-CD was synthesized by the coprecipitation method. In addition, the characterization of the inclusion complex has been proved by fluorimetry, infrared, differential scanning calorimetry and one-dimensional (1D), 2D NMR. The experimental results confirmed the existence of 1:1 inclusion complex of ciprofloxacin with HP-beta-CD. The formation constant of complex was determined by fluorescence method and 1H NMR. Spacial configuration of complex has been proposed on two-dimensional NMR technique.     

Dual fluorescence of N-phenylanthranilic acid: Effect of solvents, pH and beta-cyclodextrin

Spectral characteristics of N-phenylanthranilic acid (NPAA) have been studied in different solvents, pH and beta-cyclodextrin (beta-CD) and compared with anthranilic acid (2-aminobenzoic acid, 2ABA). In all solvents a dual fluorescence is observed in NPAA, whereas 2ABA gives single emission. Combining the results observed in the absorption, fluorescence emission and fluorescence excitation spectra, it is found that strong intramolecular hydrogen bonding (IHB) interactions present in NPAA molecule. The inclusion complex of NPAA with beta-CD is analysed by UV-vis, fluorimetry, FT-IR, (1)H NMR, scanning electron microscope and AM 1 method. The above spectral studies show that NPAA forms a 1:1 inclusion complex with beta-CD and COOH group present in the beta-CD cavity. A mechanism is proposed to explain the inclusion process.     

Preparation and spectral investigation on inclusion complex of beta-cyclodextrin with rutin

Solid inclusion complex of rutin with beta-cyclodextrin (beta-CD) was prepared by coprecipitate method. The formation of inclusion complex was confirmed by differential scanning calorimetry (DSC) and X-ray diffraction. The formation constant was obtained by steady-state fluorescence measurements and the result suggested the complex preferred 1:1 (rutin:CD) stoichiometry. Furthermore, the spatial configuration of the complex has been proposed based on NMR and molecular modeling.     

Preparation and characterization of inclusion complexes of pefloxacin mesylate with three kinds of cyclodextrins

The ability of alpha-cyclodextrin, beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin (alpha-CD, beta-CD and HP-beta-CD) to break pefloxacin mesylate (PM) aggregates by forming inclusion complexes has been studied using 1H NMR (nuclear magnetic resonance spectroscopy), 13C NMR and fluorescence spectra. The inclusion constants are determined to compare the corresponding inclusion capacity. Solid-inclusion complexes of PM with CDs are synthesized by coprecipitation method, and all the inclusion ratios are found to be 1:1. Additionally, spatial characterization of complexes has been proposed based on two-dimensional nuclear magnetic resonance technique (2D NMR) and spatial conformation is also investigated to propose two possible models between PM and CDs.     

Study on the supramolecular system of 5-(p-hydroxyphenyl)-10,15,20-tris-(4-chlorophenyl)porphyrin with cyclodextrins and its analytical characteristics

The supramolecular systems of 5-(p-hydroxyphenyl)-10,15,20-tris-(4-chlorophenyl)porphyrin (p-HTClPP) with beta-cyclodextrin (beta-CD), heptakis(2,3,6-tri-O-methyl)-beta-CD (TM-beta-CD), carboxymethyl-beta-cyclodextrin (CM-beta-CD) and sulfurbutylether-beta-CD (SBE-beta-CD) have been investigated by means of absorption, fluorescence and (1)H NMR spectroscopy. The formation of inclusion complexes has been confirmed on the base of changes of spectroscopy properties. "The double reciprocal method" has been used to determine the stoichiometry and the inclusion constants of p-HTClPP with the four cyclodextrins (CDs). The results show that p-HTClPP can form 1:1 inclusion complexes with the four CDs. Compared with parent native beta-CD, the inclusion abilities of modified beta-CDs with p-HTClPP are stronger. It indicates that the hydrophobic effect plays an important role in the inclusion procedure. The mechanism of inclusion interaction was examined by (1)H NMR technique. During the study of p-HTClPP-TM-beta-CD supramolecular complex, an efficient enhancement of fluorescence intensity was observed. Based on this phenomenon, fluorometric method for the determination of p-HTClPP was developed. The relationship between fluorescence intensity and the concentration of p-HTClPP is linear from 1.0 x 10(-9) to 7.0 x 10(-6)mol L(-1). The limit of detection is 8.3 x 10(-10)mol L(-1) and the relative standard deviation (R.S.D.) is 1.3% (n=8). This research will provide useful information for further application of p-HTClPP.     

Dual fluorescence of syringaldazine

The absorption and fluorescence spectra of syringaldazine (SYAZ) has been recorded in solvents of different polarity, pH and beta-cyclodextrin (beta-CD) and compared with syringaldehyde (SYAL). The inclusion complex of SYAZ with beta-CD is investigated by UV-vis, fluorimetry, AM 1, FT-IR, (1)H NMR and scanning electron microscope (SEM). DeltaG value suggests the inclusion process is an exothermic and spontaneous. In all solvents a dual fluorescence is observed for SYAZ, whereas, SYAL shows a dual luminescence only in polar solvents. The excitation spectra for the 410 nm is different from 340 nm indicate two different species present in this molecule. In pH solutions: (i) a large red shifted maxima is observed in the dianion and is due to large interactions between the aromatic ring and (ii) the large blue shift at pH approximately 4.5, is due to dissociation of azine group and formation of aldehyde. beta-CD studies reveal that, SYAZ forms a 1:2 complex from 1:1 complex with beta-CD.     

Molecular modeling (MM2 and PM3) and experimental (NMR and thermal analysis) studies on the inclusion complex of salbutamol and beta-cyclodextrin

The inclusion complex of salbutamol and beta-cyclodextrin (beta-CD) is studied by computational (MM2 and PM3) and experimental techniques. Molecular modeling calculations predict two different orientations of salbutamol in the beta-CD cavity in vacuo and in aqueous solution. In vacuo calculations show that the introduction of the aromatic ring of salbutamol is preferred to the introduction of the tert-butyl group into the beta-CD cavity. However, in aqueous solution both computational methods predict the introduction of the alkyl chain instead of the aromatic ring in the beta-CD cavity contrary to experimental results published previously. These quantitative predictions were experimentally confirmed here by studying the inclusion complex in solution by NMR. A 1:1 stoichiometry was found by (1)H NMR studies for this complex. A 2D ROESY (rotating-frame Overhauser enhancement spectroscopy) experiment shows that there are no cross-peaks between the aromatic protons of salbutamol and any of the protons of beta-CD. Cross-peaks for the protons of the tert-butyl group and protons inside the cavity of beta-CD demonstrate the full involvement of this group in the complexation process and confirm the orientation of the complex predicted by molecular modeling. The solid-state complex was prepared and its stoichiometry (beta-CD.C(13)H(21)NO(3).8H(2)O) and dissociation process studied by thermogravimetric analysis.     

Structure and intramolecular flexibility of beta-cyclodextrin complex with (-)-epigallocatechin gallate in aqueous solvent

The probable structure of the inclusion complex of beta-cyclodextrin (beta-CD) and (-)-epigallocatechin gallate (EGCg) in D2O was investigated using several NMR techniques. EGCg formed a 1:1 complex with beta-CD, in which the A ring and a portion of the C ring of EGCg were included at the head of the phenolic hydroxyl group attached to C7 of EGCg in the beta-CD cavity from the wide secondary hydroxyl group side. In the 1:1 complex with beta-CD, EGCg maintained the conformation in which the B and B' rings of EGCg took pseudoequatorial and pseudoaxial positions with respect to the C ring, respectively. The structure of the inclusion complexes of beta-CD and EGCg obtained from NMR experiments supported those determined from AM1 semiempirical SCF MO calculations well.     

Study on the interaction of 5-pyridine-10,15,20-tris-(p-chlorophenyl)porphyrin with cyclodextrins and DNA by spectroscopy

The interaction of 5-pyridine-10,15,20-tris-(p-chlorophenyl)porphyrin (PyTPP) with beta-CD and TM-beta-CD were examined by UV-vis absorption, fluorescence and (1)H NMR spectroscopy. PyTPP prefers to form the 1:1 inclusion complex with TM-beta-CD but hardly form inclusion complex with beta-CD. An inclusion constant (K) for the formation of PyTPP-TM-beta-CD inclusion complex has been evaluated to be 4.4x10(3)L/mol from the absorbance changes. This K value is nearly the same as that 4.5x10(3)L/mol obtained from the fluorescence intensity changes. Compared to beta-CD, the inclusion ability of TM-beta-CD with PyTPP is stronger. It indicates that the hydrophobic effect plays an important role in the inclusion procedure. The mechanism of inclusion interaction was carried out by 1H NMR technique. Furthermore, the interaction of PyTPP with DNA is shown here. It can bind DNA by out-side stacking along the DNA helix but not by intercalation because of the high electron density in the porphyrin core. The binding constant and binding number of PyTPP to DNA are 4.3x10(3) and 1.3, respectively. The interaction of PyTPP with DNA was further carried out in the presence of TM-beta-CD. The significant decrease of the binding constant and binding number were observed and the interaction of porphyrin-bound DNA has been inhibited, which was due to the fact that PyTPP inter into the cavity of TM-beta-CD and influence binding affinity of PyTPP to DNA.     

Spectroscopic investigations and crystal structure from synchrotron powder data of the inclusion complex of beta-cyclodextrin with atenolol

Inclusion complexes of atenolol with beta-cyclodextrin (beta-CD) in aqueous solution have been investigated with (1)H NMR and UV-vis spectroscopy. The stoichiometry of this inclusion complex was established to be equimolar (1:1) and its stability constant was determined by UV-vis spectroscopy. The crystal structure of the beta-CD-atenolol (1:1) inclusion compound has been solved from synchrotron powder diffraction data using direct-space search techniques. The crystal structure model and (1)H NMR data are in good agreement and, with support of Hyperchem MM+ molecular dynamics results, suggest which protons are likely to be involved in the inclusion process that leads to the supramolecular architecture of this guest-host complex.     

Study on inclusion interaction of piroxicam with beta-cyclodextrin derivatives

The inclusion behavior of piroxicam (PX) with beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and carboxymethyl-beta-cyclodextrin (CM-beta-CD) was investigated by using steady-state fluorescence and nuclear magnetic resonance (NMR) technique. The various factors affecting the inclusion process were examined in detail. The remarkable fluorescence emission enhancement upon addition of CDs suggested that cyclodextrins (CDs) were most suitable for inclusion of the uncharged species of PX. The stoichiometry of the PX-CDs inclusion complexes was 1:1, except for beta-CD where a 1:2 inclusion complex was formed. The formation constants showed the strongest inclusion capacity of beta-CD. NMR showed the inclusion mode of PX with CDs.     

Study of the interaction between a nonyl phenyl ether and beta-cyclodextrin: declouding nonionic surfactant solutions by complexation

Absorption and fluorescence measurements for aqueous solutions at 298 K containing pentaoxyethylene nonyl phenyl ether (NPE5), in the absence and presence of beta-cyclodextrin (beta-CD), were analyzed to determine the effect of the complexation on the aggregation of the surfactant. For the binary system, the appearance of a new emission band and the presence of an isoemissive point in the emission spectra at the time and frequency domains indicate the formation of an excimer within the micellar core. The addition of beta-CD induces the formation of an inclusion complex strong enough to break the aggregates and avoid the excimer formation. For the ternary system, the increase in fluorescence has been used to assess the binding constants of 1:1 + 2:1 stoichiometries. Static light scattering, 1H NMR diffusion-ordered spectroscopy (DOSY), and two-dimensional rotating-frame Overhauser enhancement spectroscopy (ROESY) experiments were used to characterize the cloud point of NPE5 at 298 K, and to ascertain the effects of complexation on the clouding process. In the presence of beta-CD, the analysis of the 1H NMR spectra and the self-diffusion coefficients reveal the existence of interactions between the beta-CD and the aggregates that increase the cloud-point concentration more than expected. Under conditions of excess of beta-CD, ROE enhancements point to a complex of dominant 2:1 stoichiometry (beta-CD:NPE5) in which the hydrophobic moiety of the surfactant threads two beta-CDs.     

NMR characterization of the host-guest inclusion complex between beta-cyclodextrin and doxepin

The interaction between doxepin, a member of the tricyclic antidepressant (TCA) class of drugs, with beta-cyclodextrin (beta-CD) was investigated using NMR. Several TCAs have been reported to form a complex with beta-CD having 1:1 stoichiometry. Previous results from UV-visible spectroscopy, fluorescence measurements, and molecular modeling indicated that for imipramine, desipramine, and amitriptyline, the TCA aliphatic tail is included in the cyclodextrin cavity with apparently no interaction of the tricyclic ring. An alternative view of the doxepin-beta-CD complex is presented in this work using analysis of complexation-induced chemical shifts (CICSs), the method of continuous variation (Job's analysis), and analysis of ROESY spectra. The Job's plot derived from the NMR spectral data confirms that the complex formed has 1:1 stoichiometry. The largest changes in the CICS data were observed for the aromatic protons of one of the doxepin rings, with much smaller chemical shift changes observed for the protons of the other aromatic ring and the doxepin tail. Perhaps the most significant evidence for inclusion of the doxepin tricyclic ring is the strong ROESY cross peaks between the doxepin aromatic resonances and the protons located inside the beta-CD cavity. Changes in the doxepin (1)H NMR spectrum and the behavior of ROESY exchange cross peaks suggest that inclusion complex formation decreases the rate of internal motions of doxepin.     

Thermodynamic study on the effects of beta-cyclodextrin inclusion with berberine.

The fluorescence enhancement of berberine (Berb) as a result of complex with beta-cyclodextrin (beta-CD) is investigated. The association constants of alpha-CD and beta-CD with Berb are 60 and 137 M(-1) at 20 degrees C in pH 7.20 aqueous solution. Effects of temperature on the forming inclusion complexes of beta-CD with Berb have been examined through using fluorescence titration. Enthalpy and entropy values calculated from fluorescence data are -33.7 kJ mol(-1) and 74.3 J x mol(-1) K(-1) respectively. It was found that the dielectric constant of beta-CD cavity is about 24 in a rough analogy with absolute alcohol. These results suggest that the extrusion of 'high energy water' molecules from the cavity of beta-CD and hydrophobic interaction upon the inclusion complex formation are the main forces of the inclusion reaction. Effect of pH on the association of beta-CD with Berb was also studied. Mechanism of the inclusion of beta-CD with Berb is further studied by absorption and NMR measurements. Results show that beta-CD forms a 1:1 inclusion complex with Berb.     

Molecular recognition thermodynamics and structural elucidation of interactions between steroids and bridged bis(beta-cyclodextrin)s

A series of bridged bis(beta-cyclodextrin(CD))s (2-7) were synthesized, i.e., bridged bis(beta-CD)s 2 and 3 bearing binaphthyl or biquinoline tethers and bridged bis(beta-CD)s 4-7 possessing dithiobis(benzoyl) tether, and their complex stability constants (KS), enthalpy (DeltaH degrees), and entropy changes (DeltaS degrees) for the 1:2 inclusion complexation with representative steroids, deoxycholate, cholate, glycocholate, and taurocholate, have been determined in an aqueous phosphate buffer solution of pH 7.20 at 298.15 K by means of titration microcalorimetry. The original conformations of bridged bis(beta-cyclodextrin)s were investigated by circular dichroism and 1H ROESY spectroscopy. Structures of the inclusion complexes between steroids and bridged bis(beta-CD)s in solution were elucidated by 2D NMR experiments, indicating that anionic groups of two steroid molecules penetrate, respectively, into the two hydrophobic CD cavities in one 6,6'-bridged bis(beta-CD) molecule from the secondary rim to give a 1:2 binding mode upon inclusion complexation. The results obtained from titration microcalorimetry and 2D NMR experiments jointly demonstrate that bridged bis(beta-CD)s 2, 3 and 5-7 tethered by protonated amino group possessing different substituted groups can enhance not only the molecular binding ability toward steroids by electrostatic interaction but also molecular selectivity. Thermodynamically, the resulting 1:2 bis(beta-CD)-steroid complexes are formed by an enthalpy-driven process, accompanied by smaller entropy loss. The increased complex stability mainly results from enthalpy gain, accompanied by large conformational change and extensive desolvation effects for the 1:2 inclusion complexation between bis(beta-CD)s and steroids.     

Synthesis and characterization of beta-cyclodextrin inclusion complex containing di(8-hydroxyquinoline) magnesium

The beta-cyclodextrin (beta-CD) inclusion complex containing di(8-hydroxyquinoline)magnesium was prepared. The product was characterized by NMR, IR, differential thermal thermogravimetric analysis (DT-TGA), spectrofluorimetry, and elemental analysis, indicating the formation of inclusion complex in which the quinoline rings of the guest were encapsulated within the beta-CD cavities. The Job's method provided 2:1 stoichiometry for the inclusion complex between beta-CD and di(8-hydroxyquinoline)magnesium. The association constant calculated with the modified Benesi-Hildebrand equation at 25 degrees C was determined. And the mean association constant was 3577 (L/mol)2, R.S.D. was 2.58%. The thermal stability and solubility of di(8-hydroxyquinoline)magnesium were improved when forming inclusion complex.