Highly sensitive and selective spectrofluorimetric determination of tolnaftate through the formation of ternary inclusion complex of beta-naphthol/beta-cyclodextrin/anionic surfactant system

An indirect spectrofluorimetric method with high sensitivity and selectivity was developed for the determination of antifungal drug: tolnaftate (TNF), depending on the supramolecualr multirecognition interaction among the anionic surfactant sodium laurylsulfate (SLS), β-cyclodextrin (β-CD) and β-naphthol (ROH). The mechanism of the inclusion was studied and discussed by means of fluorescence spectrum, infra-red spectrograms and ¹HNMR spectroscopy. Results showed that the naphthalene ring of ROH and the hydrophobic hydrocarbon chain of SLS were included into the β-CD's cavity to form a ROH:SLS:β-CD ternary inclusion complex with stoichiometry of 1:1:1 at room temperature, which provided effective protection for the excited state of ROH. At λ_ex/λ_em = 273/360 nm, the fluorescence intensity was linear over a tolnaftate concentration range of 2.46 × 10⁻⁹ to 2.10 × 10⁻⁶ mol L⁻¹. The detection limit and relative standard deviation was 7.50 × 10⁻¹⁰ mol L⁻¹ and 1.4%, respectively. The interference of 31 foreign substances was slight. The proposed method had been successfully applied to the determination of tolnaftate in artificial mixed samples with almost quantitative recovery.     

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.     

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.     

Study of inclusion complex formation between tropaeolin OO and beta-cyclodextrin by spectrophotometry and Infrared spectroscopy

The mechanism of the inclusion of tropaeolin OO (TPOO) and beta-cyclodextrin (beta-CD) has been studied by spectrophotometry. The inclusion depth of the guest molecule in the host molecule was demonstrated by infrared spectrometry. Effect of the pH, concentrations of beta-CD, solvents and ionic strength on the inclusion of TPOO and beta-CD were examined. The result showed that TPOO reacts with beta-CD to form a 1:1 host-guest complex with an apparent formation constant of 1.50 x 10(3) l mol(-1). The thermodynamic parameters of inclusion reaction, DeltaG degrees , DeltaH degrees and DeltaS degrees were obtained.     

Molecular recognition thermodynamics of bile salts by beta-cyclodextrin dimers: Factors governing the cooperative binding of cyclodextrin dimers

The complex stability constants (K(S)), standard molar enthalpy (DeltaH degrees), and entropy changes (DeltaS degrees) for the inclusion complexation of two families of beta-cyclodextrin (beta-CD) dimers, i.e. beta-CD dimers Se1-Se4 bearing 2,2'-diselenobis(benzoyl) tether (Se-dimers) and beta-CD dimers Py1-Py4 bearing 2,2'-bipyridine-4,4'-dicarboxy tether (Py-dimers), with four bile salt guests, i.e. sodium cholate (CA), sodium deoxycholate (DCA), sodium glycocholate (GCA), and sodium taurocholate (TCA), were determined at 25 degrees C in Tris buffer solution (pH 7.4) at 298.15 K by means of isothermal titration microcalorimetry. The thermodynamic parameters obtained, together with the ROESY spectra of interactions between beta-CD dimers and bile salts, consistently suggest that the length, flexibility, and structure of spacers linking the two beta-CD cavities not only determine the binding modes but also significantly alter the molecular selectivity of beta-CD dimers.     

Spectroscopic study of orange G-beta-cyclodextrin complex and its analytical application

The mechanism of the inclusion of orange G and beta-cyclodextrin (beta-CD) has been studied by using both spectrophotometry and infrared spectroscopy. Effects of the pH, concentrations of beta-CD, and ionic strength on the inclusion complex of beta-CD and orange G were examined. The result showed that orange G reacts with beta-CD to form a 1:1 host-guest complex with an apparent formation constant of 3.03 x 10(3)mol(-1)l. The thermodynamic parameters of inclusion complex, DeltaG(0), DeltaH(0), and DeltaS(0) were obtained. Based on the enhancement of the absorbance of orange G produced through complex formation, a ratiometric method spectrophotometrically for the determination of orange G in bulk aqueous solution in the presence of beta-CD was developed, which overcome the effect of condition change on the determination of orange G. The linear relationship between the absorbance and orange G concentration was obtained in the range of 1.0 x 10(-5) to 4.0 x 10(-5)mol l(-1), with a correlation coefficient of 0.9998. The detection limit was 3.6 x 10(-6)mol l(-1). The principal advantage of the proposed method is high accuracy because ratiometry was used in measurement.     

Spectrophotometric study of the inclusion complex between beta-cyclodextrin and dibenzoyl peroxide and its analytical application

The noncovalent interaction of dibenzoyl peroxide and beta-cyclodextin (beta-CD) has been studied by spectrophotometry. The mechanism of the inclusion was studied. The results showed that beta-CD reacts with dibenzoyl peroxide to form a 2:1 host-guest complex with an apparent formation constant of 2.5 x 10(4)mol(-2)L(2). The beta-CD reacts with benzoic acid to form a 1:1 host-guest complex with an apparent formation constant of 6.9 x 10(2)mol(-1)L after the dibenzoyl peroxide was reduced by hydroxyl ammonium. Based on the enhancement of the absorbance of dibenzoyl peroxide produced through complex formation, a spectrophotometric method for determination of dibenzoyl peroxide in bulk aqueous solution in the presence of beta-CD was developed. A linear relationship between the absorbance and dibenzoyl peroxide concentration was obtained in the range of 0.300-50.0 microg mL(-1). Linear regression equation of the calibration graph C=0.02926+53.25 A, with a correlation coefficient of 0.9984 and a relative standard deviation (R.S.D.) of 3.4%. The detection limit was 0.200 microg mL(-1), and the recovery was from 98.00 to 105.0%. The proposed method was used to determine the dibenzoyl peroxide in the flour with satisfactory results. The principal advantage of the proposed method is its excellent selectivity based on molecule recognition of beta-CD.     

Fluorimetric and mass spectrometric study of the interaction of beta-cyclodextrin and osthole

The inclusion complex of beta-cyclodextrin (beta-CD) and osthole was studied by the electrospray ionization mass spectrometry (ESI-MS) and fluorescence spectrometry. From the mass spectrum, the 1:1 stoichiometric inclusion complex of beta-CD and osthole was observed. The tandem mass spectrum was performed. The fluorescence intensity of osthole increased in the present of beta-CD. According to the 1:1 beta-CD-osthole mode, the dissociation constant (KD) was obtained by ESI-MS and fluorescence spectrometry. The KD of beta-CD-osthole inclusion complex is 6.96 x 10(-3) mol L(-1) obtained by mass spectrometry and that is 8.14 x10 (-3) mol L(-1) obtained by fluorescence spectrometry, which is consistent with each other.     

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.     

用去氧胆酸盐和β-环糊精的毛细管胶束电动色谱拆分手性药物

 用β－环糊精（β－ＣＤ）和去氧胆酸钠（ＳＤＣ）的环糊精改性毛细管胶束电动色谱，实际拆分了ＥＭＤ－５６４３１和扑尔敏两种手性药物，研究了ＳＤＣ和β－ＣＤ浓度及ｐＨ值对分离的影响。初步讨论了分离的机理。认为ＣＤ－ＳＤＣ体系中胶束单体分子几乎均被ＣＤ包合；ＣＤ可能与部分胶束单体包合而存在于ＳＤＣ的胶束中；该拆分体系中ＳＤＣ与β－ＣＤ的浓度比在４∶１～４∶３时拆分效果最好。并发现ＳＤＣ对β－ＣＤ有显著的增溶作用。     

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.     

Effects of solvent, pH and beta-cyclodextrin on the photophysical properties of 4-hydroxy-3,5-dimethoxybenzaldehyde: intramolecular charge transfer associated with hydrogen bonding effect

The photophysical properties of 4-hydroxy-3,5-dimethoxybenzaldehyde (HDMB) in various solvents, pH and in aqueous beta-cyclodextrin (CD) have been investigated. In non-polar solvents, HDMB gives only one emission maxima; whereas, in polar solvents it shows a dual luminescence. The increase in Stokes shift with increase in polarity is much more for longer wavelength (LW) than for a shorter wavelength (SW) band. This behaviour indicates the formation of an intramolecular charge transfer (ICT) state through relaxation from the normal excited state. Especially in water, the ICT emission is further red shifted to 430 nm with the normal emission band at 330 nm and the relative fluorescence intensities between 330 nm and 430 nm emission bands are affected by the excitation wavelength. However, this excitation wavelength dependence is not large in aqueous beta-CD solutions. These results suggest that the ICT state in polar solvents/water is stabilized through exciplex formation by the hydrogen-bonding interaction between the carbonyl group and polar solvents/water. The ground and excited state pK(a) values for the neutral-monoanion equilibrium have been measured and discussed. HDMB forms a 1:1 inclusion complex with beta-CD. A mechanism is proposed to explain the inclusion process.     

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.     

NMR studies on selectivity of beta-cyclodextrin to fluorinated/hydrogenated surfactant mixtures

The interactions between beta-cyclodextrin (beta-CD) and the equimolar/nonequimolar mixtures of sodium perfluorooctanoate (C(7)F(15)COONa, SPFO) and sodium alkyl sulfate (C(n)H(2n+1)SO(4)Na, C(n)SO(4), n = 8, 10, 12) were investigated by 1H and 19F NMR. It showed that beta-CD preferentially included the fluorinated surfactant when exposed to mixtures of hydrogenated (C(n)SO(4)) and fluorinated (SPFO) surfactants, notwithstanding whether the hydrogenated surfactant C(n)SO(4) was more or less hydrophobic than the SPFO. Such preferential inclusion of the fluorinated surfactant continued to a certain concentration of beta-CD at which time the C(n)SO(4) was then observed to be included. The longer the hydrocarbon chain of C(n)SO(4) the lower the concentration of beta-CD at which the hydrogenated surfactants began to show inclusion. The inclusion process can be qualitatively divided into three stages: first, formation of 1:1 beta-CD/SPFO complexes; second, formation of 1:1 beta-CD/C(n)SO(4) complexes; and finally, formation of 2:1 beta-CD/SPFO complexes upon further increase of beta-CD concentration. In the concentration range studied, during the last stage of inclusion both 2:1 beta-CD/C(12)SO(4) and 2:1 beta-CD/SPFO complexes appear to be simultaneously formed in the system of beta-CD/SPFO/C(12)SO(4) but not in either the systems of beta-CD/SPFO/C(8)SO(4) or beta-CD/SPFO/C(10)SO(4). The selective inclusion of the shorter fluorocarbon chain surfactant might be attributed to the greater rigidity and size of the fluorocarbon chains, compared to those of the hydrocarbon chains, which provide for a tighter fit and better interaction between the host and guest. This latter effect appears to dominate the increase in hydrophobic character as the carbon chain length increases in the hydrogenated series.     

Determination of dissociation constants of cyclodextrin-ligand inclusion complexes by electrospray ionization mass spectrometry

The inclusion complexes of four ligands binding to cyclodextrins (CDs) were studied by electrospray ionization mass spectrometry (ESI-MS) and the dissociation constants of the complexes were obtained. The 1:1 stoichiometric inclusion complex was found in the system of CD and fenbufen or aspirin. The obtained KD values of the inclusion complexes of fenbufen binding to alpha-CD and to beta-CD are 4.38x10(-4) mol L(-1) and 2.12x10(-4) mol L(-1), respectively. The KD values of the inclusion complexes of alpha-CD-aspirin and beta-CD-aspirin are 3.33x10(-4) mol L(-1) and 1.83x10(-4) mol L(-1), respectively. A non-linear least squares regression method was applied to validate the results which were consistent with each other. For the system of tetracycline hydrochloride and CD, the 1:1 and 1:2 stoichiometric inclusion complexes were found in the mass spectra. The KD,1 and KD,2 values of the 1:1 and 1:2 stoichiometric inclusion complexes of alpha-CD and tetracycline hydrochloride are 4.47x10(-4) mol L(-1) and 6.51x10(-4) mol L(-1), respectively, and those of beta-CD and tetracycline hydrochloride are 2.26x10(-4) mol L(-1) and 8.57x10(-4) mol L(-1), respectively. For the system of norfloxacin and CD, besides the 1:1 and 1:2 inclusion complexes, the 1:3 stoichiometric inclusion complex was also found. The KD,1, KD,2 and KD,3 of alpha-CD and norfloxacin inclusion complexes are 4.61x10(-4) mol L(-1), 6.05x10(-4) mol L(-1) and 1.45x10(-3) mol L(-1), respectively. The three KD values of beta-CD and norfloxacin are 1.96x10(-4) mol L(-1), 4.93x10(-4) mol L(-1) and 1.15x10(-3) mol L(-1), respectively.     

Assembly behavior of inclusion complexes of beta-cyclodextrin with 4-hydroxyazobenzene and 4-aminoazobenzene

To further reveal the factors governing the supramolecular assembly of beta-cyclodextrin (beta-CD) inclusion complexes, two aggregates (1 and 2) were prepared from the inclusion complexes of beta-CD with 4-hydroxyazobenzene and 4-aminoazobenzene, respectively, and their binding behavior were investigated by means of X-ray analysis, UV-vis, NMR, and circular dichroism spectra in both solution and the solid state. The obtained results indicated that the beta-CD/4-hydroxyazobenzene complex 1 could form head-to-head dimers (triclinic system, space group P1) in the solid state, which were further self-assembled to a linear supramolecular architecture by the intra- and interdimer hydrogen bond interactions as well as the intradimer pi-pi interactions. However, when the included guest 4-hydroxyazobenzene was switched to a 4-aminoazobenzene, the resultant beta-CD/4-aminoazobenzene complex 2 (monoclinic system, space group P2(1)) could be self-assembled to a wave-type supramolecular aggregate under similar conditions. Furthermore, the combination of crystallographic and spectral investigations jointly revealed the inclusion complexation geometry of beta-CD with 4-hydroxyazobenzene and 4-aminoazobenzene in both solution and the solid state, which demonstrated that the disparity of substituents in the azobenzenes played an important role in the inclusion complexation and molecular assembly, affecting not only the structural features of aggregates but also the binding abilities of azobenzenes with beta-CD.     

Bioactive permethrin/beta-cyclodextrin inclusion complex

Permethrin is popularly used in a variety of therapeutic areas. However, the poor water solubility of permethrin seriously limits its wider clinical applications. The present study demonstrates that solubility of permethrin in aqueous solution can considerably increase in the presence of beta-cyclodextrin (beta-CD). Extensive experimental data along with computational modeling reveal the formation of stable permethrin/beta-CD inclusion complexes, including permethrin(beta-CD) and permethrin(beta-CD)2, through hydrophobic binding. Both permethrin(beta-CD) and permethrin(beta-CD)2 complexes coexisted in aqueous solution, and the ratio of the concentration of permethrin(beta-CD) complex to that of permethrin(beta-CD)2 complex was dependent on the concentration of beta-CD. The complexation of permethrin with beta-CD significantly improved the bioavailability of permethrin and, therefore, increased the bioactivity. The significant increase of the bioactivity of permethrin in the presence of beta-CD provides an effective approach to improve the practical use of permethrin in public health and agriculture.     

Orientational dynamics of a charge transfer complex in cyclodextrin cavity as receptor

This paper reports the structure and dynamics of a twisted intermolecular charge transfer molecule 2-(4-(dimethylamino) styryl)-1-methylpyridinium iodide (o-DASPMI) included inside alpha-, beta- and gamma-cyclodextrin, investigated by using steady state and time-resolved emission spectroscopy and also theoretical modeling. A nice 1 : 1 inclusion complex with beta-CD in the excited state could be found with the dimethylamino group of the molecule sticking out as revealed from steady state and time-resolved emission. The inclusion complex has a longer decay time compared to that in neat water. Time-resolved anisotropy decay has been used to study the rotational dynamics of the molecule inside cyclodextrin cavity. The average angular structure of the inclusion complex as found from semiempirical PM3 calculations corroborates excellently the experimental results of angular orientation in beta-CD. The minimum energy of the complex is found to be nearly 5 A in the length of the molecule with the dimethylamino part sticking out in the bulk water. Hydrogen bonding at the rim hinders the inclusion complex of o-DASPMI in gamma-CD and instead it produces association at the rim. Hydrogen bond breaker urea breaks the bonding of o-DASPMI with the rim of gamma-CD and the formation of inclusion complex with gamma-CD ensues.     

Demicellization of a mixture of cationic-anionic hydrogenated/fluorinated surfactants through selective inclusion by alpha- and beta-cyclodextrin

The interactions between alpha- and beta-cyclodextrin (alpha-/beta-CD) and an equimolar mixture of octyltriethylammonium bromide (OTEAB) and sodium perfluorooctanoate (SPFO) were studied by 1H and 19F NMR, surface tension, conductivity, and dynamic light scattering. It was shown that beta-CD could destroy the mixed micelles of OTEAB-SPFO by selective inclusion of SPFO. As beta-CD was added, the system was observed to undergo a process like this: beta-CD preferentially included SPFO to form 1:1 beta-CD/SPFO complexes. As the inclusion of SPFO was almost saturated, the mixed micelles broke and all OTEAB was released and exposed to aqueous surroundings. Then 1:1 beta-CD/OTEAB and 2:1 beta-CD/SPFO complexes significantly formed simultaneously. Contrary to beta-CD, alpha-CD exhibited selective inclusion to OTEAB and only weak association with SPFO. alpha-CD could also destroy the mixed micelles of OTEAB-SPFO; however, the demicellization ability of alpha-CD is much smaller than that of beta-CD. These conclusions were also well supported by the calculations of binding constants and DeltaG degrees . Different from the complexes of CD/conventional surfactants, the complexes of beta-CD/SPFO or alpha-CD/OTEAB formed by selective inclusion of CD in the mixed cationic-anionic surfactants may have contributed to the surface activity of the aqueous mixtures. The complexes of alpha-CD/OTEAB showed much more significant contribution to the surface activity than that of the complexes of beta-CD/SPFO.     

Study of the interaction between progesterone and beta-cyclodextrin by electrochemical techniques and steered molecular dynamics

The interaction of progesterone with beta-cyclodextrin (beta-CD) was studied by differential pulse polarography. The aim of the present work was to study the effect of beta-CD on the electrochemical behavior of progesterone in aqueous solution and also to analyze the molecular interactions involved in formation of the inclusion complex. The complex with stoichiometry of 1:1 was thermodynamically characterized. In addition, steered molecular dynamics (SMD) was used to investigate the energetic properties of formation of the inclusion complex along four different pathways (reaction coordinates), considering two possible orientations. From multiple trajectories along these pathways, the potentials of mean force for formation of the beta-CD progesterone inclusion complex were calculated. The energy analysis was in good agreement with the experimental results. In the beta-CD progesterone inclusion complex, a large portion of the steroid skeleton is included in the beta-CD cavity. The lowest energy was found when the D-ring of the guest molecule is located near the secondary hydroxyls of the beta-CD cavity. In the most probable orientation, one intermolecular hydrogen bond is formed between the O of the C-20 keto group of the progesterone and a secondary hydroxyl of the beta-CD.