Effects of Natural Cyclodextrins on the Photophysical Properties of Dibenzofuran-2-carboxylic Acid

Investigation of inclusion complexes of sulfamerazine with α- and β-cyclodextrins: an experimental and theoretical study

Inclusion complexation behavior and binding ability of sulfamerazine (SMRZ) with α- and β-cyclodextrins (α-CD and β-CD) were investigated. The formation of inclusion complexes are studied by UV-visible, fluorescence, time-resolved fluorescence, (1)H NMR, FT-IR, DSC, XRD, SEM, TEM and molecular modeling methods. Both experimental and PM3 results indicated that the SMRZ is partially encapsulated in the CD cavity. The different spectral shifts observed in both the CDs indicate that different types of inclusion complexes are formed. Nanosecond time-resolved fluorescence studies demonstrated that SMRZ exhibit biexponential decay in water and triexponential decay in CD solutions. The resonance of the aromatic protons of SMRZ showed remarkably upfield shift in the complexes suggested that the aniline ring deeply encapsulated in the CD cavity. The amino and amido stretching vibrations at 3483 cm(-1) and 3379 cm(-1) respectively are strongly affected in the inclusion complexes. DSC curves for the inclusion complexes exhibited a broad endothermic effect from 106.4 °C, 123.8 °C and 234.5 6 °C for α-CD and 118.2 °C and 231.4 °C for β-CD. TEM images of both inclusion complexes are forms a nanochain like agglomerated structures with a width ranging from 40 nm to 100 nm. Thermodynamic parameters and binding affinity of the inclusion complex formation were determined and discussed.

Modulation in prototropism of the photosensitizer Harmane by host:guest interactions between β-cyclodextrin and surfactants

The present contribution demonstrates the photophysics of a prospective cancer cell photosensitizer Harmane (HM) belonging to the family of β-carboline in mixed microheterogeneous environments of β-cyclodextrin (β-CD) and surfactants having varying surface charges using steady-state and time-resolved fluorescence spectroscopic techniques. The remarkable modulations in prototropic activities of the micelle-bound drug in the presence of β-CD evinces for disruption of the micellar structural integrity by β-CD. The results are meticulously discussed in relevance to the effect of a potential drug delivery vehicle (CD) on the membrane-mimetic micellar system. Further, application of an extrinsic fluorescence probe for monitoring such interactions is fraught by the possibilities of no less than three equilibria that can operate simultaneously viz., (i) surfactant-cyclodextrin, (ii) surfactant-fluorophore and (iii) cyclodextrin-fluorophore. This aspect highlights the enormous importance of the issue of suitability of the fluorescence probe to study such complicated systems and interaction phenomena. Also the varying interaction scenario of β-CD with the nature of the surfactant highlights the importance of precise knowledge of the strength and locus of drug binding in delineating such complex interactions. The results of the present investigation advocate for the potential applicability of the drug (HM) itself as a fluorescence reporter in study of such complex microheterogeneous interactions.

Spectral characteristics of tramadol in different solvents and beta-cyclodextrin

Effect of solvents and beta-cyclodextrin on the absorption and fluorescence spectra of tramadol drug has been investigated and compared with anisole. The solid inclusion complex of tramadol with beta-CD is investigated by FT-IR, (1)H NMR, scanning electron microscope (SEM), DSC and semiempirical methods. The thermodynamic parameter (DeltaG) of inclusion process is determined. A solvent study shows (i) the spectral behaviour of both tramadol and anisole molecules is similar to each other and (ii) the cyclohexanol group in tramadol is not effectively conjugated with anisole group. However, in beta-CD, due to space restriction of the CD cavity, a weak interaction is present between the above groups in tramadol. beta-Cyclodextrin studies show that tramadol forms 1:2 inclusion complex with beta-CD. A mechanism is proposed for the inclusion process.

Friedel–Crafts alkylation of indoles with nitroolefins in the presence of β-cyclodextrin in water under neutral conditions

Various indolyl nitroalkanes were prepared by the reaction of indoles with nitroolefins in the presence of β-cyclodextrin in water under neutral conditions. β-Cyclodextrin can be recovered and re-used several times without loss of activity.Key words: β-cyclodextrin, nitroolefins, indoles, neutral conditions, water.

Application of cyclodextrin-mediated capillary electrophoresis to determine the apparent binding constants and thermodynamic parameters of the alkylnaphthalene derivatives

The separation and migration behavior of seven positional and structural neutral alkylnaphthalene derivatives in cyclodextrin-mediated capillary electrophoresis were systematically investigated. The effective separation conditions were to use 10 mM phosphate buffer with negatively charged carboxymethyl-beta-cyclodextrin (CM-beta-CD) at pH 6.0. The guest-host interactions with 1:1 or both 1:1 and 1:2 binding stoichiometries for various derivatives were evaluated by comparing their apparent binding constants. The results reveal that the substituent group(s) attached to the naphthalene ring significantly affected the inclusion stoichiometric behaviors. Alkylnaphthalene derivatives with the substituent(s) at the 1-position(s), such as 1-ethylnaphthalene, 1,4-dimethylnaphthalene, may undergo complexation with one and two CM-beta-CD molecules. The binding constants of these derivatives were consistent with the data obtained by a spectrophotometric method. The thermodynamic parameters were also calculated in order to improve our understanding of the interaction between the neutral alkylnaphthalene derivatives and CM-beta-CD at various temperatures. The positive entropy (deltaS degrees) values of the alkylnaphthalenes with the substituent(s) at the 2-position(s) indicate that the inclusion of the guest molecule into the cavity of CM-beta-CD is favored at all temperatures.