Complex of cyclodextrin

Upon formulating these relationships, phenols with branched alkyl substituents were not included in the data of a-cyclodextrin systems, though they were included in (3-cyclodextrin systems. In all the above equations, the n term was statistically significant at the 99.5 % level of confidence, indicating that the hydrophobic interaction plays a decisive role in the complexation of cyclodextrin with phenols. The Ibrnch term was statistically significant at the 99.5% level of confidence for (3-cyclo-dextrin complexes with m- and p-substituted phenols. The stability of the complexes increases with an increasing number of branches in substituents. This was ascribed to the attractive van der Waals interaction due to the close fitness of the branched substituents to the (3-cyclodextrin cavity. The steric effect of substituents was also observed for a-cyclodextrin complexes with p-substituted phenols (Eq. 22). In this case, the B parameter was used in place of Ibmch, since no phenol with a branched... 

S Hamai, H Sakurai. 2H20 effects on the inclusional complexation of cyclodextrin with sodium 2-naphthalenesulfonate in capillary electrophoresis and UV spectrometry. J Chromatogr A 800 327-332, 1998. 

Empty ft- (11) and y-cyclodextrins (12) also take normal torus shapes, as revealed by X-ray crystallography, and no significant deformations are observed for these two cyclodextrins when they bind guest molecules. It is noteworthy that all empty cyclodextrins include water molecules in their cavities as shown in Table IV and Fig. 4. Since no water molecules were observed in inclusion complexes of cyclodextrins with organic guest molecules, it is evident that the expulsion of these water molecules in the cyclodextrin cavities is one of the important factors for formation of the inclusion complexes. 

Sueishi, Y. Kasahara, M. Inoue, M. and Matsueda, K. (2003) Effect of substituent and solvent on inclusion complexation of //-cyclodextrins with azobenzene derivatives, J. Incl. Phenom. 46, 71-75. 

On completion of the reaction, the complex of cyclodextrin and precipitant is recovered by filtration or centrifugation. The precipitate is slurried in water, and the mixture is heated to distill off the precipitant. At the completion of the distillation an aqueous solution of cyclodextrin, containing with activated carbon and then cooled for crystallization. Crystals of (3-cyclodextrin are collected by filtration or centrifugation and then dried. The purity of the product is at least 98%, the major impurity being starch hydrolyzate. Since the reaction is directed to produce only (3-cyclodextrin, a- and -cydodextrins are not present in detectable quantities. 

Gamma-cyclodextrin can also be formed using a precipitant. Macrocyclic compounds, such as cyclotridecanone, which do not fit into the cavity of a- and (3-cyclodextrins are used.23,33 Such compounds do not dissolve in water or melt at temperatures compatible with the enzyme and require the presence of a solvent, such as methyl isobutyl ketone, to dissolve the precipitant and make it available to form a complex with -cyclodextrin. The precipitated complex of -cyclodextrin is collected by centrifugation or filtration. Solvent extraction is used for purification of -cyclodextrin in the same manner as described for a-cyclodextrin. 

Fragrance complexes can also be used in laundry products.102-104 Sheets for fabric softening with a complex of cyclodextrin and fragrance incorporated into them are placed into the clothes dryer, where the fragrance is released during the drying process. 

Shimada, K., Kawano, K., Ishii.J., and Nakamura, T. (1992). Structure of inclusion complexes of cyclodextrins with triglycerides at vegetable/oil/water interface. J. Food Sci. 57 655-656. 

Rearrangements.- E-Photoisomerization occurs readily in imines and in azo compounds. The syn-isomer (1), for example, is the major product of irradiation of nitrofurazone (2) in solution and is formed together with the corresponding azine on exposure to laboratory illumination. The photoisomerization of azobenzene derivatives in solution, in membranes, in host-guest complexes of cyclodextrins, and in polymers continues to attract attention. The reversibility of E-photoisomerization of azobenzene in cyclo-hexane solution has been established, and the E/ -ratios generated by irradiation of various azobenzene derivatives adsorbed on... 

A. Lopata, F. Darvas, A. Stadler-Szbke, and J. Szejtli, "Quantitative Structure-Stability Relationships Among Inclusion Complexes of Cyclodextrins. Part 2. Steroid Hormones", in QSAR and Strategies in the... 

Figure 5.7 Two models of a complex of cyclodextrin with a lipophilic guest compound (a) equatorial inclusion, (b) axial inclusion.

K. Ikeda, K. Uekama and M. Otagiri. Inclusion complexes of / -cyclodextrin with antiinflammatory dmgs fenamates in aqueous solution. Chem. Pharm. Bull, 23, 201-8 (1975)... 

Cyclodextrins are water-soluble hosts for hydrophobic guests. The formation of inclusion complexes is controlled by the dimensional compatibility of the guest and host cavity. Commercially available dextrins are, in fact, inclusion complexes of cyclodextrins with two water molecules closing the entrance to the cavity. The formation of cyclodextrin inclusion complexes is reversible and, therefore, is governed by concentration of guests competing for a place inside the cavity. 

Figure 4.2. Plot of percent prednisolone released versus time for different complexes of cyclodextrin and prednisolone. Used with permission from Kluwer Academic/Plenum Publishers and the original authors.

Yoshii H, Kometani T, Furuta T, Watanabe Y, Linko Yu-Y, Linko R 1998. Formation of inclusion complex of cyclodextrin with ethanol under anhydrous condition. Bioscience, Biotechnology and Biochemistry 62 2166-2170. 

Fig. 3. Time-averaged conformations of the inclusion complexes of -cyclodextrin with p-nitrophenyl acetate (A), phenyl acetate (B), and m-nitrophenyl acetate (C) in a 1 1 (v/v) mixture of 1 N deuterium...

Reversed-phase liquid chromatography and gas-liquid chromatography have been applied to studies on the complexation of cyclodextrin with isomeric dime-thylnaphthalenes (DMN) 19-22. Both / - and y-CyD have been found to form inclusion complexes with them. With the exception of the complex of 1,8-DMN 22 with yS-CyD, all other complexes under investigation are of weak stability. The stability constant of the former complex is always about 1.5-2.0 orders of magnitude greater than the corresponding value for the other isomers [47]. For example, at 40 °C in 40% of ethanol in water solvent, the stability constants of the complexes of yS-CyD with 1,8-DMN 22 and 1,3-DMN 19 are equal to ca. 500 and ca. 8 respectively. 

Determination of Thermodynamic Parameters for 1 2 Guest-Host Complexation of Cyclodextrin... 

Wang AS, Matsui Y, Solvent isotope effect on the complexation of cyclodextrins in aqueous solutions. 

The best catalyst was the AD isomer, the reverse of what we had seen in our ribonu-clease model studies. The pH/rate profile indicated that there was bifunctional catalysis by imidazole and imidazolium groups. This indicated that proton removal has a preferential direction of attack by base that is not directly along the C-H bond line, but instead pushes the electrons toward the carbonyl group (Figure 2.11). Such subtle information is available only because of the defined geometry in molecular complexes of cyclodextrin i w-imidazoles. 

K. Takahashi, Studies on the Control of Various Aqueous Reactions by Host-Guest Complexation of Cyclodextrins, Pharmaceutical Institute Tohoku University, 1986. 

Kano, K, S Hashimoto, A Imai and T Ogawa (1984). Three-component complexes of cyclodextrins. Exciplex formation in cyclodextrin cavity. Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2(3-4), Tyi-1 (>. 

Complexes of cyclodextrin modified with catechol groups 75 proved to be less active in phenol hydroxylation the main product was catechol and the selectivity with respect to this product exceeded 90%. For copper complexes... 

Zheng PQ, Li Z, Tong LH, Lu RH. 2002. Study of inclusion complexes of cyclodextrins with Orange II. J Inclusion Phenom Macrocyclic Chem 43(3 4) 183 186. 

Fig. 1.19 Cyclodextrins a-cyclodextrin (n=6), p-cyclodextrin (n=7), and y-cyclodextrin ( =8). Formation of the inclusion complex of cyclodextrin with a small guest molecule.

THREE-COMPONENT COMPLEXES OF CYCLODEXTRINS. CYCLODEXTRIN CAVITY... 

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