Cyclo dextrins complexes

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... 

Calculations based on simple molecular models and the charge density of the layers suggest that sulfopropylated-//-cyclodextrin and carboxyethylated-/3-cyclodextrin are arranged in the interlayer galleries with their conical axis parallel to the layers with a packing structure which is similar to that in crystalline cyclo dextrin complexes, where the molecules are arranged in a brickwork pattern [202]. 

Seo, H., Uekama, K. Enhanced bioavailability of digoxin by -cyclo-dextrin complexation evaluation for sublingual and oral administrations in human. Yakugaku. Zasshi 1989, 109, 778—782. 

Ueno, M., Ijitsu, T., Horiuchi, Y. et al. Improvement of dissolution and absorption characteristics of ubidecarenone by dimethyl-p-cyclo-dextrin complexation. Acta Pharm. Nord. 1989, 2, 99-104. 

Uekama, K., Horiuchi, Y., Kikuchi, M. et al. Enhanced dissolution and oral bioavailabiUty of a-tocopheryl esters by dimethyl-(3-cyclo-dextrin complexations. J. Inclusion Phenom. 1988, 6,167-174. 

Uekama, K., Otagiri, M., Sakai, A., et al. "(1985) Improvement in the percutaneous absorption of beclomethasone dipropionate by y-cyclo-dextrin complexation. J. Pharm. Pharmacol. 37 532-535. 

Hoshino, T., Ishida, K., Me, T., et al. (1987) Alleviation in protriptyline-photosensitized skin irritation by di-O-methyl-p-cyclo-dextrin complexation. Int. J. Pharm. 38 265-267. 

Abou-Hamdan, A. Bugnon. P. Saudan, C. Lye, P.G. Merbach, A.E. High-pressure studies as a novel approach in determining inclusion mechanisms Thermodynamics and kinetics of the host-guest interactions for -x-cyclo-dextrin complexes. J. Am. Chem. Soc. 2000. 122 (4). 592-602. 

The physico-chemical properties of PGl2Me- p-cyclo-dextrin complex in solid-state have been discussed in this paper ... 

Fig. 7. Host-guest interaction in the permethylated a-cyclo-dextrin complexes with L-mandelic acid (A) and D-mandelic acid (B). Water molecules are shown by full circles. Broken lines indicate hydrogen bonds. The Gl, G2, and G6 residues in the L-mandelic acid complex and the G4, G5, and G6 residues in the D-mandelic acid complex are shaded.

Ozoe et al.76 have determined the Kd values for complexes of ot- and fl-cyclo-dextrin with a variety of 4-substituted bicyclic phosphates (4-substituted 2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane 1-oxides, 1), which are highly toxic convulsants. 

Only the hydrophobic and steric terms were involved in these equations. There are a few differences between these equations and the corresponding equations for cyclo-dextrin-substituted phenol systems. However, it is not necessarily required that the mechanism for complexation between cyclodextrin and phenyl acetates be the same as that for cyclodextrin-phenol systems. The kinetically determined Kj values are concerned only with productive forms of inclusion complexes. The productive forms may be similar in structure to the tetrahedral intermediates of the reactions. To attain such geometry, the penetration of substituents of phenyl acetates into the cyclodextrin cavity must be shallow, compared with the cases of the corresponding phenol systems, so that the hydrogen bonding between the substituents of phenyl acetates and the C-6 hydroxyl groups of cyclodextrin may be impossible. 

Attempts to stabilize anthocyanins by complex inclusion with a- and P-cyclo-dextrins failed on the contrary, a discoloration of anthocyanin solutions was observed.Thermodynamic and kinetic investigations demonstrated that inclusion and copigmentation had opposite effects. In the anthocyanins, the cw-chalcone colorless structure is the best species adapted to inclusion into the P-dextrin cavity, shifting the equilibrium toward colorless forms. "... 

The synthesis of [Ircp Cl(bpy-cd)]Cl, where bpy-cd is a /3-cyclo-dextrin attached at the 6 position to a bpy ligand, is detailed.138 The complexes [Ircp (diimine)X]+, X = C1, H, diimine = bpy, phen, are active catalysts for the light-driven water-gas-shift reaction.139 The hydride complexes luminesce at 77 K and room temperature, whereas the chloride complexes do not.140 The three-legged piano-stool arrangement of the ligands in [Ircp (bpy)Cl]+ and [Ircp (4,4 -COOFl-bpy)Cl]+ is confirmed by X-ray crystallography.141,142 Further mechanistic studies on the catalytic cycle shown in reaction Scheme 11 indicate that Cl- is substituted by CO and the rate-determining step involves loss of C02 and H+ to leave the Ir1 species, which readily binds Fl+ to yield the lrIH hydride species.143... 

While nature uses coenzyme-dependent enzymes to influence the inherent reactivity of the coenzyme, in principle, any chemical microenvironment could modulate the chemical properties of coenzymes to achieve novel functional properties. In some cases even simple changes in solvent, pH, and ionic strength can alter the coenzyme reactivity. Early attempts to present coenzymes with a more complex chemical environment focused on incorporating coenzymes into small molecule scaffolds or synthetic host molecules such as cyclophanes and cyclo-dextrins [1,2]. While some notable successes have been reported, these strategies have been less successful for constructing more complex coenzyme microenvironments and have suffered from difficulties in readily manipulating the structure of the coenzyme microenvironment. 

Therefore after scaling it could serve as thermometer. The complicated processes involved in de- and re-colouration are not fully understood, but the latter is undoubtedly associated with the complex decomposition triggered by thermal motion of the cyclo dextrin involved. Thus it reflects the dynamic character of the phenolophthalein complex with 11 (see Section 3.4 for a short discussion of dynamic character of supramolecular complexes). Optoelectronics making use of nonlinear optical phenomena is yet another field of prospective applications of molecular assemblies [32]. 

Itraconazole oral solution contains 10 mg of itraconazole per milliliter, solubilized by hydroxypropyl-(beta)-cyclo-dextrin (400 mg/mL) as a molecular inclusion complex. The solution is clear and yellowish in color with a target... 

Among enzyme modified starch derivatives,cyclo dextrins behave as empty molecular capsules with the ability to entrap guest molecules of appropriate geometry and polarity.The included molecules are protected from surroundings light, heat,oxidation, etc. The flavor cyclodextrin com -plexes show the above advantageous properties while they are in the dry,solld state.On contact with water,cyclodextrin complexes release their flavor content. In Hungary,the spice flavor beta-cyclodextrin complexes have been on the market, since 1982. 

The molecular encapsulation of flavors with cyclo-dextrins was found to improve the resistence of light sensitive flavor constituents against daylight and ultraviolet irradiation. The photodecomposition of adsorbed and complexed flavors was tested both in the solid state and in aqueous solutions. The results of the light stability tests are demonstrated in the example of complexed and adsorbed citral,beta-ionone and cinnamaldehyde formulations /Table III./. 

Table IV. Changes of the flavor content of cyclo-dextrin spice complexes after ten years storage under nonnal conditions...

The physicochemical properties and dissolution profile of zaleplon -cyclo-dextrin (jSCD) inclusion complex were investigated. The phase solubility profile of Zaleplon with /1CD was classified as AL-type. Stability constant with 1 1 molar ratio was calculated from the phase solubility diagram and... 

In an elegant self-assembling system based on the use of cyclodextrin hosts, DeCola and coworkers noncovalently linked an alkylcarboxyan-thracene to an a-cyclodextrin bearing Ru(II) complex that also had an Os(II) bipyridyl derivative attached via noncovalent interaction with a -cyclo-dextrin substituent on the Ru complex (Fig. 14). The system yields an energy transfer cascade from the photoexcited anthracene to the Ru to bpy 3 MLCT state, which in turn transfers energy to the Os(II) complex 3MLCT state. All rate constants are > 108 s-1 [88]. 

The reaction of 2 - a r v I - N - io s v I a / i r i d i n es was studied in water containing /i-cyclo-dextrin, which formed an inclusion complex with the aziridine 49 The products were formed from attack at the benzyl carbon with inversion of configuration. The yields were high. 

A number of articles have been written which concern the poor solubilities of products. Suspension cultures of Mentha produce menthol which has very low solubility in water due to its hydrophobicity, and this is considered to be a factor responsible for its low production in the suspension cultures. Cyclo dextrin has a hydrophobic cavity inside the molecule in which menthol can be captured and allow to form a stable complex. A suspension culture of Mentha piperita showed a 70% production enhancement in a medium contain-... 

The plot of the reciprocal of k - kf against 1/[L] is linear, with a slope of 1 / [K(kc - kf)] and an intercept of 1 / (kc - kf). Figure 5.36 shows the stabilization of prostacyclin by the derivatives of P-cyclodextrin. However, not all inclusion complexes provide the stabilization of drugs. In many cases, drug degradation is enhanced via inclusion complex formation [e.g., prostaglandin E and E2/p-cyclo-dextrin (P-CD), aspirin/p-CD],... 

A good example of such a process is the template-directed chlorination of an aromatic ring by -cyclo-dextrin (Scheme 22). Hydrophobic forces hold the complex together temporarily, and within the complex the chlorination is catalyzed and directed by a hydroxy group of the cyclodextrin. An electro-... 

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