Cyclodextrin solutions

Cyclodextrin solution for extraction studies was prepared at a concentration of 1.00 x 10" iif by dissolving solid y-CDx in deionized water (Continental Water Systems, Atlanta, Georgia). Fresh solution was prepared daily to prevent bacterial growth and CDx decomposition from interfering with complexation and extraction. Cyclodextrin was purchased from Advanced Separation Technologies, Inc. (Whippany, New Jersey) and was used as received. Solid CDx from one lot number was used for all extractions. 

In the recent past separation of isomers has been attempted using aqueous liquid membranes based on p-cyclodextrin. Thus, separation of a mixture of o- and p-nitroaniline (in 80% i-octanol, 20% -heptane) has been studied, with the p-isomer showing a selectivity of 5 at 0.7 molar p-cyclodextrin. Even stereoisomers of stilbene cis and trans) were separated using a 0.02 to 0.2 M cyclodextrin solution, but the selectivity was less than 2 (Mandal et al, 1998). 

The Diels-Alder reactions of alkyl-substituted benzoquinones with penta-1,3-diene and isoprene were also studied in aqueous cyclodextrin solutions. Highly enhanced ortho- and mefa-regioselectivities were observed (Eq. 12.11).48... 

Kim YH, Cho DW, Yoon M, Kim D (1996) Observation of hydrogen-bonding effects on twisted intramolecular charge transfer of p-(N, N-diethylamino) benzoic acid in aqueous cyclodextrin solutions. J Phys Chem 100(39) 15670-15676... 

Mourtzis, N. Cordoyiannis, G. Nounesis, G. and Yannakopoulou, K. (2003) Single and Double Threading of Congo Red into y-Cyclodextrin. Solution Structures and Thermodynamic Parameters of 1 1 and 2 2 Adducts, as Obtained from NMR Spectroscopy and Microcalorimetry, Supramol. Chem. 15, 639-649. 

In treating some aqueous products, such as milk or eggs, some residual cyclodextrin might remain in the product. The residual cyclodextrin can be removed, if desired, by treating the product with a cyclodextrin transglycosylase or an a-amylase.82 If an immobilized enzyme is used, the enzyme can be removed from the product. When oils are treated with cyclodextrin, undetectable levels, if any, of cyclodextrin remain in the oil phase if the proper proportions of oil and cyclodextrin solution are used. 

Cholesterol may be removed selectively by cyclodextrins. Melted milk fat is mixed with a cyclodextrin solutions and the complex is removed by washing. The ability of cyclodextrin to form an inclusion complex with cholesterol has been applied to reduce the cholesterol content of milk fat, cream or milk (Courregelongue and Maffrand, 1989 Oakenfull et al., 1991). However, the high cost of cyclodextrin prevents its use on an industrial scale. 

Aqueous a-cyclodextrin solutions seem to be generally applicable for TLC separation of a wide variety of substituted aromatics on polyamide thin-layer stationary sheet (13-14). In most cases, the compounds moved as distinct spots and their R, values were dependent on the concentration of the cyclodextrin in tne mobile phase. In a given family of compounds, (o-, m-, and p-nitrophenols, for example) the isomer with the largest stability constant for a-cyclodextrin complex formation had the larger value. In general, the para-substituted isomers have larger R values than the meta-isomers, which in turn have larger R values than the ortho substituted ones. 

Medlicott,N. J., Foster, K. A., Audus, K. L., Gupta, S., and Stella, V. J. (1998), Comparison of the effects of potential parenteral vehicles for poorly water soluble anticancer drugs (organic cosolvents and cyclodextrin solutions) on cultured endothelial cells (HUV-EC), J. Pharm. Sci., 87,1138-1143. 

Kano, K. Zhou, B. Sakaguchi, M. Matsumoto, H. Hashimoto, S. Effects of aeration, freezing and thawing on self-aggregation of naphthalene in aqueous P-cyclodextrin solutions. Sci. Eng. Rev. Doshisha Univ. 1985, 25 (4), 253-259. 

The cyclodextrin-solute inclusion complexation is a reversible reaction with an equilibrium constant similar... 

The pH, temperature, and ionic strength of the mobile phase also affect the cyclodextrin-solute complexation and retention properties. Many enantioseparations using cyclodextrin-modified systems involve solutes with an aromatic ring substituent or similar cyclic structure at the chiral center. A variety of chiral barbiturates, hydantoins, and related compounds have been resolved by using (3-cyclodextrin and alkylated B-cyclodextrin-modified systems. 

Barone JA, Moskovitz BL, Guamieri J, Hassell AE, Colaizzi JL, Bierman RH, lessen L. Enhanced bioavailability of itraconazole in hydroxypropyl-beta-cyclodextrin solution versus capsules in healthy volunteers. Antimicrob Agents Chemother 1998 42(7) 1862-5. 

Development of parenteral formulations of all-fram-retinoic acid is possible by using 2-hydroxypropyl-P-cyclodextrin, and inclusion into the carrier also leads to an improved photostability of the drug (Lin et al 2000). Aqueous cyclodextrin solutions are shown to extract plastic additives when stored in containers of polypropylene (Peiris et al., 1999 see Section 14.3). The result may be photosensitized decomposition of the drug. Photochemical stability of drug-cyclodextrin inclusion complexes are further discussed in Chapter 16. 

Peiris, D.M., Mohanty, D.K., and Sharma, A. (1999) Undesirable reaction of aqueous cyclodextrin solutions with polypropylene, Micmchem.. /., 62, 266-272. 

By measuring activation parameters (Eq. (2) and Table 2), it has been shown that the cceleration arises from a favorable change of activation entropy, which is an indication of the implication of the hydrophobic effect [32], Concentrated aqueous carbohydrate solutions (glucose and saccharose for instance) have been shown to accelerate the Diels-Alder reaction. The acceleration is even greater than that observed with saturated fi-cyclodextrin solution (Eq. (3) and Table 3) [32],... 

Frequently, co-solvents are added to aqueous cyclodextrin solutions in most cases, these co-solvents are employed to solubilize the probes. In Section IV.C, the decrease of the exit rate constant of triplet xanthone from CDs with the addition of alcohols was described. This effect was also apparent when studying the dynamics of 1-halonaphthalenes with P-CD in the presence of acetonitrile [141]. When the nitrite ion was used as quencher, the association rate constants decreased in the presence of the organic solvent while the dissociation rate constant increased (Table 21). The main rationalization to explain the change in mobility properties was that acetonitrile was small enough to coinclude inside the cavity a small amount of acetonitrile could preferentially solvate the entrances of the CD thereby leading to a different environment for the probe. 

Similarly, in tests with dredged sediment and gas plant soil, substantial electroosmotic flow was produced because of high acid buffering capacity, but phenanthrene removal efficiency was very low because PAHs were strongly adsorbed to organic matter. The organic matter proportions were 19% and 4% in the sediment and gas plant soil, respectively (Reddy and Ala, 2006 Reddy et al, 2006). Particularly, in tests with cyclodextrin solution, it was found that the low PAH removal efficiency was caused by adsorption of cyclodextrin-PAH complexes onto minerals and organic matter in the sediments (Reddy and Ala, 2006). 

Turro to be a strong phosphor at room temperature in deaerated P-cyclodextrin solution (28). Indeed, halonaphthalenes were among the examples employed by early workers to establish the favourable heavy atom effect on low temperature phosphorescence (36,37). The other essential piece of inspiration came from... 

Similarly, the volume of an injection should be less than 5 ini, or even better, not more than 2-3 ml, i.e.. sufficient to dissolve the necessary amount of drug in 2-3 ml of 40% HPBCD (=2-hydroxypropyl- 5-cyclodextrin) solution—800-1200 mg HPBCD can be used. In liquid formulations the use of CD derivatives in excess is possible. In the case of Prostavasin injection, the molar ratio of prostaglandin E] to otCD is 1 11 (20 pg... 

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