Effect of cyclodextrin

In these equations, Dmax is the larger of the summed values of STERIMOL parameters, Bj, for the opposite pair 68). It expresses the maximum total width of substituents. The coefficients of the ct° terms in Eqs. 37 to 39 were virtually equal to that in Eq. 40. This means that the a° terms essentially represent the hydrolytic reactivity of an ester itself and are virtually independent of cyclodextrin catalysis. The catalytic effect of cyclodextrin is only involved in the Dmax term. Interestingly, the coefficient of Draax was negative in Eq. 37 and positive in Eq. 38. This fact indicates that bulky substituents at the meta position are favorable, while those at the para position unfavorable, for the rate acceleration in the (S-cyclodextrin catalysis. Similar results have been obtained for a-cyclodextrin catalysis, but not for (S-cyclodextrin catalysis, by Silipo and Hansch described above. Equation 39 suggests the existence of an optimum diameter for the proper fit of m-substituents in the cavity of a-cyclodextrin. The optimum Dmax value was estimated from Eq. 39 as 4.4 A, which is approximately equivalent to the diameter of the a-cyclodextrin cavity. The situation is shown in Fig. 8. A similar parabolic relationship would be obtained for (5-cyclodextrin catalysis, too, if the correlation analysis involved phenyl acetates with such bulky substituents that they cannot be included within the (5-cyclodextrin cavity. 

The effects of cyclodextrins on this reaction, while potentially of great interest, have been rarely studied, presumably because amide hydrolysis is generally slow and so tedious to study. As a result, only two examples are considered here. 

The object of this review was to show how Kurz s approach to quantifying transition state stabilization is useful in the discussion of the kinetic effects of cyclodextrins on organic reactions, while at the same time pointing out its comparable utility for various other types of catalyst. It is hoped that the approach gains wider acceptance and employment since it provides a framework for the discussion of factors affecting transition state stability in both catalysed and retarded reactions. 

Jozefaciuk, G. Muranyi, A. Fenyvesi, E. Effect of Cyclodextrins on Surface and Pore Properties of Soil Clay Minerals. Environ. Sci. Technol 2001, 35, 4947-4952. 

Kim J-M, Lee J-S, Lee J-S, Woo S-Y, Ahn DJ. Unique effects of cyclodextrins on the formation and colorimetric transition of polydiacetylene vesicles. Macromol Chem Phys 2005 206 2299-2306. 

The present paper is intended to provide a survey on the stabilizing effects of cyclodextrin complexation. Beyond this,other practical consequences of the molecular entrapment of flavors will also be mentioned. 

Nakanishi, K., Nadai, T., Masada, M., and Miyajima, K. 1992. Effect of cyclodextrins on biological... 

Long-Acting Absorption-Enhancing Effects of Cyclodextrins.154... 

Inhibitory Effects of Cyclodextrins of Drug Irritancy in Rectal Delivery.157... 

Frijlink, H.W., et al. 1992. The effects of cyclodextrins on drug release from fatty suppository bases. III. Application of cyclodextrin derivatives. Eur J Pharm Biopharm 38 174. 

Nakanishi, K., et al. 1990. Effect of cyclodextrins on biological membrane. I. Effect of cyclodextrins on the absorption of a non-absorbable drug from rat small intestine and rectum. Chem Pharm Bull 38 1684. 

Hovgaard, L., and H. Brondsted. 1995. Drug delivery studies in Caco-2 monolayers. IV. Absorption enhancer effects of cyclodextrins. Pharm Res 12 1328-1332. 

Merkus, F.W., et al. 1991. Absorption enhancing effect of cyclodextrins on intranasally administered insulin in rats. Pharm Res 8 588. 

Teshima D, Otsubo K, Higuchi S, Hirayama F, Uekama K, Aoyama T. Effects of cyclodextrins on degradation of emetine and cephaeline in aqueous solutions. Chem Pharm Bull 1989 37 1591-1594. 

The effect of cyclodextrin complexation on the bromination of styrene, methyl cinnamate, phenylacetylene, and allylbenzene has been studied.27 The corresponding bromohydrin was obtained as a major product along with dibromide in the bromination... 

The retention order of propyl- and isopropylbenzenes is the same on liquid crystals as on cyclodextrins. However, as can be seen from Table I, the difference in the relative retentions is exceptionally large on a-CD, which again illustrates the more pronounced stereospecific effects of cyclodextrins. 

Piel, G., Piette, M., Barillaro, V., Castagne, D., Evrard, B., and Delattre, L. (2006), Beta-methasone-in-cyclodextrin-in-liposome The effect of cyclodextrins on encapsulation efficiency and release kinetics, Int. I. Pharm., 312,75-82. 

Cyclodextrins can form inclusion complexes with some drugs, modifying their physical and chemical properties. Because cyclodextrins are mainly used to increase the solubility of poorly soluble drugs, most investigations in this field focus on photostability of drugs in solution. Here, the positive effect of cyclodextrins on the photostability of colchicine (36), emetine and cephaeline (37) could be shown. However, these results show that the photoprotective effect depends on the particular cyclodextrin used. For some forms of cyclodextrin, an increase of the photodegradation rate can be obtained, as the example of molsidomine shows (13). 

A limited amount of published information on the effect of cyclodextrins on the photostability in the solid state is available. Results similar to those reported for solutions, related to the choice of cyclodextrin type can be expected for the solid state. This was confirmed by Tomono et al.who showed that the remaining content of four different drugs increased or decreased after irradiation, depending on the selected cyclodextrin type (38). 

Other related studies concerned with the effects of cyclodextrin complexation on the properties of surfactants of various n-alkyl chain lengths, also incorporating a covalently attached electroactive group, have been reported.Thus, the nature of... 

Kamiya M., Nakamura K., and Sasaki C. (1994) Inclusion effects of cyclodextrins on photodegradation rates of parathion and paraoxon in aquatic medium [iic]. Chemo-sphere 1961—1966. 

Loftsson, T. Effects of cyclodextrins on the chemical stability of drugs in aqueous solutions. Drug Stab. 1995,1 (1), 22-33. 

Tokihiro, K. Irie, T. Uekama, K. Varying effects of cyclodextrin derivatives on aggregation and thermal behavior of insulin in aqueous solution. Chem. Pharm. Bull. 

Lutka, A. Effect of cyclodextrin complexation on aqueous solubility and photostability of phenothiazine. Pharmazie 2000, 55, 120-123. 

Zia V, Rajewski RA, Stella VJ. Effect of cyclodextrin charge on complexation of neutral and charged substrates comparison of (SBE)7 -Beta-CD to HP-Beta-CD. Pharm Res 2001 18(5) 667-673. 

Quitschke WW, Steinhauff N, Rooney J (2013) The effect of cyclodextrin-solubilized curcuminoids on amyloid plaques in Alzheimer transgenic mice Brain uptake and metabolism after intravenous and subcutaneous injection. Alzheimers Res Ther 5 16... 

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