128
proceeded in the heterogeneous phase with dimethyl sulfate, using a solvent in
which cyclodextrins and bases used were poorly soluble or insoluble. However, in
the presence of phase transfer catalysts, methylation proceeded with good yields.
The products were a mixture of randomly methylated β-cyclodextrins containing
60–70% of DIMEB, 10–15% of heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin
TRIMEB, and some mono-methylated isomers. These methylated derivatives were
used as new detergents and also as solubilizing agents, e.g., to increase the solubility
of hydrocortisone (Bakó et al. 1994).
Professor Szejtli also studied the complex-forming ability of partially acetylated
cyclodextrins which proved to be useful for complexation of taxoid anticancer
drugs, especially when applied together with hydroxypropyl cyclodextrin (Szejtli
et al. 2004). On the other hand, the water-insoluble peracetylated derivatives gave
the opportunity to study inclusion complex formation in organic solvents (Buchanan
et al. 2001). His group participated in the development of hydroxybutenyl cyclodextrins on the analogy of hydroxypropyl derivatives (Buchanan et al. 2002, 2004),
sulfate, phosphate, and amino derivatives to mention only a few (Morva et al. 1999;
Mikuni et al. 2000; Kis et al. 2003).
A special HPLC column was developed for the analysis of cyclodextrin derivatives based on inclusion complex-forming ability with phenyl moieties on the surface of the stationary phase (Varga et al. 2005). This column was useful for detecting
residual unreacted cyclodextrins as well as separating the isomer groups with different degrees of substitution, thus providing a fingerprint characteristic to the product
and the manufacturing process. Therefore, it was later selected by the European
Pharmacopoeia for official identification of hydroxypropyl-beta-cyclodextrin.
2.5 Selected Highlights in the Fields of Applications Studied
by Professor Szejtli
2.5.1 Cyclodextrin in Foods
Table 2.5 describes the applications of cyclodextrins as multifunctional food ingredients in various domains (Szejtli et al. 1977a, 1979a; Dalla Bella and Szejtli 1983;
Szente and Szejtli 1988, 2004). As “empty capsules,” native cyclodextrins can be
used either for stabilization of substances or for the elimination of undesired compounds and microbial contaminations. They also served to protect lipophilic food
components or to encapsulate substances, e.g., vitamins, aroma, and flavors.
In 1977, Professor Szejtli and his collaborators patented a promising method for
the stabilization of food flavors and fragrances using cyclodextrins, which was realized on industrial scale (Szejtli et al. 1977a, 1979a). The active ingredient content
of complexes, e.g., benzaldehyde, was 6–15% w/w, and the complexes were very
stable in dry state. Their oxygen uptake, measured by the Warburg method, was less
than that of free benzaldehyde (Szejtli et al. 1979a).
G. Crini et al.
proceeded in the heterogeneous phase with dimethyl sulfate, using a solvent in
which cyclodextrins and bases used were poorly soluble or insoluble. However, in
the presence of phase transfer catalysts, methylation proceeded with good yields.
The products were a mixture of randomly methylated β-cyclodextrins containing
60–70% of DIMEB, 10–15% of heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin
TRIMEB, and some mono-methylated isomers. These methylated derivatives were
used as new detergents and also as solubilizing agents, e.g., to increase the solubility
of hydrocortisone (Bakó et al. 1994).
Professor Szejtli also studied the complex-forming ability of partially acetylated
cyclodextrins which proved to be useful for complexation of taxoid anticancer
drugs, especially when applied together with hydroxypropyl cyclodextrin (Szejtli
et al. 2004). On the other hand, the water-insoluble peracetylated derivatives gave
the opportunity to study inclusion complex formation in organic solvents (Buchanan
et al. 2001). His group participated in the development of hydroxybutenyl cyclodextrins on the analogy of hydroxypropyl derivatives (Buchanan et al. 2002, 2004),
sulfate, phosphate, and amino derivatives to mention only a few (Morva et al. 1999;
Mikuni et al. 2000; Kis et al. 2003).
A special HPLC column was developed for the analysis of cyclodextrin derivatives based on inclusion complex-forming ability with phenyl moieties on the surface of the stationary phase (Varga et al. 2005). This column was useful for detecting
residual unreacted cyclodextrins as well as separating the isomer groups with different degrees of substitution, thus providing a fingerprint characteristic to the product
and the manufacturing process. Therefore, it was later selected by the European
Pharmacopoeia for official identification of hydroxypropyl-beta-cyclodextrin.
2.5 Selected Highlights in the Fields of Applications Studied
by Professor Szejtli
2.5.1 Cyclodextrin in Foods
Table 2.5 describes the applications of cyclodextrins as multifunctional food ingredients in various domains (Szejtli et al. 1977a, 1979a; Dalla Bella and Szejtli 1983;
Szente and Szejtli 1988, 2004). As “empty capsules,” native cyclodextrins can be
used either for stabilization of substances or for the elimination of undesired compounds and microbial contaminations. They also served to protect lipophilic food
components or to encapsulate substances, e.g., vitamins, aroma, and flavors.
In 1977, Professor Szejtli and his collaborators patented a promising method for
the stabilization of food flavors and fragrances using cyclodextrins, which was realized on industrial scale (Szejtli et al. 1977a, 1979a). The active ingredient content
of complexes, e.g., benzaldehyde, was 6–15% w/w, and the complexes were very
stable in dry state. Their oxygen uptake, measured by the Warburg method, was less
than that of free benzaldehyde (Szejtli et al. 1979a).
G. Crini et al.