Cyclodextrins

Abstract

Enzymic degradation of starch generally results in the production of glucose, maltose, maltotriose, etc., Le. a long series of linear or branched chain malto-oligomers, known as dextrins.Dextrins are heterogeneous, amorphous, hygroscopic substances, produced in large quantities for the food, textile, paper and other industries. They are also consumed without prior isolation in such products as e.g. beer and bread. This type of starch degradation is a true hydrolytic process, as the primary product from the splitting of the glycosidic linkage reacts with one molecule of water.If however, the starch is degraded by the glucosyltransferase enzyme (CGT), the primary product of the chain splitting undergoes an intramolecular reaction without the participation of a water molecule. The ex-1,4-linked cyclic products are formed; they are known as cyclodextrins (Figure 1-1). a-AMYLASE ~ .. ~ C> C> c:> J. Szejtli, Cyclodextrin Technology © Springer Science+Business Media Dordrecht 1988 CYCLODEXTRIN TECHNOLOGY APOLAR CAVITY SECONDARY HYDROXYLS ~PRIMARY HYDROXYLS Fig .1-6. Functional structural scheme of cyc1odextrins.making it a rigid structure. This is the probable explanation for the observation that ~-cyclodextrin has the lowest solubility of all the cyclodex trins. The hydrogen-bond belt is incomplete in the a-cyclodextrin molecule, as one glucopyranose unit is in a distorted position [ 301,304 J. As a consequence only four of the six possible H-bonds can be established. The y-cyclodextrin is a non-coplanar, more flexible structure, and is therefore the more soluble of the three. Equilibrium constants for the hydrogendeuterium exchange in the secondary hydroxyls (0.65 for 6-cyclodextrin, 0.75 for a-cyclodextrin and 0.85 for amylose) indicate the strongest H-bond system to be in ~-cyclodextrin [ 51 J.According to conformation-energy maps [ 325 J, hydrogen bonding between the C2 and C3 hydroxyls results in a lowering of energy by 20 kcal/mole (83.7 kJ/mole) in a-cyclodextrin, and of 30 kcal/mole (125 kJ/mole) in ~-cyclodextrin. J'2 J 23 J 34 J 45 J 56 .. J 561> J s .. , 0$1>

Cyclodextrin in polymer chemistry: Kinetic studies on the free-radical polymerization of cyclodextrin-complexed styrene from homogeneous aqueous solution

“…They consist of 6(α), 7(β), 8(γ) or more units of 1,4-linked glucose and exhibit a truncated-conus-shaped structure with a hydrophobic cavity and hydrophilic rim. This structure is the key to enclose smaller hydrophobic molecules to form hostguest compounds, in which the host is entrapped in the cavity of the cyclodextrin torus [1][2][3][4]. Despite the fact that the guest molecule is water-insoluble like, e.g., styrene (1), the complex formed by treatment with an aqueous solution of cyclodextrin becomes water-soluble without any chemical modification done during the complexation.…”

A fehérje–ciklodextrin kölcsönhatás terápiás és diagnosztikai jelentősége

“…1 nm átmérõjû apoláris üregét. 3 A peptidek, fehérjék esetében ez a gazda-vendég típusú kölcsönhatás azonban sajátosan jelentkezik, mivel a vendégmolekulák mérete sokszorosa a ciklodextrinének. Egy ciklodextrin-fehérje Dávid-Góliát szerû kölcsönhatása során nyilvánvalóan nem történik meg a fehérje molekuláris kapszulázása, hiszen a ciklodextrinek e makromolekulák bizonyos egységeihez, az aromás aminosavakhoz asszociálódnak.…”

Identification and Potency of Cyclodextrin-Lipid Inhibitors ofStaphylococcus aureusα-Toxin

“…12 Cyclodextrins (CD) are asymmetrical toroidal oligosaccharides that are formed by cyclization of starch via the enzyme cyclodextrin glucosyltransferase. 15 Natural occurring forms of CD include the α, β, and γ rings that are produced by the connection of α-1,4 glucosidic bonds between each of the 6, 7, or 8 glucopyranose units, respectively. The unique structure of water soluble CDs, with their lipophilic inner cavity and hydrophilic outer edges, make these macro-rings useful as aqueous carriers for hydrophobic molecules.…”

“…The unique structure of water soluble CDs, with their lipophilic inner cavity and hydrophilic outer edges, make these macro-rings useful as aqueous carriers for hydrophobic molecules. 15 β-cyclodextrin (β-CD) derivates have relatively low toxicity, a central cavity size suitable for molecular encapsulation of a wide range of lipophilic drugs and are currently used for a variety of pharmaceutical applications. 16 MβCD and 2-hydroxypropyl-β-cyclodextrin (HPβCD) were chosen for the present study because of their significantly improved aqueous solubility over the unaltered β-CD.…”