Complexation of glucose by α- and β-cyclodextrins

Abstract

The concentration of glucose in aqueous solutions was monitored, using a blood glucose meter, as small weighed cyclodextrin portions were added. Equilibrium constants for the formation of inclusion complexes were calculated. A binding constant determined by this method has been verified by a technique involving competition of the guest with methyl orange indicator dye. AH' values for the reactions were estimated using calorimetry. These values along with AGO provided estimates of the standard entropies. The values calculated compare favorably with those from a previously determined empirical equation. The possibility of hydrogen bond formation is suggested by the large negative enthalpies as well as by molecular mechanics calculations.Key words: a-, P-cyclodextrin, glucose, binding constants.RCsumC : Utilisant un glucomktre pour le sang, on a mesure la concentration du glucose dans des solutions aqueuses alors qu'on y ajoutait des portions mesurCes de cyclodextrine. On a calculC les constantes d'equilibre pour la formation de complexes d'inclusion. Faisant appel ii une technique impliquant une compCtition de l'h6te pour I'indicateur color6 mCthylorange, on a vCrifiC une constante de fixation dCterminCe par cette methode. On a CvaluC les AH' des ces rkactions en utilisant la calorimktrie. Ces valeurs utilisCes de concert avec des AGO ont fourni des Cvaluations des entropies standard. Les valeurs calculCes se comparent avantageusement avec celles obtenues sur la base d'une equation empirique dCterminCe antkrieurement. La possibilitC de formation de liaison hydrogkne est suggtrCe par les fortes enthalpies nCgatives ainsi que par des calculs de mCcanique molCculaire.

Electrochemical Sensor for Electrochemically Inactive β-d(+)-Glucose Using α-Cyclodextrin Template Molecules

“…While it is generally true that the formation constant of a complex between an organic compound and CD molecules would be larger in aqueous media than in organic solvents, there are cases reported in the literature in which the formation constant is larger in DMF than in water. 17,18 The formation constant measured for the complex between -D-glucose and R-CD, both dissolved in water, is reported to be 36 and 447 M -1 , 19,20 both of which are significantly smaller than the ones we obtained from our experiments. We believe this is because (1) the solubility of glucose is significantly smaller in water-ethanol mixed solvent than in water, which would the make association process more favorable, and (2) we already have decreased the entropy of the system by immobilizing the R-CD on the gold surface, making a further decrease in entropy of the reaction easier.…”

Studies of volumetric and activity behaviors of binary and ternary aqueous solutions containing β-cyclodextrin and glucose

“…Using the value of k s , we obtained the log K value for β-CD:glucose complex as 4.24. Hirsch et al [28] have reported the value of 2.62 for log K while the value of −0.22 for log K is reported by Hacket et al [42] from spectroscopic, fluorimetry and calorimetric measurements respectively. Considering the drawbacks of these techniques, we feel that our value of log K for β-CD:glucose complexation is much reliable.…”

“…Recently, we came across two conflicting publications in which complexation reactions of carbohydrates with β-cyclodextrin [β-CD] as a host have been studied [28,29]. According to Hirsch et al [28], concentration of glucose can be monitored using β-CD as a complexing host.…”

“…According to Hirsch et al [28], concentration of glucose can be monitored using β-CD as a complexing host. They suggested a possibility of hydrogen bond formation on the basis of large negative enthalpies.…”

Enzymeless creatinine estimation using poly(3,4-ethylenedioxythiophene) -β-cyclodextrin

“…Alternatively, enzyme-less approaches using neutral carriers such as cyclodextrin and crown ethers, as ionophores for sensing biologically important molecules have received significant recent attention [13,14]. Cyclodextrins are the basket-shaped cyclic glucopyranose oligomer molecules with a hydrophobic internal cavity and hydrophilic exterior.…”