Search results for "dextrin"

Cyclodextrins in polymer chemistry: Influence of methylated β-cyclodextrin as host on the free radical copolymerization reactivity ratios of isoborny…

1999

Methylated β-cyclodextrin (me-β-CD) was used to complex the hydrophobic monomers isobornyl acrylate (1) and butyl acrylate (2) yielding the water-soluble host/guest complexes isobornyl acrylate/me-β-CD (1a) and butyl acrylate/me-β-CD (2a). The included monomers were copolymerized in water by free-radical mechanism and the kinetics were studied. In order to evaluate these results, the corresponding uncomplexed monomers 1 and 2 were also copolymerized in organic solution. The reactivity ratios of 1a and 2a (r1a = 0.3, r2a = 1.7) differ significantly from the reactivity ratios of the corresponding uncomplexed acrylates 1 and 2 in organic solution (r1 = 1.3, r2 = 1.0). In addition, we found tha…

Supramolecular assemblies of phenyl-pyridyl-triazolopyridine and β-cyclodextrin as sensor of divalent cations in aqueous solution

2014

The chemosensor 3-phenyl-7-(pyrid-2-yl)-[1,2,3]triazolo[1,5-a]pyridine (PhPTP) used in combination with two different cyclodextrins, enable its solubilization and stabilization in aqueous solution. The behavior of the inclusion complex, and its binding ability in both cyclodextrins were investigated by means of absorption and fluorescence spectroscopy. The best results were obtained for PhPTP-DMβCD assembly, and its orientation in the DMβCD nano cavity was obtained by 2D-NMR. This inclusion geometry was confirmed by docking studies. The binary complex was proved as chemosensor upon the presence of different divalent cations in aqueous solutions. The PhPTP-DMβCD system, displays a high sensi…

Complexation of phosphine ligands with peracetylated β-cyclodextrin in supercritical carbon dioxide: Effect of temperature and cosolvent on the equil…

2009

Abstract The interaction between peracetylated-β-cyclodextrin and tert-butyl and adamantyl functionalized triphenylphosphine derivatives was studied in supercritical carbon dioxide (scCO 2 ) based solvent media by UV–vis spectroscopy. The equilibrium constant for a 1:1 complexation reaction was obtained from titration spectra both in pure carbon dioxide and in the presence of methanol as a cosolvent in the temperature range 308–323 K to estimate the internal energy and entropy of the inclusion equilibrium. The values of the equilibrium constants were found significantly smaller than those obtained in aqueous solution with analogous phosphines and substantially independent of the nature of t…

Chiral separation of ephedrines by liquid chromatography using β-cyclodextrins

2001

β-cyclodextrins (β-CDs) have been evaluated as chiral recognition agents for the enantioseparation of ephedrines by liquid chromatography (LC). The compounds tested were norephedrine, ephedrine, pseudoephedrine, N-methylephedrine and N-methylpseuoephedrine. Two possibilities have been investigated, the employment of a chiral stationary phase consisting of immobilized β-cyclodextrin, and the addition of the chiral selector to the mobile phase. In the latter approach the following chiral agents have been assayed, native β-cyclodextrin (β-CD), methyl-β-cyclodextrin (M-β-CD), carboxyethyl-β-cyclodextrin (CE-β-CD), carboxymethyl-β-cyclodextrin (CM-β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD)…

Thermodynamic Properties of Sodium n-Alkanecarboxylates in Water and in Water + Cyclodextrins Mixtures

1998

Densities and heat capacities of water−substrate, water−cyclodextrin, and water−substrate−cyclodextrin systems were determined at 298 K. The substrates studied are sodium n-alkanecarboxylates (CnCOONa) (from sodium acetate to sodium decanoate) and the cyclodextrins are hydroxypropyl-α-cyclodextrin (HP-α-CD), hydroxypropyl-β-cyclodextrin, (HP-β-CD), hydroxypropyl-γ-cyclodextrin (HP-γ-CD) and β-cyclodextrin (β-CD). The apparent molar volumes and heat capacities of CnCOONa in water were calculated as functions of concentration. The standard partial molar properties agree with those obtained by using the additivity rule. HP-β-CD essentially does not affect the thermodynamic properties of C1COON…

An On/Off Circular Dichroism Signal Reveals a pH Dependent Competition between a Cyclodextrin and a Polyelectrolyte for an Atropisomeric Aromatic Gue…

1997

Structure and Photochemical Behavior of the Cyclodextrin Inclusion Complexes of the Benzoylthiophene-Derived Drugs Tiaprofenic Acid (=5-Benzoyl-α-met…

2001

The effect of β-cyclodextrin (β-CD) on the excited-state reactivity of the two benzoylthiophene derivatives, tiaprofenic acid (TPA; 2) and suprofen (SPF; 3) in their carboxylate forms is studied. The presence of β-cyclodextrin does not affect the nature of the photoproduced transients and the photoproducts, but increases the photodegradation quantum yields of both drugs. The efficiency of the photodecarboxylation process is enhanced. This effect is rationalized in the light of the inclusion of 2 and 3 in the β-CD cavity, affecting the energy of the lowest excited states of the drugs. The structure of the complexes is determined by induced circular dichroism, and molecular-mechanics and dyna…

Inhibition of cyclodextrins on α-galactosidase.

2017

This work successfully investigated the effects of different influential factors and hydrophobic cavities of cyclodextrins (CDs) on α-galactosidase (α-Gal) by detecting α-Gal activity. The highest inhibitory concentration of three kinds of CDs (α-, β-, and γ-CD) on α-Gal was 10mM. Moreover, the highest inhibition of α-Gal was obtained under the following conditions: reaction time of 90min, temperature of 30°C, and pH 6.0. Compared with other CDs, β-CD showed more ability to interact with α-Gal due to its appropriate cavity geometric dimensions. From circular dichroism and nuclear magnetic resonance it was observed that β-CD changed the secondary structure of α-Gal and formed a hydrogen bond…

Binding properties of heptakis-(2,6-di-O-methyl)-β-cyclodextrin and mono-(3,6-anhydro)-β-cyclodextrin: a polarimetric study

2011

The binding constants for the inclusion complexes formed between heptakis-(2,6-di-O-methyl)-β-cyclodextrin (MβCD) and mono-(3,6-anhydro)-β-cyclodextrin (AβCD) with a set of suitably selected organic guests, were measured by means of polarimetry. Measurements were carried out at various pH values in order to ensure the correct protonation state for ionizable guests. Experimental data suggest that the binding properties of MβCD may be rationalized considering the less polar and more hydrophobic character of the cavity, although similar variations in conformational/dynamic behaviour occur as for native βCD. On the other hand, AβCD shows some similarities with αCD, due to the significant distor…

Direct Visualization of Pyrrole Reactivity upon Confinement within a Cyclodextrin Metal–Organic Framework

2019

Metal–organic frameworks can be used as porous templates to exert control over polymerization reactions. Shown here are the possibilities offered by these crystalline, porous nanoreactors to capture highly-reactive intermediates for a better understanding of the mechanism of polymerization reactions. By using a cyclodextrin framework the polymerization of pyrrole is restricted, capturing the formation of terpyrrole cationic intermediates. Single-crystal X-ray diffraction is used to provide definite information on the supramolecular interactions that induce the formation and stabilization of a conductive array of cationic complexes.