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Abstract
The stability of β-cyclodextrinethyl benzoate6H2O(β-CDC6H5COOC2H56H2O) was investigated by TG and DSC. The mass loss takes place in three stages: the dehydration occurs at 50-120C; the dissociation of β-CDC6H5COOC2H5occurs at 200-260C; the decomposition of β-CD begins at 280C. The kinetics of the dissociation of β-CDC6H5COOC2H5in a dry nitrogen flow was studied by means of thermogravimetry both at constant temperature and linearly increasing temperature. The results show that the dissociation of β-CDC6H5COOC2H5is dominated by a three-dimensional diffusion process (D3). The activation energy E is 116.19 kJ mol-1and the pre-exponential factor A 6.5358109min-1. Cyclodextrin is able to form inclusion complexes with a great variety of guest molecules, and the studies focus on the energy of binding between cyclodextrin and the guest molecule. In this paper, the β-cyclodextrinethyl benzoate inclusion complex was studied by fluorescence spectrophotometry and infrared absorption spectroscopy, and the results show that the stable energy of inclusion complexes of β-CD with weakly polar guest molecules consists mainly of van der Waals interaction.
Abstract
The antibacterial action of amoxicillin (AMPC) and the inclusion complexes of AMPC with α-, β- and γ-cyclodextrins (α-CD, β-CD and γ-CD, respectively) to Escherichia coli B (E. coli) was evaluated by isothermal titration microcalorimetry and by petri-dish bioassay method. The effects of the compounds on produced heat during the exponential phase of the E. coli growing were measured and the growing rate constants of the cells was calculated from the power-time (p-t) curve before and after the treatment with AMPC. Results from the both methods showed that the antibacterial activity became stronger in the following order: AMPC-βCD > AMPC-γCD ≈ AMPC-αCD > AMPC only.
Abstract
The inclusion complex of benzaldehyde (BA) with β-cyclodextrin (β-CD) was prepared and was studied by thermal analysis and X-ray diffractometry. The composition of the complex was identified by TG and elemental analysis as β-CDBA9H2O. TG and DSC studies showed that the thermal dissociation of β-CDBA9H2O took place in three stages: dehydration in the range 70-120C; dissociation of β-CDBA in the range 235-270C; and decomposition of β-CD above 280C. The kinetics of dissociation of β-CDBA in flowing dry nitrogen was studied by means of TG both at constant temperature and at linearly increasing temperature. The results showed that the dissociation of β-CDBA was dominated by a one-dimensional random nucleation and subsequent growth process (A2). The activation energy E was 124. 8 kJ mol-1, and the pre-exponential factor A 5.041011 min-1.
Abstract
The complexation of β-lactam antibiotics, amoxicillin (AMPC), ampicillin (ABPC) and benzylpenicillin (PCG), with 2-hydroxypropyl-β-cyclodextrin (HPCD) was studied at various pH values using microcalorimetry, 1H NMR spectroscopy, and molecular dynamic simulation. In the strong acid solution, two different types of inclusion complex with a 1:1 stoichiometry, Complex I with a phenyl ring of β-lactam antibiotics penetrated into the cavity of HPCD and Complex II with a penam included in the cavity, were formed by hydrophobic interaction, and Complex II was more stable than Complex I. In aqueous solution at pH≥4.5, only Complex I was formed, where the penam of PCG was more deeply penetrated into the cavity to keep it stable than those of AMPC and ABPC. The charged carboxyl-group on the penam was less affinity to form Complex II.
Preparation and thermal characterization of inclusion complex of Brazilian green propolis and hydroxypropyl-β-cyclodextrin
Increased water solubility of the chemical constituents and antioxidant activity
foods [ 4 , 23 , 24 ]. Cyclodextrins (CDs) are chemically and physically stable molecules and formed by the enzymatic modification of starch [ 25 ]. They have the ability to form inclusion complexes with a wide variety of organic compounds
size of the hydrophobic parts and the positional effect of polar groups of a guest molecule on inclusion reactions, the thermodynamic properties of inclusion complexes of CD with aliphatic alcohols and other alcohols have been investigated
Abstract
The stability of β-cyclodextrin-cinnamyl alcohol inclusion complex (β-CD·C9H10·8H2O) was investigated using TG and DSC. The mass loss took place in three stages: the dehydration occurred between 50–120°C; the dissociation of β-CD·C9H10O occurred in the range of 210–260°C; and the decomposition of β-CD began at 280°C. The dissociation of β-CD·C9H10O was studied by means of thermogravimetry, and the results showed: the dissociation of β-CD·C9H10O was dominated by a two-dimensional diffusion process (D2). The activation energyE was 161.2 kJ mol−1, the pre-exponential factorA was 4.5×1013 min−1.
Cyclodextrin is able to form inclusion complexes with a great variety of guest molecules, and the interesting of studies focussed on the energy binding cyclodextrin and the guest molecule.
In this paper, β-cyclodextrin-cinnamyl alcohol inclusion complex was studied by fluorescence spectrophotometry and infrared absorption spectroscopy, and the results show: the stable energy of inclusion complexes of β-CD with weakly polar guest molecules consists mainly of Van der Waals interaction.
Abstract
Calorimetry, densimetry, 1H NMR and UV–vis spectroscopy were used to characterize inclusion complex formation of hydroxypropylated α- and β-cyclodextrins with meta- and para-aminobenzoic acids in aqueous solutions at 298.15 K. Formation of more stable inclusion complexes between para-aminobenzoic acid and cyclodextrins was observed. The binding of aminobenzoic acids with hydroxypropyl-α-cyclodextrin was found to be enthalpy-governed owing to the prevalence of van der Waals interactions and possible H-binding. Complex formation of hydroxypropyl-β-cyclodextrin with both acids is mainly entropy driven. The increased entropy contribution observed in this case is determined by dehydration of solutes occurring during the revealed deeper insertion of aminobenzoic acids into the cavity of hydroxypropyl-β-cyclodextrin. By comparing complex formation of aminobenzoic acids with native and substituted cyclodextrins it was found that the availability of hydroxypropyl groups slightly influenced the thermodynamic parameters and did not change the binding mode or driving forces of interaction.
Abstract
Citronellol and citronellyl acetate have been entrapped with α-, β- and γ-cyclodextrin (CD). Evolved gas detection and TG-MS coupling was applied to prove the actual inclusion complex formation between monoterpens and CDs. The terpene content was determined by UV-VIS specrophotometry and RP-HPLC and the effect of storage time on the terpene content was also investigated. The α- and γ-cyclodextrin inclusion complexes showed higher thermal stabilities vs. dynamic heating compared to the β-CD complexes. On the contray, the retention of guest using β-cyclodextrin even after 10 years of storage was much more pronounced. Experimental data other than 1:1 complex compositions are assumed. Molecular modeling experiments also suggested multiple complex compositions.
Abstract
Solvent and melt techniques were used to obtain molecular dispersion of the poorly soluble spironolactone (SPIR) model drug enhancing its dissolution rate. DSC study of the interaction between SPIR and hydroxypropyl-β-cyclodextrin confirmed the need for molecular dispersion if their complexation is required. Solvent-free twin-screw extrusion was suitable for forming inclusion complex significantly below the melting temperature of the SPIR. According to DSC, Raman and XRPD results fine dispersion of both components was achieved in a hydrophilic polymer. The molecules of the active ingredient are separated from each other in the polymer and the lack of the lattice energy causes faster dissolution.
