Search Results
physicochemical properties of econazole- β -cyclodextrin complexes . J Incl Phenom Macrocycl Chem 60 : 85 – 93 10.1007/s10847-007-9356-6 . 5. Zielenkiewicz , W , Kozbiał , M , Golankiewicz , B
Thermodynamics of water/β-cyclodextrin system
An interaction model
Abstract
The thermodynamics of β-cyclodextrin dehydration is investigated, by parallel DSC/TG experiments, on both fully and partially hydrated samples. The apparent dehydration enthalpies per mole of water are impossibly high and this fact suggests that another phenomenon, in addition to the rupture of the β-cyclodextrin/H2O hydrogen bonds, contributes to the peak area. All the experimental evidence agrees with an ‘interaction model’ which assumes that deydration is accompanied by a slow and reversible rearrangement of the β-cyclodextrin structure.
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
hydroxypropyl-β-cyclodextrin for analysis solubility in water and evaluation of antioxidant activity. Materials and methods Reagents, chemicals, and equipments The following compounds were used as standards in HPLC
complexation of nevirapine with β-cyclodextrin (β-CD) along with its methyl-β-CD (M-β-CD) and hydroxypropyl-β-CD (HP-β-CD) derivatives including the studies in the presence of non-ionic surfactant (Tween 80). The focus is tilted toward numerical values of K
Abstract
The search for the lowest energy conformation of complex {β-cyclodextrin (β-CD)+chlorambucil} were carried out by molecular mechanics method. Theoretical calculations of molecular interactions of complex were carried out using the molecular orbital method. The correlation between energy changes and molecular structures are discussed. The large interaction energies calculated by the molecular orbital method bears out the inclusion phenomenon.
Abstract
Solid formulas obtained between furosemide and two β-cyclodextrin derivatives (HP-β-CD and RAMEB) were prepared by different methods and in various ratios (1:1 and 1:2). The inclusion complex formation between the drug and the β-CDs of 1:1 ratio was evaluated by mean of thermal analysis (DSC, TG and EGD). Supplementary techniques, such as X-ray diffraction, were also applied to interpret the results of the thermal study of physically mixed and kneaded products. Both studies demonstrated the formation of inclusion complexes in all samples except the physical mix samples; formation of true inclusion complexes was then possible only when the components were in melted form. The complexation increased the solubility and the rate of dissolution of the drug. RAMEB was found to be a better complexing agent than HP-β-CD; in both ratios it can be selected as a vehicle in furosemide tablet preparations.
Abstract
The enthalpies of solution of α- and β-cyclodextrins is aqueous peptide solutions were determined experimentally at 298.15 K. The obtained results were used to calculate pair cross interaction parameters between solutes. The results are discussed in terms of the likelysolute–solute interactions. For systems α-cyclodextrin+peptide and β-cyclodextrin+peptide the diametrically opposite character of interaction defined by structure and solvation of the molecules is observed.
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.
Introduction
It was previously shown that intracerebroventricular administration of pituitary adenylate cyclase-activating polypeptide (PACAP) prior to GnRH mobilization in proestrus prevents ovulation in rats. In this study, we examined whether PACAP given intranasally could influence luteinizing hormone (LH) and prolactin (PRL) surges and ovulation.
Methods
On the day of proestrus PACAP, β-cyclodextrin (modifier of blood–brain barrier) or PACAP + β-cyclodextrin was applied intranasally between 12:30 and 13:00. Blood samples were taken at 16:00, 18:00, and 20:00 for measuring plasma hormone levels. In the next morning, the expelled ova were counted. β-Cyclodextrin was also administered to male and diestrous female rats between 12:30 and 13:00 and blood was taken at 18:00.
Results
PACAP prevented LH and PRL surges and ovulation in about half of the rats, β-cyclodextrin alone more effectively prevented ovulation. When PACAP and β-cyclodextrin were administered together, more rats ovulated like when PACAP given alone. β-Cyclodextrin did not influence LH and PRL levels in diestrous females; however, in males, it significantly enhanced PRL level.
Discussion
Not only the intracerebroventricular, but the intranasal application of PACAP prevented ovulation. β-Cyclodextrin alone is more effective than PACAP and enhances PRL levels in male rats. PACAP and β-cyclodextrin given together weaken each other’s effect. β-Cyclodextrin, as excipient of various drugs, has to be used carefully in human medications.
Summary
Enantiomeric resolution of two commonly used β-blockers, namely, (±)-propranolol and (±)-atenolol, has been achieved on silica gel layers which were bulkimpregnated with β-cyclodextrin. Solvent systems DMF-ethyl acetate-butanol (3:2:5, υ/υ) and butanol-acetic acid-ethyl acetate-ammonia (5:2:2:0.5, υ/υ) successfully resolved the enantiomers of (±)-propranolol and (±)-atenolol, respectively. The spots were located with iodine vapor. The effects of concentration of the chiral selector and mobile phase variation were also studied.
