Investigation of buffer-cyclodextrin systems

Yi, Zhengping; Zhao, Changchun; Huang, Zhengzi; Chen, Huilan; Yu, Junsheng

doi:10.1039/a807916a

Cited by 23 publications

(13 citation statements)

References 19 publications

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“…Stability constants of complexes were higher in acetate buffer than phosphate buffer (pH 3.0), which was attributed to weaker interactions of phosphate buffer than acetate buffer as in 3-hydroxy-2-naphthoic acid (Yi et al, 1999). K s in phosphate buffer at pH 3 was higher than at pH 7, as for diclofenac and celecoxib (Al Omari et al, 2006;Perlovich et al, 2003).…”

Section: Phase/equilibrium Solubilitymentioning

confidence: 91%

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Dihydroartemisinin-cyclodextrin complexation: Solubility and stability

2009

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Dihydroartemisinin (DHA) is a major metabolite of artemisinin and its derivatives, including arteether, artemether, and artesunate. To improve the solubility and stability of poorly soluble DHA, we prepared inclusion complexes with hydroxypropyl-beta-cyclodextrin (HPbetaCD) and recrystalized DHA to study its thermal stability. The complexes were characterized by differential scanning calorimetery (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction patterns (XRD), thermal stability, phase, and equilibrium solubility studies. Pure DHA was crystalline and remained crystalline after recrystallization, but its unit cell dimensions changed as exhibited by XRD. DHA-HPbetaCD complexes showed a phase transitions towards amorphous in DSC thermograms, FTIR spectra, and XRD patterns. The phase solubility profiles of complexes prepared in water, acetate buffer, and phosphate buffers were classified as A(L)-type, indicating the formation of a 1:1 stoichiometric inclusion complex. The equilibrium solubility of DHA was enhanced as a function of HPbetaCD concentration. DHA-HPbetaCD complexes showed an 89-fold increase in solubility compared to DHA. Solubilities of complexes containing 275.1 mM HPbetaCD in water, acetate buffer (pH 3.0), and phosphate buffer (pH 3.0 and 7.4) were 10.04, 7.96, 6.30, and 11.61 mg/ml, respectively. Hydrogen bonding was found between DHA and HPbetaCD, and it was stronger in complexes prepared in water than in buffers. However, the AH values were higher in buffer than water. DHA-HPbetaCD complexes prepared using commercial (untreated) or recrystallized DHA (no detectable impurity) showed a 40% increase in thermal stability (50 degrees C) and a 29-fold decrease in hydrolysis rates compared with DHA. The rank order of stability constants (K(s)) was: water, acetate buffer (pH 3.0), phosphate buffer (pH 3.0), and phosphate buffer (pH 7.4). Thus, HPbetaCD complexation with recrystalized DHA increases DHA solubility and stability.

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Section: Phase/equilibrium Solubilitymentioning

confidence: 91%

“…pH and buffer composition can also affect inclusion complex formation (Al Omari et al, 2006;Perlovich et al, 2003 (Yi et al, 1999). Thermal-induced degradation causes the active compound to undergo molecular rearrangements.…”

Section: Introductionmentioning

confidence: 98%

Dihydroartemisinin-cyclodextrin complexation: Solubility and stability

2009

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“…Competitive Guest Complexation-Fluorescence emission intensity of 3-hydroxy-2-naphtholic acid (3H2NA; 20 M) was measured at ex 350 nm and peak em 521 nm (50) in the presence and absence of CDs and/or TSF buffer components at pH 7.4 and 25°C using a Cary Eclipse fluorescence spectrometer (Varian Inc., Palo Alto, CA). 3H2NA concentration and final volumes were kept constant.…”

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confidence: 99%

Reversible Pore Block of Connexin Channels by Cyclodextrins

Locke

Koreen

Liu

et al. 2004

Journal of Biological Chemistry

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Cyclodextrins (CDs), a series of hollow cyclic glucosaccharides, can reversibly block molecular permeation through channels formed by connexin-32 and/or connexin-26 reconstituted into liposomes. The character of the block changes as a function of the size of the CD relative to the connexin pore diameter, suggesting that the block occurs via entry of the CD into the pore lumen and occlusion of the permeability pathway. The block occurs only when the CD is applied to the side of the pore that is normally cytoplasmic and not from the side that is normally extracellular. The block is potentiated when organic analytes are sequestered in the hydrophobic interior of the CDs. CDs may be useful as molecular tools with which to explore the structure of the connexin pore and to alter molecular movement through connexin channels.

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“…One important difference is that the thiocyanide anion was shown to bind to α-and β-CD, whereas the chloride and sulfate anions seem to bind only weakly to CDs (23)(24)(25). It is possible that the changes observed in the presence of NaSCN were due to competitive binding in addition to a change in the hydration ability of water.…”

Section: Discussionmentioning

confidence: 81%

“…The addition of salts can affect the magnitude of the equilibrium constants between guests and CDs for 1:1, 1:2, and 2:2 (guest:CD) complexes (20)(21)(22)(23). The effect depends on the nature and the concentration of the salts.…”

Section: Introductionmentioning

confidence: 96%

A temperature-annealing effect on the hostguest complexation with γ-cyclodextrin

Wright¹,

Bohne²

2005

Can. J. Chem.

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Pyrene binds to γ-cyclodextrin and forms host-guest complexes with different stoichiometries. The fluorescence of pyrene was employed as a qualitative signature for these different complexes. Solutions prepared at room temperature were shown not to be in thermodynamic equilibrium, since a heating cycle of 20 min at 80°C followed by cooling led to changes in the relative concentrations of the pyrene-γ-cyclodextrin complexes. This temperatureannealing effect has consequences when determining thermodynamic parameters such as equilibrium constants and host-guest stoichiometries.Résumé : Le pyrène se lie à la γ-cyclodextrine pour former des complexes hôte-invité de stoechiométries diverses. On a utilisé la fluorescence du pyrène comme signature qualitative de ces différents complexes. On a démontré que des solutions préparées à la température ambiante ne présentent pas d'équilibre thermodynamique puisqu'un cycle de chauffage de 20 min à 80°C, suivi par un refroidissement, conduit à des changements dans les concentrations relatives des complexes pyrène-γ-cyclodextrine. Cet effet d'annellation lié à la température a des conséquences lorsqu'on veut déter-miner des paramètres thermodynamiques, tels les constantes d'équilibre et les stoechiométries hôte-invité.

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Investigation of buffer-cyclodextrin systems

Cited by 23 publications

References 19 publications

Dihydroartemisinin-cyclodextrin complexation: Solubility and stability

Dihydroartemisinin-cyclodextrin complexation: Solubility and stability

Reversible Pore Block of Connexin Channels by Cyclodextrins

A temperature-annealing effect on the hostguest complexation with γ-cyclodextrin

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Investigation of buffer-cyclodextrin systems

Cited by 23 publications

References 19 publications

Dihydroartemisinin-cyclodextrin complexation: Solubility and stability

Dihydroartemisinin-cyclodextrin complexation: Solubility and stability

Reversible Pore Block of Connexin Channels by Cyclodextrins

A temperature-annealing effect on the hostguest complexation with γ-cyclodextrin

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A temperature-annealing effect on the hostguest complexation with γ-cyclodextrin