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1.
Mahmoud M. Al Omari Mohammad B. Zughul J. Eric D. Davies Adnan A. Badwan 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):247-254
The interaction of celecoxib (Celox) with cyclodextrins (CDs) has been investigated by phase solubility techniques. In this study, the influences of CD type, pH, buffer type, buffer concentration and temperature on the tendency of Celox to form inclusion complexes with CDs were examined. The tendency of Celox to complex with CDs is in the order HP-β-CD > β-CD > γ-CD > α-CD, where the complex formation constants (K
11) were 1377, 693, 126 and 60 M−1, respectively. Also ionization of the slightly acidic Celox (pK
a=9.7) was found to reduce its tendency to complex (i.e., The K
11 values of Celox/β-CD in 0.05 M phosphate buffer were 976 and 210 M−1 for neutral and ionized Celox, respectively). Increasing citrate and phosphate buffer concentration enhances the tendency of ionized Celox to complex with β-CD as a result of a corresponding decrease in the inherent solubility (S
0) of the Celox anion. On the other hand, these two buffers interact differently with neutral Celox and β-CD, where increasing phosphate buffer concentration at low pH enhances the complexation of neutral Celox by lowering S
0, while increasing citrate buffer concentration at low pH reduces complex formation as citrate buffer species, mainly citric acid, act as a solublizer and a competitor for Celox and β-CD. The contribution of Celox hydrophobicity for complex stability constitutes about 77% of the driving force for complex stability. The complex formation of neutral Celox with β-CD (ΔG
0=−28.6 kJ/mol) is driven by both enthalpy (ΔH
0=−21.7 kJ/mol) and entropy (ΔS
0=23.3 J/mol K) changes. 相似文献
2.
F. O. Yousef M. B. Zughul A. A. Badwan 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):519-523
The results of rigorous modeling of phase solubility diagrams, pH solubility profiles and potentiometric titrations revealed
the following for benzimidazole (BZ) and BZ/β-CD complexation in aqueous solution: (a) the pK
a value of BZ estimated at 5.66 ± 0.08 was reduced to 5.33 ± 0.06 in the presence of 15 mM β-CD at 25 °C, thus indicating inclusion complex
formation; (b) BZ forms soluble 1:1 and 2:1 BZ/β-CD complexes with complex formation constants K
11 = 104 ± 8 M−1 and K
21 = 16 ± 6 M−1; (c) protonated BZ forms only 1:1 complex with K
11 = 42 ± 12 M−1; (d) 1H-NMR studies in D2O showed significant upfield chemical shift displacements for inner cavity β-CD protons indicating inclusion complex formation,
while (e) Molecular modeling of BZ-β-CD interactions in water clearly indicated complete inclusion of one BZ molecule into the β-CD cavity. 相似文献
3.
Tze-Loon Neoh Yasuhiro Noda Hidefumi Yoshii Takeshi Furuta 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):117-123
The effect of cyclodextrins (CDs) on water solubility of iodine was investigated. Modified CDs greatly enhanced the solubility of iodine. On the contrary, enhancement by natural CDs was rather moderate whereby the solubility was only doubled at the highest β-CD concentration examined. Desorption experiment of iodine from solution was carried out with addition of various CDs to study the effect of CDs on iodine retention. α-CD was the most efficient in retarding iodine desorption. Later, various concentrations of α-CD were used in the desorption experiment to observe its volatile suppression effect and determine the stability constant of iodine/α-CD complexation. At α-CD concentration of 10.3 mM, no lost of iodine from the solution was detected. A model was developed for desorption of iodine from the solution based on mass transfer theory. The stability constant K given by this model was 3.28×104 M−1 which was in the same order as the value estimated in this study by solubility method and as well those reported by other authors. In release experiments of solid state inclusion complexes, stability of inclusion complex powders decreased in the order of α-CD>β-CD>randomly methylated β-CD (RM-β-CD). 相似文献
4.
Tatsuya Morozumi Nao Sato Hiroshi Nakamura 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):141-148
Inclusion complexation behavior of 2,3,6−tri-O-methyl-β-cyclodextrin (TM-β-CD) with zinc(II) 5,10,15-tri-(4-t-butyl-phenyl)-20-(4-(n-alkyloxy)phenylporphyrin covalently linked with violgen by a polymethylene chain (Zn-t- bu-PC
n
V2+; n=4, 6, 8, 10 and 12) was investigated by means of 1H NMR, UV/Vis absorption spectroscopies in acetonitrile-water (1:1, v/v). The 1H NMR spectra indicated that Zn-t-bu-PC
n
V2+ presumably existed as a mixture of a dimer and a monomer in high concentration (>1×10−3 mol dm−3), and the dimer was degraded by the complex formation with TM-β-CD. The 1H NMR spectra of these compounds as a function of [TM-β-CD] showed the selective formation of 1:1 (=Zn-t-bu-PC
n
V2+: TM-β-CD) pseudo-rotaxane type complexes. The chemical modification by t-butyl groups on porphyrin showed a good protective effect on inclusion of benzene groups into the TM-β-CD cavity. These rotaxane formation constants (K) were determined by titration studies using UV/Vis absorption spectroscopy. These complex formation constants were somewhat affected by the spacer methylene chain between the porphyrin and viologen. The value of K for Zn-t-bu-PC4V2+·TM-β-CD is 1.0×103 M−1 which is the smallest whereas those for Zn-t-bu-PC
n
V2+·TM-β-CD (n=8, 10, 12) were similar (1.0×104 M−1). 相似文献
5.
Ameer Ghuzlaan Mahmoud M. Al Omari Khaldoun A. Al-Sou’od 《Journal of solution chemistry》2009,38(1):83-94
Guest–host interaction of prednisone (PN) with cyclodextrins (CDs) have been investigated using phase solubility diagrams
(PSD), differential scanning calorimetry (DSC), X-ray powder diffractometry (XRPD), scanning electron microscopy (SEM) and
molecular mechanical modeling (MM). Estimates of the complex formation constant (K
11) show that the tendency of PN to complex with CDs follows the order: β-CD>γ-CD>HP-β-CD>α-CD. At the same pH of 7.0, β-CD forms soluble 1:1 and insoluble 1:2 PN/CD complexes (BS-type PSDs). The thermodynamic functions for 1:1 PN/β-CD estimated at pH = 7.0 (ΔG
11o=−20.8 kJ⋅mol−1) show that complexation is driven by enthalpy (−30.7 kJ⋅mol−1) but retarded by entropy (ΔS
11o=−33.1 J⋅mol−1⋅K−1) changes. The MM modeling study indicates the formation of different isomeric 1:1 complexes with CDs. PSD, DSC, XRPD, SEM
and MM studies established the formation of inclusion complexes in solution and the solid state. 相似文献
6.
YU LIU RUI CAO YING-WEI YANG 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):183-191
Complex stability constants (K
S), standard molar enthalpy changes (ΔH°) and entropy changes (TΔS°) for the inclusion complexation of native β-cyclodextrin (β-CD) (1) and some modified β-CDs, i.e., mono(6-ethylenediamino-6-deoxy)-β-CD (3), mono[6-diethylenetriamino-6-deoxy]-β-CD (4) and their corresponding copper complexes 5 and 6, with four representative bile acid guests, i.e., cholate (CA), deoxycholate (DCA), glycocholate (GCA) and taurocholate (TCA), were determined at 25 °C in aqueous phosphate buffer solution (pH 7.20) by means of isothermal titration microcalorimetry (ITC). The stoichiometry of resulting inclusion complexes between CDs and bile acids was demonstrated by UV and conductivity as well as ITC experiments, showing 1:1 binding model upon all inclusion complexation except for metal-mediated dimer 5. The complex stability constants for modified β-CD 2–4 are dramatically magnified with the extended length of amino tether. As compared with 3 and 4, copper(II) complexes 5 and 6 significantly enhance not only binding ability but also molecular selectivity toward bile guest molecule CA through multipoint recognition, but decreased complexes stability toward TCA could be attributed to the decreased hydrophobic microenvironment of CDs cavity due to the introduction of copper(II) coordination center. Thermodynamically, the resulting complexes between hosts and bile guests are driven absolutely by enthalpy, accompanied by entropy gain or loss. Using the present data and those previously reported for mono(6-amino-6-deoxy)-β-CD (2), thermodynamic behavior and enhanced molecular selectivity could be discussed from the viewpoint of hydrophobic interactions, electrostatic cooperation and van der Waals between the hosts and guests. 相似文献
7.
Yoshimi Sueishi Naoya Inazumi Tatsuhiro Ide Tadashi Hanaya 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):201-208
The inclusion complexation of 6-O-α-D-glucosyl-β-cyclodextrin (G-β-CD), in which the glucosyl side chain is introduced to β-CD, with various kinds of phenols was studied spectrophotometrically at high pressures. The characteristic effects of substituent and pressure were found for the inclusion complexation of G-β-CD. The association constants K for the G-β-CD inclusion complexation increased with an increase in the bulkiness of the 4-substituent groups in phenols. As the external pressure increases, the inclusion constants for the G-β-CD complexation increased and the reaction volumes were estimated to be −3.8 to −19.4 cm3 mol−1 from their pressure dependences. From analysis of the effect of pressure on the inclusion complexation with G-β-CD, the number of water molecules included in the G-β-CD cavity in water was estimated. The number of water molecules repelled from the CD cavity plays an important role in the change in volume upon inclusion. In addition, the structures of the inclusion complexes of G-β-CD with phenols have been established by 1D and 2D NMR measurements. Based on the results, we suggested that the ability of the G-β-CD inclusion complexation is enhanced by the interaction between guest molecules and the glucosyl side chain of G-β-CD. 相似文献
8.
Improvement of Steroid Biotransformation with Hydroxypropyl-β-Cyclodextrin Induced Complexation 总被引:1,自引:0,他引:1
Liting Zhang Min Wang Yanbing Shen Yinhu Ma Jianmei Luo 《Applied biochemistry and biotechnology》2009,159(3):642-654
The inclusion complexes induced by cyclodextrins and its derivates have been shown previously to enhance the biotransformation
of hydrophobic compounds. Using hydroxypropyl-β-cyclodextrin (HP-β-CD; 20% w/v), the water solubility of cortisone acetate increased from 0.039 to 7.382 g L−1 at 32 °C. The solubilization effect of HP-β-CD was far superior to dimethylformamide (DMF) and ethanol. The dissolution rate
also significantly increased in the presence of HP-β-CD. The enzymatic stability of Δ1-dehydrogenase from Arthrobacter simplex TCCC 11037 was not influenced by the increasing concentrations of HP-β-CD contrary to the organic cosolvents which negatively
influenced in the order DMF > ethanol. The activity inhibition effect caused by HP-β-CD was not so conspicuous as ethanol
and DMF. Inactivation constants of ethanol, DMF, and HP-β-CD were 5.832, 4.541, and 1.216, respectively. The inactivation
energy (E
a) was in the order of HP-β-CD (55.1 kJ mol−1) > ethanol (39.9 kJ mol−1) > DMF (37.1 kJ mol−1). 相似文献
9.
Mahmoud M. Al Omari Musa I. El-Barghouthi Mohammad B. Zughul J. Eric D. Davies Adnan A. Badwan 《Journal of solution chemistry》2008,37(2):249-264
The interaction of two benzocycloheptanes namely, pizotifen (Pizo) and ketotifen (Keto), with cyclodextrins (CDs: α-, β-, γ-, and HP-β-CDs) has been investigated by several techniques including phase solubility, X-ray powder diffractometry, 1H-nuclear magnetic resonance and molecular mechanical modeling. The effects of CD type, pH, ionic strength and temperature
on complex stability were also explored. The complex formation constant (K
11) values for the Pizo/CD system follows the decreasing order β-CD > γ-CD > HP-β-CD > α-CD. However, for the Keto/CD system it follows the decreasing order γ-CD > β-CD > HP-β-CD > α-CD. The tendency of Pizo and Keto to complex with β-CD is driven to the extent of 70% by the hydrophobic effect. Complex formation of Keto and Pizo was substantially driven
by entropy (>100 J⋅mol−1⋅K−1) but slightly retarded by enthalpy (3–8 kJ⋅mol−1). 1H-NMR and MM+ studies indicate multimodal inclusion of the methylpiperadine, thiophene and phenyl moieties into the β-CD cavity. 相似文献
10.
Emilio Alvarez-Parrilla Laura A. De La Rosa Francisco Torres-Rivas Joaquín Rodrigo-Garcia Gustavo A. González-Aguilar 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(1-2):121-129
The complexation and antioxidant activity of the major apple polyphenols: Chlorogenic Acid (CA), Rutin (Rt) and Quercetin
(Qc) with β-cyclodextrin (β-CD) were studied, by fluorescence spectroscopy and Ferric Reducing/Antioxidant Power Assay (FRAP) techniques. All polyphenols
formed 1:1 stoichiometry complexes. Their stability constants decreased in the order Qc (1138 M−1) > CA (465 M−1) > Rt (224 M−1). The complex formation was also confirmed in the solid state by DSC measurements. Qc showed the highest antioxidant activity,
followed by Rt and CA. In all cases, the complexation process produced a slight increment in their antioxidant activity (between
7 and 14%), more evident for Rt and CA than for Qc.
*Part of this paper was presented at the Food Science and Food Biotechnology in Developing Countries Conference, Durango,
Mexico, June 2004. 相似文献
11.
Hideyoshi Abe Akira Kenmoku Noriyuki Yamaguch Kenjiro Hattori 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):39-47
Bi-galactose-branched cyclodextrins (Bi-Gal-CDs)(1–6) having different spacer arm lengths between two terminal galactoses were foundto have the optimum length for association with PNA lectin. Also, the inclusioninteraction of the drug depended on the length of the spacer arms. The dual association of thesecompounds was quantitatively evaluated by SPR and compared to the other oligosaccharide-branchedCDs (Scheme 1). The number and the length of the spacer arm are important for theassociation both with the lectin and drug for the purpose of targeting drug-delivery systems.The association constants K of bi-Gal-CD (2) with rat liver cells showed a 60 timeshigher association than with PNA. Direct evidence of the association between PNA andbi-Gal-CD (2) was characterized by AFM observations. The results obtained strongly suggested a method to find a new design for the targeting drug carrier. In order toincrease the association with the cell, a sufficient spacer arm length is necessary for the effectivedual recognition of the oligosaccharide-CDs. In order to increase the inclusion of thedrug, the CD structure of a multi-saccharide branch is necessary. 相似文献
12.
V. B. Nazarov V. G. Avakyan S. P. Gromov M. V. Fomina T. G. Vershinnikova V. Yu. Rudyak M. V. Alfimov 《Russian Chemical Bulletin》2007,56(2):281-289
The electronic absorption spectra and fluorescence spectra of 4-(2-naphthyl)pyridine (1), 2-(4-methyl-2-pyridyl)-4-(2-naphthyl)pyridine (2), and 4-(2-naphthyl)-2-phenylpyridine (3) in solutions and in complexes with β-cyclodextrin (β-CD) and well water-soluble hydroxy-propyl-β-cyclodextrin (HP-β-CD)
were studied. Fluorescence near 475 nm observed in aqueous solutions of compounds 1–3 arises from protonated forms of these compounds produced in the excited state. Results of DFT quantum chemical calculations
show an increase in proton affinity energies of excited-state naphthylpyridines 2 and 3. The formation of inclusion complexes with cyclodextrins makes protonation of compounds 2 and 3 more difficult, which manifests in large hypsochromic shifts of fluorescence band maxima. The stability constants of the
complexes 1·HP-β-CD and 2·HP-β-CD determined from their fluorescence spectra are 3425 and 3760 L mol−1, respectively. The stability constant of the complex 3·HP-β-CD (5500±600 L mol−1) was found from the changes in the solubility of naphthylpyridine 3 in water upon complexation. Semiempirical quantum chemical calculations of the molecular structures and thermodynamic characteristics
of pseudorotaxane inclusion complexes of trans-2, cis-2, and trans-2·H2O with HP-β-CD were carried out.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 272–280, February, 2007. 相似文献
13.
Iwao Suzuki Akiyo Yamauchi 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):193-200
Pseudo[3]rotaxane type complexation of α- and β-cyclodextrins (α- and β-CDs, respectively) with N,N′-Diheptyl-4,4′-bipyridinium (diheptyl viologen; HV2+) was investigated. A spectral displacement method using p-nitrophenol as a dye revealed that α-CD and HV2+ formed a 2:1 host-guest complex with stability constants being 3280 and 976 M−1 as the first and second steps of complexation, respectively. 1H-NMR spectra strongly indicated that α-CD accommodated the heptyl groups of HV2+. Although previous studies based on circular dichroism spectroscopy suggested the primary hydroxy side of α-CD faced to the positively charged bipyridinium moiety od HV2+, 2D-NMR studies clearly demonstrated that the secondary hydroxy side of α-CD faced to the bipyridinium moiety. β-CD also formed a 2:1 complex with HV2+ with a similar fashion. 相似文献
14.
Mahmoud M. Al Omari Mohammad B. Zughul J. Eric D. Davies Adnan A. Badwan 《Journal of solution chemistry》2008,37(6):875-893
Guest–host interaction of astemizole (Astm) with cyclodextrins (CDs) has been investigated using phase solubility diagrams
(PSD), differential scanning calorimetry (DSC), X-ray powder diffractometry (XRPD), proton nuclear magnetic resonance (1H-NMR) and molecular mechanical modeling (MM+). Estimates of the complex formation constant, K
11, show that the tendency of Astm to complex with CDs follows the order: β-CD>HP-β-CD>γ-CD, α-CD. 1:1 Astm/β-CD complex formation at pH=5.0 was largely driven by the hydrophobic effect (desolvation), which was quantitatively estimated
at −16.5 kJ⋅mol−1, whereas specific interactions contribute only −5.3 kJ⋅mol−1 to 1:1 complex stability (ΔG
11o=−22.7 kJ⋅mol−1). The percentage contributions of the hydrophobic effect and specific interactions were therefore 73 and 27%, respectively.
Both enthalpic and entropic factors contribute equally well (−11 kJ⋅mol−1 each) to 1:1 Astm/β-CD complex stability. 1H-NMR and MM+ molecular modeling studies indicate the formation of different isomeric 1:1 and 1:2 complexes. The dominant driving force
for complexation is evidently van der Waals with very little electrostatic contribution. PSD, 1H-NMR, DSC, XRPD and MM+ studies proved the formation of inclusion complexes in solution and the solid state. 相似文献
15.
K. Phatthiyaphaibun W. Som-Aum M. Srisa-ard J. Threeprom 《Journal of Analytical Chemistry》2010,65(7):755-759
A capillary zone electrophoresis procedure has been developed for the chiral determination of pheniramine in eye drop. Native
and derivative cyclodextrins (CDs) including γ-CD, β-CD, hydroxypropyl-β-CD and dimethyl-β-CD were tested as chiral selectors. Using 30 mM hydroxypropyl-β-CD
in 50 mM phosphate buffer (pH 3.0), the acceptable resolution value (R = 1.55) was obtained. The assay was validated for linearity (3.3 × 10−6–5.0 × 10−4 M; R
2 = 0.9996), limit of detection (3.3 × 10−6 M), limit of quantification (8.5 × 10−6 M), analytical precision by terms of intra- and inter-day variability (RSD ≤ 2.57%), and accuracy (recovery ≥ 89.3%). The
content of pheniramine in eye drop obtained by the proposed method was in good agreement with the declared value. The results
indicated that pheniramine in the eye drop was present as the racemate. 相似文献
16.
M. I. El-Barghouthi N. A. Masoud J. K. Al-Kafawein M. B. Zughul A. A. Badwan 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(1-2):15-22
The solubility of risperidone (Risp) in aqueous buffered cyclodextrin (CD) solution was investigated for α-, β-, γ- and HP-β-CD. The effects of pH, ionic strength and temperature on complex stability were also explored. Neutral Risp tends to form
higher order complexes (1:2) with both β- and HP-β-CD, but only 1:1 type complexes with α-, and γ-CD. The tendency of Risp to complex with cyclodextrins is in the order β-CD > HP-β-CD > γ-CD > α-CD. The 1:1 complex formation constant of Risp/HP-β-CD increases with increasing ionic strength in an opposite trend to the inherent solubility (S
0) of Risp, thus indicating significant hydrophobic effect. The hydrophobic effect contributes to the extent of 72% towards
neutral Risp/HP-β-CD complex stability, while specific interactions contribute only 4.7 kJ/mol. Thermodynamic studies showed that 1:1 Risp/HP-β-CD complex formation is driven by a favorable enthalpy change (ΔH
0=−31.2 kJ/mol, ΔS
0=−7 J/mol.K) while the 1:2 complex is largely driven by entropy changes (ΔH
0=−5.0 kJ/mol, ΔS
0=42 J/mol.K). Complex stability was found to vary with pH, with a higher formation constant for neutral Risp. Molecular mechanical
computations using MM (atomic charges and bond dipole algorithms) and Amber force fields, which were carried out to explore
possible sites of interactions between Risp and CDs and to rationalize complex stoichiometry, produced similar results concerning
optimal inclusion complex geometries and stoichiometries. 相似文献
17.
Rimiko Ozawa Takashi Hayashita Takahiro Matsui Chiaki Nakayama Akiyo Yamauchi Iwao Suzuki 《Journal of inclusion phenomena and macrocyclic chemistry》2008,60(3-4):253-261
N,N-Dimethyl-4-aminophenylboronic acid (DMAPB) showed pH-dependent dual fluorescence at 360 and 462 nm originating from locally
excited (LE) and twisted intramolecular charge transfer (TICT) states, respectively, in aqueous solutions. Upon complexation
with α-CD, LE fluorescence was markedly increased while TICT fluorescence was decreased. In contrast, both LE and TICT fluorescence
were increased when DMAPB was complexed with β-CD. The fluorescence variations enabled us to determine the 1:1 and 1:2 binding
constants of the DMAPB/α-CD complex to be 10 and 40 M−1, respectively, and the 1:1 binding constant of the DMAPB/β-CD complex to be 635 M−1. The dual fluorescence of DMAPB alone was found to be a good indicator of saccharide sensing. Under weakly alkaline conditions,
saccharides suppressed TICT fluorescence while increasing LE fluorescence. Among the saccharides investigated, d-fructose induced the largest fluorescence change, followed by d-ribose and d-glucose. This order is consistent with the stability of the boronate esters of DMAPB with saccharides. In the presence of
β-CD, saccharide selectivity was unchanged, while fluorescence was amplified. These results demonstrate the superiority of
the supramolecular DMAPB/β-CD complex to DMAPB alone as a ratiometric fluorescence sensor for saccharides in water. 相似文献
18.
Iulia Matei Anca Nicolae Mihaela Hillebrand 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):597-601
The complex formed by the inclusion of the polarity-sensitive fluorescent probe 2-[2′-quinoxalinyl]-phenoxathiin (QP) into
β-cyclodextrin (β-CD) was investigated by steady-state fluorescence spectroscopy in order to confirm the previously stated intramolecular charge
transfer nature of the first excited singlet state of QP. A decrease in the emission intensity in the presence of β-CD was observed and explained on this basis. The 1:1 stoichiometry of the inclusion complex and its association constant
of 2,223 M−1 were computed. The QP–β-CD complex was further studied by molecular mechanics (MM+ force field), in order to determine its structure and the type
of interactions between QP and β-CD. All possible ways QP could penetrate the β-CD cavity were considered and several structures were generated and optimized. The interaction, binding (van der Waals and
electrostatic contributions) and perturbation energies were also calculated. The results have showed that the β-CD cavity incorporates the central part of QP and that complexation is mainly due to van der Waals host–guest interactions. 相似文献
19.
Wojciech Zielenkiewicz Małgorzata Koźbiał Bożenna Golankiewicz Jarosław Poznański 《Journal of Thermal Analysis and Calorimetry》2010,101(2):555-560
Solubilities of tricyclic acyclovir derivatives in buffered aqueous solutions of hydroxypropyl-β-cyclodextrin (HP-β-CD) at
pH 5.5 and 7.0 were determined at 25 and 37 °C. Complexation of these compounds with HP-β-CD resulted in a noticeable increase
of their solubility; nevertheless it was limited to tricyclic derivatives of acyclovir carrying an aryl substituent. Combination
of 1H NMR and DSC techniques demonstrated the existence of inclusion complexes between acyclovir derivatives and HP-β-CD. The
stability constants, estimated using the Higuchi–Connors method, were found in the range of 10–100 M−1. Additionally, the pK
a values at 25 °C and molar extinction coefficients in aqueous buffered solutions were also determined for all studied compounds. 相似文献
20.
Mame Diabou Gaye Seye C. Parrain J.J. Aaron N. Motohashi 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):271-277
The electronic absorption and fluorescence spectral properties of 11-methyl-12H-benzo[a]phenothiazine (11-MeBPHT) were investigated in various media (water, ethanol, β-cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) aqueous solutions). Fluorescence quantum yields were respectively about 20 and 2 times larger in HP-β-CD and β-CD than in water. The formation of a 1:1 stoichiometry inclusion complex between 11-MeBPHT and HP-β-CD (association constant K
f=118±3 M−1 at 20 °C) was studied in aqueous medium by fluorescence spectroscopy. Analytical figures of merit were satisfactory for 11-MeBPHT with linear dynamic ranges over at least two orders of magnitude and limits of detection (LODs) between 0.2 and 1 ng/ml according to the medium. An analytical application to the determination of 11-MeBPHT in human urine samples by the standard addition procedure led to satisfactory recovery percentages (91–108%). 相似文献