Inclusion complexation of loratadine with natural and modified cyclodextrins: Phase solubility and thermodynamic studies

被引:34
|
作者
Omar, L.
El-Barghouthi, M. I.
Masoud, N. A.
Abdoh, A. A.
Al Omari, M. M.
Zughul, M. B.
Badwan, A. A.
机构
[1] Hashemite Univ, Dept Chem, Zarqa 13115, Jordan
[2] Jordanian Pharmaceut Mfg Co, Naur, Jordan
[3] Univ Jordan, Dept Chem, Amman, Jordan
关键词
cyclodextrins; inclusion complexes; loratadine; molecular mechanical modeling; phase solubility diagrams; hydrophobic effect; thermodynamics;
D O I
10.1007/s10953-007-9136-3
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The extent and mode of solubility enhancement exerted by the cyclodextrins (alpha-, beta-, gamma-, and HP-beta-CDs) on loratadine (Lort) have been experimentally measured under controlled conditions in buffered aqueous solutions. Rigorous nonlinear regression analysis of the phase solubility diagrams obtained in 0.1 mol center dot L-1 phosphate buffer at pH = 7.0 and 25 degrees C revealed the following: neutral Lort (pK(a) = 4.6) tends to form soluble 1: 1 and 1:2 Lort/CD complexes with all four of the examined CDs, where complex stability follows the decreasing order -CD > HP-P-CD > gamma-CD > alpha-CD. The hydrophobic character of Lort constitutes about 66% of the driving force for complex formation whereas specific interactions contribute 11.2 kJ center dot mol(-1) towards the stability of the complexes. Thermodynamic studies showed that Lort/CD complex formation was favored by large enthalpic contributions but was impeded by negative entropic changes. Dissolution studies indicate that the dissolution rate of Lort from the freeze-dried Lort/beta-CD complex is significantly higher than that of the corresponding physical mixture. Both DSC studies and molecular mechanical modeling of Lort/beta-CD interactions were carried out to explore the possible formation of inclusion complexes.
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页码:605 / 616
页数:12
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