Authors:
H. AkiFukuoka University Faculty of Pharmaceutical Sciences 8-19-1 Nanakuma Jonan-ku, Fukuoka 814-0180 Japan 8-19-1 Nanakuma Jonan-ku, Fukuoka 814-0180 Japan

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T. NiiyaFukuoka University Faculty of Pharmaceutical Sciences 8-19-1 Nanakuma Jonan-ku, Fukuoka 814-0180 Japan 8-19-1 Nanakuma Jonan-ku, Fukuoka 814-0180 Japan

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Y. IwaseFukuoka University Faculty of Pharmaceutical Sciences 8-19-1 Nanakuma Jonan-ku, Fukuoka 814-0180 Japan 8-19-1 Nanakuma Jonan-ku, Fukuoka 814-0180 Japan

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M. GotoFukuoka University Faculty of Pharmaceutical Sciences 8-19-1 Nanakuma Jonan-ku, Fukuoka 814-0180 Japan 8-19-1 Nanakuma Jonan-ku, Fukuoka 814-0180 Japan

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T. KimuraKinki University Faculty of Science and Technology Kowakae 3-4-1, Higashi-Osaka 3-4-1 Osaka 577-8502 Japan Kowakae 3-4-1, Higashi-Osaka 3-4-1 Osaka 577-8502 Japan

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Abstract  

The formation of inclusion complexes between amoxicillin (AMPC) and 2-hydroxypropyl-β-cyclodextrin (HPCD) was investigated by isothermal microcalorimetry and molecular dynamics simulation to evaluate the inhibitory effects on the degradation of AMPC in aqueous solutions at various pH. The process depended significantly on the ionic species of AMPC in the solution. In a strong acid solution, cationic AMPC and HPCD formed two different types of inclusion complexes with a 1:1 stoichiometry: the first-type had a high association constant K 1 of 4.0-8.0103 M-1 and included the penam ring of AMPC in the HPCD cavity (Mode I), while the second-type with a K 2 of 1.0103 M-1 contained the phenyl group of AMPC (Mode II). Furthermore, a complex with a 1:2 (AMPC:HPCD) stoichiometry was realized in a two-step reaction and was characterized by a smaller K 1:2of 4.0102 M-1 and larger negative enthalpy and entropy changes than the complexes with a 1:1 stoichiometry. Since the β-lactam ring of AMPC could be protected by inclusion with HPCD in the 1:2 complex and Mode I of 1:1 complexes, the degradation of AMPC in the presence of HPCD was approximately four times slower than in its absence at pH 1.2 and 37C. In weak acid and neutral solutions, zwitterionic AMPC and HPCD formed only one type of inclusion complex with a 1:1 stoichiometry, where the phenyl group was included (Mode II). AMPC was very stable in these solutions (t 1/2=226 h at pH=6.0) and there is little significant difference in the degradation rate between complexed AMPC and uncomplexed AMPC. Thus, the results indicated that the inclusion complex of AMPC with HPCD, effectively increasing the stability of AMPC in a strong acidic solution like that the stomach, would be useful for eradicating Helicobacter pylori infection and as a drug delivery system.

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Journal of Thermal Analysis and Calorimetry
Language English
Size A4
Year of
Foundation
1969
Volumes
per Year
1
Issues
per Year
24
Founder Akadémiai Kiadó
Founder's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
Publisher's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher
Chief Executive Officer, Akadémiai Kiadó
ISSN 1388-6150 (Print)
ISSN 1588-2926 (Online)

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