Examination of the physicochemical properties of caffeic acid complexed with γ-cyclodextrin

Autor: Kengo Suzuki, Mami Yokota, Isamu Murata, Toshinari Ezawa, Ikuo Kanamoto, Yutaka Inoue, Yoshihiro Tokudome
Rok vydání: 2015
Předmět:
Zdroj: Journal of Inclusion Phenomena and Macrocyclic Chemistry. 83:289-298
ISSN: 1573-1111
1388-3127
DOI: 10.1007/s10847-015-0564-1
Popis: Caffeic acid (CA) is a hydrophobic polyphenol with a high antioxidant capacity and γ-cyclodextrin (γ-CD) is a cyclic polysaccharide. The current study prepared a coprecipitate (CP), a freeze-dried (FD) preparation, a ground mixture (GM), and a physical mixture (PM) of CA and γ-CD, and this study then assessed the physicochemical properties and antioxidant capacity of these preparations. PXRD patterns revealed that a PM and a GM prepared at a certain molar ratio (CA/γ-CD = 1/1) produced a diffraction peak due to CA crystals. Diffractions peaks characteristic of CA and γ-CD disappeared with the CP, but new peaks were noted. In addition, an FD with CA and γ-CD at a molar ratio of 1/1 produced a halo pattern. DSC measurements revealed that the PM produced an endothermic peak at 220 °C due to the melting of CA, but the endothermic peak due to CA disappeared with the CP, FD, and GM. IR spectra revealed that the absorption peak due to the carbonyl group (C=O) of CA shifted for both the CP and the FD. The absorption peak due to C=C in the aromatic ring of CA also shifted. These findings presumably indicate molecular interaction between CA and γ-CD when the 2 substances are present at a molar ratio of 1/1 (CA/γ-CD). In the GM, molecular interaction presumably occurred as a result of heat. The preparations were compared to CA alone in dissolution testing, which revealed that the CP and FD both had a high rate of dissolution. 1H-1H NMR (NOESY) spectra revealed cross peaks involving protons of the γ-CD cavity and protons of the aromatic ring of CA. Thus, the formation of CA and γ-CD inclusion complexes helped to improve the dissolution of CA and γ-CD at a molar ratio of 1/1. The CP and FD had a higher antioxidant capacity than did CA alone. This presumably indicates that the formation of CA and γ-CD inclusion complexes helped to increase the electron density of CA in the CD cavity.
This is a post-peer-review, pre-copyedit version of an article published in Journal of Inclusion Phenomena and Macrocyclic Chemistry. The final authenticated version is available online at: http://dx.doi.org/10.1007/s10847-015-0564-1
Databáze: OpenAIRE
Externí odkaz: