2015年10月16日
Structural analysis of crystalline R(+)-α-lipoic acid-α-cyclodextrin complex based on microscopic and spectroscopic studies
International Journal of Molecular Sciences
- 巻
- 16
- 号
- 10
- 開始ページ
- 24614
- 終了ページ
- 24628
- 記述言語
- 英語
- 掲載種別
- DOI
- 10.3390/ijms161024614
© 2015 by the authors; licensee MDPI, Basel, Switzerland. R(+)-α-lipoic acid (RALA) is a naturally-occurring substance, and its protein-bound form plays significant role in the energy metabolism in the mitochondria. RALA is vulnerable to a variety of physical stimuli, including heat and UV light, which prompted us to study the stability of its complexes with cyclodextrins (CDs). In this study, we have prepared and purified a crystalline RALA-αCD complex and evaluated its properties in the solid state. The results of 1H NMR and PXRD analyses indicated that the crystalline RALA-αCD complex is a channel type complex with a molar ratio of 2:3 (RALA:α-CD). Attenuated total reflection/Fourier transform infrared analysis of the complex showed the shift of the C=O stretching vibration of RALA due to the formation of the RALA-αCD complex. Raman spectroscopic analysis revealed the significant weakness of the S–S and C–S stretching vibrations of RALA in the RALA-αCD complex implying that the dithiolane ring of RALA is almost enclosed in glucose ring of α-CD. Extent of this effect was dependent on the direction of the excitation laser to the hexagonal morphology of the crystal. Solid-state NMR analysis allowed for the chemical shift of the C=O peak to be precisely determined. These results suggested that RALA was positioned in the α-CD cavity with its 1,2-dithiolane ring orientated perpendicular to the plane of the α-CD ring.
- リンク情報
- ID情報
-
- DOI : 10.3390/ijms161024614
- ISSN : 1422-0067
- ISSN : 1661-6596
- eISSN : 1422-0067
- PubMed ID : 26501268
- SCOPUS ID : 84945219110