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Spectroscopic studies of R(+)-α-lipoic acid--cyclodextrin complexes.

Ikuta N, Tanaka A, Otsubo A, Ogawa N, Yamamoto H, Mizukami T, Arai S, Okuno M, Terao K, Matsugo S - Int J Mol Sci (2014)

Bottom Line: The FT-IR results showed that the C=O stretching vibration of RALA appeared at 1717 cm⁻¹ and then shifted on formation of the RALA-CD complexes.Several peaks indicative of O-H vibrations also shifted or changed in intensity.These results indicate that RALA and CDs form host-guest complexes by interacting with one another.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Medicine, Kobe University, Kobe 650-0017, Japan. naoko.ikuta@people.kobe-u.ac.jp.

ABSTRACT
α-Lipoic acid (ALA) has a chiral center at the C6 position, and exists as two enantiomers, R(+)-ALA (RALA) and S(-)-ALA (SALA). RALA is naturally occurring, and is a cofactor for mitochondrial enzymes, therefore playing a major role in energy metabolism. However, RALA cannot be used for pharmaceuticals or nutraceuticals because it readily polymerizes via a 1,2-dithiolane ring-opening when exposed to light or heat. So, it is highly desired to find out the method to stabilize RALA. The purpose of this study is to provide the spectroscopic information of stabilized RALA and SALA through complexation with cyclodextrins (CDs), α-CD, β-CD and γ-CD and to examine the physical characteristics of the resultant complexes in the solid state. The RALA-CD structures were elucidated based on the micro fourier transform infrared (FT-IR) and Raman analyses. The FT-IR results showed that the C=O stretching vibration of RALA appeared at 1717 cm⁻¹ and then shifted on formation of the RALA-CD complexes. The Raman spectra showed that the S-S and C-S stretching vibrations for RALA at 511 cm⁻¹ (S-S), 631 cm⁻¹ (C-S) and 675 cm⁻¹ (C-S) drastically weakened and almost disappeared upon complexation with CDs. Several peaks indicative of O-H vibrations also shifted or changed in intensity. These results indicate that RALA and CDs form host-guest complexes by interacting with one another.

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Microscopic Fourier transform infrared (FT-IR) spectra of (a) RALA and (b) SALA.
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ijms-15-20469-f003: Microscopic Fourier transform infrared (FT-IR) spectra of (a) RALA and (b) SALA.

Mentions: The IR spectra of RALA and SALA are shown in Figure 3 and the following characteristic bands were observed: 2933 (–CH2–); 1717 (C=O); 1466 (CH) and 936 (OH) cm−1. These bands are in accordance with the reported data [25], however the S–S and C–S bands were not observed.


Spectroscopic studies of R(+)-α-lipoic acid--cyclodextrin complexes.

Ikuta N, Tanaka A, Otsubo A, Ogawa N, Yamamoto H, Mizukami T, Arai S, Okuno M, Terao K, Matsugo S - Int J Mol Sci (2014)

Microscopic Fourier transform infrared (FT-IR) spectra of (a) RALA and (b) SALA.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4264178&req=5

ijms-15-20469-f003: Microscopic Fourier transform infrared (FT-IR) spectra of (a) RALA and (b) SALA.
Mentions: The IR spectra of RALA and SALA are shown in Figure 3 and the following characteristic bands were observed: 2933 (–CH2–); 1717 (C=O); 1466 (CH) and 936 (OH) cm−1. These bands are in accordance with the reported data [25], however the S–S and C–S bands were not observed.

Bottom Line: The FT-IR results showed that the C=O stretching vibration of RALA appeared at 1717 cm⁻¹ and then shifted on formation of the RALA-CD complexes.Several peaks indicative of O-H vibrations also shifted or changed in intensity.These results indicate that RALA and CDs form host-guest complexes by interacting with one another.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Medicine, Kobe University, Kobe 650-0017, Japan. naoko.ikuta@people.kobe-u.ac.jp.

ABSTRACT
α-Lipoic acid (ALA) has a chiral center at the C6 position, and exists as two enantiomers, R(+)-ALA (RALA) and S(-)-ALA (SALA). RALA is naturally occurring, and is a cofactor for mitochondrial enzymes, therefore playing a major role in energy metabolism. However, RALA cannot be used for pharmaceuticals or nutraceuticals because it readily polymerizes via a 1,2-dithiolane ring-opening when exposed to light or heat. So, it is highly desired to find out the method to stabilize RALA. The purpose of this study is to provide the spectroscopic information of stabilized RALA and SALA through complexation with cyclodextrins (CDs), α-CD, β-CD and γ-CD and to examine the physical characteristics of the resultant complexes in the solid state. The RALA-CD structures were elucidated based on the micro fourier transform infrared (FT-IR) and Raman analyses. The FT-IR results showed that the C=O stretching vibration of RALA appeared at 1717 cm⁻¹ and then shifted on formation of the RALA-CD complexes. The Raman spectra showed that the S-S and C-S stretching vibrations for RALA at 511 cm⁻¹ (S-S), 631 cm⁻¹ (C-S) and 675 cm⁻¹ (C-S) drastically weakened and almost disappeared upon complexation with CDs. Several peaks indicative of O-H vibrations also shifted or changed in intensity. These results indicate that RALA and CDs form host-guest complexes by interacting with one another.

Show MeSH
Related in: MedlinePlus