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Type: Journal article
Title: Femtosecond transient absorption spectroscopy of the medicinal agent curcumin in diamide linked γ-cyclodextrin dimers
Other Titles: Femtosecond transient absorption spectroscopy of the medicinal agent curcumin in diamide linked Y-cyclodextrin dimers
Author: Harada, T.
McTernan, H.
Pham, D.
Lincoln, S.
Kee, T.
Citation: The journal of physical chemistry B, 2015; 119(6):2425-2433
Publisher: ACS Publications
Issue Date: 2015
ISSN: 1520-6106
Statement of
Takaaki Harada, Hamish L. McTernan, Duc-Truc Pham, Stephen F. Lincoln, and Tak W. Kee
Abstract: Curcumin is a biologically active polyphenol and a yellow pigment extracted from turmeric. Our previous study has shown effective encapsulation of curcumin using diamide linked γ-cyclodextrin dimers, namely 66γCD2su and 66γCD2ur, through cooperative 1:1 host-guest complexation. In this study, the excited state dynamics of curcumin complexed with either 66γCD2su or 66γCD2ur in water are investigated using femtosecond transient absorption spectroscopy. Both 66γCD2su-curcumin and 66γCD2ur-curcumin complexes in water show only an excited state absorption (ESA) band at 530 nm without any stimulated emission (SE) signals, indicating non-radiative decays as the major relaxation pathway. The ESA dynamics of 66γCD2su-curcumin are similar to those of 66γCD2ur-curcumin, consisting of a rapid growth component and three decay components. The growth component, which has a time constant of 0.25- 0.41ps, is assigned to solvent reorganization. The relatively fast decay components with time constants of 9.3-21.8ps show significant deuterium isotope effect, indicating the presence of excited state intramolecular hydrogen atom transfer (ESIHT) of curcumin. The small-amplitude and slow decay components may be attributed to the dynamics of complexed curcumin and molecular motions due to flexibility of 66γCD2su and 66γCD2ur. In addition, transient absorption anisotropy measurements reveal slow rotational motions of 66γCD2su-curcumin and 66γCD2ur-curcumin complexes. The overall results show that complexation in 66γCD2su and 66γCD2ur has pronounced effects on the photophysics of curcumin.
Keywords: Diamide; Curcumin; gamma-Cyclodextrins; Spectrum Analysis; Dimerization; Anisotropy; Time Factors; Absorption, Physicochemical
Rights: Copyright © 2014 American Chemical Society
RMID: 0030009731
DOI: 10.1021/jp507272f
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Appears in Collections:Chemistry and Physics publications

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