Kinetic Study of the Mechanism of Free-Radical Scavenging Action in Curcumin

A kinetic study was performed for the free-radical scavenging actions of curcumin and half-curcumin, which has a half-structure of curcumin, in order to clarify the mechanism of free-radical-scavenging in curcumin. The second-order rate constants for radical-scavenging reactions of curcumin and half...

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Bibliographic Details
Published in:Bulletin of the Chemical Society of Japan 2005-04, Vol.78 (4), p.615
Main Authors: Ohara, Keishi, Mizukami, Wataru, Tokunaga, Aiko, Nagaoka, Shin-ichi, Uno, Hidemitsu, Mukai, Kazuo
Format: Article
Language:English
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Summary:A kinetic study was performed for the free-radical scavenging actions of curcumin and half-curcumin, which has a half-structure of curcumin, in order to clarify the mechanism of free-radical-scavenging in curcumin. The second-order rate constants for radical-scavenging reactions of curcumin and half-curcumin were measured by a stopped-flow spectrophotometer in several organic solvents (methanol, ethanol, acetonitrile, chloroform, and benzene) and in aqueous Triton X-100 (5.0 wt %) micelle solutions at various pH. The difference in the rate constant and solvent dependence between curcumin and half-curcumin suggests that the enol structure with the intramolecular hydrogen-bond of curcumin strongly enhances the radical-scavenging activity. Furthermore, notable pH dependences were observed for the rate constants of curcumin and half-curcumin in micelle solutions, suggesting that the acid-base dissociation equilibrium of phenol-protons in curcumin and half-curcumin affects their radical-scavenging activities.
ISSN:0009-2673
1348-0634