The role of charge in the surfactant-assisted stabilization of the natural product curcumin

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dc.contributor.authorWang, Z.
dc.contributor.authorLeung, H.
dc.contributor.authorKee, T.
dc.contributor.authorEnglish, D.
dc.date.issued2010
dc.description.abstractColloidal solutions of surfactants that form micelles or vesicles are useful for solubilizing and stabilizing hydrophobic molecules that are otherwise sparingly soluble in aqueous solutions. In this paper we investigate the use of micelles and vesicles prepared from ionic surfactants for solubilizing and stabilizing curcumin, a medicinal natural product that undergoes alkaline hydrolysis in water. We identify spectroscopic signatures to evaluate curcumin partitioning and deprotonation in surfactant mixtures containing micelles or vesicles. These spectroscopic signatures allow us to monitor the interaction of curcumin with charged surfactants over a wide range of pH values. Titration data are presented to show the pH dependence of curcumin interactions with negatively and positively charged micelles and vesicles. In solutions of cationic micelles or positively charged vesicles, strong interaction between the Cur(-1) phenoxide ion and the positively charged surfactants results in a change in the acidity of the phenolic hydrogen and a lowering of the apparent lowest pK(a) value for curcumin. In the microenvironments formed by anionic micelles or negatively charged bilayers, our data indicates that curcumin partitions as the Cur(0) species, which is stabilized by interactions with the respective surfactant aggregates, and this leads to an increase in the apparent pK(a) values. Our results may explain some of the discrepancies within the literature with respect to reported pK(a) values and the acidity of the enolic versus phenolic protons. Hydrolysis rates, quantum yields, and molar absorption coefficients are reported for curcumin in a variety of solutions.
dc.description.statementofresponsibilityZifan Wang, Mandy H. M. Leung, Tak W. Kee and Douglas S. English
dc.identifier.citationLangmuir: the ACS journal of surfaces and colloids, 2010; 26(8):5520-5526
dc.identifier.doi10.1021/la903772e
dc.identifier.issn0743-7463
dc.identifier.issn1520-5827
dc.identifier.orcidKee, T. [0000-0002-4907-4663]
dc.identifier.urihttp://hdl.handle.net/2440/61355
dc.language.isoen
dc.publisherAmer Chemical Soc
dc.rightsCopyright © 2009 American Chemical Society
dc.source.urihttps://doi.org/10.1021/la903772e
dc.subjectCurcumin
dc.subjectSolutions
dc.subjectSurface-Active Agents
dc.subjectHydrolysis
dc.subjectMicelles
dc.subjectHydrogen-Ion Concentration
dc.subjectModels, Theoretical
dc.subjectHydrophobic and Hydrophilic Interactions
dc.titleThe role of charge in the surfactant-assisted stabilization of the natural product curcumin
dc.typeJournal article
pubs.publication-statusPublished

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