Shift of acid-base equilibrium of curcumin in its complexes with gemini surfactant hexamethylene-1,6-bis-(dodecyldimethyl ammonium bromide)

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• 作者：Dan Ke ; Yue Wu ; Xiaoyong Wang
• 关键词：Gemini surfactant ; Curcumin ; Acid&ndash ; base equilibrium ; Absorption ; Fluorescence
• 刊名：Colloids and Surfaces A: Physicochemical and Engineering Aspects
• 出版年：20 February, 2014
• 年：2014
• 卷：443
• 期：Complete
• 页码：481-487
• 全文大小：871 K

文摘

Surfactant micelles are suitable carriers for solubilizing and stabilizing curcumin that is a natural polyphenolic compound with many biological and pharmacological activities but suffers poor bioavailability. In this paper, the acid-base equilibrium of curcumin (Cur⁰ = Cur^{鈭?/sup> + H+) has been studied in surfactant concentration dependent complexes of curcumin with gemini surfactant hexamethylene-1,6-bis-(dodecyldimethyl ammonium bromide) (12-6-12). The absorption and fluorescence spectra of curcumin show that Cur鈭?/sup> electrostatically binds with cationic 12-6-12 monomer to form curcumin/monomer complexes, whereas Cur0 and Cur鈭?/sup> are located in the palisade layer of 12-6-12 aggregates with different positions in curcumin/premicelle and curcumin/micelle complexes. The increase of surfactant concentration often leads to the right-shift of acid-base equilibrium of curcumin and higher amount of anionic Cur鈭?/sup>, as shown in the fluorescence spectra, pK_a1 and [Cur鈭?/sup>]/[Cur0] of curcumin. By contrast, the added salt is found to be beneficial for curcumin to shift the acid-base equilibrium to the left side and keep in neutral Cur0.}