Electrochemical oxidation of curcuminoids: an experimental and computational investigation

Authors: ZEYNEP KALAYCIOĞLU, NURGÜL KARADAŞ, MEHMET EMİN ÇINAR, SİBEL AYŞIL ÖZKAN, DURİŞEHVAR ÖZER ÜNAL, AYŞEGÜL GÖLCÜ, FATMA BEDİA ERİM

Abstract: Curcuminoids, reported to have important biological properties, such as antioxidant, anti-Alzheimer, and antidiabetic properties, comprise curcumin (CRM; 1,7-bis [4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione) and its derivatives demethoxycurcumin (DMC; (E,6E)-1-(3,4-dimethoxy-cyclohexyl)-7-(3,4-dimethoxyphenyl)hepta-1,6-diene-3,5-dione) and bisdemethoxycurcumin (BDMC; 1,7-bis[4-hydroxyphenyl]-1,6-heptadiene-3,5-dione). Their electrochemical oxidations are thoroughly explored by applying cyclic and differential pulse voltammetric techniques. The dependence of current intensities and potentials on pH, concentration, scan rate, and nature of the buffer was investigated. The outcome is supported by density functional theory computations indicating the transfer of 4-e$^{-}$/H$^{+}$, 6-e$^{-}$/H$^{+}$, and 8-e$^{-}$/H$^{+}$ couples involved in the oxidation mechanisms of CRM, DMC, and BDMC, respectively, leading to the formation of the same oxidized product.

Keywords: Cyclic voltammetry, curcuminoids, density functional theory, differential pulse voltammetry

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