On the Curcumin and β‐Cyclodextrin Interaction in Aqueous Media. Spectrophotometric and Electrochemical Study

Abstract

AbstractIt is shown from UV/Vis spectrophotometry measurements, that up to two inclusion complexes between curcumin and β‐cyclodextrin, namely H3Cur(β‐CD) and H3Cur(β‐CD)2, can be formed in aqueous solution at pH=3.6, where the fully protonated and neutral species of curcumin, H3Cur, predominate depending on the β‐CD concentration. The thermodynamic formation constants of these supramolecular complexes were determined and the molar absorptivity coefficients of H3Cur, H3Cur(β‐CD) and H3Cur(β‐CD)2 species were assessed. In the absence of β‐CD, curcumin degradation increases linearly with time at a rate of 3.25 % min−1. However, in its presence, the rate drastically diminishes to 0.11 % min−1. These results were corroborated from independent electrochemical measurements using a bare carbon paste electrode. At 0.01 M β‐CD the first voltammogram cycle displayed single anodic and cathodic peaks while the second cycle is formed by two anodic peaks and one cathodic, all of them being due to single‐electron adsorption‐controlled processes. The current of these peaks can be used to quantify curcumin concentration in real samples.