Binding of curcumin to β-lactoglobulin and its effect on antioxidant characteristics of curcumin

• A partial change of β-Lg structure occurs when CCM binds with it.
• β-Lg interacts with CCM via hydrophobic interaction.
• One molecule of protein combines with one molecule of CCM.
• CCM binds respectively on the surface and central of β-Lg at pH 6.0 and 7.0.
• The antioxidant activity of CCM might be improved by binding with β-Lg.

The binding of curcumin (CCM) to bovine β-lactoglobulin (β-Lg) was investigated by Fourier transform infrared and fluorescence. The effect of binding on antioxidant activity of CCM was determined by using ABTS and hydroxyl radical scavenging capacity and total reducing ability. Our results showed that when CCM binds to β-Lg, it lead to a partial change in protein structure. In fact, CCM was bound respectively to two different sites of protein at pH 6.0 and 7.0 via hydrophobic interaction. CCM–β-Lg complex was formed by one molecule of protein combining with one molecule of CCM. Moreover, the average distance from one binding site to Trp residues in protein is similar with another. This result suggested that fluorescence resonance energy transfer cannot be used as unique method to study the characteristics of binding of ligands to proteins. The antioxidant activity of CCM might be improved by binding with β-Lg.