Ovalbumin as a carrier to significantly enhance the aqueous solubility and photostability of curcumin: Interaction and binding mechanism study

Egg ovalbumin (OVA) as a macromolecular carrier has the potential to improve the solubility and stability of insolubility bioactive molecules, however, their binding behavior and the mechanism is still ambiguous. In this work, the curcumin was selected as the target to study the interaction and binding mechanism between curcumin and OVA by thermodynamic titration technique in combination with molecular dynamic simulation. The results suggested that the binding included two steps: first, curcumin molecule entered into the hydrophobic pocket of OVA by hydrophobic interaction; and second the interaction was enhanced via hydrogen bonds, resulting in static fluorescence quenching and secondary structural change of OVA. This study provided further evidence in support of the proposed mechanism of the polyphenol-protein binding by the “Hands-gloves” model. Furthermore, when the OVA was as a carrier, the solubility of curcumin has been increased ~370 times to 32.73 μg/mL compared to that of free curcumin at pH 7.0. The photostability was enhanced significantly indicating that it is an efficient way to improve the stability of curcumin in contributing to its application in nutritional supplements or functional foods.