Oleic acid as a protein ligand improving intestinal absorption and ocular benefit of fucoxanthin in water through protein-based encapsulation

Abstract

In this work, fucoxanthin–oleic acid–protein complexes were constructed to improve the dispersibility and intestinal absorption of fucoxanthin in water. The in vivo absorption/antioxidant capacity was evaluated using a mouse model, and the binding processes were investigated using multi-spectroscopic methods and molecular docking. Results showed that the oleic acid–protein delivery system dramatically improved the absorption of fucoxanthin mainly in its original form. When the molar ratio of oleic acid to bovine serum albumin (BSA) was 4 : 1, the plasma response level of fucoxanthin at 4 h could reach 91.25% that of the pure soybean oil delivery system (336.9 pg mL⁻¹vs. 369.2 pmol mL⁻¹). Furthermore, the loading capacity of BSA to fucoxanthin was increased 5 times when oleic acid acted as a protein ligand. Fucoxanthin, oleic acid and BSA can form complexes with good water dispersibility (transmittance nearly 90% and particle size 265 nm) at the molar ratio of 5 : 4 : 1. Spectral analysis and molecular docking indicated that oleic acid and fucoxanthin have different binding domains in BSA and that fucoxanthin can bind to the hydrophobic cavity of BSA in a static manner. After administration of fucoxanthin–oleic acid–BSA complexes for 15 days in mice, only fucoxanthinol accumulation was discovered in eyes and the ocular antioxidant capability increased by 71.02%. These results suggest that the oleic acid–protein delivery system may be useful in facilitating the application of fat-soluble active substances to hydrophilic food systems.