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

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(-1)vs. 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.