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.

Dietary lipids are key ingredients during cooking, processing, and seasoning of carotenoid-rich fruits and vegetables, playing vitals in affecting the absorption and utilization of carotenoids for achieving their health benefits. Besides, dietary lipids have also been extensively studied to construct various delivery systems for carotenoids, such as micro/nanoparticles, micro/nanoemulsions, and liposomes. Currently, the efficacies of these techniques on improving carotenoid bioavailability are often evaluated using the micellization rate or “bioaccessibility” based on in vitro models. However, recent studies have found that dietary lipids may also affect the carotenoid uptake via intestinal epithelial cells and the efflux of intracellular chyle particles via lipid transporters. An increasing number of studies reveal the varied impact of different dietary lipids on the absorption of different carotenoids and some lipids may even have an inhibitory effect. Consequently, it is necessary to clarify the relationship between the addition of dietary lipids and the intestinal absorption of carotenoid to fully understand the role of lipids during this process. This paper first introduces the intestinal absorption mechanism of carotenoids, including the effect of bile salts and lipases on mixed micelles, the types and regulation of lipid transporters, intracellular metabolizing enzymes, and the efflux process of chyle particles. Then, the regulatory mechanism of dietary lipids during intestinal carotenoid absorption is further discussed. Finally, the importance of selecting the dietary lipids for the absorption and utilization of different carotenoids and the design of an efficient delivery carrier are emphasized. This review provides suggestions for precise dietary carotenoid supplementation and offere an important reference for constructing efficient transport carriers for liposoluble nutrients.

Active polysaccharides as safe and natural polymers against bacterial diarrhea have been reconsidered as an alternative to antibiotics. This work investigated the inhibiting effect of depolymerized sulfated galactans from Eucheuma serra and Gracilaria verrucosa on the growth and adhesion of diarrheagenic enterotoxigenic Escherichia coli (ETEC) K88. Results showed that the sulfated polysaccharides with molecular weight distribution ≤20.0 kDa exhibited antibacterial activity against ETEC K88. A structure–activity study revealed that the anti-ETEC K88 activity of sulfated polysaccharides is strictly determined by their molecular weight distribution, sulfate group content, and monosaccharide composition. In addition, the promoted nucleic acid release and the fluorescence quenching of membrane proteins were observed after the treatment with selected polysaccharides. Scanning electron microscopy further confirmed that the depolymerized sulfated galactans can effectively inhibit ETEC K88 adhesion. In conclusion, depolymerized sulfated galactans exhibited an inhibitory effect on the growth and adhesion of ETEC K88.