Non-covalent interactions between ovotransferrin and catechin: Characterization, molecular dynamics, and applications in DHA microcapsules

Docosahexaenoic acid (DHA) is known for its susceptibility to oxidation. In this research, the focus was on investigating the non-covalent interactions between ovotransferrin (OVT) and catechin, and assessing the potential of catechin-OVT complexes and chitosan as effective wall materials for microencapsulating DHA. Spectroscopic, thermal, and computational analyses showed that catechin-OVT complexes were stabilized mainly by hydrogen bonding and van der Waals forces, with a docking binding energy of -9.3 kcal/mol. Surface hydrophobicity analysis revealed that as the concentration of catechin increased, the surface hydrophobicity decreased. Molecular docking and visualization studies showed that catechin binds to specific regions of OVT, when small-molecule ligands occupy these hydrophobic sites, they hinder the contact between the ANS probe and the hydrophobic residues of the protein, directly leading to a decrease in detectable surface hydrophobicity. Furthermore, the presence of catechin was found to enhance the antioxidant properties of OVT (ABTS: 79.05%), improve its thermal stability, and promote structural compactness. The prepared microcapsules achieved a high encapsulation efficiency of 90.23 ± 0.31%. Interestingly, the particle size of the microcapsules exhibited an initial decrease followed by an increase, while the turbidity showed a continuous rise with increasing catechin concentration, the DSC thermal denaturation temperature increased to 80.75 °C, indicating that the thermal stability of the microcapsules was enhanced, The TBARS assay further confirmed that the microcapsules significantly reduced lipid oxidation during storage (P < 0.05). These results not only shed light on the molecular mechanisms underlying protein-polyphenol interactions but also introduce a promising approach for achieving stable encapsulation of DHA in functional food products.