In vitro and in silico studies of the structure and functional properties of the lactoferrin-chlorogenic acid complex

Lactoferrin (LF) is a bioactive protein that has many techno-functional and biological properties. In this study, chlorogenic acid (CGA) – a commonly found polyphenol compound was used to interact with LF to form a nanoscale complex (approximately 800 nm). The structure and function of LF complexed with CGA at different ratios were analyzed through spectroscopic, biochemical and in silico experiments. UV and fluorescence studies indicated that CGA could interact with LF to change its characteristic UV and fluorescent spectra. The dynamic thermal experiment showed that the fluorescence quenching mechanism of LF induced by CGA was static quenching and one molecule of LF could bind to at least one CGA molecule. The apparent hydrophobicity (H0) of the LF-CGA complex decreased while its solubility increased with increasing CGA content. After interaction with CGA, the foaming ability and antioxidant activity in vitro of LF were enhanced. The predicted molecular docking pattern showed that the most likely binding site was in the cavity at the junction of N and C leaves of LF. The driving forces for the non-covalent binding of LF and CGA under this condition were hydrophobic interaction, van der Waals force and hydrogen bond. Further correlation analysis (Pearson) and principal component analysis (PCA) showed that the interaction between LF and CGA was affected by the concentration and structure, which determined the techno-functional and antioxidant activity of LF. Therefore, we have systematically resolved the interaction mechanism between LF and CGA, which will provide support for the function enhancement of LF by polyphenol modifications to expand its application.