Interaction of glycosylated legumin with EGCG and quercetin: structure and stability analysis

BACKGROUND: Polyphenols have a strong binding capacity with proteins, but the binding behavior of polyphenols with glycosylated proteins and the effects of binding on the structure of glycosylated proteins have been less studied. RESULTS: This study used enzymatic modification to prepare an oligochitosan-legumin complex (OLC) to investigate its interaction with (-)-epigallocatechin gallate (EGCG) and quercetin. Fluorescence spectroscopy experiments showed that the binding site of OLC to EGCG was 27.7 ± 2.47 and that of quercetin to OLC was 19.5 ± 2.92; the binding of one polyphenol affected the other's ability to bind to OLC. The FTIR and CD results showed secondary structural changes in OLC after incorporating polyphenols, with a decrease in the content of α-helix and an increase in the content of β-sheet. The OLC and OLC-polyphenol complexes showed smaller particle size and denser micromorphology. Moreover, OLC had a protective effect on EGCG and quercetin against thermal and ultraviolet light treatments compared to polyphenols alone. CONCLUSION: Transglutaminase was used to catalyze the crosslinking of legumin and oligochitosan. The interaction between OLC and two polyphenols with different properties was studied, and OLC was successfully developed as a carrier to protect two bioactive substances. This study demonstrated the interaction mechanism between glycosylated proteins and polyphenols, providing a basis for the application of glycosylated proteins in encapsulation, protection, and delivery of bioactive substances.