Thermodynamic and kinetic study of epigallocatechin-3-gallate-bovine lactoferrin complex formation determined by surface plasmon resonance (SPR): A comparative study with fluorescence spectroscopy.

The complexation between protein and polyphenol affects their biological functions. A complete understanding of such interactions requires comprehensive thermodynamic and kinetic characterizations. Surface plasmon resonance (SPR) and fluorescence spectroscopy (FS) described similarly the thermodynamic of interaction between bovine lactoferrin (bLF) and epigallocatechin-3-gallate (EGCG). The formation of the bLF-EGCG complex is spontaneous (Δ G S P R o ≈ -29.00 kJ mol−1, Δ G F S o ≈ -26.00 kJ mol−1) and entropically driven (Δ H S P R o = 14.26, Δ H F S o = 10.20 kJ mol−1 and T Δ S S P R o ≈ 43.00, T Δ S F S o ≈ 36.00 kJ mol−1). The kinetic parameters obtained by SPR showed that the reaction occurs through an activated complex, whose energetic formation parameters from the association of free molecules ( E a c t (a) = 49.5 kJ mol−1, Δ H a ‡ = 47.0 kJ mol−1, and T Δ S a ‡ = −2.10 kJ mol−1) were higher than those in the opposite direction (namely the dissociation of the stable complex, E a c t (d) = 17.4 kJ mol−1, Δ H d ‡ = 32.8 kJ mol−1, and T Δ S d ‡ = −45.10 kJ mol−1), except for Δ G ‡ (Δ G a ‡ = 49.1 kJ mol−1 and Δ G d ‡ = 77.9 kJ mol−1). This study provides useful information for optimizing the use of bLF – EGCG complex as a bioactive compound in different systems, such as medical, food, cosmetic, and pharmaceutical formulations. Image 1 • Epigallocatechin-3-gallate (EGCG) and bovine lactoferrin (bLF) form a stable complex. • bLF – EGCG complex formation was driven by enthalpic and entropic interactions. • bLF – EGCG complex formation proceeded through an intermediate complex. • Intermediate formation from free EGCG and bLF was accompanied by an entropy decrease. • Fluorescence spectroscopy supported SPR thermodynamic binding parameters. [ABSTRACT FROM AUTHOR]