Galloyl moieties enhance the binding of (−)-epigallocatechin-3-gallate to β-lactoglobulin: A spectroscopic analysis.

The current study was designed to examine the role of galloyl moieties in the interaction of β -lactoglobulin ( β -Lg) with (−)-epigallocatechin-3-gallate (EGCG) using fluorescence and CD spectroscopic methods. The interactions with β -Lg were investigated for EGCG, (−)-epigallocatechin (EGC), and the phenolic compound methyl gallate (MeG) at pH values 3.0, 5.0 and 7.4. The spectroscopic data indicated the binding constants for polyphenol complexes with β -Lg in phosphate buffer pH 7.4 to be in the order of MeG > EGCG > EGC. MeG exhibited the strongest quenching efficiency compared to EGCG and EGC, and EGC exhibited the weakest quenching efficiency. The quenching efficiency of EGCG on β -Lg fluorescence decreased with increasing pH. Polyphenols binding results in a slight secondary structural change of β -Lg, consistent with the fluorescence analysis. This study confirmed that the high binding affinity of EGCG to β -Lg is due to the galloyl functional group. [ABSTRACT FROM AUTHOR]