Role of the Flavan-3-ol and Galloyl Moieties in the Interaction of (−)-Epigallocatechin Gallate with Serum Albumin

Abstract

The principal green tea polyphenol, (−)-epigallocatechin-3-O-gallate (EGCg), may provide chemoprotection against conditions ranging from cardiovascular disease to cancer. Binding to plasma proteins stabilizes EGCg during its transport to targeted tissues. This study explored the details EGCg binding to bovine serum albumin. Both fluorescence lifetime and intensity data showed that the hydrophobic pocket between subdomains IIA and IIIA is the binding site for EGCg. Fluorescence and circular dichroism were used to establish the roles of the flavan-3-ol and galloyl moieties of the EGCg in binding and to demonstrate a binding-dependent conformational change in the protein. Competitive binding experiments confirmed the location of binding, and molecular modeling identified protein residues that play key roles in the interaction. This model of EGCg–BSA interactions improves the understanding of the likely physiological fate of this green tea-derived bioactive polyphenol.

Multi-site binding of epigallocatechin gallate to human serum albumin measured by NMR and isothermal titration calorimetry

“…Data processing with SVD was useful in improving the quality of the fitting. On comparing our results with previous determinations, it is clear that fluorescence quenching is somewhat misleading, because it only characterizes binding at Sudlow site I, where the single tryptophan of HSA is located and therefore only gives n =1 [8–10]. This is to be expected, but is not clear from previous reports.…”

Effect of (-)-epigallocatechin-3-gallate on glucose-induced human serum albumin glycation

“…We propose that the protein binding activity of EGCg [31] provides a mechanistic basis for the concentration-dependent effects of EGCg on lightly glycated protein. We suggest that when the concentration of EGCg is low and the protein is relatively undamaged, the polyphenol binds specifically to the hydrophobic pocket of the protein [32], and does not damage the protein. However, if excess EGCg is added, nonspecific binding to the protein is initiated, leading to damage similar to that induced by glycation.…”

Data for β-lactoglobulin conformational analysis after (-)-epigallocatechin gallate and metal ions binding

“…The working solution of β -Lg (25 µM) was prepared in 20 mM PBS buffer, pH 7.4 and stored in a refrigerator prior to use. The β -Lg and EGCg concentrations were determined spectrophotometrically by their extinction coefficients: ε 280 ( β -Lg)=17600 M −1  cm −1 and ε 280 (EGCg)=9700 M −1  cm −1 at 280 nm [4], [5]. For in vitro experiments, the working solutions of Cu 2+ and Al 3+ (1.0 mM) were prepared by dissolving CuCl 2 ·2H 2 O and AlCl 3 , respectively, in double-distilled water containing 0.1 M HCl to facilitate dissolution.…”