The molecular property-affinity relationship of dietary flavonoids for bovine gamma-globulin (γ-globulin) was investigated by fluorescence titration analysis. The quenching effects of flavonoids on γ-globulin fluorescence depended on the structures of flavonoids. The magnitudes of binding constants between flavonoids and γ-globulin were within the range of 103–105 L mol−1. These data were much smaller than the affinities between flavonoids and purified bovine and human serum albumins. The affinities of flavonoids for γ-globulin were strongly influenced by the structural differences of the compounds under study. The affinities for γ-globulin decreased with increasing partition coefficients and increased with increasing hydrogen bond acceptor numbers of flavonoids, which suggested that the binding interaction was mainly caused by hydrogen bond forces.
