Article 5.indd

The relationship between the molecular structure of dietary flavonoids and their affinities for bovine serum albumin (BSA) were fully investigated by fluorescence titration analysis. The binding process with BSA was significantly affected by the molecular structure of flavonoids under study. The methylation of hydroxyl group in flavonoids enhanced their binding affinities for BSA by 1 to 794 times. Hydroxylation on rings A, B and C also strongly influenced the affinity for BSA. The glycosylation weakened the affinities for BSA by 1-2 orders of magnitude depending on the conjugation site and the class of sugar moiety. The hydrogenation of the C2=C3 double bond slightly increased the binding affinity. The galloylated catechins and pyrogallol-type catechins exhibited higher binding affinities for BSA than non-galloylated and catecholtype catechins, respectively. The affinities for BSA increased with increasing partition coefficients and decreased with increasing hydrogen bond donor and acceptor numbers of flavonoids, which suggested that the binding interaction was mainly caused by hydrophobic forces.