Molecular property-affinity relationship of flavanoids and flavonoids for HSA in vitro

The relationship between the structural properties of selected dietary flavanoids and flavonoids and their affinities for HSA were investigated by fluorescence analysis. The binding process with HSA was strongly influenced by the structural differences of the compounds under study. Methylation of hydroxyl groups improved the affinities for HSA by 2-16-fold. Hydroxylation on rings A, B, and C also affected the affinity for HSA significantly. Glycosylation decreased the affinities for HSA by 1-3 orders of magnitude depending on the conjugation site and the class of sugar moiety. Hydrogenation of the C2=C3 double bond also decreased the binding affinity. Galloylated catechins and pyrogallol-type catechins exhibited higher binding affinities for HSA than non-galloylated and catechol-type catechins, respectively. The affinities for HSA increased with increasing partition coefficients and decreased with increasing hydrogen bond donor and acceptor numbers of flava(o)noids, which suggested that the binding interaction was mainly caused by hydrophobic forces.