Interaction of natural polyphenols with α-amylase in vitro: molecular property-affinity relationship aspect.

The relationship between the structural properties of natural polyphenols and their affinities for α-amylase were investigated by fluorescence titration analysis. The binding process with α-amylase was strongly influenced by the structural differences of the compounds under study. For instance, the methylation of the hydroxyl group in flavonoids increased their binding affinities for α-amylase by 2.14 to 7.76 times. The hydroxylation on rings A, B, and C of flavonoids also significantly affected their affinities for α-amylase. The glycosylation of isoflavones and flavanones reduced their affinities for α-amylase and the glycosylation of flavones and flavonols enhanced their affinities for α-amylase. Hydrogenation of the C2=C3 double bond of flavonoids decreased the binding affinities. The galloylated catechins had higher binding affinities with α-amylase than non-galloylated catechins and the pyrogallol-type catechins had higher affinities than the catechol-type catechins. The presence of the galloyl moiety is the most decisive factor. The glycosylation of resveratrol decreased its affinity for α-amylase. The esterification of gallic acid significantly reduced the affinity for α-amylase. The binding interaction between polyphenols and α-amylase was mainly caused by hydrophobic forces.