Non-covalent interaction of dietary polyphenols with total plasma proteins of type II diabetes: molecular structure/property–affinity relationships

The molecular structure/property-affinity relationships of dietary polyphenols non-covalently binding to total plasma proteins of type II diabetes (IIDTPP) were investigated by comparing the binding constants obtained from the fluorescence titration method. An additional methoxy group in flavonoids increased their binding affinities for IIDTPP by 1.38 to 15.85 times. The hydroxylation at the 4' position (Ring B) of flavonols and the 5 position (Ring A) of isoflavones weakened the binding affinities; however, hydroxylation at other positions on flavonoids slightly enhanced or little affected the binding affinities for IIDTPP. The glycosylation of flavonoids slightly decreased or little affected the affinities for IIDTPP by less than 1 order of magnitude. The hydrogenation of the C2[double bond, length as m-dash]C3 double bond of flavone, 6-hydroxyflavone, 6-methoxyflavone and myricetin decreased the binding affinities. The galloylation of catechins significantly improved the binding affinities with IIDTPP approximately 10 to 1000 times. The esterification of gallic acid increased its binding affinity. The hydrophobic force played an important role in the binding interaction between polyphenols and IIDTPP.