Interaction of dietary polyphenols with bovine milk proteins: Molecular structure-affinity relationship and influencing bioactivity aspects

Scope: Dietary flavonoids and stilbenes are important polyphenols in foods, such as, e. g. fruits, vegetables, nuts, and tea as they are of great interest for their bioactivities, which are related to the anti-oxidative property. Methods and results: The relationship between the structural properties of dietary polyphenols and their affinities for milk proteins (MP) was investigated. Methylation and methoxylation of flavonoids decreased (or hardly affected) the affinities for MP. Hydroxylation on the rings A and B of flavones and flavonols enhanced the interaction slightly. The hydroxylation on the ring A of flavanones significantly improved the affinities. Glycosylation of flavonoids weakened the affinities by 1-2 orders of magnitude. The hydrogenation of the C2=C3 double bond of flavonoids decreased the binding affinities by 7.24-75.86-fold. Galloylation of catechins significantly improved the binding affinities by about 100-1000-fold. Glycosylation of resveratrol decreased its affinity for MP. Esterification of gallic acid increased its binding affinity. MP significantly weakened the DPPH radical scavenging activity of polyphenols. The decreasing DPPH scavenging percentages of polyphenols increased with increasing affinities of MP-polyphenol complexes. Conclusion: The binding affinities with MP were strongly influenced by the structural differences of dietary polyphenols. The MP-polyphenol interaction weakened with the DPPH free radical scavenging potential of polyphenols.