Interaction Mechanism between OVA and Flavonoids with Different Hydroxyl Groups on B-Ring and Effect on Antioxidant Activity

Ovalbumin (OVA) is a common carrier with high efficiency to deliver flavonoids. The aim of this study was to investigate the interaction mechanism of OVA and four flavonoids (quercetin (Que), myricetin (Myri), isorhamnetin (Ish), and kaempferol (Kaem)) with similar structures by fluorescence spectra, SDS-PAGE, FT-IR, and molecular docking analysis, and the effect on the antioxidant abilities of flavonoids was also evaluated. Results indicated that the antioxidant activity of flavonoids was positively correlated to the number of phenolic hydroxyl groups of on the B-ring, and weakened when the C-3' position was replaced by a methoxy group. The addition of OVA enhanced the antioxidant activity of Que/Kaem, while it masked the antioxidant activity of Myri. The formation of Que/Myri/Ish/Kaem-OVA complexes was a spontaneous exothermic process driven mainly by hydrogen bond and van der Waals force, which could result in the change in OVA conformation and induce the transformation of alpha-helix to beta-sheet. Among these, Kaem exhibited the strongest binding ability with OVA, and showed the greatest impact on the secondary and conformational structure of OVA, followed by Que. The hydroxylation of C-3' and methoxylation of C-5' weaken the interaction of Kaem with OVA. Molecular docking analysis suggested that Que, Myri, Ish, and Kaem formed six, three, five, and four hydrogen bonds with OVA, and the number of hydrogen bonds was not positively correlated with their binding constants. Our findings can provide a theoretical basis for the application of OVA on improving the antioxidant activity of flavonoids, and may help to explain the delivery efficiency of OVA on different bioactive constituents.

Automated summary

This study investigated the interaction mechanism between ovalbumin (OVA) and four flavonoids and evaluated their effect on antioxidant abilities. The results showed that the antioxidant activity of flavonoids was positively correlated with phenolic hydroxyl groups and weakened with methoxy substitution at C-3'. OVA enhanced the antioxidant activity of certain flavonoids but masked the activity of others. The formation of OVA-flavonoid complexes was driven by hydrogen bonds and van der Waals force. Molecular docking analysis revealed the number of hydrogen bonds did not correlate with binding constants. The findings provide a theoretical basis for improving the antioxidant activity of flavonoids and understanding the delivery efficiency of OVA.