A DFT Study on the Kinetics of HOO•, CH3OO•, and O2•- Scavenging by Quercetin and Flavonoid Catecholic Metabolites.

Abstract

Reaction kinetics have been theoretically examined to ascertain the potency of quercetin (Q) and flavonoid catecholic metabolites 1-5 in the inactivation of HOO•, CH3OO•, and O2•- under physiological conditions. In lipidic media, the koverallTST/Eck rate constants for the proton-coupled electron transfer (PCET) mechanism indicate the catecholic moiety of Q and 1-5 as the most important in HOO• and CH3OO• scavenging. 5-(3,4-Dihydroxyphenyl)-γ-valerolactone (1) and alphitonin (5) are the most potent scavengers of HOO• and CH3OO•, respectively. The koverallMf rate constants, representing actual behavior in aqueous media, reveal Q as more potent in the inactivation of HOO• and CH3OO• via single electron transfer (SET). SET from 3-O- phenoxide anion of Q, a structural motif absent in 1-5, represents the most contributing reaction path to overall activity. All studied polyphenolics have a potency of O2•- inactivation via a concerted two-proton-coupled electron transfer (2PCET) mechanism. The obtained results indicate that metabolites with notable radical scavenging potency, and more bioavailability than ingested flavonoids, may contribute to human health-promoting effects ascribed to parent molecules.