The Relative Antioxidant Activities of Plant-Derived Polyphenolic Flavonoids

TLDR

The study assessed the antioxidant activities of various plant‑derived polyphenolic flavonoids against aqueous‑phase radicals. Quercetin and cyanidin, possessing 3′,4′‑dihydroxy groups and ring conjugation, exhibited antioxidant activity four times that of Trolox, while loss of ortho‑dihydroxy groups or the 2,3 double bond reduced activity by over 50%, yet these compounds remained more potent than α‑tocopherol or ascorbate. Keywords: flavonoid, polyphenol, antioxidant activity, anthocyanidin.

Abstract

AbstractThe relative antioxidant activities, against radicals generated in the aqueous phase, of a range of plant-derived polyphenolic flavonoids, constituents of fruit, vegetables, tea and wine, have been assessed. The results show that compounds such as quercetin and cyanidin, with 3′,4′ dihydroxy substituents in the B ring and conjugation between the A and B rings, have antioxidant potentials four times that of Trolox, the vitamin E analogue. Removing the ortho-dihydroxy substitution, as in kaempferol, or the potential for electron deloculisation by reducing the 2.3 double bond in the C ring, as in catechin and epicatechin, decreases the antioxidant activity by more than 50%. but these structures are still more effective than α-tocopherol or ascorbate. The relative significance of the positions and extents of hydroxylation of the A and B rings to the total antioxidant activity of these plant polyphenols is demonstrated.Key Words: flavonoid. polyphenolantioxidant activityanthocyanidin.