Structure-antioxidant Activity Relationships of Flavonoids: A Re-examination

Abstract

The antioxidant and prooxidant activities of flavonoids belonging to several classes were studied to establish their structure-activity relationships against different oxidants. Special attention was paid to the flavonoids quercetin (flavone), taxifolin (flavanone) and catechin (flavanol), which possess different basic structures but the same hydroxylation pattern (3,5,7,3'4'-OH). It was found that these three flavonoids exhibited comparable antioxidant activities against different oxidants leading to the conclusion that the presence of ortho-catechol group (3',4'-OH) in the B-ring is determinant for a high antioxidant capacity. The flavone kaempferol (3,5,7,4'-OH), however, in spite of bearing no catechol group, also presents a high antioxidant activity against some oxidants. This fact can be attributed to the presence of both 2,3-double bond and the 3-hydroxyl group, meaning that the basic structure of flavonoids becomes important when the antioxidant activity of B-ring is small.

The roles of polyphenols in cancer chemoprevention

“…The strong antioxidant activity of quercetin appears to be attributable to the presence of an orthocatechol group (3',4'-OH) in the Bring [104].…”

2-Styrylchromones: Novel strong scavengers of reactive oxygen and nitrogen species

“…Flavonoids have been deeply studied and have shown to possess innumerous biological activities from which the antioxidant properties are the best-described. [22][23][24][25][26][27] Considering the structural similarities, some of these properties are likely to be shared with 2-styrylchromones, although it needs to be experimentally confirmed. Thus, the present work consisted in studying the scavenging activities for the above-referred ROS and RNS of various 2-styrylchromone derivatives (Fig.…”

DFT and1H NMR molecular spectroscopic studies on biologically anti-oxidant active paramagnetic lanthanide(III)-chrysin complexes

“…This indicated that the inhibitory ratio of the free radicals in the polyphenolic complexes increased after complexation. Although free radicals may have useful physiological functions, they can damage biomolecules when generated in excess and are therefore implicated in the etiology of several diseases and ageing [18][19][20][21][22]. Another antioxidant mechanism of flavonoids may result from the interactions between transition metal ions and flavonoids to produce complexes that prevent the participation of these metal ions in free radical generating reactions [10][11][12][13][14].…”