2-2--azino-di-(3-ethylbenzothiazoline)-6-sulfonic-acid and flavanone

Rapid scavenging of the model stable radical cation, ABTS(*+), has been applied to screen for the antioxidant activity of flavonoids. The reaction follows two distinct phases. For compounds with a monophenolic B-ring there is a rapid initial phase of reduction of ABTS(*+) within 0.1 s with no further change in the subsequent 2.9 s. In contrast, compounds with a catechol-containing B ring follow a fast initial scavenging phase with a slow secondary phase. Flavonoids with an unsubstituted B ring do not react within this time scale. The findings suggest that the structure of the B ring is the primary determinant of the antioxidant activity of flavonoids when studied through fast reaction kinetics.

Topics: Antioxidants; Benzopyrans; Benzothiazoles; Catechin; Catechols; Chromans; Coumaric Acids; Flavanones; Flavonoids; Flavonols; Free Radical Scavengers; Kinetics; Structure-Activity Relationship; Sulfonic Acids