Structure-function analysis of the radioprotective and antioxidant activity of flavonoids

The recombination kinetics of a series of flavonoids with stable DPPH radic als are studied. Flavonols are the most reactive. Polarization of the carbo nyl in flavones reduces the reactivity. Substitution on C-7 and the B ring has practically no effect on the reactivity. Glycosylation of C-3 reduces t he reactivity if the sugar can form two intramolecular H-bonds. The reactiv ity of the flavonoid phenol hydroxyls, with the exception of the hydroxyl o n C-5, is proportional to their number. The most promising antioxidants are lespedin, kaempferitrin, kaempferol, kaempferol-7-rhamnoside, kaempferol-3 -robinobioside, and robinin.