RATE CONSTANTS OF THE REACTIONS OF FLAVONOIDS AND RELATED-COMPOUNDS OF NATURAL ORIGIN WITH OH RADICALS IN AQUEOUS-SOLUTIONS UPON RADIOLYSIS

The rate constants of reactions of bioflavonoids (quercetin, luteolin, salifozid, dihydroquercetin, fellavin, and anthocyan), of xanthones ( alpizarin), and of synthetic radioprotectants (AET and mexamine) with OH radicals in aqueous solutions at pH 6.0 and 7.2 were determined by the scavenging technique (using p-nitrozodimethylaniline). For all of the compounds examined, these constants lie in the range (0.5-2.3) x 1 0(10) 1 mol(-1) s(-1). The highest values found for flavones, (1.3-2.3 ) x 10(10) (depending on pH), can be due to the unsaturated 2-3 bond i n the O-heterocycle. Natural compounds were found to be as active scav engers of OH radicals as the radioprotectants AET, MEA, and mexamine.