Inhibitory Action of some Flavonoids on Enhanced Spontaneous Lipid Peroxidation Following Glutathione Depletion

Depletion of hepatic glutathione in phenobarbital-induced rats by phorone (diisopropylidene acetone) led to an enhancement of spontaneous lipid peroxidation in vitro . Addition of exogenous glutathione, dithiocarb or one of the flavonoids (+)-catechin, (-)-epicatechin, 3-O-methylcatechin, quercetin, taxifolin, rutin, naringin or naringenin led in every case to a dose-dependent inhibition of this peroxidative activity. The concentration values yielding 50% inhibition (I 50 ) varied from 1.0 × 10 -6 M for glutathione to 1.9 × 10 -5 M for naringenin. Naringin and naringenin, which lack the 3′-OH-group, were the least active inhibitors. The only structural feature of the flavonoids which affects their antioxidative action appears thus to be the 3′,4′-dihydroxy-grouping.