Flavonoid inhibition of enzymic and nonenzymic lipid peroxidation in rat liver differs from its influence on the glutathione-related enzymes.

Eight flavonoids were tested for their antiperoxidative activities against lipid peroxidation induced in liver cell membranes either by nonenzymic way (ascorbic acid-Fe2+ system, FeAs) or by enzymic way (arachidonic acid, AA). When lipid peroxidation is induced by FeAs, the order in the inhibitory potency for the different flavonoids assayed is: (-)-epicatechin approximately luteolin > quercetin approximately (+)-catechin > delphinidin > kaempferol >> apigenin > naringenin. However, when lipid peroxidation is induced by AA, the potency order is markedly modified: delphinidin > (-)-epicatechin > (+)-catechin > kaempferol > quercetin > luteolin > naringenin > apigenin. These flavonoids were also tested for their influence on glutathione-related enzymes, which constitute one of the aim physiological antioxidant systems. It is concluded that the antiperoxidative effect shown by most of the flavonoids is exerted without modifying these enzymes.