Inhibition of peroxidations of lipids and membranes by estrogens

The antioxidant activity of 2‐hydroxyestradiol was measured quantitatively and compared with those of other estrogens in oxidations of methyl linoleate in homogeneous solution and in aqueous dispersions, oxidations of soybean phosphatidylcholine liposomal membranes and oxidative haemolysis of rabbit erythrocytes, all induced by free radicals generated from a radical initiator. Similar antioxidant activities of estrogens were observed, irrespective of the oxidation system. 2‐Hydroxyestradiol was found to be a potent radical scavenger and its antioxidant activity was close to that of α‐tocopherol, the strongest natural antioxidant. Other phenolic estrogens such as estrone, estriol and β‐estradiol showed a modest antioxidant activity and testosterone did not act as an antioxidant.