Action of 21-aminosteroid U74006F as an antioxidant against lipid peroxidation

The dynamics of the action of the 21-aminosteroid U74006F as an antioxidant against lipid peroxidation were studied in organic solution and membranes. It was confirmed that the reactivities of this compound toward stable phenoxyl radical and peroxyl radical were quite low. In fact, U74006F did not exert appreciable antioxidant effect against the free radical-driven oxidation of methyl linoleate in acetonitrile solution. However, it suppressed the oxidation of phosphatidylcholine liposomal membranes into which it was incorporated in a concentration-dependent manner. The 21-aminosteroid U74006F did not exert any sparing effect on the rate of alpha-tocopherol consumption in the oxidation of methyl linoleate in solution, but when they were simultaneously incorporated into the membrane, U74006F spared alpha-tocopherol and exerted a synergistic effect against the oxidation of liposomal membranes. This suggests that lipophilic U74006F acts as an antioxidant against lipid peroxidation through a physicochemical and not a pure chemical mechanism, and that a physical interaction with the liposomal membrane may facilitate the inhibition of lipid peroxidation with U74006F.