Action of Fatty Acid Esters of l-Ascorbic Acid as Antioxidants in Phosphatidylcholine Liposomal Membranes

Abstract

Abstract The antioxidant activities of saturated fatty acid esters of l-ascorbic acid were studied in the oxidations of soybean phosphatidylcholine liposomes in aqueous dispersions aiming at elucidating their action as antioxidants in the liposomal membranes, especially the effects of number and length of the fatty acid ester side chains at either 6- or both 5- and 6-positions. Ascorbic acid esters were found to act as radical-scavenging antioxidants in the oxidations initiated by either aqueous free radical attacking from outside of the membrane or by lipophilic radical generated within the membranes. They inhibited the oxidation cooperatively with α-tocopherol in the membranes and reduced the rate of α-tocopherol consumption, their sparing effects on α-tocopherol being greatest for the monoesters and for the esters with the shortest fatty acid chains within the diester group. It was concluded that the intramembrane and intermembrane mobilities of ascorbic acid esters decreased with increasing number and length of fatty acid chains.