Impact of phosphatidylethanolamine on the antioxidant activity of α-tocopherol and trolox in bulk oil.

The amphiphilic phospholipids dioleoylphosphatidylcholine (DOPC) and dioleoylphosphatidylethanolamine (DOPE), can form reverse micelles in bulk oils, which affects lipid oxidation chemistry. Previous studies showed that reverse micelles formed by DOPC and DOPE shorten the oxidation lag phase of stripped soybean oil. This study examined how these reverse micelles influence the activity of primary antioxidants such as the nonpolar α-tocopherol and the polar trolox in stripped and commercial soybean oils. The results showed that DOPC reverse micelles decreased the activity of 100 μM α-tocopherol or trolox. On the other hand, DOPE increased the antioxidant activity of both α-tocopherol and trolox. The polar trolox exhibited better antioxidant activity than the nonpolar α-tocopherol in the presence of both DOPC and DOPE reverse micelles because trolox partitioned more at the interfaces, which was confirmed by a fluorescence steady state study. Different ratios of DOPE to DOPC were added to oil containing 100 μM α-tocopherol, and antioxidant activity increased with increasing DOPE/DOPC ratio. Addition of DOPE to commercial oil inhibited lipid oxidation, whetrsd DOPC was ineffective. HPLC showed that DOPE regenerated α-tocopherol. This study indicates that the antioxidant activity of tocopherols could be improved by utilizing phosphatidylethanolamine (PE) to engineer the properties of reverse micelles in bulk oil.