EFFECT OF FATTY-ACID COMPOSITION OF PHOSPHOLIPIDS ON THEIR ANTIOXIDANT PROPERTIES AND ACTIVITY INDEX

Various phospholipids may act as antioxidants or prooxidants. This stu dy investigated the effects of three phospholipid classes and their fa tty acid composition on antioxidant activity. Antioxidant properties o f sphingomyelin, phosphatidylcholine and phosphatidylethanolamine from salmon and menhaden oil were measured by oxidation induction time. An antioxidant activity index was determined in these systems with the R ancimat 617. Fatty acid profiles of the individual phospholipids and t otal oils were determined by gas-liquid chromatography before and afte r oxidation. The index was significantly (P < 0.05) influenced by the headgroup and fatty acid composition of the phospholipid. Lipids with a choline headgroup had oxidation induction times greater than 60 h in the salmon oil system. The choline-containing phospholipid also offer ed better(P < 0.05) protection from oxidation to the n-3 and total pol yunsaturated fatty acids in salmon oil. Phospholipids containing more saturated fatty acids had longer oxidation induction times (>84 h) and higher antioxidant index (>9). Chainlength of the fatty acids may hav e contributed to the observed index, as phospholipids with longer chai ns (i.e., C-18 and above) had longer oxidation induction times. Phosph olipids tested in this study had little or no antioxidant activity in menhaden oil, nor did they offer protection to n-3 or total polyunsatu rated fatty acids in this oil. These findings suggest that fatty acid profiles of individual oils may influence the antioxidant index of eac h phospholipid.