Effect of soybean oil and fish oil on individual molecular species of Atlantic salmon head kidney phospholipids determined by normal-phase liquid chromatography coupled to negative ion electrospray tandem mass spectrometry

The effect of soybean oil (SO) and fish oil (FO) on the relative molecular species distribution of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylserine (PS) in Atlantic sal mon head kidney was studied using normal-phase liquid chromatography couple d with negative ion electrospray tandem mass spectrometry. The conformation of identity of the phospholipid species was based on retention time, the m ass of the [M-H](-) ([M-15](-) for PC) molecular ions and the carboxylate a nion fragments in the product ion spectrum. The intensity ratio of sn-1/sn- 2 fragment ions increased with increasing number of double bonds in the sn- 2 acyl chain but was not affected by increasing number of double bonds in t he sn-1 acyl chain of the species examined. The relative distribution of th e molecular species was determined by multiple reaction monitoring of the c arboxylate anion fragment from the sn-1 position. A total of 68 different p hospholipid species were determined in the head kidney and the largest amou nt was found in PE (22 species). Depending on the diet, the main species id entified in the different phospholipid classes were; PC 16:0/18:1, PE 16:0/ 22:6, PI 18:0/20:4 and PS 16:0/22:6. The SO diet significantly increased th e 18:2, 20:3 and most 20:4 containing species and significantly reduced the 14:0 and most 20:5 and 22:6 fatty acid containing species. The increase of the 20:4 and the decrease of the 20:5 and 22:6 containing species were dep endent on the fatty acid combination of the species (C) 2000 Elsevier Scien ce B.V. All rights reserved.