FR-900452

Previously, we reported that induction of peroxidation of synthetic phosphatidylcholines (PCs) containing a polyunsaturated fatty acid by Fe(2+)-EDTA in the presence of ascorbate resulted in the formation of four types of PCs with an sn-2-oxidatively fragmented acyl group, which had platelet-aggregating activity due to interaction with platelet-activating factor (PAF) receptors. These PCs were compounds with a short-chain monocarboxylate, omega-hydroxymonocarboxylate, dicarboxylate, and dicarboxylate semialdehyde residue, respectively. In this study, we investigated the PAF-like lipids formed during peroxidation of PCs from hen egg yolk, salmon roe, sea urchin eggs, and krill in an FeSO4/EDTA/ascorbate system. The platelet-aggregating activities of these oxidized PCs were all inhibited by FR-900452, an antagonist of PAF. The activity of oxidized krill PC, which was equivalent of 89.8 +/- 8.8 pmol 16:0-PAF/mumol of starting PC, was about 5 times those of oxidized PCs from salmon roe and sea urchin eggs, and about 50 times that of oxidized hen egg yolk PC. The PAF-like phospholipids that had different combinations of long-chain alkyl or acyl groups with one of the above four types of short-chain acyl groups were identified by gas chromatography-mass spectrometry. The results indicated that foodstuffs that are rich in 1-O-alkyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine are potential sources of compounds with high PAF-like activity formed by deleterious lipid peroxidation.

Previously, we reported the formation of four kinds of phosphatidylcholines (PC) with a short-chain monocarboxylate, dicarboxylate, dicarboxylate semialdehyde or omega-hydroxymonocarboxylate group by oxidation of PCs containing polyunsaturated fatty acid (PUFA) in an FeSO4/ascorbate/EDTA system. In this study, we identified these novel phospholipids by GC-MS as oxidation products of two alkyl ether-linked PCs, 1-O-hexadecyl-2-docosahexaenoyl and 1-O-hexadecyl-2-arachidonoyl-sn-glycero-3- phosphocholine (GPC). The sn-2-acyl moieties of oxidatively fragmented PCs derived from PCs containing docosahexaenoate were one methylene unit shorter than those detected as major oxidation products of PCs containing arachidonate. The platelet-aggregations induced by the oxidized PCs were all inhibited by FR-900452, an antagonist of platelet activating factor (PAF). The PAF-like activity of oxidized 1-O-hexadecyl-2-docosahexaenoyl-GPC, which was equivalent of 1372 +/- 262 pmol 16:0-PAF/mumol starting PC, was 5 times that of oxidized 1-O-hexadecyl-2-arachidonoyl-GPC and 150 times that of oxidized 1-palmitoyl-2-docosahexaenoyl-GPC, suggesting that both an sn-1-alkyl ether linkage and an sn-2-acyl group with a short chain length are important structural requirements for induction of platelet aggregation. These possibilities were confirmed by experiments on the platelet-aggregating activities of synthetic PAF-like compounds. Quantitative measurements by GC-MS of PAF-like phospholipids formed by lipid peroxidation and the activities of synthetic PAF-like phospholipids, suggested that the activities of most oxidized PCs containing PUFA were ascribable to those of PCs with an sn-2-short-chain monocarboxylate group.