Mass spectrometric identification of molecular species of phosphatidylcholine and lysophosphatidylcholine extracted from shark liver.

The profile and structural characterization of molecular species of phosphatidylcholine (PC) and lysophosphatidylcholine (LysoPC) from shark liver using liquid chromatographic/electrospray ionization mass spectrometry (LC-ESI/MS) and tandem mass spectrometry (MS/MS) are described for the first time in this paper. The presence of (i) a relatively high content of ether PC species, such as 1-O-alkyl- and 1-alk-1'-enyl-2-polyunsaturated PC species (about 20%), and (ii) a high percentage of docosahexaenoic acid (DHA)-containing LysoPC (about 27%) is the characteristic of this marine material. 1-Hexadecanoyl-2-docosahexaenoyl-PC (16:0/22:6; about 24%) and 1-docosahexaenoyl-2-hydroxyl-LysoPC (22:6; about 27%) are the two most abundant species in shark liver. The other polyunsaturated PC species including ether PC are tentatively identified as 1-heptadecanoyl-2-docosahexaenoyl-PC (17:0/22:6), 1-octadecyl-2-docosahexaenoyl-PC (alkyl-18:0/22:6), 1-hexadecyl-2-docosahexaenoyl-PC (alkyl-16:0/22:6), 1-octadecenyl-2-eicosapentaenoyl-PC (alkyl-18:1/20:5), 1-octadecenyl-2-eicosatetraenoyl-PC (alkyl-18:1/20:4), 1-hexadecyl-2-docosapentaenoyl-PC (alkyl-16:0/22:5), 1-(1 Z-hexadecenyl)-2-docosahexaenoyl-PC (alkenyl-16:0/22:6), and 1-octadecenoyl-2-docosahexaenoyl-PC (18:1/22:6). These results establish that high contents of ether DHA-PC and DHA-LysoPC species can be obtained from shark liver.