Synthesis of Alkyl-Glycerolipids Standards for Gas Chromatography Analysis: Application for Chimera and Shark Liver Oils.

Natural O-alkyl-glycerolipids, also known as alkyl-ether-lipids (AEL), feature a long fatty alkyl chain linked to the glycerol unit by an ether bond. AEL are ubiquitously found in different tissues but, are abundant in shark liver oil, breast milk, red blood cells, blood plasma, and bone marrow. Only a few AEL are commercially available, while many others with saturated or mono-unsaturated alkyl chains of variable length are not available. These compounds are, however, necessary as standards for analytical methods. Here, we investigated different reported procedures and we adapted some of them to prepare a series of 1-O-alkyl-glycerols featuring mainly saturated alkyl chains of various lengths (14:0, 16:0, 17:0, 19:0, 20:0, 22:0) and two monounsaturated chains (16:1, 18:1). All of these standards were fully characterized by NMR and GC-MS. Finally, we used these standards to identify the AEL subtypes in shark and chimera liver oils. The distribution of the identified AEL were: 14:0 (20-24%), 16:0 (42-54%) and 18:1 (6-16%) and, to a lesser extent, (0.2-2%) for each of the following: 16:1, 17:0, 18:0, and 20:0. These standards open the possibilities to identify AEL subtypes in tumours and compare their composition to those of non-tumour tissues.