Regiospecific Analysis of Shark Liver Triacylglycerols

The liver oils of six shallow-water shark species, silky (Carcharhinus falciformis), thresher (Alopias superciliosus), oceanic whitetip (Carcharhinus longimanus), blue (Prionace glauca), hammerhead (Sphyrna lewini) and salmon (Lamna ditropis) were analyzed with particular attention to the regioisomeric composition of triacylglycerols (TAG). The TAG compositions were analyzed by using an HPLC-evaporative light scattering detector and each molecular species identified by HPLC-atmospheric pressure chemical ionization/mass spectrometry. Major lipid components of all sharks’ oils were TAG (~80 %) made up of omega-3 polyunsaturated fatty acids at 26–40 % and 20–25 % docosahexaenoic acid (DHA). Forty different molecular species were detected in the TAG fractions. TAG consisting of one palmitic acid, one DHA and one oleic acid (12.5–19.9 %) and TAG consisting of two palmitic acids and one DHA (8.4–15.4 %) were the predominant form while 30–50 % TAG molecular species were bound to one or more DHA. Distribution of fatty acids in the primary (sn-1 and sn-3) and secondary (sn-2) position of the glycerol backbones was examined by regiospecific analysis by using pancreatic lipase and it was found that DHA was preferentially positioned at sn-2. These findings greatly extend the utilization of shark liver oils in food productions and may have a significant impact on the future development of the fish oil industry.