Lipidomic Profiling of Edible Japanese Sea Urchins by LC-MS

Sea urchins (Echinoidea) are marine echinoderms commonly consumed as seafood in East Asia. To date, various metabolic components of sea urchins have been analyzed, and their health benefits for humans have also been attracting attention. Lipids are the major biomolecules present in sea urchins. However, the comprehensive lipid profiling of sea urchins is limited. In this study, we aimed to perform the comprehensive lipid profiling of six types of sea urchins using liquid chromatography-mass spectrometry (LC/MS). The application of untargeted lipidomics led to the identification of 281 lipid molecular species in six varieties of fresh sea urchin gonads. Each lipid metabolite was identified based on its retention time and MS/MS fragmentation pattern. The results of the analysis showed the highest abundance of lipid percentage in Kitamurasakiuni (14.3%), followed by Hokuyobafununi (12.4%). In all the analyzed sea urchins, glycerolipids such as triacylglycerols were found to be the most abundant lipid components. Multivariate analysis revealed that Murasakiuni showed a different lipid profile from the other types. Interestingly, the polyunsaturated fatty acid to saturated fatty acid ratios and health-related nutritional indices factors were found to be higher in Hokuyobafununi compared to other varieties. The ω-3 fatty acids, such as docosapentaenoic acid (FA 22:6) and eicosapentaenoic acid (FA 20:5), were also abundant in Hokuyobafununi. Lipids such as ether and N-acyl-type lysophosphatidylethanolamines were detected for the first time in sea urchins. This study highlights the nutritional significance of sea urchins and their potential use in the development of functional foods.