Omega-3 Source Matters: Comparative Lipid Signatures and Quantitative Distribution of EPA/DHA Across Marine Resources

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are essential omega-3 polyunsaturated fatty acids (n-3 PUFAs) with well-established health benefits. They occur primarily in marine resources, while their quantitative distribution within the glycerolipidome is rarely analyzed. Therefore, we investigated major commercial sources, including 12 microalgal species, the protist <i>Schizochytrium</i> sp., four fish species, and nine commercial n-3 supplements (fish, krill and <i>Schizochytrium</i>-derived "algal" oils) by high-performance thin-layer chromatography-gas chromatography-mass spectrometry (HPTLC-GC-MS). The class-resolved mapping of EPA and DHA revealed signature lipid profiles across all sources. In microalgae, 60-80% of EPA was localized in glycolipids, whereas in <i>Schizochytrium</i> and fish, >90% of DHA occurred in triacylglycerols. Krill oils exhibited phospholipid-rich profiles with ~70% of phosphatidylcholine-bound DHA. Nutritional indices also highlighted major differences: fish and fish oils showed favorable PUFA-to-saturated FA ratios (>0.45) and hypocholesterolemic-to-hypercholesterolemic ratios (>1), while <i>Schizochytrium</i>-based "algal" oils even surpassed these values. The microalgae <i>Nannochloropsis granulata</i> contained the highest EPA content in biomass form, combined with favorable nutritional indices. Beyond total n-3 content in relation to recommended daily intake values, the lipid-class distribution and nutritional indices should be considered decisive metrics for evaluating the health relevance of n-3 resources in the human diet.