An Emerging Omega-3 Fatty Acid-Octadecapentaenoic Acid (18:5n-3): Biosynthesis, Potential Sources and Applications

Octadecapentaenoic acid (OPA, 18:5n-3) is an emerging and poorly characterized omega-3 polyunsaturated fatty acid (PUFA) that is primarily produced by certain marine microalgae. Although it is structurally similar to the well-studied eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), OPA's specific biological and ecological roles remain largely unknown. The purpose of this review is to comprehensively examine and critically analyze the current knowledge on OPA, including its biosynthesis, natural sources, and metabolic fate in consumers to assess its functional and nutraceutical potential. Current evidence suggests that OPA contributes to membrane structure in primary producers but is rapidly metabolized in consumers, acting more as an energy source or metabolic intermediate rather than a stored end product. While OPA shows the potential for applications in aquaculture and human nutrition, its practical utility is largely inferred from structurally related fatty acids. Many application questions remain unanswered due to its low natural abundance, analytical challenges, and a lack of targeted functional studies. Future research is therefore required for a better understanding its stability, bioactivity and metabolism to determine its true functional importance and practical uses.