Human Metabolome Database (HMDB): Eicosapentaenoic acid (EPA or also icosapentaenoic acid) is an important polyunsaturated fatty acid found in fish oils. It serves as the precursor for the prostaglandin-3 and thromboxane-3 families. A diet rich in eicosapentaenoic acid lowers serum lipid concentration, reduces incidence of cardiovascular disorders, prevents platelet aggregation, and inhibits arachidonic acid conversion into the thromboxane-2 and prostaglandin-2 families. Eicosapentaenoic acid is an omega-3 fatty acid. In physiological literature, it is given the name 20:5(n-3). Its systematic chemical name is all-cis-5,8,11,14,17-icosapentaenoic acid. It also has the trivial name timnodonic acid. Chemically, EPA is a carboxylic acid with a 20-carbon chain and five cis double bonds; the first double bond is located at the third carbon from the omega end. Because of the presence of double bonds, EPS is a polyunsaturated fatty acid. Metabolically it acts as a precursor for prostaglandin-3 (which inhibits platelet aggregation), thromboxane-3 and leukotriene-5 groups. It is found in fish oils of cod liver, herring, mackerel, salmon, menhaden and sardine. It is also found in human breast milk. -- Wikipedia. EPA is a biomarker for the consumption of salt-water fish.