(±)8,9-DiHETE is a major metabolite of the 20:5 ω-3 fatty acid eicosapentaenoic acid .[1] It is produced in rat liver microsomes, but not renal microsomes, by the generation of the unstable intermediate 8,9-epoxy eicosatetraenoic acid from EPA by cytochrome P450 monooxygenases. Dietary EPA supplementation in humans results in substantial urinary excretion of vicinal diols, including 8,9, 11,12, and 14,15 forms.[2]