α-Eleostearic acid (α-ESA), also known as 9(Z),11(E),13(E)-octadecatrienoic acid, is a conjugated polyunsaturated fatty acid and peroxisome proliferator-activated receptor γ (PPARγ) agonist that has been found in tung tree seed oil.^1,2 It is converted to 9(Z),11(E)-conjugated linoleic acid by the cytochrome P450 (CYP) isoform CYP4F13 in rats.³ α-ESA (10 µM) activates PPARγ transcriptional activity in a reporter assay using RAW 264.7 cells.¹ It is an inhibitor of DNA polymerase α, -β, -γ, -Δ, and -ε (IC50s = 10.7, 13.4, 10.6, 14, and 22 µM, respectively) and topoisomerase I and -II (IC50s = 20 and 5 µM, respectively).⁴ α-ESA reduces the viability of, and induces apoptosis in, MCF-7 breast cancer cells in a concentration-dependent manner.⁵ It induces ferroptosis in MDA-MB-231 breast cancer cells, increasing lipid peroxidation when used at concentrations of 50 and 100 µM and inducing cell death when used at concentrations ranging from 10 to 40 µM.² These effects are dependent on long-chain acyl-CoA synthetase 1 (ACSL1) and can be blocked by ferrostatin-1. Dietary administration of α-ESA reduces clinical signs of disease in a model of inflammatory bowel disease (IBD) induced by dextran sodium sulfate in PPARγ-expressing, but not PPARγ-knockout, mice.¹