Polyunsaturated fatty acids such as arachidonate and linoeate, while essential to health maintenance, are subject to random peroxidation by ambient oxygen, resulting in fragmented and reactive decomposition products. One prominent autoxidation product of either trilinolein or arachidonic acid is trans-4,5-epoxy-2(E)-decenal. This aldehyde is responsible for a pungent metallic flavor of decomposed lipids, with a detection threshold of 1.5 pg/l in air. trans-4,5-epoxy-2(E)-Decenal also reacts with nucleophiles (lysine amino groups) on proteins, leading to loss of cell function and viability. This reactive aldehyde is therefore a useful tool in elucidating the effects of peroxidative damage in experimental models.