Isoprostanes are prostaglandin (PG)-like products of free-radical induced lipid peroxidation.{320} Although the isoprostanes derived from arachidonic acid are the best characterized, many other polyunsaturated fatty acids can form isoprostanes.{7323} (±)5-iPF2α-VI is one of dozens of possible stereo- and regioisomeric isoprostanes which can be formed from arachidonic acid. To date, the most extensively studied of these is 8-isoprostane (8-epi-PGF2α, iPF2α-III).{3064,5011} However, 8-isoprostane is a minor isoprostane constituent when compared to some of the other isomers which form in natural conditions of oxidative stress.{8367} (±)5-iPF2α-VI is an isoprostane from the unique Type VI class of isoprostanes. This class has been shown to be one of the major isoprostane products, in contrast to 8-isoprostane. In addition to being produced in greater abundance than 8-isoprostane, Type VI isoprostanes form internal lactones, which facilitates their extraction and purification from biological samples.{8367,9408,6910,6390}