– 4-hydroxy Nonenal is a lipid peroxidation product derived from oxidized ω-6 polyunsaturated fatty acids, such as linoleic acid and arachidonic acid, that is widely used as a marker of oxidative stress. 4-HNE exhibits various biological activities such as cytotoxicity, growth inhibiting activity, genotoxicity, and chemotactic activity. 4-hydroperoxy 2-Nonenal is the immediate precursor of 4-HNE formed from the cleavage of ω-6 hydroperoxides. Analogous reactions are expected to occur with hydroperoxides from other ω-6 fatty acids, particularly arachidonic acid.