9(S)-HODE is produced by the lipoxygenation of linoleic acid in both plants and animals.[1],[2] It has been detected in atherosclerotic plaques, as an esterified component of membrane phospholipids and in oxidized LDL particles.[3]
9(S)-HODE cholesteryl ester was originally extracted from atherosclerotic lesions. It remains uncertain whether the oxidized fatty acid portion of the molecule results from enzymatic lipoxygenation or from random lipid peroxidation. 9(S)-HODE cholesteryl ester can be used as a standard for analysis of chiral HODE cholesteryl esters.
9(R)-HODE is one of several monohydroxylated products of linoleic acid. All known mammalian lipoxygenases appear to catalyze the oxygenation of arachidonic and linoleic acid to give products having strictly the (S) configuration at the site of oxygen insertion. However, both human umbilical vein endothelial cells and bovine aorta endothelial cells have been shown to produce 9(R)-HODE when incubated with linoleic acid. The physiological function of 9(R)-HODE and the enzyme that catalyzes its formation have not been determined.
(±)9-HpODE is a racemic mixture of the fatty acid hydroperoxide product (9(S)-HpODE) formed from lipoxygenase action on linoleic acid. It shows antimicrobial activity against various fungal and bacterial pathogens and thus may play a role in plant defense. In mammalian species, monocyte-induced oxidization of LDL generates significant amounts of esterified 9-HpODE, which is rapidly reduced to 9-HODE.
9-OxoODE, formed through the oxidation of the allylic hydroxyl group in both 9(S)-HODE and 9(R)-HODE, is present in rabbit reticulocyte plasma and mitochondrial membranes as both 9- and 13-oxoODEs, constituting approximately 2% of the total linoleate residues. The majority of these oxidized linoleate residues are esterified to membrane lipids.