This 3-hydroxyoctanoic acid is a high purity standard that is ideal for analysis and biological systems. 3-Hydroxyoctanoic acid is found primarily as polyhydroxyalkenoates in bacteria and other microorganisms where they can be as much as 90% of the dry weight in some circumstances. 3-Hydroxy fatty acids are intermediates in fatty acid biosynthesis and have been found to be converted to the omega-fatty acid by the enzyme CYP4F11 and then into dicarboxylic acids in vivo.1 3-Hydroxy fatty acids are used as biomarkers for fatty acid oxidative disorders of both the long- and short-chain 3-hydroxy-acyl-CoA dehydrogenases.2,3 Polyhydroxyalkenoates, polyesters produced by bacteria fermentation, are used for carbon and energy storage and are of interest in studies regarding their synthesis, properties and mechanisms and are used as biodegradable plastics.4 Medium chain-length polyhydroxyalkenoate monomers such as 3-hydroxyoctanoic acid may have pharmaceutical properties. 3-Hydroxyoctanoic acid is a beta-oxidation intermediate in humans and it demonstrates anti-lipolytic activity in adipocytes.5