This high purity monounsaturated fatty acid methyl ester is ideal as a standard and for biological systems. Being an odd numbered long-chain fatty acid that is unusual in most biological systems it is often useful as an internal standard and for comparison against other fatty acids.1 cis-10-Nonadecenoic acid, as well as other monounsaturated fatty acids, demonstrates human p53 DNA binding domain inhibition.2 This fatty acid has a cis double bond at an even carbon (carbon 10) and therefore cannot be enzymatically degraded via the usual beta-oxidation pathway. Instead, a reductase-isomerase or an epimerase pathway must be employed in the metabolism of this fatty acid.3