This high purity monounsaturated fatty acid is ideal as a standard and for use in biological systems. cis-11-hexadecenoic acid is found in some insects where it acts as a pheromone precursor.1 It is the main monoene fatty acid of some organisms, such as the myxobacteria Cytophaga hutchinsonii, where it is predominantly found acylated to phosphatidylethanolamine.2 cis-11- hexadecenoic acid is formed by the delta 11-desaturase enzyme from palmitic acid.3