Fatty acids (or their salts) do not often occur as such in biological systems. Instead fatty acids like oleic acid occur as their esters, commonly triglycerides, which are the greasy materials in many natural oils. Fatty acids can be obtained by the saponification of triglycerides.
Oleic acid is emitted by the decaying corpses of a number of insects, including bees and Pogonomyrmexants, and triggers the instincts of living workers to remove the dead bodies from the hive. If a live bee or ant is dabbed with oleic acid, it is dragged off for disposal as if it were dead. The oleic acid smell also may indicate danger to living insects, prompting them to avoid others who have succumbed to disease or places where predators lurk.
Esters of azelaic acid find applications in lubrication and plasticizers.
The stereoisomer of oleic acid is called elaidic acid or trans-9-octadecenoic acid. These isomers have distinct physical properties and biochemical properties. Elaidic acid, the most abundant trans fatty acid in diet, appears to have an adverse effect on health. A reaction that converts oleic acid to elaidic acid is called elaidinization.
In chemical analysis, fatty acids are separated by gas chromatography of their methyl ester derivatives. Alternatively, separation of unsaturated isomers is possible by argentation thin-layer chromatography.
The principal use of oleic acid is as a component in many foods, in the form of its triglycerides. It is a component of the normal human diet as a part of animal fats and vegetable oils.
Oleic acid as its sodium salt is a major component of soap as an emulsifying agent. It is also used as an emollient. Small amounts of oleic acid are used as an excipient in pharmaceuticals, and it is used as an emulsifying or solubilizing agent in aerosol products.
Oleic acid is also used to induce lung damage in certain types of animals, for the purpose of testing new drugs and other means to treat lung diseases. Specifically in sheep, intravenous administration of oleic acid causes acute lung injury with corresponding pulmonary edema. This sort of research has been of particular benefit to premature newborns, for whom treatment for underdeveloped lungs (and associated complications) is often a matter of life and death.
Oleic acid is used as a soldering flux in stained glass work for joining lead came.
Oleic acid is also widely used in the solution phase synthesis of nanoparticles, functioning as a kinetic knob to control the size and morphology of nanoparticles.
Oleic acid may be responsible for the hypotensive (blood pressure reducing) effects of olive oil. Adverse effects also have been documented, however, since both oleic and monounsaturated fatty acid levels in the membranes of red blood cells have been associated with increased risk of breast cancer, although the consumption of oleate in olive oil has been associated with a decreased risk of breast cancer.
^Villarreal-Lozoya, Jose E.; Lombardini, Leonardo; Cisneros-Zevallos, Luis (2007). "Phytochemical constituents and antioxidant capacity of different pecan Carya illinoinensis (Wangenh.) K. Koch] cultivars". Food Chemistry. 102 (4): 1241-1249. doi:10.1016/j.foodchem.2006.07.024.
^Purnamadjaja, Anies Hannawati; Russell, R. Andrew (2005). "Pheromone communication in a robot swarm: Necrophoric bee behaviour and its replication". Robotica. 23 (6): 731-42. doi:10.1017/S0263574704001225.
^Ayasse, M.; Paxton, R. (2002). "Brood protection in social insects". In Hilker, M.; Meiners, T. Chemoecology of Insect Eggs and Egg Deposition. Berlin: Blackwell. pp. 117-48. ISBN978-1-4051-0694-8.
^Tardy, Anne-Laure; Morio, Beatrice; Chardigny, Jean-Michel; Malpuech-Brugere, Corinne "Ruminant and industrial sources of trans-fat and cardiovascular and diabetic diseases" Nutrition Research Reviews 2011, volume 24, pp. 111-117. doi:10.1017/S0954422411000011
^Pala, V.; Krogh, V.; Muti, P.; Chajes, V.; Riboli, E.; Micheli, A.; Saadatian, M.; Sieri, S.; Berrino, F. (2001). "Erythrocyte Membrane Fatty Acids and Subsequent Breast Cancer: A Prospective Italian Study". JNCI Journal of the National Cancer Institute. 93 (14): 1088-95. doi:10.1093/jnci/93.14.1088. PMID11459870.
^Martin-Moreno JM, Willett WC, Gorgojo L, Banegas JR, Rodriguez-Artalejo F, Fernandez-Rodriguez JC, Maisonneuve P, Boyle P (1994). "Dietary fat, olive oil intake and breast cancer risk". International Journal of Cancer. 58 (6): 774-780. doi:10.1002/ijc.2910580604. PMID7927867.