Arachidonic acid. Molecular model of arachidonic acid (5, 8, 11, 14-eicosatetraenoic acid, C20. H32. O2), a fatty acid essential for health. Atoms are shown as spheres and are colour-coded: carbon (yellow), oxygen (red) and hydrogen (blue). This is an omega 6 acid, a type of polyunsaturated fatty acid (PUFA). These are healthier than saturated fats, which can cause heart disease. PUFAs are found mainly in fish and vegetable oils. Arachidonic acid is also a precursor of prostaglandins and leukotrienes, chemicals which lower blood pressure, protect the stomach lining from ulcers, cause inflammation and aid blood clotting.