Arachidonic acid (AA, sometimes ARA) is an omega-6 fatty acid 20:4(ω-6). It is the counterpart to the saturated arachidic acid found in peanut oil, (L. arachis – peanut.)
Arachidonic acid is a polyunsaturated fatty acid that is present in the phospholipids of membranes of the body's cells, and is abundant in the brain.
It is also involved in cellular signaling as a second messenger.