Aspirin, also known as acetylsalicylic acid, is a nonsteroidal anti-inflammatory drug NSAID that works to decrease pain and reduce inflammation in the body. Its mechanism of action involves the inhibition of the enzyme cyclooxygenase COX , which plays a crucial role in the synthesis of prostaglandins.Prostaglandins are hormone-like substances that are involved in various physiological processes, including pain sensation, inflammation, and regulation of body temperature. They are synthesized from arachidonic acid, a fatty acid found in cell membranes, through the action of the COX enzyme.There are two main isoforms of COX: COX-1 and COX-2. COX-1 is constitutively expressed in most tissues and is responsible for the production of prostaglandins that protect the stomach lining and regulate blood clotting. COX-2 is induced during inflammation and is responsible for the production of prostaglandins that mediate pain and inflammation.Aspirin exerts its anti-inflammatory and analgesic effects by irreversibly acetylating a serine residue in the active site of both COX-1 and COX-2 enzymes. This acetylation blocks the access of arachidonic acid to the active site, thereby inhibiting the conversion of arachidonic acid to prostaglandins. As a result, the production of prostaglandins involved in pain and inflammation is reduced, leading to decreased pain and inflammation in the body.In summary, aspirin works to decrease pain and reduce inflammation by inhibiting the COX enzyme, which is responsible for the synthesis of prostaglandins. The chemical reaction involved in its mechanism of action is the acetylation of a serine residue in the active site of the COX enzyme, preventing the conversion of arachidonic acid to prostaglandins.