Salicylic acid Salicylic acid Salicylic acid (from Latin "salix", "willow tree") is a lipophilic monohydroxybenzoic acid, a type of phenolic acid, and a beta hydroxy acid (BHA). It has the formula CHO. This colorless crystalline organic acid is widely used in organic synthesis and functions as a plant hormone. It is derived from the metabolism of salicin. In addition to serving as an important active metabolite of aspirin ("acetylsalicylic acid"), which acts in part as a prodrug to salicylic acid, it is probably best known for its use as a key ingredient in topical anti-acne products. The salts and esters of salicylic
4-Aminosalicylic acid because aminosalicylic acid inhibits the synthesis of thyroid hormones. Drug interactions include elevated phenytoin levels. When taken with rifampicin, the levels of rifampicin in the blood fall by about half. The U.S. FDA assigned PAS to pregnancy category C, indicating that it is not known whether it will harm an unborn baby. With heat, aminosalicylic acid is decarboxylated to produce CO and 3-aminophenol. PAS has been shown to be a pro-drug and it is incorporated into the folate pathway by dihydropteroate synthase (DHPS) and dihydrofolate synthase (DHFS) to generate a hydroxyl dihydrofolate antimetabolite, which in turn inhibits dihydrofolate reductase (DHFR)