<Tr> <Td_colspan="2"> Infobox references </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> </Tr> <P> 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 C H O . 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 acid are known as salicylates . The medicinal part of the willow tree is the inner bark . </P> <P> It is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system . </P>

What is a natural source of salicylic acid