Natural product to modern discovery of their active ingredients and eventually to the development of new drugs. A large number of currently prescribed drugs have been either directly derived from or inspired by natural products. A few representative examples are listed below. Some of the oldest natural product based drugs are analgesics. The bark of the willow tree has been known from antiquity to have pain relieving properties. This is due to presence of the natural product salicin which in turn may be hydrolyzed into salicylic acid. A synthetic derivative acetylsalicylic acid better known as aspirin is a widely used pain reliever.
Arsanilic acid Arsanilic acid Arsanilic acid, also known as aminophenyl arsenic acid or aminophenyl arsonic acid, is an organoarsenic compound, an amino derivative of phenylarsonic acid whose amine group is in the 4-position. A crystalline powder introduced medically in the late 19th century as Atoxyl, its sodium salt was used by injection in the early 20th century as the first organic arsenical drug, but it was soon found prohibitively toxic for human use. Arsanilic acid saw long use as a veterinary feed additive promoting growth and to prevent or treat dysentery in poultry and swine. In 2013, its approval by US government