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.
Polyacrylic acid of PAA have been prepared that are responsive to pH and temperature stimuli, demonstrating the possibility to be used for drug delivery purposes. ATRP has been used to growth PAA brushes from the surface. One reported approach was with surface-initiated ATRP of tert-butyl acrylate that was subsequently deprotected through pyrolysis to form the carboxylic acid. These PAA brushes can form chelate complex with silver and can therefore exhibit antibacterial activity. Polyacrylic acid Poly(acrylic acid) (PAA; trade name Carbomer) is a synthetic high-molecular weight polymers of acrylic acid. The IUPAC name is poly(1-carboxyethylene. They may be homopolymers of acrylic acid, or