Monoterpenes are aliphatic mono-, di- or tricyclic terpenes that are formally made up of 2 isoprene units (C10H16). Monoterpenes are mostly volatile natural substances. Together with other terpenes, they are the main ingredients (about 90%) of essential oils(Olea aetherea), which are obtained by pressing, steam distillation, oil extraction or solvent extraction. Monoterpenes are used in large quantities in the pharmaceutical, food, perfume and paint industries. They are biosynthesized from geranyl pyrophosphate (isoprenoids - see terpenes below).
Acyclic monoterpenes are formed by hydrolysis of the phosphate bond. In various further chemical steps, monoterpene alcohols, monoterpene aldehydes and ketones are formed as well as the mono- and bicyclic monoterpenes through cyclization reactions.
Examples of monoterpenes: linalool, citronellol, eugenol, terpineol, menthol, terpinene, sabinene, limonene, alpha- and beta-pinene, camphor, myrtenol and others.
Monoterpenes have analgesic, antioxidant and anti-inflammatory effects to varying degrees. Some monoterpenes play a role as pheromones in animal organisms.
Monoterpenes are of great allergological importance.