Terpene

Terpenes (/ˈtɜːrpiːn/) are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, and by some insects. They often have a strong odor and may protect the plants that produce them by deterring herbivores and by attracting predators and parasites of herbivores. Although sometimes used interchangeably with 'terpenes', terpenoids (or isoprenoids) are modified terpenes as they contain additional functional groups, usually oxygen-containing. Terpenes are hydrocarbons.Limonene, a monoterpene.Carvone is a monoterpenoid, a modified monoterpene.Humulene, a sesquiterpene.Taxadiene, a diterpene, precursor to the diterpenoid taxol, an anticancer agent.Squalene, a triterpene and universal precursor to natural steroids. Terpenes (/ˈtɜːrpiːn/) are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, and by some insects. They often have a strong odor and may protect the plants that produce them by deterring herbivores and by attracting predators and parasites of herbivores. Although sometimes used interchangeably with 'terpenes', terpenoids (or isoprenoids) are modified terpenes as they contain additional functional groups, usually oxygen-containing. Terpenes are hydrocarbons. Terpenes are the major components of rosin and of turpentine produced from resin. The name 'terpene' is derived from the word 'terpentine', an obsolete form of the word 'turpentine'. Terpenes are also major biosynthetic building blocks. Steroids, for example, are derivatives of the triterpene squalene. Terpenes and terpenoids are the primary constituents of the essential oils of many types of plants and flowers. Essential oils are used widely as fragrances in perfumery and traditional medicine, such as aromatherapy. Synthetic variations and derivatives of natural terpenes and terpenoids also greatly expand the variety of aromas used in perfumery and flavors used in food additives. Vitamin A is a terpenoid. The term 'terpene' was coined in 1866 by the German chemist August Kekulé. Terpenes are derived biosynthetically from units of isopentenyl pyrophosphate. Although the structures of terpenoids are rationalized as derivatives of isoprene (2-methyl-1,3-butadiene), isoprene is not involved in the biosynthesis. The biogenetic isoprene rule or the C5 rule was described in 1953, by Leopold Ružička, who explained that terpinoids can be visualized as the result of linking isoprene units 'head to tail' to form chains, which can be arranged to form rings. There are two metabolic pathways that create terpenoids: Many organisms manufacture terpenoids through the HMG-CoA reductase pathway, known as the Mevalonate pathway, which also produces cholesterol. One of the intermediates in this pathway is mevalonic acid. The reactions take place in the cytosol. The pathway was discovered in the 1950s. The 2-C-methyl-D-erythritol 4-phosphate/1-deoxy-D-xylulose 5-phosphate pathway (MEP/DOXP pathway), also known as non-mevalonate pathway or mevalonic acid-independent pathway, takes place in the plastids of plants and apicomplexan protozoa, as well as in many bacteria. It was discovered in the late 1980s.