Template:Short description The terpenoids, also known as isoprenoids, are a class of naturally occurring organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeably with "terpenes", terpenoids contain additional functional groups, usually containing oxygen.<ref>Template:Cite book</ref> When combined with the hydrocarbon terpenes, terpenoids comprise about 80,000 compounds.<ref>Template:Cite journal</ref> They are the largest class of plant secondary metabolites, representing about 60% of known natural products.<ref>Template:Cite book</ref> Many terpenoids have substantial pharmacological bioactivity and are therefore of interest to medicinal chemists.<ref name="wink10">Template:Cite book</ref>
Plant terpenoids are used for their aromatic qualities and play a role in traditional herbal remedies. Terpenoids contribute to the scent of eucalyptus, the flavors of cinnamon, cloves, and ginger, the yellow color in sunflowers, and the red color in tomatoes.<ref>Template:Cite magazine</ref> Well-known terpenoids include citral, menthol, camphor, salvinorin A in the plant Salvia divinorum, ginkgolide and bilobalide found in Ginkgo biloba and the cannabinoids found in cannabis. The provitamin beta carotene is a terpene derivative called a carotenoid.
The steroids and sterols in animals are biologically produced from terpenoid precursors. Sometimes terpenoids are added to proteins, e.g., to enhance their attachment to the cell membrane; this is known as isoprenylation. Terpenoids play a role in plant defense as prophylaxis against pathogens and attractants for the predators of herbivores.<ref>Template:Cite journal</ref>
Structure and classificationEdit
Terpenoids are modified terpenes,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> wherein methyl groups have been moved or removed, or oxygen atoms added. Some authors use the term "terpene" more broadly, to include the terpenoids. Just like terpenes, the terpenoids can be classified according to the number of isoprene units that comprise the parent terpene:
| Terpenoids | Analogue terpenes | Number of isoprene units | Number of carbon atoms | General formula | Examples<ref name=Terpenoids>Template:Cite journal</ref> |
|---|---|---|---|---|---|
| Hemiterpenoids | Isoprene | 1 | 5 | C5H8 | DMAPP, isopentenyl pyrophosphate, isoprenol, isovaleramide, isovaleric acid, HMBPP, prenol |
| Monoterpenoids | Monoterpenes | 2 | 10 | C10H16 | Bornyl acetate, camphor, carvone, citral, citronellal, citronellol, geraniol, eucalyptol, hinokitiol, iridoids, linalool, menthol, thymol |
| Sesquiterpenoids | Sesquiterpenes | 3 | 15 | C15H24 | Farnesol, geosmin, humulone |
| Diterpenoids | Diterpenes | 4 | 20 | C20H32 | Abietic acid, ginkgolides, paclitaxel, retinol, salvinorin A, sclareol, steviol |
| Sesterterpenoids | Sesterterpenes | 5 | 25 | C25H40 | Andrastin A, manoalide |
| Triterpenoids | Triterpenes | 6 | 30 | C30H48 | Amyrin, betulinic acid, limonoids, oleanolic acid, sterols, squalene, ursolic acid |
| Tetraterpenoids | Tetraterpenes | 8 | 40 | C40H64 | Carotenoids |
| Polyterpenoid | Polyterpenes | >8 | >40 | (C5H8)n | Gutta-percha, natural rubber |
Terpenoids can also be classified according to the type and number of cyclic structures they contain: linear, acyclic, monocyclic, bicyclic, tricyclic, tetracyclic, pentacyclic, or macrocyclic.<ref name=Terpenoids /> The Salkowski test can be used to identify the presence of terpenoids.<ref>Template:Cite journal</ref>
- Selected terpenoids
- Taxol.svg
Paclitaxel is a diterpenoid anticancer drug.
- Terpineol alpha.svg
Terpineols are monoterpenoids.
- (S)-Humulone.svg
Humulones are classified as sesquiterpenoids.
- All-trans-Retinol2.svg
Retinol is a diterpenoid.
- Beta-thujaplicin.png
Hinokitiol is a monoterpenoid, a tropolone derivative.
- Geosmin Structural Formulae.svg
Geosmin is a sesquiterpenoid.
BiosynthesisEdit
Template:Further Terpenoids, at least those containing an alcohol functional group, often arise by hydrolysis of carbocationic intermediates produced from geranyl pyrophosphate. Analogously hydrolysis of intermediates from farnesyl pyrophosphate gives sesquiterpenoids, and hydrolysis of intermediates from geranylgeranyl pyrophosphate gives diterpenoids, etc.<ref name=Crot>Template:Cite journal</ref>
Impact on aerosolsEdit
In air, terpenoids are converted into various species, such as aldehydes, hydroperoxides, organic nitrates, and epoxides<ref name="WennbergScienceDaily">Organic Carbon Compounds Emitted By Trees Affect Air Quality, ScienceDaily, Aug. 7, 2009</ref> by short-lived free radicals (like the hydroxyl radical) and to a lesser extent by ozone.<ref name="IupacDatasheetIsopreneozone">IUPAC Subcommittee on Gas Kinetic Data Evaluation – Data Sheet Ox_VOC7, 2007</ref> These new species can dissolve into water droplets and contribute to aerosol and haze formation.<ref name="PaulotScienceNews">A source of haze, ScienceNews, August 6, 2009</ref> Secondary organic aerosols formed from this pathway may have atmospheric impacts.<ref>Template:Cite journal</ref>
As an example the Blue Ridge Mountains in the U.S. and Blue Mountains of New South Wales in Australia are noted for having a bluish color when seen from a distance. Trees put the "blue" in Blue Ridge, from their terpenoids released into the atmosphere.<ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
See alsoEdit
- List of antioxidants in food
- List of phytochemicals in food
- Nutrition
- Phytochemistry
- Secondary metabolites
ReferencesEdit
External linksEdit
Template:Secondary metabolites Template:Terpenoids Template:Authority control