Triterpene

Short description: Class of chemical compounds

Squalene: One of the most important triterpenes

Hopane: An example of a pentacyclic triterpene

Triterpenes are a class of terpenes composed of six isoprene units with the molecular formula C30H48; they may also be thought of as consisting of three terpene units. Animals, plants and fungi all produce triterpenes, including squalene, the precursor to all steroids.[1][2]

## Contents

* 1 Structures
* 2 Triterpenoids
* 2.1 Steroids
* 2.2 Triterpenoid saponins
* 3 References

## Structures

Triterpenes exist in a great variety of structures. Nearly 200 different skeletons have been identified.[3] These skeletons may be broadly divided according to the number of rings present. In general pentacyclic structures (5 rings) tend to dominate.

Number of rings | Examples

|

0 | Squalene
1 | Achilleol A [4]
2 | Polypodatetraene
3 | Malabaricane
4 | Lanostane, Cucurbitacin
5 | Hopane, Oleanane, Ursolic acid
6  | Chamaecydin

Squalene is biosynthesized through the head-to-head condensation of two farnesyl pyrophosphate units. This coupling converts a pair of C15 components into a C30 product. Squalene serves as precursor for the formation of many triterpenoids, including bacterial hopanoids and eukaryotic sterols.

## Triterpenoids

Cholesterol: one of the simplest but most important triterpenoids

By definition triterpenoids are triterpenes that possess heteroatoms, usually oxygen. The terms triterpene and triterpenoid often are used interchangeably.

Triterpenoids possess a rich chemistry and pharmacology (e.g. cholesterol) with several pentacyclic motifs. Lupane, oleanane and ursane show particular promise as anti-cancer agents.[5][6]

### Steroids

Steroids feature a cucurbitane core, although in practice they are biosynthesised from either lanosterol (animals and fungi) or cycloartenol (plants) via the cyclization of squalene. Steroids have two principal biological functions, being either key components of cell membranes or signaling molecules that activate steroid hormone receptors. Important sub-classes include sterols and cucurbitacins.

### Triterpenoid saponins

Triterpenoid saponins are triterpenes which belong to the saponin group of compounds, making them triterpenoid glycosides. They are produced by plants as part of their self-defense mechanism[7] with important sub-classes including ginsenosides[8] and eleutherosides.

## References

1. ↑ Eberhard Breitmaier (2006). "Triterpenes". Terpenes: Flavors, Fragrances, Pharmaca, Pheromones. pp. 86–108. doi:10.1002/9783527609949.ch6. ISBN 9783527609949.
2. ↑ Davis, Edward M.; Croteau, Rodney (2000). "Cyclization Enzymes in the Biosynthesis of Monoterpenes, Sesquiterpenes, and Diterpenes". Topics in Current Chemistry 209: 53–95. doi:10.1007/3-540-48146-X_2. ISBN 978-3-540-66573-1.
3. ↑ Xu, Ran; Fazio, Gia C.; Matsuda, Seiichi P.T. (February 2004). "On the origins of triterpenoid skeletal diversity". Phytochemistry 65 (3): 261–291. doi:10.1016/j.phytochem.2003.11.014. PMID 14751299.
4. ↑ Barrero, A.F.; Alvarez-Manzaneda, E.J.R.; Alvarez-Manzaneda r, R. (1989-01-01). "Achilleol A: A new monocyclic triterpene skeleton from Achillea odorata L." (in en). Tetrahedron Letters 30 (25): 3351–3352. doi:10.1016/S0040-4039(00)99242-6. ISSN 0040-4039. https://www.sciencedirect.com/science/article/abs/pii/S0040403900992426.
5. ↑ Laszczyk, Melanie (2009). "Pentacyclic Triterpenes of the Lupane, Oleanane and Ursane Group as Tools in Cancer Therapy". Planta Medica 75 (15): 1549–60. doi:10.1055/s-0029-1186102. PMID 19742422.
6. ↑ Liu, Jie (December 1995). "Pharmacology of oleanolic acid and ursolic acid". Journal of Ethnopharmacology 49 (2): 57–68. doi:10.1016/0378-8741(95)90032-2. PMID 8847885.
7. ↑ Augustin, Jörg M.; Kuzina, Vera; Andersen, Sven B.; Bak, Søren (April 2011). "Molecular activities, biosynthesis and evolution of triterpenoid saponins". Phytochemistry 72 (6): 435–457. doi:10.1016/j.phytochem.2011.01.015. PMID 21333312.
8. ↑ Attele, Anoja S; Wu, Ji An; Yuan, Chun-Su (December 1999). "Ginseng pharmacology". Biochemical Pharmacology 58 (11): 1685–1693. doi:10.1016/S0006-2952(99)00212-9. PMID 10571242.

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Types of terpenes and terpenoids (# of isoprene units)

Basic forms:|

* Acyclic (linear, cis and trans forms)
* Monocyclic (single ring)
* Bicyclic (2 rings)
* Iridoids (cyclopentane ring)
* Iridoid glycosides (iridoids bound to a sugar)
* Steroids (4 rings)

Hemiterpenoids (1)|

* Isoprene (C5H8)
* Prenol
* Isovaleric acid

Monoterpene (C10H16)(2)|

| Acyclic|

* Ocimene
* Myrcenes

|

Monocyclic|

* Limonene
* Terpinene
* Phellandrene
* Umbellulone

Bicyclic|

* Pinene (β and α)
* Camphene
* Thujene
* Sabinene
* Carene

Monoterpenoids (2,modified)|

| Acyclic|

* Linalool
* Citronellal
* Citral
* Citronellol
* Geraniol
* Geranyl pyrophosphate

|

Monocyclic|

* Grapefruit mercaptan
* menthol
* p-Cymene
* thymol
* Perillyl alcohol
* Carvacrol

Bicyclic|

* Camphor
* Borneol
* Eucalyptol
* Halomon
* Pinene
* Ascaridole

Sesquiterpenoids (3)|

* Farnesyl pyrophosphate
* Artemisinin
* Bisabolol

Diterpenoids (4)|

* Geranylgeranyl pyrophosphate
* Gibberellin
* Retinol
* Retinal
* Phytol
* Taxol
* Forskolin
* Aphidicolin
* Salvinorin A

Sesterterpenoids (5)|

* geranylfarnesol

Triterpenoids (6)|

| Steroids|

* Phytosterols
* Campesterol
* beta Sitosterol
* gamma sitosterol
* Stigmasterol
* Tocopherols
* Cholesterol
* Testosterone
* Cholecalciferol (Vit D)
* Ecdysones

|

Other|

* Saponins
* Squalane
* Lanosterol
* Acids
* Oleanolic acid
* Ursolic acid
* Betulinic acid
* Moronic acid

Sesquarterpenes/oids (7)|

* ferrugicadiol
* tetraprenylcurcumene

Tetraterpenoids
(Carotenoids) (8)|

| Carotenes|

* Alpha-Carotene
* Beta-Carotene
* Gamma-Carotene
* Delta-Carotene
* Lycopene
* Neurosporene
* Phytofluene
* Phytoene

|

Xanthophylls:|

* Canthaxanthin
* Cryptoxanthin
* Zeaxanthin
* Astaxanthin
* Lutein
* Rubixanthin

Polyterpenoids (many)|

* sap, resins, latex of many plants, e.g. rubber

Norisoprenoids (modified)|

* 3-oxo-α-ionol
* 7,8-dihydroionone

Synthesis|

* Terpene synthase enzymes (many), having in common a Terpene synthase N terminal domain (protein domain)

Activated isoprene forms|

* Isopentenyl pyrophosphate (IPP)
* Dimethylallyl pyrophosphate (DMAPP)

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