Terpenoid

{{Short description|Class of aromatic organic chemicals found in plants}}

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.{{cite book|url=https://goldbook.iupac.org/html/T/T06279.html|title=IUPAC Compendium of Chemical Terminology|first=International Union of Pure and Applied|last=Chemistry|publisher=IUPAC|doi=10.1351/goldbook.T06279}} When combined with the hydrocarbon terpenes, terpenoids comprise about 80,000 compounds.{{cite journal |doi=10.1021/acs.chemrev.7b00287|title=Structural and Chemical Biology of Terpenoid Cyclases |year=2017 |last1=Christianson |first1=David W. |journal=Chemical Reviews |volume=117 |issue=17 |pages=11570–11648 |pmid=28841019 |pmc=5599884 }} They are the largest class of plant secondary metabolites, representing about 60% of known natural products.{{cite book | last = Firn | first = Richard | name-list-style = vanc |title=Nature's Chemicals|date=2010|publisher=Oxford: Biology}} Many terpenoids have substantial pharmacological bioactivity and are therefore of interest to medicinal chemists.{{cite book |doi=10.1002/9781444320503.ch5|chapter=Biochemistry of Terpenoids: Monoterpenes, Sesquiterpenes and Diterpenes|title=Biochemistry of Plant Secondary Metabolism|year=2010|last1=Ashour|first1=Mohamed|last2=Wink|first2=Michael|last3=Gershenzon|first3=Jonathan|pages=258–303|isbn=9781444320503}}

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.{{Cite magazine |url=http://www.newyorker.com/reporting/2009/09/28/090928fa_fact_specter?currentPage=all |magazine=The New Yorker |title=A Life of Its Own | first = Michael | last = Specter | name-list-style = vanc |date=September 28, 2009}} 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.{{Cite journal |last1=Singh |first1=Bharat |last2=Sharma |first2=Ram A. |date=April 2015 |title=Plant terpenes: defense responses, phylogenetic analysis, regulation and clinical applications |journal=3 Biotech |volume=5 |issue=2 |pages=129–151 |doi=10.1007/s13205-014-0220-2 |issn=2190-572X |pmc=4362742 |pmid=28324581}}

Structure and classification

Terpenoids are modified terpenes,{{cite web |last1=Houghton |first1=Isaac |title=The Physiology of Cannabis Terpenes and Terpenoids – A Brief Overview |url=https://cannabis-kings.net/the-physiology-of-cannabis-terpenes-and-terpenoids-a-brief-overview/ |publisher=Elliot Barker |access-date=3 May 2016}} 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:

Class = "wikitable"

! Terpenoids

! Analogue terpenes

! Number of isoprene units

! Number of carbon atoms

! General formula

! Examples{{cite journal |last1=Ludwiczuk |first1=A. |last2=Skalicka-Woźniak |first2=K. |last3=Georgiev |first3=M.I. |title=Terpenoids |journal=Pharmacognosy |date=2017 |pages=233–266 |doi=10.1016/B978-0-12-802104-0.00011-1|isbn=9780128021040 }}

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. The Salkowski test can be used to identify the presence of terpenoids.{{cite journal| vauthors = Ayoola GA | title=Phytochemical Screening and Antioxidant Activities of Some Selected Medicinal Plants Used for Malaria Therapy in Southwestern Nigeria|journal=Tropical Journal of Pharmaceutical Research|date=2008|volume=7|issue=3|pages=1019–1024|ref=2|doi=10.4314/tjpr.v7i3.14686|doi-access=free|hdl=1807/60332|hdl-access=free}}

File:Taxol.svg|Paclitaxel is a diterpenoid anticancer drug.

File:Terpineol alpha.svg|Terpineols are monoterpenoids.

File:(S)-Humulone.svg|Humulones are classified as sesquiterpenoids.

File:All-trans-Retinol2.svg|Retinol is a diterpenoid.

File:Beta-thujaplicin.png|Hinokitiol is a monoterpenoid, a tropolone derivative.

File:Limonin.svg|Limonin, a common limonoid, is a triterpenoid.

File:Geosmin_Structural_Formulae.svg|Geosmin is a sesquiterpenoid.

Biosynthesis

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.{{cite journal|title=Cyclization Enzymes in the Biosynthesis of Monoterpenes, Sesquiterpenes, and Diterpenes|author1=Davis, Edward M. |author2=Croteau, Rodney |journal=Topics in Current Chemistry|year=2000|volume=209|pages=53–95|doi=10.1007/3-540-48146-X_2|isbn=978-3-540-66573-1}}

Impact on aerosols

In air, terpenoids are converted into various species, such as aldehydes, hydroperoxides, organic nitrates, and epoxides[https://www.sciencedaily.com/releases/2009/08/090806141518.htm Organic Carbon Compounds Emitted By Trees Affect Air Quality], ScienceDaily, Aug. 7, 2009 by short-lived free radicals (like the hydroxyl radical) and to a lesser extent by ozone.IUPAC Subcommittee on Gas Kinetic Data Evaluation – [http://www.iupac-kinetic.ch.cam.ac.uk/datasheets/pdf/Ox_VOC7_O3_CH2C%28CH3%29CHCH2.pdf Data Sheet Ox_VOC7], 2007 These new species can dissolve into water droplets and contribute to aerosol and haze formation.[https://www.sciencenews.org/article/source-haze A source of haze], ScienceNews, August 6, 2009 Secondary organic aerosols formed from this pathway may have atmospheric impacts.{{Cite journal |last1=D'Ambro |first1=Emma L. |last2=Schobesberger |first2=Siegfried |last3=Gaston |first3=Cassandra J. |last4=Lopez-Hilfiker |first4=Felipe D. |last5=Lee |first5=Ben H. |last6=Liu |first6=Jiumeng |last7=Zelenyuk |first7=Alla |last8=Bell |first8=David |last9=Cappa |first9=Christopher D. |last10=Helgestad |first10=Taylor |last11=Li |first11=Ziyue |date=2019-09-05 |title=Chamber-based insights into the factors controlling epoxydiol (IEPOX) secondary organic aerosol (SOA) yield, composition, and volatility |url=https://acp.copernicus.org/articles/19/11253/2019/ |journal=Atmospheric Chemistry and Physics |language=English |volume=19 |issue=17 |pages=11253–11265 |doi=10.5194/acp-19-11253-2019 |issn=1680-7316|doi-access=free |bibcode=2019ACP....1911253D |hdl=10138/305801 |hdl-access=free }}

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.{{cite book| vauthors = Johnson AW |title=Invitation To Organic Chemistry|publisher=Jones & Bartlett Learning |date=1998|page= [https://archive.org/details/invitationtoorga0000john/page/261 261] |isbn= 978-0-7637-0432-2 |url=https://archive.org/details/invitationtoorga0000john|url-access=registration|quote=blue mountains chemical terpene.}}{{cite web |title=Blue Ridge Parkway, Frequently Asked Questions |publisher=National Park Service |year=2007 |url=http://www.nps.gov/blri/faqs.htm |access-date=December 29, 2007 |archive-date=December 28, 2007 |archive-url=https://web.archive.org/web/20071228054036/http://www.nps.gov/blri/faqs.htm |url-status=live }}{{Cite web |last=CSIRO |title=Beating the eucalypt blues – new ways to model air quality |url=https://www.csiro.au/en/news/all/articles/2016/april/beating-eucalypt-blues-new-ways-model-air-quality |access-date=2023-12-10 |website=www.csiro.au |language=en}}

References

External links

[https://goldbook.iupac.org/terms/view/T06279 IUPAC definition of terpenoids]

Category:Plant communication

cs:Izoprenoidy

es:Terpenoides

it:Terpeni