Editing Terpenoid

{{Short description|Class of aromatic organic chemicals found in plants}}
The '''terpenoids''', also known as '''isoprenoids''', are a class of naturally occurring [[organic compound|organic chemicals]] derived from the 5-carbon compound [[isoprene]] and its derivatives called [[terpene]]s, [[diterpene]]s, etc.  While sometimes used interchangeably with "terpenes", terpenoids contain additional [[functional group]]s, usually containing oxygen.<ref>{{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}}</ref> When combined with the hydrocarbon terpenes, terpenoids comprise about 80,000 compounds.<ref>{{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 }}</ref> They are the largest class of plant [[secondary metabolites]], representing about 60% of known [[Natural Products|natural products]].<ref>{{cite book | last = Firn | first = Richard | name-list-style = vanc |title=Nature's Chemicals|date=2010|publisher=Oxford: Biology}}</ref>  Many terpenoids have substantial [[pharmacological]] bioactivity and are therefore of interest to medicinal chemists.<ref name="wink10">{{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}}</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 [[sunflower]]s, and the red color in [[tomato]]es.<ref>{{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}}</ref> Well-known terpenoids include [[citral]], [[menthol]], [[camphor]], [[salvinorin A]] in the plant ''[[Salvia divinorum]]'', [[ginkgolide]] and [[bilobalide]] found in ''[[Ginkgo biloba]]'' and the [[Cannabinoid|cannabinoids]] found in cannabis. The provitamin [[beta carotene]] is a terpene derivative called a [[carotenoid]].

The [[steroid]]s and [[sterol]]s in animals are biologically produced from terpenoid precursors. Sometimes terpenoids are added to [[protein]]s, 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 [[attractant]]s for the predators of herbivores.<ref>{{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}}</ref>

==Structure and classification==
Terpenoids are modified [[terpene]]s,<ref>{{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}}</ref> wherein [[methyl group]]s 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 [[terpene]]s
! Number of [[isoprene]] units
! Number of carbon atoms
! General formula
! Examples<ref name=Terpenoids>{{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 }}</ref>
|-
| [[Hemiterpenoid]]s
| [[Isoprene]]
| 1
| 5
| C<sub>5</sub>H<sub>8</sub>
| [[Dimethylallyl pyrophosphate|DMAPP]], [[isopentenyl pyrophosphate]], [[isoprenol]], [[isovaleramide]], [[isovaleric acid]], [[(E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate|HMBPP]], [[prenol]]
|-
| [[Monoterpenoid]]s
| [[Monoterpene]]s
| 2
| 10
| C<sub>10</sub>H<sub>16</sub>
| [[Bornyl acetate]], [[camphor]], [[carvone]], [[citral]], [[citronellal]], [[citronellol]], [[geraniol]], [[eucalyptol]], [[hinokitiol]], [[iridoid]]s, [[linalool]], [[menthol]], [[thymol]]
|-
| [[Sesquiterpenoid]]s
| [[Sesquiterpene]]s
| 3
| 15
| C<sub>15</sub>H<sub>24</sub>
| [[Farnesol]], [[geosmin]], [[humulone]]
|-
| [[Diterpenoid]]s
| [[Diterpene]]s
| 4
| 20
| C<sub>20</sub>H<sub>32</sub>
| [[Abietic acid]], [[ginkgolide]]s, [[paclitaxel]], [[retinol]], [[salvinorin A]], [[sclareol]], [[steviol]]
|-
| [[Sesterterpenoid]]s
| [[Sesterterpene]]s
| 5
| 25
| C<sub>25</sub>H<sub>40</sub>
| [[Andrastin A]], [[manoalide]]
|-
| [[Triterpenoid]]s
| [[Triterpene]]s
| 6
| 30
| C<sub>30</sub>H<sub>48</sub>
| [[Amyrin]], [[betulinic acid]], [[limonoid]]s, [[oleanolic acid]], [[sterol]]s, [[squalene]], [[ursolic acid]]
|-
| [[Tetraterpenoid]]s
| [[Tetraterpene]]s
| 8
| 40
| C<sub>40</sub>H<sub>64</sub>
| [[Carotenoid]]s
|-
| [[Polyterpenoid]]
| [[Terpene|Polyterpene]]s
| >8
| >40
| (C<sub>5</sub>H<sub>8</sub>)<sub>n</sub>
| [[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>{{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}}</ref>

<gallery caption="Selected terpenoids">
File:Taxol.svg|[[Paclitaxel]] is a diterpenoid anticancer drug.
File:Terpineol alpha.svg|[[Terpineol]]s are monoterpenoids.
File:(S)-Humulone.svg|[[Humulone]]s 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]].
</gallery>

==Biosynthesis==
{{Further|Terpene#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 [[sesquiterpenoid]]s, and hydrolysis of intermediates from [[geranylgeranyl pyrophosphate]] gives [[diterpenoid]]s, etc.<ref name=Crot>{{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}}</ref>

==Impact on aerosols==
In air, terpenoids are converted into various species, such as [[aldehyde]]s, [[hydroperoxide]]s, organic nitrates, and [[epoxide]]s<ref name="WennbergScienceDaily">[https://www.sciencedaily.com/releases/2009/08/090806141518.htm 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 – [http://www.iupac-kinetic.ch.cam.ac.uk/datasheets/pdf/Ox_VOC7_O3_CH2C%28CH3%29CHCH2.pdf Data Sheet Ox_VOC7], 2007</ref> These new species can dissolve into water droplets and contribute to [[aerosol]] and [[haze]] formation.<ref name="PaulotScienceNews">[https://www.sciencenews.org/article/source-haze A source of haze], ScienceNews, August 6, 2009</ref> [[Secondary organic aerosol|Secondary organic aerosols]] formed from this pathway may have atmospheric impacts.<ref>{{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 }}</ref>

As an example the [[Blue Ridge Mountains]] in the U.S. and [[Blue Mountains (New South Wales)|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>{{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.}}</ref><ref>{{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 }}</ref><ref>{{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}}</ref>

== See also ==
* [[List of antioxidants in food]]
* [[List of phytochemicals in food]]
* [[Nutrition]]
* [[Phytochemistry]]
* [[Secondary metabolites]]

== References ==
{{reflist|30em}}

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

{{Secondary metabolites}}
{{Terpenoids}}
{{Authority control}}

[[Category:Terpenes and terpenoids| ]]
[[Category:Plant communication]]

[[cs:Izoprenoidy]]
[[es:Terpenoides]]
[[it:Terpeni]]