Editing Terpenoid (section)

==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>