Editing Chili pepper (section)

=== Capsaicin ===

{{main|Capsaicin}}

{{multiple image
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|image1    = Capsaicin.svg
|caption1  = Chemical structure
|image2    = Capsaicin-3D-vdW.png
|caption2  = Space-filling model
|footer    = [[Capsaicin]], the principal molecule that gives chili its heat<ref name="Kosuge 1961"/>
}}

The substances that give chili peppers their [[pungency]] (spicy heat) when ingested or applied topically are [[capsaicin]] (8-methyl-''N''-vanillyl-6-nonenamide) and several related chemicals, collectively called ''capsaicinoids''.<ref name="Kosuge 1961">{{cite journal |vauthors=Kosuge S, Inagaki Y, Okumura H |date=1961 |title=Studies on the pungent principles of red pepper. Part VIII. On the chemical constitutions of the pungent principles. |journal=Nippon Nogeikagaku Kaishi |volume=35 |pages=923–927 |doi=10.1271/nogeikagaku1924.35.10_923 |doi-access=free }} Chem. Abstr. 1964, 60, 9827g.</ref><ref>{{cite journal |language=Japanese |vauthors=Kosuge S, Inagaki Y |title=Studies on the pungent principles of red pepper. Part XI. Determination and contents of the two pungent |journal=Journal of the Agricultural Chemical Society of Japan |date=1962 |volume=36 |pages=251–254 }}</ref> Pure capsaicin is a [[hydrophobic]], colorless, odorless, and crystalline-to-waxy solid at room temperature.<ref name="pubchem">{{cite web |url=https://pubchem.ncbi.nlm.nih.gov/compound/1548943 |publisher=PubChem, US National Library of Medicine |title=Capsaicin |date=27 May 2023 |access-date=1 June 2023}}</ref> The quantity of capsaicin varies by variety, and depends on growing conditions. Water-stressed peppers usually produce stronger fruits. When a [[habanero]] plant is stressed, for example by shortage of water, the concentration of capsaicin increases in some parts of the fruit.<ref>{{cite journal |vauthors=Ruiz-Lau N, Medina-Lara F, Minero-García Y, Zamudio-Moreno E, Guzmán-Antonio A, Echevarría-Machado I, Martínez-Estévez M |title=Water Deficit Affects the Accumulation of Capsaicinoids in Fruits of Capsicum chinense Jacq. |journal=HortScience |date=1 March 2011 |volume=46 |issue=3 |pages=487–492 |doi=10.21273/HORTSCI.46.3.487 |doi-access=free}}</ref>

When peppers are consumed by mammals such as humans, capsaicin binds with [[nociceptor|pain receptors]] in the mouth and throat, potentially evoking pain via spinal relays to the [[brainstem]] and [[thalamus]] where heat and discomfort are perceived.<ref name="oneill">{{cite journal |vauthors=O'Neill J, Brock C, Olesen AE, Andresen T, Nilsson M, Dickenson AH |title=Unravelling the mystery of capsaicin: a tool to understand and treat pain |journal=Pharmacological Reviews |volume=64 |issue=4 |pages=939–971 |date=October 2012 |pmid=23023032 |pmc=3462993 |doi=10.1124/pr.112.006163 }}</ref> However, birds are unable to perceive the hotness and so they can eat some of the hottest peppers.<ref name="Tewksbury Nabhan 2001"/> The intensity of the "heat" of chili peppers is commonly reported in [[Scoville scale|Scoville heat units]] (SHU), invented by American pharmacist [[Wilbur Scoville]] in 1912. Historically, it was a measure of the dilution of an amount of chili extract added to sugar syrup before its heat becomes undetectable to a panel of tasters; the more it has to be diluted to be undetectable, the more powerful the variety, and therefore the higher the rating.<ref>{{cite web |url=http://www.tabasco.com/info_booth/faq/scoville_how.cfm |title=History of the Scoville Scale &#124; FAQS |publisher=Tabasco.Com |access-date=23 December 2010 |archive-url=https://web.archive.org/web/20100823044606/http://www.tabasco.com/info_booth/faq/scoville_how.cfm |archive-date=23 August 2010 }}</ref> Since the 1980s, spice heat has been assessed quantitatively by [[high-performance liquid chromatography]] (HPLC), which measures the concentration of heat-producing capsaicinoids, typically with capsaicin content as the main measure.<ref name="guzman">{{cite journal |vauthors=Guzmán I, Bosland PW |title=Sensory properties of chili pepper heat - and its importance to food quality and cultural preference |journal=Appetite |volume=117 |pmid=28662907 |year=2017 |pages=186–190 |doi=10.1016/j.appet.2017.06.026 |doi-access=free}}</ref>

Capsaicin is produced by the plant as a [[Plant defense against herbivory|defense against mammalian predators]]. A study suggests that by protecting against attack by a [[hemiptera]]n bug, the risk of disease caused by a ''[[Fusarium]]'' fungus carried by the insects is reduced.<ref name="pnas">{{cite journal |vauthors=Tewksbury JJ, Reagan KM, Machnicki NJ, Carlo TA, Haak DC, Peñaloza AL, Levey DJ |title=Evolutionary ecology of pungency in wild chilies |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=105 |issue=33 |pages=11808–11811 |date=August 2008 |pmid=18695236 |pmc=2575311 |doi=10.1073/pnas.0802691105 |doi-access=free |bibcode=2008PNAS..10511808T }}</ref> As evidence, the study notes that peppers increased the quantity of capsaicin in proportion to the damage caused by fungi on the plant's seeds.<ref name=pnas/>