Editing Mentha pulegium

{{short description|Species of plant}}
{{Speciesbox
|image = Gardenology.org-IMG 2751 rbgs11jan.jpg
|status = LC
|status_system = IUCN3.1
|status_ref = <ref name=IUCN>{{cite iucn |last1=de Belair |first1=G. |last2=Rhazi |first2=L. |last3=Lansdown |first3=R.V. |year=2014 |title=''Mentha pulegium'' |volume=2014 |page=e.T164256A42395474 |doi=10.2305/IUCN.UK.2014-1.RLTS.T164256A42395474.en |access-date=10 December 2024}}</ref>
|genus = Mentha
|species = pulegium
|authority = [[Carl Linnaeus|L.]]
}}

'''''Mentha pulegium''''', commonly '''(European) pennyroyal''', or '''pennyrile''', also called '''mosquito plant'''<ref>{{cite journal |last=Gunby |first=Phil |title=Medical News: Plant Known for Centuries Still Causes Problems Today |journal=[[Journal of the American Medical Association]] |volume=241 |issue=21 |pages=2246–2247 |year=1979 |doi=10.1001/jama.241.21.2246}}</ref> and '''pudding grass''',<ref>Keville, Kathi (1994). ''Herbs: An Illustrated Encyclopedia''. New York City: Friedman/Fairfax Publishers. pp. 128.</ref> is a [[species]] of [[flowering plant]] in the [[Mentha|mint]] [[Family (biology)|family]], [[Lamiaceae]], native to [[Europe]], [[North Africa]], and the [[Middle East]].<ref>[http://apps.kew.org/wcsp/namedetail.do?name_id=125243 Kew World Checklist of Selected Plant Families]</ref> Crushed pennyroyal leaves emit a very strong fragrance similar to [[spearmint]]. Pennyroyal is a traditional [[folk remedy]], [[emmenagogue]], [[abortifacient]], and [[culinary herb]], but is toxic to the liver and has caused some deaths.<ref>{{cite web |title=Pennyroyal Oil Poisoning and Hepatotoxicity |url=https://jamanetwork.com/journals/jama/article-abstract/368096 |website=JAMA Network |publisher=Journal of the American Medical Association |access-date=31 October 2023}}</ref> European pennyroyal is related to an American species, ''[[Hedeoma pulegioides]]''. Though they differ in [[genera]], they share similar chemical properties.<ref name="Ilene"/>

==Description==
[[File:Mentha_pulegium_003.JPG|thumb|Flowers of pennyroyal]]
An annual to perennial plant with creeping or erect branched stems to about 40&nbsp;cm in height. The stems are square in cross-section and can vary from hairless on some plants to densely hairy on others, with a green to sometimes red or purplish colour. The leaves, which grow in [[Phyllotaxis|opposite]] pairs, are narrowly oval, 2–3&nbsp;cm long x 1&nbsp;cm wide, downy, sparsely toothed towards the tip, and taper into a short [[Petiole (botany)|stalk]]. All parts of the plant are strongly scented when crushed but it does not have noticeable glands on its surface. The small (6&nbsp;mm) flowers are densely packed in whorls at the nodes, widely separated, above pairs of leaf-like [[bract]]s. The [[Calyx (botany)|calyx]] is a ribbed tube about 3&nbsp;mm long, with five triangular teeth, the lower two being narrower and slightly longer than the upper three; it is hairy both on the inside and the outside. The [[petal|corolla]] has four mauve lobes or "petals" and is hairy only on the outside. The flowers are [[Plant reproductive morphology|bisexual]] and have four long [[stamens]], two (or all four) of which project well beyond the corolla lobes. There is one long [[style (botany)|style]] which is forked to produce two [[Stigma (botany)|stigmas]], which also project from the flower. The fruits consist of a cluster of four brown, 1-seeded [[nut (fruit)|nutlets]], each about 0.7&nbsp;mm long.<ref name=Sell>{{cite book |last1=Sell |first1=Peter |last2=Murrell |first2=Gina |title=Flora of Great Britain and Ireland, vol 3 |publisher=[[Cambridge University Press]] |location=Cambridge |date=2009}}</ref>

[[File:Mentha_pulegium_abundant.jpg|thumb|Pennyroyal can be very abundant in riverside grassland.]]

The flowering period starts in June and continues into mid-summer,<ref name=Blamey>{{cite book |last1=Blamey |first1=Marjorie |last2=Grey-Wilson |first2=Christopher |title=Wild Flowers of the Mediterranean |publisher=A & C Black |location=London |date=2004}}</ref> although in northern countries it flowers rather later, sometimes as late as September, when it can fail to set seed.<ref name=Rose>{{cite book |last=Rose |first=Francis |title=The Wild Flower Key |publisher=Frederick Warne |location=London |date=2006}}</ref>

Its [[Ploidy|chromosome number]] is 2n = 20.<ref name=Stace>{{cite book |last=Stace |first=C.A. |title=New Flora of the British Isles |location=Suffolk, UK |date=2019 |isbn=978-1-5272-2630-2}}</ref>

==Distribution==
The native range of pennyroyal is thought to be around the eastern [[Mediterranean]], where it grows in damp meadows, around pools and in stream margins.<ref name="Blamey" /> It is, however, very widely established around the world, including North and South America, throughout Africa, Asia, Australia and New Zealand. In many places it is considered a troublesome weed of agriculture.<ref name=CABI>{{cite web |author=Global Biodiversity Information Facility |title=Mentha pulegium L. |url=https://www.gbif.org/species/2927189}}</ref><ref>{{cite web |author=CABI |title=Invasive Species Compendium: Mentha pulegium datasheet |url=https://www.cabi.org/isc/datasheet/115572}}</ref> Towards the northern edge of its range, as in Britain, it is considered to be rare and declining,<ref>{{cite book |last=Wigginton |first=Martin |title=British Red Data Books 1: vascular plants. |publisher=Joint Nature Conservation Committee |location=Peterborough, UK |date=1999}}</ref> except where introduced.{{Cn|date=April 2024}}

==Habitat and ecology==
[[File:Mentha_pulegium_at_Weston_Favell.jpg|thumb|Typical habitat of pennyroyal in a seasonally inundated field by the River Nene in Northamptonshire, UK]]
The habitat of pennyroyal is seasonally damp pasture, where standing water over the winter leaves bare ground in the summer, and where livestock preferentially graze other plants. An analogue of this habitat is found on roadsides, where trampling or disturbance of the ground produces similarly bare soil, particularly where there is waterlogging in winter. It is also found along watercourses, in wet woodland and in abandoned fields.<ref name="CABI" />

In California, where it is considered an invasive species, it occupies a similar niche, in seeps, streamsides, vernal pools and swales, marshes, and ditches. There is some speculation that it may displace native species in these areas.<ref>{{cite web |author=California Invasive Plant Council |title=Mentha pulegium |url=https://www.cal-ipc.org/plants/profile/mentha-pulegium-profile/ |date=20 March 2017 |access-date=17 February 2022}}</ref>

Few animals eat pennyroyal. In Britain, the only insect known to feed on it is the bug ''[[Heterogaster artemisiae]]'' Schilling, which is a seed bug that normally feeds on [[Thymus praecox|wild thyme]].<ref>{{cite web |author=Biological Records Centre |title=Database of Insects and their Food Plants |url=https://www.brc.ac.uk/dbif/}}</ref>

It is considered an [[axiophyte]] in many British counties, because low-intensity pasture is a rare habitat, although it has been spreading in recent decades.<ref>{{cite web |last=Lockton |first=Alex |title=BSBI species accounts: Mentha pulegium |url=http://sppaccounts.bsbi.org/content/mentha-pulegium-0.html#:~:text=At%20the%20species%20level%2C%20Mentha,%2D%20an%20upright%20form%20(var. |access-date=31 August 2010}}</ref> Its [[Indicator value|Ellenberg values]] in Britain are L = 8, F = 7, R = 5, N = 7, and S = 0.<ref>{{cite book |last1=Hill |first1=M.O. |last2=Mountford |first2=J.O. |last3=Roy |first3=D.B. |last4=Bunce |first4=R.G.H. |title=Ellenberg's indicator values for British plants. ECOFACT Volume 2. Technical Annex |url=http://nora.nerc.ac.uk/6411/1/ECOFACT2a.pdf |archive-url=https://web.archive.org/web/20091111045128/http://nora.nerc.ac.uk/6411/1/ECOFACT2a.pdf |archive-date=2009-11-11 |url-status=live |publisher=Institute of Terrestrial Ecology |date=1999 |access-date=29 May 2017 |isbn=1870393481}}</ref>

==History==

===Ancient and modern use===
[[File:Medievalpreg.jpg|thumb|right|230px|A 13th-century image of a woman preparing a pennyroyal mixture using a mortar and pestle for a pregnant woman]]
Documented use of pennyroyal dates back to ancient [[Ancient Greece|Greek]], [[Ancient Rome|Roman]], and [[Middle Ages|Medieval]] cultures. Its name – although of uncertain etymology – is associated with Latin ''pulex'' (flea), alluding to the manner it was used to drive away fleas when smeared on the body.<ref name="Riddle">{{cite book |last=Riddle |first=John |title=Eve's Herbs--A History of Contraception and Abortion in the West |publisher=[[Harvard University Press]] |date=April 1999 |isbn=9780674270268}}{{page needed|date=September 2021}}</ref> Pennyroyal was commonly incorporated as a cooking [[herb]] by the [[Greeks]] and [[Ancient Rome|Romans]]. A large number of the recipes in the Roman cookbook of [[Apicius]] called for the use of pennyroyal, often along with such herbs as [[lovage]], [[oregano]] and [[coriander]]. Although it was commonly used for cooking also in the [[Middle Ages]], it gradually fell out of use as a culinary herb and is seldom used as such today.<ref>{{cite book |last=Kains |first=Maurice Grenville |title=Culinary Herbs: Their Cultivation Harvesting Curing and Uses |url=https://archive.org/details/culinaryherbs00kain |publisher=Orange Judd Company |location=New York |date=1912}}</ref>

Records from Greek and Roman physicians and scholars contain information pertaining to pennyroyal's medicinal properties, as well as recipes used to prepare it. [[Pliny the Elder]], in his encyclopedia ''[[Naturalis Historia]]'' (''Natural History''), described the plant as an [[emmenagogue]], and that it also expelled a dead [[fetus]].<ref name="Riddle2"/> [[Galen]] only listed pennyroyal as an emmenagogue, as did [[Oribasius]]. Roman and Greek writers Quintus [[Serenus Sammonicus]] and [[Aspasia the Physician]] however both agreed that pennyroyal, when served in tepid water, was an effective abortive method.<ref name="Riddle2"/> A medical text on [[gynecology]] attributed to [[Cleopatra]] (though it was actually written by a female Greek physician [[Metrodora]]) recommends the use of pennyroyal with wine to induce abortions.<ref name="Riddle2">{{cite book |last=Riddle |first=John |title=Contraception and Abortion from the Ancient World to the Renaissance |publisher=Harvard University Press |date=January 1994 |isbn=9780674168763}}{{page needed|date=September 2021}}</ref>

In regard to its contraceptive properties, it was referred to in a joking manner in [[Aristophanes]]' play ''[[Peace (play)|Peace]]'' (421 BCE). The god [[Hermes]] provides the male character Trygaios a female companion; when Trygaios asks if there would be a problem if she became pregnant, Hermes responds, "Not if you add a dose of pennyroyal."<ref name="Riddle"/> In a similar manner, in Aristophanes' comedy ''[[Lysistrata]]'', after a pregnant female character on stage is told to withhold her body sexually from her husband, a slender female character, in comparison to the pregnant woman, is described as "a very lovely land Well croppy, and trimmed and spruced with pennyroyal."<ref name="Riddle"/>

Early settlers in [[colonial Virginia]] used dried pennyroyal to eradicate pests. Pennyroyal was such a popular herb that the [[Royal Society]] published an article on its use against rattlesnakes in the first volume of its [[Philosophical Transactions]] in 1665.<ref>{{cite journal |title=Of a Way of Killing Rattle-Snakes |journal=Philosophical Transactions of the Royal Society of London |volume=1 |issue=43 |date=1665 |doi=10.1098/rstl.1665.0022 |doi-access=free}}</ref> 17th-century apothecary and physician [[Nicholas Culpeper]] mentions pennyroyal in his medical text ''[[List of plants in The English Physitian|The English Physitian]]'', published in 1652.<ref name="Culpeper"/> In addition to its abortive properties, Culpeper recommends its use for [[gastrointestinal]] ailments, such as [[constipation]] and [[hemorrhoids]], as well as [[itching]] and blemishes to the skin, and even [[toothaches]].<ref name="Culpeper">{{cite book|last=Culpeper|first=Nicholas|title=Culpeper's English Physician and Complete Herbal|date=1652}}</ref>

Pennyroyal is an essential ingredient in the North african dish, which is still eaten to this day, called {{Interlanguage link|Batata fliou|fr|Batata fliou}}.

Pennyroyal continued to be used up through the 20th and 21st centuries. Its oil is still commercially available today, though little is known about the appropriate dosages for humans. Scientists therefore likely consider it unsafe for use, as it is potentially toxic.<ref>{{cite web|title=Pennyroyal|url=https://medlineplus.gov/druginfo/natural/480.html|website=U.S. National Library of Medicine|access-date=27 April 2017}}</ref>

==Uses==
[[File:Chichester Pennyroyal Pills (1905 advertisement).jpg|right|thumb|A 1905 advertisement for pennyroyal pills]]
Pennyroyal is frequently used as an [[insecticide]] and pest repellent.<ref>{{cite journal|last1=Moore|first1=Sarah|last2=Ferreria Maia|first2=Marta|title=Plant-based insect repellents: a review of their efficacy, development and testing|journal=Malaria Journal|year=2011|volume=10|issue=Suppl 1 |pages=S11|doi=10.1186/1475-2875-10-S1-S11|pmid=21411012|pmc=3059459 |doi-access=free}}</ref> As a pest repellent, it is used to keep fleas away from household animals as well as on humans to ward off gnats and mosquitos. Some flea collars for pets have pennyroyal oil or the herb can be crushed in the lining. Humans have also put crushed pennyroyal stems in their pockets or on their clothing to ward off unwanted insects.<ref>{{cite web |last=Pleasant |first=Barbara |title=What You Need to Know about Pennyroyal |website=Mother Earth News |date=3 September 2020 |url=https://www.motherearthnews.com/natural-health/herbal-remedies/pennyroyal-safety}}</ref> However, when using the pennyroyal plant as a pest repellent, the use of the concentrated pennyroyal oil should be avoided. Pennyroyal oil can be extremely toxic to both humans and animals, even in small quantities. With the use of pennyroyal around animals and humans comes the risk of it being absorbed through the skin and causing negative health effects. The less concentrated leaves of the plant should be used instead as an insect repellent.

Pennyroyal has historically also been used as a mint flavoring in herbal teas and foods. Pennyroyal tea has been used for cold relief, fevers, coughs, indigestion, liver and kidney problems and headaches.<ref>{{cite web|title=Pennyroyal Tea|url=http://www.teainfusion.com/types/pennyroyal-tea.html|website=Tea Infusion}}</ref> The fresh or dried leaves of pennyroyal have also been used when treating influenza, abdominal cramps, to induce sweating, as well as in the treatment of diseases such as smallpox and tuberculosis.<ref>{{cite web|title=Pennyroyal|url=http://www.webmd.com/vitamins-supplements/ingredientmono-480-pennyroyal.aspx?activeingredientid=480&activeingredientname=pennyroyal|website=WebMD|access-date=27 April 2017}}</ref> To make the tea, the leaves of the plant are boiled in hot water. The lower concentrations of toxic chemicals in these teas are less harmful than pennyroyal oil. It is recommended that people only drink pennyroyal tea periodically, as it is taxing on the body and should not be drunk on a regular basis. Consumption of pennyroyal tea can be fatal to infants and children.<ref>{{cite journal |last=French |first=Larry G. |title=Isolation of (R)-(+)-Pulegone from the European Pennyroyal Mint, Mentha Pulegium |journal=The Chemical Educator |date=October 2002 |volume=7 |issue=5 |pages=270–277 |doi=10.1007/s00897020599a |s2cid=94269073 |url=https://repositorio.unal.edu.co/handle/unal/80633}}</ref>

In Italy the fresh leaves of this plant, which in Rome and the surrounding area is called ''menta romana'', are used in [[Roman cuisine|the capital's cuisine]] to flavour lamb and [[trippa alla romana|tripe]].<ref name="AzBon">{{cite web|url=http://www.azienda-bonato.com/aromi/menta_romana.html|title=Menta Romana|access-date=29 August 2013|url-status=dead|archive-url=https://web.archive.org/web/20140203033812/http://www.azienda-bonato.com/aromi/menta_romana.html|archive-date=3 February 2014|language=it}}</ref> In culinary use it should not be confused with [[lesser calamint]] (''Clinopodium nepeta''), which in Rome is used to prepare [[Carciofi alla Romana|artichoke]]s.

The pennyroyal plant has also been used as an [[emmenagogue]] and an [[abortifacient]].<ref name="NIH1">{{cite web|title=Pulegone|url=https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+8146|website=Toxnet|publisher=National Library of Medicine|access-date=27 April 2017}} {{Dead link|date=January 2023}}</ref> Chemicals in the pennyroyal plant cause the uterine lining to contract, causing a woman's uterine lining to shed. Women who struggle with regulating their menstrual cycle or suffer from a cystic ovary syndrome may choose to drink pennyroyal tea. Pennyroyal tea is subtle enough to induce menstrual flow with minimal risk of negative health effects. More concentrated versions of the plant, such as the oil, are much more toxic and will likely force a miscarriage if ingested by a pregnant woman.<ref>{{cite web|title=Herbal Abortifacients|url=https://epigee.org/pregnancy/herbal.html|website=Epigee Woman's Health}}</ref> Since the U.S. Congress passed the Dietary Supplement Health and Education Act in October 1994, all manufactured forms of pennyroyal in the United States have carried a warning label against its use by pregnant women, but pennyroyal is not regulated by the U.S. Food and Drug Administration.<ref>{{cite web|title=Dietary Supplement Health and Education Act of 1994|url=https://ods.od.nih.gov/About/DSHEA_Wording.aspx|publisher=National Institute of Health|date=1994}}</ref>

Rennie's 1833 supplement to the pharmacopeias admitted its use as an "expectorant, diuretic, and emmenagogue" in doses of 10 [[Grain (unit)|grains]] to 1 [[Scruple (unit)|scruple]] (0.6–1.3g) of the powdered dried herb, but dismissed the use of the Pennyroyal Water (Aqua Pulegii) as "popularly but erroneously supposed" to be an abortifacient [no mention is made of toxicity].<ref>{{cite book |last=Rennie |first=James |title=A New Supplement to the Pharmacopœias of London, Edinburgh, Dublin, and Paris |publisher=Baldwin and Cradock|location=London|date=1833 |pages=357, 33}}</ref>

At least one study has shown pennyroyal oil to have potent [[acaricidal]] activity against [[house dust mites]].<ref>{{cite journal |last1=Rim |first1=In-Sook |last2=Jee |first2=Cha-Ho |title=Acaricidal effects of herb essential oils against Dermatophagoides farinae and D. pteronyssinus (Acari: Pyroglyphidae) and qualitative analysis of a herb Mentha pulegium (pennyroyal) |journal=The Korean Journal of Parasitology |date=June 2006 |volume=44 |issue=2 |pages=133–138 |doi=10.3347/kjp.2006.44.2.133 |pmid=16809961 |pmc=2532629}}</ref>

==Toxicity==
[[File:Mentha pulegium.jpg|thumb|200px|Pennyroyal]]
Pennyroyal is toxic to humans and has differing effects dependent on the volume and concentration ingested. The most concentrated and toxic form of the pennyroyal plant is pennyroyal oil. The oil contains 80% to 92% of cyclohexanone pulegone. [[Pulegone]], the molecule in highest concentration in the pennyroyal plant, causes a variety of ailments in those who ingest it and is what causes the plant to have its peppermint flavor.<ref>{{cite journal|last1=Siano|first1=F|last2=Catalfamo|first2=M|last3=Cautela|first3=D|last4=Servillo|first4=L|last5=Castaldo|first5=D|s2cid=40095436|title=Analysis of pulegone and its enanthiomeric distribution in mint-flavoured food products|journal=Food Additives & Contaminants|date=2005|volume=22|issue=3|pages=197–203|doi=10.1080/02652030500041581|pmid=16019787}}</ref>

Symptoms that may persist after ingesting a small dose (<10 mL) of pennyroyal oil are nausea, vomiting, abdominal pain and dizziness. Larger volumes may result in multiorgan failure that could lead to death. There are no current toxicokinetics studies performed on humans for the effects of pulegone, but there are some studies performed on other mammals. When pulegone is ingested, it is broken down by the liver and reacts to form multiple toxic metabolites that can wreak havoc in the body. Some identified metabolites are [[menthofuran]], piperitenone, [[piperitone]], and [[menthone]].<ref name="ReferenceA">{{cite journal|last1=Da Rocha|first1=Mitscheli S.|last2=Dodmane|first2=Puttappa R.|last3=Arnold|first3=Lora L.|last4=Pennington|first4=Karen L.|last5=Anwar|first5=Muhammad M.|last6=Adams|first6=Bret R.|last7=Taylor|first7=Sean V.|last8=Wermes|first8=Clint|last9=Adams|first9=Tim B.|last10=Cohen|first10=Sam M.|title=Mode of Action of Pulegone on the Urinary Bladder of F344 Rats|journal=Toxicological Sciences|date=12 April 2012|volume=128|issue=1|pages=1–8|doi=10.1093/toxsci/kfs135|pmid=22499580|doi-access=}}</ref>

==Chemistry==

===Structure and reactivity===
[[File:Pulegon.svg|thumb|left|110px|Pulegone]]
The active chemical in pennyroyal is pulegone. Pulegone is a [[ketone]] and on the cellular level, ketones can act as [[enzyme inhibitor]]s. The carbonyl center of the pulegone structure acts as a strong electrophile, causing active sites on enzymes to bind with pulegone instead of the target protein.

The exocyclic [[double bond]] found in pulegone is vital to the activation and binding mechanism of the molecule and causes it to be an effective [[hepatotoxin]]. When ingested, pulegone targets the liver and kidney, among other organs. Studies conducted on rats show that one of the main effects is the inhibition of contractile activity in the [[myometrium]] and death by [[kidney failure]]. The studies also found that long-term exposure to pennyroyal increased incidences of urinary bladder tumors.<ref name="ReferenceA"/>

===Mechanism of action===
[[File:Menthofuran.svg|thumb|left|130px|Menthofuran]]
The exact [[mechanism of action]] by which pennyroyal induces [[menses]] and [[abortion]]s in humans is still unknown. Studies using animal models speculate the source of liver toxicity is due to one of the many constituents the plant contains: pulegone, a monoterpene. Pulegone is metabolized by [[cytochrome P450]] (CYP 1A2 and 2E1) and converted to several toxins.<ref>{{cite book|last1=Cassileth|first1=Barrie|last2=Yeung|first2=Simon|last3=Gubili|first3=Jyothirmai|title=Herb-drug Interactions in Oncology|date=2010|publisher=People's Medical Publishing House|location=Shelton, CT}}</ref> Both ''[[in vitro]]'' and ''[[in vivo]]'' studies have found the pulegone metabolite [[menthofuran]] to be an inhibitor of [[CYP2A6]], accounting for a significant degree of pennyroyal's [[hepatotoxicity]].<ref>{{cite journal|last1=Khojasteh-Bakh |first1=S.C.|last2=Koenigs |first2=L.L.|last3=Peter |first3=R.M.|last4=Trager |first4=W.F.|last5=Nelson |first5=S.D.|title=(R)-(+)-Menthofuran is a potent, mechanism-based inactivator of human liver cytochrome P450 2A6|journal=Drug Metabolism and Disposition|date=July 1998|volume=26|issue=7|pages=701–704|pmid=9660853}}</ref><ref name="Gordon">{{cite journal|last1=Gordon |first1=W.P.|last2=Huitric |first2=A.C.|last3=Seth |first3=C.L.|last4=McClanahan |first4=R.H.|last5=Nelson |first5=S.D.|title=The metabolism of the abortifacient terpene, (R)-(+)-pulegone, to a proximate toxin, menthofuran|journal=Drug Metabolism and Disposition|date=February 26, 1989|volume=15|issue=5|pages=589–594|pmid=2891472}}</ref><ref>{{cite journal|last1=Thomassen|first1=D.|last2=Pearson |first2=P.G.|last3=Slattery |first3=J.T.|last4=Nelson |first4=S.D.|title=Partial characterization of biliary metabolites of pulegone by tandem mass spectrometry. Detection of glucuronide, glutathione, and glutathionyl glucuronide conjugates.|journal=Drug Metabolism and Disposition|date=January 17, 1991|volume=19|issue=5|pages=997–104|pmid=1686249}}</ref>

The exact pathway pulegone undergoes to be converted to menthofuran is unknown, but one study strongly suggested it included allylic oxidation of a methyl group (from CYP450), intramolecular cyclization to form a hemiketal, and subsequent dehydration to form the furan.<ref name="Gordon"/> Additionally, pulegone and menthofuran may deplete glutathione levels, leaving hepatocytes vulnerable to free radical damage.<ref name="Gordon"/>

==Treatment==
There is no known antidote for pennyroyal toxicity.<ref name="NIH1"/> Case studies involving pennyroyal poisonings have reported the use of [[gastric lavage]]s and administration of [[emetic]]s or [[vomiting]] inducing agents, or absorbents like [[activated charcoal]].<ref name="Ilene">{{cite journal|last1=Ilene|first1=Anderson B.|last2=Walter|first2=Mullen H.|last3=James|first3=Meeker E.|last4=Siamak|first4=Khojasteh-Bakht|last5=Shimako|first5=Oishi|last6=Sidney|first6=Nelson D.|last7=Paul|first7=Blanc D.|s2cid=24375611|title=Pennyroyal Toxicity: Measurement of Toxic Metabolite Levels in Two Cases and Review of the Literature|journal=Annals of Internal Medicine|date=15 April 1996|volume=124|issue=8|pages=726–734|doi=10.7326/0003-4819-124-8-199604150-00004|pmid=8633832}}</ref> As [[glutathione]] depletion has been shown to regulate liver toxification, administration of [[N-acetylcysteine]] in similar doses as given for [[acetaminophen]] toxicity have been given to patients.<ref name="NIH">{{cite web|title=Drug Record Pennyroyal Oil (Mentha Pulegium)|url=https://livertox.nih.gov/Pennyroyal.htm|website=LiverTox|publisher=United States National Library of Medicine|access-date=2017-05-07}}</ref>

A study testing pulegone toxicity found inhibitors of cytochrome P450, such as [[cobaltous chloride]] or [[piperonyl butoxide]], blocked toxicity.<ref name="Gordon"/> Such testing has not been expanded to humans, however, as the pennyroyal mechanism of toxicity is still not entirely understood.

==See also==
* ''[[Hedeoma pulegioides]]'' (American pennyroyal, a distantly related species)
* [[Pennyroyal Tea]] (1993 song by American rock band [[Nirvana (band)|Nirvana]])

==References==
{{Reflist|colwidth=30em}}

==External links==
{{Commons|Mentha pulegium}}
{{Cite EB1911|wstitle=Pennyroyal}}
*ARKive - [https://web.archive.org/web/20060516093813/http://www.arkive.org/species/ARK/plants_and_algae/Mentha_pulegium/ images and movies of the Pennyroyal ''(Mentha pulegium)'']

{{Taxonbar|from=Q161235}}
{{Mint}}

[[Category:Abortifacients]]
[[Category:Mentha|pulegium]]
[[Category:Medicinal plants]]
[[Category:Herbs]]
[[Category:Flora of Europe]]
[[Category:Flora of North Africa]]
[[Category:Plants described in 1753]]
[[Category:Taxa named by Carl Linnaeus]]