Peppermint (Mentha × piperita) is a
hybrid species of
mint, a cross between
watermint and
spearmint.[1] Indigenous to Europe and the Middle East,[2] the plant is now widely spread and cultivated in many regions of the world.[3] It is occasionally found in the wild with its parent species.[3][4]
Although the genus Mentha comprises more than 25 species, the one in most common use is peppermint.[5] While Western peppermint is derived from Mentha × piperita, Chinese peppermint, or bohe, is derived from the fresh leaves of M. haplocalyx.[6][7][8]M. × piperita and M. haplocalyx are both recognized as plant sources of
menthol and
menthone, and are among the oldest herbs used for both culinary and medicinal products.[5][9]
Botany
Peppermint was first identified in Hertfordshire, England, by a Dr. Eales, a discovery which John Ray published 1696 in the second edition of his book Synopsis Methodica Stirpium Britannicarum. He initially gave it the name Mentha spicis brevioribus et habitioribus, foliis Mentha fusca, sapore fervido piperis and later in his 1704 volume Historia Plantarum he called it Mentha palustris or Peper–Mint. The plant was then added to the London Pharmacopoeia under the name Mentha piperitis sapore in 1721.[10][11][12][13] It was given the name Mentha piperita in 1753 by Carl Linnaeus in his Species Plantarum Volume 2.[14] Linnaeus treated Peppermint as a
species, but it is now universally agreed to be a hybrid between Mentha viridis and Mentha aquatica with Mentha viridis itself also being a hybrid between Mentha sylvestris and Mentha rotundifolis.[15][16]
It is an
herbaceous, rhizomatous,
perennial plant that grows to be 30–90 cm (12–35 in) tall, with smooth stems, square in cross section. The
rhizomes are wide-spreading and fleshy, and bear fibrous
roots. The
leaves can be 4–9 cm (1+1⁄2–3+1⁄2 in) long and 1.5–4 cm (1⁄2–1+1⁄2 in) broad. They are dark green with reddish veins, with an acute apex and coarsely toothed margins. The leaves and stems are usually slightly fuzzy. The
flowers are purple, 6–8 mm (1⁄4–5⁄16 in) long, with a four-lobed
corolla about 5 mm (3⁄16 in) diameter; they are produced in whorls (verticillasters) around the stem, forming thick, blunt spikes. Flowering season lasts from mid- to late summer. The
chromosome number is variable, with 2n counts of 66, 72, 84, and 120 recorded.[17][18][19] Peppermint is a fast-growing plant; once it sprouts, it spreads very quickly.
Ecology
Peppermint typically occurs in moist habitats, including stream sides and drainage ditches. Being a hybrid, it is usually
sterile, producing no
seeds and reproducing only
vegetatively, spreading by its
runners.[4][19]
Outside of its native range, areas where peppermint was formerly grown for oil often have an abundance of feral plants, and it is considered
invasive in Australia, the
Galápagos Islands, New Zealand,[20] and the United States[21] in the
Great Lakes region, noted since 1843.[22]
Cultivation
Peppermint generally grows best in moist, shaded locations, and expands by underground rhizomes. Young shoots are taken from old stocks and
dibbled into the ground about 0.5 m (1.5 ft) apart. They grow quickly and cover the ground with runners if it is permanently moist. For the home gardener, it is often grown in containers to restrict rapid spreading. It grows best with a good supply of water, without being water-logged, and planted in areas with partial sun to shade.
The leaves and flowering tops are used; they are collected as soon as the flowers begin to open and can be dried. The wild form of the plant is less suitable for this purpose, with cultivated plants having been selected for more and better oil content. They may be allowed to lie and wilt a little before distillation, or they may be taken directly to the still.
Cultivars
Several
cultivars have been selected for garden use:
Mentha × piperita 'Candymint' has reddish stems.[23]
Mentha × piperita 'Chocolate Mint'. Its flowers open from the bottom up; its flavour is reminiscent of the flavour in
Andes Chocolate Mints, a popular confection.[24][25][26]
Mentha × piperita 'Citrata' includes a number of varieties including
Eau de Cologne mint,[27] grapefruit mint, lemon mint,[28] and orange mint. Its leaves are aromatic and hairless.
Mentha × piperita 'Crispa' has wrinkled leaves.[29]
'Roberts Mitcham', also verticillium-resistant[36] and also the product of
mutation breeding
Diseases
Verticillium wilt is a major constraint in peppermint cultivation. 'Todd's Mitcham', 'Refined Murray', 'Roberts Mitcham' (see above), and a few other cultivars have some degree of
resistance.[36]
Peppermint has a high menthol content. The essential oil also contains menthone and carboxyl esters, particularly
menthyl acetate.[40] Dried peppermint typically has 0.3–0.4% of volatile oil containing menthol (7–48%), menthone (20–46%), menthyl acetate (3–10%),
menthofuran (1–17%), and 1,8-
cineol (3–6%). Peppermint oil also contains small amounts of many additional compounds, including
limonene,
pulegone,
caryophyllene, and
pinene.[41]
Peppermint oil has a high concentration of natural pesticides, mainly pulegone (found mainly in M. arvensis var. piperascens (cornmint, field mint, or Japanese mint),[43] and to a lesser extent (6,530 ppm) in Mentha × piperita subsp. notho[44]) and menthone.[45] It is known to repel some pest insects, including
mosquitos, and has uses in organic gardening. It is also widely used to repel rodents.[46][47][48][49]
Menthol activates cold-sensitive
TRPM8 receptors in the skin and mucosal tissues, and is the primary source of the cooling sensation that follows the topical application of peppermint oil.[56]
Candy canes are one of the most common peppermint-flavored candies
Mentha × piperita hybrid known as 'Chocolate Mint'
Freeze-dried leaves
Peppermint oil is also used in construction and plumbing to test for the tightness of pipes and disclose leaks by its odor.[57]
Safety
Medicinal uses of peppermint have not been approved as effective or safe by the US
Food and Drug Administration.[58] With caution that the concentration of the peppermint constituent pulegone should not exceed 1% (140 mg), peppermint preparations are considered safe by the
European Medicines Agency when used in topical formulations for adult subjects.[59][60] Diluted peppermint essential oil is safe for oral intake when only a few drops are used.[53][59]
Although peppermint is commonly available as a
herbal supplement, no established, consistent manufacturing standards exist for it, and some peppermint products may be contaminated with toxic metals or other substituted compounds.[58]Skin rashes, irritation, or
allergic reactions may result from applying peppermint oil to the skin,[58] and its use on the face or chest of young children may cause side effects if the oil menthol is inhaled.[53][59] A common side effect from oral intake of peppermint oil or capsules is
heartburn.[58] Oral use of peppermint products may have
adverse effects when used with iron supplements,
cyclosporine, medicines for heart conditions or high blood pressure, or medicines to decrease stomach acid.[58]
Standardization
ISO 676:1995—contains the information about the nomenclature of the variety and cultivars[61]
ISO 5563:1984—a specification for its dried leaves of Mentha piperita Linnaeus[62]
^
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^Ray, John (1696). Synopsis Methodica Stirpium Britannicarum. p. 234.
^Flückiger, Friedrich August (1874). Pharmacographia: A History of the Principal Drugs of Vegetable Origin, met with in Great Britain and British India. Macmillan. pp. 481–2.
^Harley, R. M. (1975). Mentha L. In:
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^Wong, Warren (1972). The Changes that Occur in Peppermint Oil During Aging, Including the Relationship Between Changes in Chemical Composition and Flavor Characteristics. Ph.D. dissertation. Rutgers. p. 10.
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