Peppermint

Peppermint (Mentha × piperita, also known as M. balsamea Willd. ) is a hybrid mint, a cross between the watermint (Mentha aquatica) and spearmint (Mentha spicata). The plant, indigenous to Europe, is now widespread in cultivation throughout all regions of the world. It is found wild occasionally with its parent species.

Botany
Peppermint was first described in 1753 by Carolus Linnaeus from specimens that had been collected in England; he treated it as a species, but it is now universally agreed to be a hybrid.

It is a herbaceous rhizomatous perennial plant growing to 30 - 90 cm tall, with smooth stems, square in cross section. The rhizomes are wide-spreading, fleshy, and bare fibrous roots. The leaves are from 4 - 9 cm long and 1.5 - 4 cm cm broad, dark green with reddish veins, and with an acute apex and coarsely toothed margins. The leaves and stems are usually slightly hairy. The flowers are purple, 6 - 8 mm long, with a four-lobed corolla about 5 mm diameter; they are produced in whorls (verticillasters) around the stem, forming thick, blunt spikes. Flowering is from mid to late summer. The chromosome number is variable, with 2n counts of 66, 72, 84, and 120 recorded.

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 rhizomes. If placed, it can grow anywhere, with a few exceptions.

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, and in the United States. in the Great Lakes region, noted since 1843.

Cultivation
Peppermint generally thrives in moist, shaded locations, and expands quickly by underground stolons. It is often grown in containers to restrict rapid spreading. It grows best with a good supply of water, and is often planted in areas with part-sun to shade.

The leaves and flowering tops are used; they are collected as soon as the flowers begin to open and then are carefully 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.

Seeds sold at stores labelled peppermint generally will not germinate into true peppermint, but often produce a less intensely scented spearmint-like plant. The true peppermint plant rarely produces seeds, and then only by fertilization from a spearmint plant, which contributes only spearmint genes, diluting the scent and flavour.

See below for list of cultivars.

Uses
Peppermint has a long tradition of medicinal use, with archaeological evidence placing its use at least as far back as ten thousand years ago.

Peppermint has a high menthol content, and is often used as tea and for flavouring ice cream, confectionery, chewing gum, and toothpaste. The oil also contains menthone and menthyl esters, particularly menthyl acetate. Dried peppermint typically has 0.3-0.4% of volatile oil containing menthol (29-48%), menthone (20-31%), menthyl acetate (3-10%), menthofuran (1-7%) and many trace constituents including limonene, pulegone, eucalyptol, and pinene. It is the oldest and most popular flavour of mint-flavoured confectionery. Peppermint can also be found in some shampoos and soaps, which give the hair a minty scent and produce a cooling sensation on the skin. Used in this way, it has been known to help with insomnia.



Peppermint has promising radioprotective effects for cancer patients undergoing cancer treatment.

The aroma of peppermint has been found to enhance memory. As such, it can be administered by instructors to their students before examinations, to aid recall.

Peppermint flowers are large nectar producers and honey bees as well as other nectar harvesting organisms forage them heavily. A mild, pleasant varietal honey can be produced if there is a sufficient area of plants.

Peppermint oil
Peppermint oil has a high concentration of natural pesticides, mainly menthone.

In 2007, Italian investigators reported that 75% of the patients in their study who took peppermint oil capsules for four weeks had a major reduction in irritable bowel syndrome (IBS) symptoms, compared with just 38% of those who took a placebo. A second study in 2010, conducted in Iran, found similar results. 2011 research showed that peppermint acts through a specific anti-pain channel called TRPM8 to reduce pain sensing fibres. The authors feel that this study provides information that is potentially the first step in determining a new type of mainstream clinical treatment for Irritable Bowel Syndrome.

Similarly, some poorly designed earlier trials found that peppermint oil has the ability to reduce colicky abdominal pain due to IBS with an NNT (number needed to treat) around 3.1, but the oil is an irritant to the stomach in the quantity required and therefore needs wrapping for delayed release in the intestine. This could also be achieved by using the whole herb or leaves rather than the volatile components alone. Peppermint relaxes the gastro-esophageal sphincter, thus promoting belching.

Peppermint oil is also used in some Chinese medicines, such as the medicated oil Po Sum On.

Toxicology
The toxicity studies of the plant have received controversial results. Some authors reported that the plant may induce hepatic diseases (liver disease), while others found that it protects against liver damage that is caused by heavy metals. In addition to that, the toxicities of the plant seem to vary from one cultivar to another and are dose dependent. This is probably attributed from the content level of pulegone.

List of the cultivars
A number of cultivars have been selected for garden use:
 * Mentha × piperita 'Candymint'. Stems reddish.
 * Mentha × piperita 'Citrata' (Includes a a number of varieties including Orange Mint, Eau De Cologne Mint, Grapefruit Mint). Leaves aromatic, hairless.
 * Mentha × piperita 'Crispa'. Leaves wrinkled.
 * Mentha × piperita 'Lime Mint'. Foliage lime-scented.
 * Mentha × piperita 'Variegata'. Leaves mottled green and pale yellow.
 * Mentha × piperita 'Chocolate Mint'. Flowers open from bottom up; reminiscent of flavour in Andes Chocolate Mints, a popular confection.

Commercial cultivars may include
 * Dulgo pole
 * Zefir
 * Bulgarian population #2
 * Clone 11-6-22
 * Clone 80-121-33
 * Mitcham Digne 38
 * Mitcham Ribecourt 19
 * Todd's#x2019

Standardization of its products and services

 * ISO 676:1995 - contains the information about the nomenclature of the variety and cultivars
 * ISO 5563:1984 - a specification for its dried leaves of Mentha piperita Linnaeus
 * Aromatherapy
 * Candy cane
 * Chewing gum
 * Peppermint oil - ISO 856:2006
 * Insect repellent
 * Mint chocolate
 * Peppermint tea
 * Peppermint candy