Major species of Mentha plant used for medical purpose.
In different parts of the world, herbs were utilized for medicines, food, and many other purposes. In various countries, research is being done to discover the potential applications of medicinal plants in favor of human beings . Mentha was described and named by Jussieu in 1789. It is a member of the Lamiaceae family, and their plants generally contain flowers with prominent liplike lower petals. Small trees, perennial or annual herbs, and shrubs are members of this family. The genus Mentha has been in a state of flux with especial reference to its taxonomy, as more than 3000 names have been being published since 1753. Keeping in view the chromosome numbers, phylogenetic analysis, and major essential oil components, Mentha has been redefined to comprise of 18 species and 11 hybrids, which are divided into four sections . These species are herbaceous and perennial plants, commonly cultivated for flavor and a pleasant aroma. Natural menthol has a soothing and relaxing cooling impact on the mucous membrane of the human body and on the skin. Oil extracted from Mentha has cosmetic, pharmaceutical, and perfumery applications. Sometimes, it is also used for culinary purposes for food and flavors .
Kingdom: Plantae plants
Species: Piperita 
Mints have the potential to grow nears water pools, rivers, lakes, and partially moist cool spots. They also can grow under the sun. These can grow throughout the year . For its cultivation, Mediterranean Basin is a primary resource, but tropical and temperate regions are mostly noted as the best resource. Mentha is not cultivated in South America and Antarctica. But in all other countries, it is widely distributed. Australia, Europe, Central Asia, and North Africa are the main centers of the genus Mentha cultivation .
Mints are the aromatic and perennial herbs, having overground and underground stolons, which are quite widespread. They also have square, erect, and branched stems. The arrangement of their leaves is in opposite pairs, from oblong to lanceolate with the downy approach and sharp edges. The color profile of Mentha leaves is quite broad ranging from blue, dark green, grayish green to purple, and it could be pale yellow. Mentha flowers are being produced in false whorls also known as verticillasters, and their color range is from white to purple. A flower having two-lipped corolla portion with four lobes and its fruit has 1–4 seeds, covered with a stony layer .
The following is a list of some major species of Mentha used for medicinal purpose (Table 1).
5.1 Mentha arvensis
Mentha arvensis is an aromatic branched herb that can reach a height of 40 cm, with terminal branches in ascending position. Leaves are 1.5–2 cm in length, round-tipped with tooted margins having the shape of oblong-ovate. The flowers produced on this plant are purplish to light blue in color, having hairs on them. It is used to cure the maladies of asthma, liver, jaundice, and spleen. Oil is procured from the distillation of leaves having 40–50% of menthol. Its oil is carminative, stimulant, antiseptic, and diuretic. Menthol is being used in drugs for the cure of stomach issues and in ointments for the remedy of headache. Its leaves are also deployed as a remedy for rheumatic pains and indigestion. Its active constituents comprise of menthone, menthol, limonene, methyl acetate, isomenthone, beta-caryophyllene, tannins, neomenthol, alpha- and beta-pinene, flavonoids, and piperitone. Its oil consists of 4.5–10% esters, menthyl acetate along with ketones with a percentage of 15–20% .
Mentha arvensis produces 70–90% of menthol along with cineol piperitone, sesquiterpene, and cineol piperitone as the other ingredients. The plant of mint contains chrysoeriol, eriocitrin, isorhoifolin, hesperidoside, methyl rosmarinate, linarin, narirutin, acacetin, tilicine, hesperidin, rutin, menthoside, luteolin, nodifloretin, and flavonoids diosmin. It also consists of the phenolic acids including lithospermic acid, protocatechuic acid, rosmarinic acid, daucosterol, β-sitosterol, anthraquinones aloe-emodin, phytosterols, chrysophanol, protocatechuic aldehyde, tannins, emodin, and caffeic acid  (Figure 1).
5.2 Mentha longifolia (L.) L.—horsemint
Mentha longifolia also called the horsemint; it is a native plant of Europe but not of Ireland and Britain. It is also present in the central and western Asia and in the northern and southern Africa. It is a herbaceous
5.3 Mentha pulegium L.—pennyroyal
Mentha pulegium, commonly (European) pennyroyal, or pennyrile, also called squaw mint, mosquito plant, and pudding grass, is a species of flowering plant in the mint family, Lamiaceae, which is native to Europe, North Africa, and the Middle East. Crushed pennyroyal leaves give a very strong scent similar to spearmint . Pennyroyal is a traditional folk remedy
5.4 Mentha aquatic
Mentha aquatic is a flowering plant which also belongs to the family Lamiaceae. It can grow in wet and moist areas and is native to northwest Africa, southwest Asia, and most parts of Europe. It has also been introduced to South America, North America, few Atlantic islands, and Australia. It can grow along the channels and margins of rivers, dikes, streams, wet meadows, pools, marshes, ditches, canals, and fens. The suitable soil for its growth is slightly acidic to mineral soil. It is a rhizomatous and herbaceous perennial plant that can grow up to 35 inches tall. Its stems are less hairy to almost hairy, having purple or green in color square area. Its rhizomes are fleshy, wide-spreading, and having fibrous roots. Its leaves are 1–4 cm in width, 2–6 cm in length, with hairs on the surface. The flowers of the water mint plant are densely crowded, tiny in size, and tubular, with the flowering season ranging from mid to late summer  (Figure 4).
6. Mentha uses
Fresh mint leaves have been utilized for the chewing purpose. It is also used as mouthwashes to treat bleeding gums . Crushed mint leaves were utilized for the brightness of teeth during ancient times. It is also utilized in making oral dentifrices to clean and polish natural teeth. However, peppermint is beneficial for the gums of babies as it reduces the pain and gives germ-free teeth. Mentha plant comprises essential oil whose major constituent is menthol, which is used for oral hygiene products, pharmaceuticals, cosmetics, and foods . There are four major varieties of mint cultivated commonly such as spearmint, corn mint, scotch spearmint, and peppermint. Mint was initially utilized as a medicinal herb to cure body pains and stomachache, and its tea is good for the gastrointestinal tract, digestion, and dyspepsia and is used to treat biliary disorders .
6.1 Conventional medicine and cosmetics
Menthol from mint is a source of essential oil which accounts for 40–90%, and it is being utilized in cosmetics and many fragrances . Menthol and mint essential oil are used in aromatherapy, which might become helpful to decrease the effect of post-surgery nausea .
6.2 Allergic effect
It is utilized in various customer products. In several people, mint can give allergic reactions including heartburn, stinging, diarrhea, headache, abdominal cramps, and anaphylaxis .
6.3 Room fragrance and aromatherapy
In ancient times, peppermint was known as the herb of kindness and warmth, and it was the first herb used in Europe as a room deodorizer. To diminish the smell of soil, the floor was covered with a sprinkled herb which spread its sweet scent throughout the room. Nowadays, because of the essential oil, peppermint is used for aromatherapy .
7. Unfavorable and toxic effect
There are several adverse side effects regarding peppermint. Peppermint and its major chemical components like menthone, menthol, pulegone, and menthofuran are proved to be toxic with a moderate effect on some individuals. Its essential oil combines with the cytochrome P450 isoenzyme in the liver microsomes of humans. The use of peppermint is restricted or must be used with caution in patients having inflammation in gall bladder and blockage of bile duct  (Table 2).
The authors are highly obliged to the Library Department, Government College University Faisalabad, Pakistan and IT department, Higher Education Commission (HEC, Islamabad) for access to journals, books and valuable database.
Conflict of interest
The authors declare no conflict of interest.