Name currently accepted: Mentha spicata

Authority: Linn.

Taxonomic serial no.: 32272 (ITIS, 2016)

Synonyms: The Plant List provides 91 synonyms (Anon., 2010).

Family: Lamiaceae (Kingdom: Plantae; Subkingdom: Viridiplantae; Infrakingdom Streptophyta (land plants); Division: Tracheophyta (vascular plants); Subdivision: Spermatophytina; Class: Magnoliopsida; Superorder: Asteranae; Order: Lamiales; Family: Lamiaceae; Subfamily: Nepetoideae; Tribe: Mentheae; Genus: Mentha; Species: spicata; Binomial: Mentha spicata Linn.).

Subspecific taxa: Mentha spicata subsp. spicata L. (=Mentha spicata L.), Mentha spicata ssp. glabrata (Lej. & Courtois) Lebeau., Mentha spicata ssp. condensata (Briq.) Greuter & Burdet, Mentha spicata var. crispata (Schrad.) Beck (Porcher, 2007).

Common names: Spearmint, brook mint, bush mint, English mint, fish mint, garden mint, German spearmint, green mint, horsemint, lamb mint, mackerel mint, our lady´s mint.

Vernacular/regional names: Arabic: naana; Bulgarian: džodžen, giozum; Chinese: liu lan xiang; Danish: groen mynte, krusemynte; Dutch: groene munt, kruizemunt; Finnish: kähäräminttu, viherminttu; French: menthe crépue, menthe nanah, menthe verte; German: grüne minze, krause minze, krause wasserminze, krauseminze, marokkanische minze; Greek: dyosmos; Hungarian: fehér ménta; Italian: menta verde; Japanese: kaarii minto, midori hakka, oranda hakka, supea minto, supea-minto; Korean: spio-mintu; Polish: mita zielona; Portuguese: hortelã-comum, hortelã-peluda, hortelã-rasteiro; Romanian: iarbă creaţă, izmă, mintă, nintă bună; Russian: miaty kolosovoi list, mjata kolosovaja; Spanish: menta romana, yerba buena (Cuba), yerbabuena; Swedish: grönkrusmynta, grönmynta, krusmynta; Vietnamese: húng du͂i, rau hung du͂i (Porcher, 2007; Anon., 2014a).

Spearmint (Mentha spicata) is a widely used flavouring and fragrant herb, one of the four mints that are most widely used, the others being peppermint (Mentha piperita), Japanese mint or menthol mint (Mentha arvensis) and the bergamot mint (Mentha citrata). Spearmint has been used from ancient times; the first recorded use dates as far back as 400 BC. It is a native of the Mediterranean region, collected and used throughout the Roman Empire, where people valued this herb for its pleasant aroma so used to clear unpleasant odours, freshen breath and protect food stores from rodents (Hanrahan, 2001). Subsequently it was carried to Britain where its medicinal properties were unravelled. During the period of colonial expansion, spearmint was taken to many countries including North America. In 1893, a privately owned company, Wrigley Incorporated, transformed the way spearmint was used in North America by introducing it as a breath-freshening gum, resulting in the origin of chewing gum. Even now this is the most widespread use for spearmint (Hanrahan, 2001; Hanrahan and Frey, 2005; Anon., 2017a,b).

Spearmint is grown all over the world under temperate and subtropical climates and as a winter herb in many tropical countries. The top producing countries are the USA, India and China (Septer, 2014). It is also grown commercially in many countries in Europe, Asia (Pakistan), Australia, New Zealand, Africa and South America (especially in Brazil). It is a perennial herb, cultivated either as a perennial crop or as an annual crop depending upon the prevailing conditions. Plant herbage is harvested periodically, dried and steam-distilled for the production of oil. The bulk of the oil is used for flavouring chewing gums. Many other products, bubble gums, toothpastes, pharmaceutical preparations, etc., are flavoured with spearmint oil (Anon., 2017a).

The species description given below is based mainly on the Flora of China (Li and Hedge, 1998), Flora of Pakistan (Hedge, 2014), and the Illinois Wildflowers database (Kurz, 2014). Spearmint plants are stoloniferous perennial herbs, cultivated either as a perennial crop or an annual. The entire plant has a strong, pleasant, minty smell. The stem is erect, up to 120–130 cm, branched, glabrous or semiglabrous, striate and four-angled. Leaves are sessile or sub-sessile, ovate–oblong to oblong–lanceolate, with the base broadly cuneate to round, margin irregularly serrate and apex acute. Flowers are produced in terminal long, interrupted spikes, arranged in axillary whorls and arising from the axils of opposite, subtending bracts; the inflorescence is technically known as verticillaster. The individual flower is pedicellate, with the pedicel c. 2 mm. The calyx is campanulate, glandular, obscurely five-veined, with teeth triangular–lanceolate. The corolla is purplish, or lavender–violet, glabrous and tube c. 2 mm; lobes are subequal and the apex emarginate. Stamens are four, epipetalous and didynamous; anthers are four-lobed and two-celled and extrorse. The gynoecium consists of a superior ovary, bicarpellary, syncarpous, four-lobed, each with a single ovule with a single style and bifid stigma. Flowering is generally July–September. Flowers produce four nutlets each, found inside the persistent calyx. Nutlets are ovoid and dark brown. Natural populations are found from sea level to an altitude of about 400 m (Nawrocki, 2010; Klinkenberg, 2010; Anon., 2014b). Chromosome number reports indicated a polyploid series in the species; somatic numbers reported include 2n = 18, 36, 48 and 72 (Ahmad et al., 1992; Li and Hedge, 1998; Kurz, 2004; IPCN, 2014).

Spearmint (M. spicata) played an active role in the origin of species included in the genus Mentha. At least three species have been evolved through hybridization involving M. spicata. Mentha arvensis × M. spicata gave rise to the species Mentha × gracilis, Mentha aqualtica × M. spicata gave rise to peppermint Mentha × piperita, and M. longifolia × M. spicata produced Mentha × villoso-nervata (Tucker and Kitto, 2012).

Spearmint is propagated through seeds or by vegetative means. In the USA, spearmint is grown as a perennial crop, maintaining it in the field for 4–5 years, whereas in India it is grown mostly as an annual crop, sometimes even two crops a year depending on the land-use pattern and moisture availability. Its growth is best in full sunlight but it can also tolerate partial shade. Presently spearmint cultivation is pegged on the improved high-yielding cultivars. In India, the major improved cultivars used in commercial production are: MSS-5 (clonal selection from MSS-1), Arka (clonal selection from MSS-5), Neera (unknown origin), neer kalika (F1 hybrid from the cross Mentha arvensis × Mentha spicata cv. neera), Supriya (a clonal selection) Ganga (clonal selection), hybrid 77, Shivalik, EC41911, Gomti, Himalaya (resistant to rust, blight, mildew and leafspot), Kosi, Saksham (developed through tissue culture from cv. Himalaya) and Kushal (a variety through tissue culture) (Patra and Kumar, 2006; Padalia et al., 2013). Flavour-wise, the Moroccan mint is considered the best. This is a type known as nana that belongs to the variety known as Mentha spicata var. crispa.

The chemical composition of spearmint growing under natural conditions varies greatly and different chemotypes exist. Depending on the predominant components, nine chemotypes are recognized. They are: the carvone–limonene type; piperitone–oxide type; piperitenone–oxide type; menthone–piperitone type; glyoxal–1,8-cineole type; linalool–1,8-cineole–carvone type; piperitenone oxide–1,8-cineole type; piperitenone–carvone type; and piperitenone–limonene type (Garg et al., 2000; Patra and Kumar, 2006).

In farming situations the carvone–limonene type is the predominant chemotype and only the oil from this type is traded globally. Spearmint oil is a complex mixture of volatile compounds with carvone and limonene as the major constituents. The quality, however, depends on the genetic make-up, geographical and ecological conditions and stage of plant growth. Bahl et al. (2000) reported that herbage harvested 100 days after planting gave a carvone- and limonene-rich oil. Early harvesting yields an oil with a higher carvone content and a lower concentration of limonene. Telci et al. (2004) reported a chemotype from Turkey, the oil of which contained 81–83% linalool with the carvone content reduced to 4–9% and no limonene. The essential oil from a Tunisian sample of spearmint was dominated by the oxygenated monoterpenes (92.18%), followed by monoterpene hydrocarbons and sesquiterpenes (2.74% and 3.1%, respectively). The major compound was l-menthone (32.74%), followed by pulegone (25.67%) (Dhifi et al., 2013). Snoussi et al. (2015) also analysed Tunisian spearmint and identified 34 compounds representing 99.9% of the whole constituents of the essential oil. The oil contains 50.6% oxygenated monoterpenes, 45.1% monoterpene hydrocarbons and 2.8% sesquiterpene hydrocarbons. The main constituents were carvone (40.8% ± 1.23%) and limonene (20.8% ± 1.12%), followed by 1,8-cineole (17.0% ± 0.60%), β-pinene (2.2% ± 0.25%), cis-dihydrocarvone (1.9% ± 0.49%) and dihydrocarveol (1.7% ± 0.31%). The oil yield of this Tunisian variety of spearmint was 1.1% and it can be ascribed to the carvone–limonene chemotype.

Variability in the essential oil composition of spearmint cultivars was investigated by Padalia et al. (2013). They found that in five of the cultivars the major constituents were carvone (51.3–61.1%), limonene (15.1–25.2%), β-pinene (1.3–3.2%) and 1,8-cineole (0.1–3.6%). In one cultivar the major constituents were piperitenone oxide (76.7%), α-terpineol (4.9%) and limonene (4.7%). Spearmint also contains tannin, alkaloids, flavonoids, steroids, phenolic acids and lignans. These compounds include: protocatechic aldehyde, protocatechuic acid, rosmarinic acid, caffeic acid derivatives, flavonoids (rutin, luteolin, apigenin, thymonin), polyphenolic compounds [(+)-catechin, (−)-epicatechin], 5, 6-dihydroxy-7, 8, 3′, 4′-tetramethoxyflavone, nodifloretin, lignans (spicatolignan A and spicatolignan B) and many fatty acid methyl esters (Khan and Abourashed, 2010; Naidu et al., 2012). Duke (2016) provides a detailed listing of the chemical composition of spearmint.

A comprehensive list of functional properties for spearmint is presented by Duke (2002) and the properties of the major components such as carvone are covered in Duke (2016). Yousuf et al. (2013) reviewed the analgesic, anti-inflammatory and antipyretic effect of spearmint. Some of the more important activities are mentioned below.

• Antimicrobial effect: Spearmint oil was effective against antibiotic resistant strains of Klebsiella pneumoniae, at an in vitro concentration of 32 μg/ml (equivalent to 20 mg/kg body weight). The essential oil also showed significant antifungal activity against pathogenic fungi and bacteria, including Helicobacter pylori (Lixandru et al., 2010; Orhan et al., 2011).
• Insect-repellent effect: Spearmint oil has shown significant repellent activity against salt marsh mosquito. The essential oil exhibited a good larvicidal property against a number of mosquito strains (Koc et al., 2011; Govindarajan et al., 2011).
• Cartilage inflammation: Spearmint extract, under in vitro conditions, inhibited lipopolysaccharide (LPS) induced cartilage inflammation and reduced prostaglandin-E2 (PGE2), nitric oxide (NO) and cartilage breakdown (glycosaminoglycan (GAG) release from cartilage). Such effects were validated by feeding dried whole plant of spearmint in an equine model of cartilage inflammation, demonstrating a significant inhibition of LPS-induced PGE₂ and GAG in synovial fluid (Pearson et al., 2010, 2011). The anti-inflammatory activity of spearmint was supported by the work of Arumugam et al. (2008), who showed that carrageenan-induced paw oedema was inhibited by the spearmint extract; the extract also increased anti-oxidant enzymes (glutathione and glutathione peroxidase) and reduced lipid peroxidation.
• Respiratory diseases: Spearmint oil has a protective effect on rats with emphysematous changes. The oil improved alveolar destruction, pulmonary inflammation and goblet cell metaplasia, concomitantly reduced TNF-α (tumour necrosis factor α) and interleukin-β (IL-β) content and inhibited the over-expression of matrix metalloprtoteinase-9 in lung tissues. Spearmint oil reduced inflammatory cells in broncho-alveolar fluid in rats with chronic obstructive pulmonary diseases, inhibited bronchiolitis, pulmonary interstitial inflammation and cell infiltration. The essential oil decreased the destruction of pulmonary alveoli and thickening of bronchiole walls and inhibited goblet cell proliferation (Zhao et al., 2008; Liu, et al., 2011).

Spearmint also exhibited anti-oxidant properties and a moderate anti-gout effect (Hudaib et al., 2011).

Spearmint is a mild herb and generally considered safe. Some herbalists counsel against administering mint tea to young children, infants and pregnant women. People with hiatal hernia or having an acute gallstone attack should not use spearmint. Rarely, spearmint might cause allergic reactions in susceptible people. Carvone present in spearmint has been implicated as the main allergen.

The overuse of spearmint tea could inhibit iron absorption. It should be used cautiously in individuals with gastrointestinal reflux diseases. It should be used cautiously in individuals taking central nervous system depressants because spearmint might enhance the effect of the drug. It should be used cautiously in individuals with kidney disorders and liver problems. There is evidence that spearmint tea caused lipid peroxidation and uterine damage in rats and spearmint tea was shown to affect hormone levels and testicular tissue in rats. Spearmint may also interact with hormonal agents, antibiotics, antifungals, anti-inflammatory agents, cholesterol-lowering agents, anti-cancer agents and radioprotective drugs (Hanrahan and Frey, 2005; Maier, 2016; Anon., 2017b). A more recent study reported, however, that spearmint extract has no significant toxic effect on the reproductive system, fertility and number of offspring in adult male rats at the dose levels of 10, 20 and 40 mg/kg tested for 45 days (Nozhat et al., 2014).