Plectranthus amboinicus

''Coleus amboinicus'', synonym ''Plectranthus amboinicus'', is a semi-succulent perennial plant in the family Lamiaceae with a pungent oregano-like flavor and odor. ''Coleus amboinicus'' is considered to be native to parts of Africa, the Arabian Peninsula, and India, although it is widely cultivated and naturalized elsewhere in the tropics where it is used as a spice and ornamental plant. Common names in English include Indian borage, country borage, French thyme, Indian mint, Mexican mint, Cuban oregano, soup mint, Spanish thyme. The species epithet, ''amboinicus'' refers to Ambon Island, in Indonesia, where it was apparently encountered and described by João de Loureiro (1717–1791).

Description

A member of the mint family Lamiaceae, ''Coleus amboinicus'' grows up to tall. The stem is fleshy, about , either with long rigid hairs (hispidly villous) or densely covered with soft, short and erect hairs (tomentose). Old stems are smooth (glabrescent).

Leaves are by , fleshy, undivided (simple), broad, egg/oval-shaped with a tapering tip (ovate). The margins are coarsely crenate to dentate-crenate except in the base. They are thickly studded with hairs (pubescent), with the lower surface possessing the most numerous glandular hairs, giving a frosted appearance. The petiole is . The aroma of the leaves can be described as a pungent combination of the aromas of oregano, thyme, and turpentine.''Culinary herbs'', by Ernest Small, National Research Council of Canada NRC Research Press, 1997, p. 488. The taste of the leaves is described as being similar to the one of oregano, but with a sharp mint-like flavor.

Flowers are on a short stem (shortly pedicelled), pale purplish, in dense 10-20 (or more) flowered dense whorls (cymes), at distant intervals, in a long slender spike-like raceme. Rachis , fleshy and pubescent. The bracts are broadly ovate, long, acute. The calyx is campanulate, long, hirsute and glandular, subequally 5-toothed, upper tooth broadly ovate-oblong, obtuse, abruptly acute, lateral and lower teeth acute. Corolla blue, curved and declinate, long, tube long. Trumpet-like widened; limb 2-lipped, upper lip short, erect, puberulent, lower lip long, concave. Filaments are fused below into a tube around the style.

The seeds (nutlets) are smooth, pale-brown, roundish flattened, c. .

Distribution and habitat

''Coleus amboinicus'' is native to Southern and Eastern Africa, from South Africa (KwaZulu-Natal) and Eswatini to Angola and Mozambique and north to Kenya and Tanzania, where it grows in woodland or coastal bush, on rocky slopes and loamy or sandy flats at low elevations.Codd, L. E. W. et al. ''Flora of Southern Africa : the Republic of South Africa, Basutoland, Swaziland and South West Africa''. Vol. 28, part 4, 1981, page 148. Available on Biodiversity Heritage Library at https://www.biodiversitylibrary.org/page/51375271. From Southern Africa it would have been carried by Arabs and other traders to Arabia, India and Southeast Asia along the Indian Ocean maritime trade routes. The plant also currently grows in mainland India. The plant was later brought to Europe, and then from Spain to the Americas, hence the name Spanish thyme.

Research

In basic research, the effects of the essential oil were tested with other plant essential oils for possible use as a mosquito repellant.

Uses

The leaves are strongly flavoured. The herb is used as a substitute for oregano to mask the strong odors and flavors of fish, mutton, and goat. Fresh leaves are used to scent laundry and hair. It is also grown as an ornamental plant.

Phytochemicals

The main chemical compounds found in the essential oil of ''Coleus amboinicus'' are carvacrol (28.65%), thymol (21.66%), α-humulene (9.67%), undecanal (8.29%), γ-terpinene (7.76%), ''p''-cymene (6.46%), caryophyllene oxide (5.85%), α-terpineol (3.28%), and β-selinene (2.01%). Another analysis obtained thymol (41.3%), carvacrol (13.25%), 1,8-cineole (5.45%), eugenol (4.40%), caryophyllene (4.20%), terpinolene (3.75%), α-pinene (3.20%), β-pinene (2.50%), methyl eugenol (2.10%), and β-phellandrene (1.90%). The variations can be attributed to the methodology used in the extraction process, seasonal variations, soil type, climate, genetic and geographical variations of the plant.

Cultivation

''Coleus amboinicus'' is a fast-growing plant commonly grown in gardens and indoors in pots. Propagation is by stem cuttings, but it can also be grown from seeds. In dry climates the herb grows easily in a well-drained, semi-shaded position. It is frost tender (USDA hardiness zones 10–11) and grows well in subtropical and tropical locations, but will do well in cooler climates if grown in a pot and brought indoors, or moved to a warm, sheltered position in winter. In Hawaii and other humid tropical locations, the plant requires full sun. It can be harvested throughout the growing season to be used fresh, dried, or frozen.

Common names

* Cuban oreganoGary Allen, ''The Herbalist in the Kitchen'', University of Illinois Press, 2010, p
198

* Country borageTropicos, http://www.tropicos.org/Name/17602719, accessed 21 August 2012
* French thyme
* Indian borage
* Mexican mint (US, favored common nameEncyclopedia of Life, http://eol.org/pages/486424/names/common_names, accessed 21 August 2012)
* Orégano francés (in Cuba and other Spanish language sources)
an

(both in Spanish)
* Pudina (in Trinidad and Tobago, Guyana and Suriname by the Indian population)
* Soup mint
* Spanish thyme
* Oregano brujo (witch oregano) in Puerto Rico
* Thick leaf thyme or broad leaf thyme

Gallery

File:A closeup of Indian Borage (Oregano).JPG, Indian borage
File:Cuban Oregano.jpg, Cuban oregano
File:Flower of Coleus aromaticus.jpg, Flowers
File:Panikkoorkka poov.JPG, Flower
File:Plectranthus amboinicus flowers.jpg, Flowers

See also

* ''Hedeoma patens'', Spanish common name ('small oregano')
* ''Lippia graveolens'', Mexican oregano or ('wild oregano')

References

{{Taxonbar, from1=Q39087854, from2=Q2359202

amboinicus
Plants described in 1825
Flora of Africa
Herbs
Plants used in traditional African medicine
Leaf vegetables