Plectranthus amboinicus

Plectranthus amboinicus, once identified as Coleus amboinicus, is a semi-succulent perennial plant in the family Lamiaceae with a pungent oregano-like flavor and odor. It is native to Southern and Eastern Africa. It is widely cultivated and naturalized elsewhere in the tropics where it is used as a traditional medicine, spice, and ornamental plant. A member of the mint family Lamiaceae, Plectranthus amboinicus grows up to 1 m (3.3 ft) tall. The stem is fleshy, about 30–90 cm (12–35 in), either with long rigid hairs (hispidly villous) or densely covered with soft, short and erect hairs (tomentose). Old stems are smooth (glabrescent). Leaves are 5–7 cm (2.0–2.8 in) by 4–6 cm (1.6–2.4 in), 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 2–4.5 cm (0.79–1.77 in). 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 10–20 cm (3.9–7.9 in), fleshy and pubescent. The bracts are broadly ovate, 3–4 cm (1.2–1.6 in) long, acute. The calyx is campanulate, 2–4 mm (0.079–0.157 in) 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, 8–12 mm (0.31–0.47 in) long, tube 3–4 mm (0.12–0.16 in) 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. 0.7 by 0.5 mm (0.028 by 0.020 in). The aroma of the leaves can be described as a pungent combination of the aromas of oregano, thyme, and turpentine. The taste of the leaves is described as being similar to the one of oregano, but with a sharp mint-like flavor. It is native to Southern and Eastern Africa, from South Africa (KwaZulu-Natal) and Swaziland 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. 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 was later brought to Europe, and then from Spain to the Americas, hence the name Spanish thyme. In traditional medicine, Plectranthus amboinicus is thought to have medicinal properties, but there is no evidence from clinical research to support such claims. In basic research, the effects of the essential oil were tested with other plant essential oils for possible use as a mosquito repellant. The leaves are strongly flavoured and used for stuffings of meat and poultry, beef, lamb and game. 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. The main chemical compounds found in the essential oil of Plectranthus 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.