The genus Coleus of the family Lamiaceae (Labiatae) comprises a number of herbaceous medicinal plants which are particularly employed in home remedies for various ailments. Three species are most popular and commonly cultivated. They are Coleus aromaticus, C. vettiveroides and C. forkoshlii.
1. Coleus aromaticus Benth. syn. C. amboinicus Lour., Plectranthus amboinicus (Lour.) Spreng.
Eng: Country borage, Indian borage;
San: Karpuravalli, Sugandhavalakam;
Mal: Panikkurkka, kannikkurkka;
It is found through out the tropics and cultivated in homestead gardens. It is a large succulent aromatic perennial herb with hispidly villous or tomentose fleshy stem. Leaves are simple, opposite, broadly ovate, crenate and fleshy. Flowers are pale purplish in dense whorls at distant intervals in a long slender raceme. Fruits are orbicular or ovoid nutlets. The leaves are useful in cephalagia, otalgia, anorexia, dyspepsia, flatulence, colic, diarrhoea, cholera, halitosis, convulsions, epilepsy, cough, asthma, hiccough, bronchitis, strangury, hepatopathy and malarial fever (Warrier et al,1995).
2. Coleus vettiveroides K.C. Jacob, syn. Plectranthus vettiveroides (Jacob) Singh & Sharma.
San: Valakam, Hriberam;
It is seen in tropical countries and cultivated in gardens. It is a small profusely branched, succulent aromatic herb with quadrangular stems and branches and deep straw coloured aromatic roots. Leaves are glandular hairy, broadly ovate with dentate margins and prominent veins on the bark. Blue flowers are borne on terminal racemes. Fruits are nutlets. The whole plant is useful in hyperdipsia, vitiated conditions of pitta, burning sensation, strangury, leprosy, skin diseases, leucoderma, fever, vomiting, diarrhoea, ulcers and as hair tonic.
3. Coleus forskohlii Briq. syn. C. barbatus Benth.
Kan: Maganiberu, Makandiberu
It is a perennial aromatic herb grown under tropical to temperate conditions for its carrot-like tubers which are used as condiments in the preparation of pickles. Its tuberous roots are an exclusive source of a diterpenoid forskolin which has the unique property of activating almost all hormone sensitive adenylate cyclase enzymes in a biological system. It is useful in the treatment of congestive heart failure, glaucoma, asthma, cancer and in preventing immature greying of hair (Hegde,1997).
Agrotechnology: The Coleus group of plants grows in tropical to subtropical situations and in warm temperate climatic zone on mountains of India, Nepal, Burma, Sri Lanka, Thailand and Africa. It comes up well on the sun exposed dry hill slopes from 300m to 1800m altitude. A well drained medium fertile soil is suitable for its cultivation. it is propagated vegetatively through stem and root cuttings. Vine cuttings to a length of 10-15cm from the top portion are most ideal for planting. The land is ploughed or dug to a depth of 15-20cm and ridges are formed 30cm apart. Vine cuttings are planted on the ridges at 30cm spacing after incorporating basal manure. 10t of FYM and NPK at 50:50:50kg/ha are incorporated into the soil. Top dressing of N and K is also suggested for improved yields. Weeding and earthing up at 45 days after planting along with topdressing is highly beneficial. Bacterial wilt and root knot nematode are reported in the crop. Drenching the soil with fungicide, deep ploughing in the summer, burning of crop residues and crop rotation are helpful to tide over the disease and pest problem. The crop can be harvested after 5-6 months.
Properties and activity: The medicinal property of Coleus amboinicus is attributed to codeine, carvacrol, flavones, aromatic acids and tannins present in the plant. The essential oil from the plant contains carvacrol, ethyl salicylate, thymol, eugenol and chavicol. Leaves also contain cirsimaritin, -sitosterol- -D-glucoside and oxalacetic acid. Leaves are bitter, acrid, thermogenic, aromatic, anodyne, appetising, digestive, carminative, stomachic, anthelmintic, constipating, deodorant, expectorant, diuretic and liver tonic.
Coleus vettiveroides is bitter, cooling, diuretic, trichogenous and antipyretic.
Coleus forskohlii roots are rich in diterpenoids like forskolin, coleonols, coleons, barbatusin, cyclobutatusin, coleosol, coleol, coleonone, deoxycoleonol, 7-deacetylforskolin and 6-acetyl-7-deacetylforskolin. Its root is spasmolytic, CNS active, hypothermic and diuretic. Forskolin is bronchodialative and hypotensive (Hussain et al,1992). Forskolin is also useful in preventing the clotting of blood platelets, in reducing intraocular pressure in glaucoma and as an aid to nerve regeneration following trauma (Sharma, 1998)