Trachyspermum ammi (Ajwain)

Trachyspermum ammi

English: Ajowan, omum, bishop's weed
Hindi: Ajwain
Sanskrit: Yavanika, agnivardhana

The name agnivardhana implies stimulation of the digestive fire or agni. It has been employed medicinally since ancient times and was described by the seer Charaka as useful in urticaria and as an antiflatulent and anticolic drug. Ajowan, with its characteristic aromatic smell and pungent taste, is widely used as a spice in curries, pickles, biscuits, confectionery and beverages. The crushed seeds are also dried for use in scented powders and pot pourri.

Habitat

The herb originated in the Mediterranean region and is now cultivated in Iraq, Iran, Afghanistan and Pakistan. Commercial ajowan is mainly produced in India and grown throughout the country, mainly in the plains but also at higher altitudes. Under irrigation, it is grown extensively as a garden crop or in small fields. The plant also grows in Africa, China and other countries of central Asia.

Botanical description

An erect, glabrous or minutely pubescent, branched annual up to 30-90 cm tall (Plate 65). Stems striate; leaves rather distant, 2-3 pinnately divided, segments linear, ultimate segments 1-2.5 cm long. The flowers are white and small, occurring in terminal or lateral pedunculate, compound umbels. Fruits ovoid, muricate, cremocarps, 2-3 mm long, greyish brown; mericarps compressed, with distinct ridges and tubercular surface. The essential oil obtained from the seed is a yellowish-orange or reddish liquid with a herbaceous-spicy medicinal odour, much like thyme.

Parts used

Seed, oil.

Traditional and modern use

The seeds are carminative, stimulant and antispasmodic and are given in colic and diarrhoea. For the relief of flatulence andx dyspepsia, they may be eaten with betel leaves or rock salt and a mixture of the seeds and buttermilk is a commonly used expectorant. They are considered efficacious in sore throats, bronchitis and for habitual drunkenness and as a stimulating decongestant for the respiratory and digestive tracts. Internally the seeds are given for colds, coughs, influenza, asthma, arthritis and rheumatism and are a component of many important Ayurvedic formulations. Crude crystals from the oil, known as Ajwain-ka­phool, are used in stomach ache. In Unani medicine ajowan is used as a liver tonic, an antiinflammatory agent and for paralysis. The tincture, essential oil and extracted thymol have been used in Indian medicine to treat cholera. The distilled oil in water, sometimes known as 'omum water', is used as an antiseptic, to aid digestion and applied externally for relief of rheumatic and neuralgic pains. A paste of the seeds may be applied topically to relieve colic pains and a hot dry fomentation of the seeds is a household remedy for asthma. For relief of migraine and delirium the seeds are sometimes smoked or taken as snuff.

Ethnoveterinary usage

The seeds are used in stoppage of rumination and chewing the cud, pox, fever, mastitis, tympanitis, haematuria, ascites and indigestion.

Major chemical constituents

Monoterpenoids

The essential oil contains thymol as the major component, with p-cymene, dipentene, a-pinene, â-pinene, y-terpinene, camphene, myrcene, b-3-carene, limonene, carvacrol and others.

Glycosides

The seed contains 6-0-â-D­glucopyranosyloxyth ymol.

Fatty acids

Fixed oil extracted from the seeds was found to contain resin acids, palmitic acid, petroselenic acid, oleic acid and linoleic acid.

Vitamins and trace elements

The fruit contains riboflavin, thiamin, nicotinic acid, carotene, calcium, chromium, cobalt, copper, iodine, iron, manganese, phosphorus and zinc.

Medicinal and pharmacological activities

Antiplatelet activity: An ether extract of Trachyspermum ammi inhibited platelet aggregation induced by arachidonic acid (AA), epinephrine and collagen. It reduced thromboxane B2 formation from added arachidonate in intact platelet preparations and also after stimulation with Ca2+ ionophore A23187. A direct action on cyclooxygenase was indicated as there was no effect on the release of AA from labelled platelets. An increased formation of lipoxygenase- derived products from exogenous AA in treated platelets was also observed, apparently due to the redirection of AA metabolism from the cyclooxygenase to the lipoxygenase pathway.

Hypotensive activity: In anaesthetised rats, thymol (1-10 mglkg) produced a dose­dependent fall in blood pressure and heart rate. These effects were not blocked by atropine (1 mg/kg) and thymol did not modify the presser response of norepinephrine, eliminating the possibility of cholinergic stimulation or adrenergic blockade. In spontaneously beating atria, thymol caused a decrease in force and rate of atrial contractions which remained unaltered in the presence of atropine. In rabbit aorta, thymol caused relaxation of norepinephrine­and potassium-induced contractions in a concentration- dependent manner. These relaxant effects remained unchanged after the removal of the endothelium. Moreover, atropine, propranolol, indomethacin and glibenclamide did not alter vasorelaxation, suggesting that thymol exhibits calcium channel blocking activity, which may explain the hypotensive and bradycardiac effects.

Inhibition of the hepatitis C virus: The methanol extract of Trachyspermum ammi showed inhibitory effects on hepatitis C virus protease, using in vitro assay methods. It showed 90% inhibition at 100 Ilglml.

Insecticidal activity: The oil of Trachyspermum spp. exhibited significant larvicidal activity against Aedes aegypti and Culex quinquefasciatus. It also produced significant metamorphic inhibition against Dysdercus koenigii, oviposition deterrence against Phthorimaea operculella and antifeedant effects against Spodoptera litura and Achoea
janata.