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-Dglucopyranosyloxythymol.
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.
Molluscicidal activity: The effects of sublethal treatment with Trachyspermum ammi in combination with piperonyl butoxide (PBO) on the reproduction of the snail Lymnaea acuminata were studied. The combination of its active molluscicidal component (thymol) with PBO caused a significant reduction in fecundity, rate of hatching and survival of young snails. In vivo exposure of Lymnaea acuminata to thymol indicated that it significantly altered acetylcholinesterase, lactic dehydrogenase, succinic dehydrogenase and cytooxidase activity in the nervous tissue of snails. However, in vitro exposure produced an effect only on acetylcholinesterase and lactic dehydrogenase. Thymol affected all known neurotransmission mechanisms in the snail via a complex interaction, which may account for its toxicity to snails.
Antifungal activity: The essential oil demonstrated toxicity to Aspergillus niger and Curvularia ovoidea, two common storage fungi, inhibiting the mycelial growth of both test fungi completely at a minimum inhibitory concentration (MIC) of 500 ppm, at which level it was fungicidal. The oil also showed a broad fungitoxic spectrum. Toxicity to the mycelial growth of Macrophomina phaseolina was also seen in vitro, at an MIC of 200 ppm. At this concentration the oil was fungistatic, but not phytotoxic, to germinating French beans (Phaseolus vulgaris). The oil was thermostable and more efficacious than some synthetic fungicides, including Benlate, Ceresan, copper oxychloride, Oithan M-45 and Thiovit. Thymol was also isolated as the main fungitoxic factor. In another study Trachyspermum ammi oil inhibited growth of Aspergillus flavus and A. niger completely at an MIC of 800 ppm. At this concentration it was fungicidal in 50 seconds and the effect persisted for at least 365 days of storage. Peanuts, the seeds of Arachis hypogea, could be protected from fungal deterioration during storage by treating with the oil at 5000 ppm. Thymol and p-cymene isolated from the oil showed antifungal properties at 1000 ppm. The oil was more active than some synthetic fungicides to Helminthosporium oryzae and was also toxic to various human pathogens.
Antibacterial activity: The oil was shown to be antibacterial to Salmonella typhosa, Micrococcus pyogenes var. aureus and E. coli. Thymol is well known as an antiseptic.
Spermicidal activity: Oil of ajowan showed spermicidal activity on human spermatozoa in vitro.
Safety profile
The undiluted oil is a mucous membrane and dermal irritant. Due to the high thymol content it should be avoided in pregnancy. The acute oral LDso of thymol is reported as 0.98 g/kg in the rat and 0.88 g in the guinea pig.
Dosage
Powder: 3-6 g
Extract: 125 mg
Ayurvedic properties
Rasa: Katu (pungent), tikta (bitter)
Guna: Laghu (light). ruksha (dry). tikshna (sharp)
Veerya: Ushna (hot)
Vipaka: Katu (pungent)
Dosha: Promotes pitta, pacifies vata and kapha
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