Habitat
It is cultivated throughout most of India.

Morphology Description (Habit)
An erect, glabrous or minutely pubescent, branched annual. The stems are striate; the leaves are rather distant, 2-3-pinnately divided, the segments linear. The flowers occur in terminal or seemingly-lateral pedunculate, compound umbels, white and small; the fruits are ovoid, muricate, aromatic cremocarps, greyish brown; the mericarps, which are the components of the fruit, are compressed, with distinct ridges and tubercular surface, 1-seeded.

Principal Constituents
The alcoholic extract was found to contain a highly hygroscopic saponin, with a hemolytic index of 500. A yellow, crystalline flavone (m.p. 291-94°) and a steroidal substance (m.p.140-50°) have also been isolated from the fruits¹. The principal constituents of the essential oil from the fruits are the phenols, mainly thymol and some carvacrol. The Indian Pharmacopoeia requires ajowan oil to contain not less than 40 per cent thymol. The remainder of the oil is called 'thymene'. Thymene, which constitutes c.45 per cent of the oil, has the following composition: p-cymene, 50-55; g-terpinene, 30-35; a- and ß-pinenes, 4-5; and dipentene, 4-6%. Presence of minute 'amounts of camphene, myrcene and D3-carene is also reported².

Pharmacology
Preliminary pharmacological studies of the oil indicated that it had a parasympathomimetic effect and produced contraction of the isolated ileum, tracheal chain and bronchial musculature in guinea pigs. It depressed the cardiac musculature in frogs and caused a marked fall in blood pressure in cats. On account of its low toxicity, further trials of the oil as an hypotensive agent are recommended. The drug also seems to possess some anti-diuretic effect³.

Indications
Ajowan is much valued for its antispasmodic, stimulant, tonic and carminative properties. It is administered in flatulence, atonic dyspepsia and diarrhea, and often recommended for cholera. In the Unani system, ajowan is used as a crude drug to enhance the body's resistance, and is prescribed in amebiasis. It is a potent antimicrobial agent.

References

1. Nutritive Value of Indian Foods, 85, 120, 129; Roychowdhury, J. Instn Chem. India, 1963, 35, 202; Mukherjee et. al., Indian J. med. Res., 1967, 55, 1003; Rao, Bombay Technol.,1962, 12, 106; Chakraborti, Trans. Bose Res. Inst.,1956-58, 21, 61.
2. Guenther, IV, 551; Krishna & Badhwar, J. sci. industr. Res.,1953, 12A(2), suppl., 288-89; I.P., 1966, 32; Bhargava & Haksar, Indian Oil & Soap J.,1961-62, 27, 147; Bhargava & Haksar, Perfum. essent. Oil Rec.,1965, 56, 18; Nigam et. al., ibid., 1963, 54, 25.
3. I.P.C., 162; Menon, 2; Chem. Abstr.,1947, 41, 2209 Mukherjee et. al., Indian J. med. Res., 1967, 55, 1003.