Medically reviewed on Nov 1, 2017
Scientific Name(s): Trachyspermum ammi Sprague. Family: Apiaceae (carrots). The scientific name is synonymous with Carum copticum (L.) Benth., Ammi copticum L. and Hook. f. and Trachyspermum copticum (L.) Link. 1
Common Name(s): Bishop's weed , Carum , Ajowan , Ajowan caraway , Ajowan seed , Ajava seeds , Yavani (Sanskrit), Ajowanj (Hindi), Omum.
Bishop's weed has been used in Ayurvedic medicine as an antiseptic, a spice, and a preservative, as well as for respiratory and GI ailments. It is used in the Unani system of medicine as an enhancer of the body's resistance. However, there are no clinical trials available to date to support these uses.
None yet identified.
Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use.
None well documented.
In vivo animal studies demonstrate hypotensive and bradycardic effects. In vitro studies show inhibitory effects on platelet aggregation.
High doses may result in fatal poisoning.
Bishop's weed is a smooth or slightly hairy branched annual (or perennial) reaching a height of 90 cm. It is an aromatic spice, resembling thyme in flavor. The plant is indigenous to India, Iran, and Egypt, but also has been introduced into the United States. 1 , 2 Bishop's weed has small white flowers and leaves that are pinnately divided in twos or threes. The fruit is harvested from February to March and is separated when dried. The oval fruits are one-seeded. The aromatic seeds are grayish-brown in color. 1 , 3
The seeds of bishop's weed traditionally have been used for GI ailments including diarrhea, dyspepsia, cholera, flatulence, and indigestion. 3 Bishop's weed is used in Ayurvedic medicine and Unani systems. 4 , 5 , 6
The fruit of bishop's weed yields 2% to 4% brownish essential oil, with thymol as the major constituent (35% to 60%). 7 It crystallizes easily and is sold in India as “flowers of Ajowan.” 3 The nonthymol fraction (thymene) contains para-cymene, γ-terpenine, α- and β-pinenes, dipentene, α-terpinene, and carvacrol. 3 Minute amounts of caphene, myrcene, and α-3-carene also have been found in the plant. Alcoholic extracts of bishop's weed contain a highly hygroscopic saponin. From the fruits, a yellow, crystalline flavone and a steroid-like substance have been isolated. The seeds also contain 6-O-β-glucopyranosyloxythymol, a glucoside. 8 Several other chemical studies have reported 69% carvacrol in T. ammi , 9 and a yield of 25% oleoresin containing 12% volatile oil (thymol, γ-terpinene, para-cymene, and α- and β-pinene) 10 . The principal oil constituents of T. ammi are carvone (46%), limonene (38%), and dillapiole (9%) 11 . The essential oil obtained by steam distillation of the fruits of T. copticum yielded thymol (61%), para-cymene (15%), and γ-terpinene (12%). 12
Uses and Pharmacology
Traditionally, bishop's weed has been used as a spice and as a preservative. The fruits (seeds) are used to flavor curries, pickles, biscuits, confections, and beverages. 8 , 10 The plant also is used in soaps and perfumes. 3 The oil, called Ajowan oil, is used in India as an antiseptic to treat nasal catarrh and as an antifungal for skin diseases. It is used as a mouthwash, gargle, or toothpaste preparation in dentistry. Bishop's weed has been used as an insecticide and anthelmintic. 3 The plant has been made into solutions, ointments, lotions, powders, and deodorants.
Ayurvedic use of bishop's weed has been to treat atrophy, cachexia, spasms, and rheumatism. Patients with fever and lung ailments, including bronchitis, the common cold, cough, consumption, and emphysema are said to benefit from bishop's weed. A paste of crushed fruit is applied on the chest for asthma and used for colic. Bishop's weed is thought to be helpful in treating several GI disorders, including diarrhea, gastrosis, dyspepsia, cholera, flatulence, and indigestion. In the Unani system of medicine, Ajowan is used as an enhancer of the body's resistance. 5Antimicrobial properties
Studies have been conducted to evaluate the antimicrobial properties of bishop's weed. In 1 study, the essential oil demonstrated in vitro activity against gram-positive and negative bacteria as well as against yeast, 13 while in another study a greater in vitro activity than 7 antibacterial drugs against clinically relevant pathogens (including Pseudomonas aeruginosa , Escherichia coli , Corynebacterium diphtheriae , and Staphylococcus aureus ). 14 Another investigation revealed antifungal properties. 15 The inhibitory effects of extracts on hepatitis C viral (HCV) protease have been reported, 16 and an aqueous extract of bishop's weed was demonstrated to have potent activity against Helicobacter pylori , even against metronidazole- and tinidazole-resistant isolates. 17Ophthalmic uses
Use of a combination preparation containing bishop's weed was evaluated for efficacy and side effects in ophthalmic conditions. The preparation was effective in acute conjunctivitis and dacrocystitis, as well as in postcataract surgery and conjunctival xerosis, with no side effects reported. 4Effects on platelets
An in vitro study with human platelets demonstrated inhibition of arachidonic acid-induced platelet aggregation by an extract of bishop's weed. The mechanism, in part, was postulated to be caused by redirection of arachidonic acid from the cyclooxygenase to the lipoxygenase pathway, reducing thromboxane B 2 formation. The same study showed antiaggregatory effects and alteration of arachidonic acid metabolism by the extract. 18Animal studies
Animal studies have shown thymol (the active principle of bishop's weed) to exert a blood pressure-lowering action, suggesting a channel-blocking mechanism and possibly explaining the hypotensive and bradycardic effects observed in in vivo studies. 19
Alcohol and aqueous extracts of bishop's weed demonstrated anti-inflammatory effects in rats, comparable with aspirin and phenylbutazone. 5
Competitive antagonism of histamine H 1 receptors has been demonstrated in guinea pig tracheal chains. A β-adrenergic stimulatory effect and anticholinergic properties of bishop's weed were suggested. 2Antidiarrheal effects
A combination preparation ( Arque-Ajeeb ) containing bishop's weed was evaluated for its antidiarrheal activity. The preparation was less effective than diphenoxylate in serotonin- and prostaglandin E2-induced diarrhea. It reduced propulsive activity in the gut in a dose-dependent manner, and reduced the number and amount of stools. 6
Studies regarding safety and efficacy in pregnancy and lactation are lacking. Avoid use.
None well documented. Consider a theoretical additive effect on inhibition of platelet aggregation. 18
Because of its ability to inhibit platelet aggregation, 18 caution is warranted in pregnancy or in those taking drugs such as warfarin or nonsteroidal anti-inflammatory drugs.
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