Scientific Name(s): Trachyspermum ammi L. Sprague.
Common Name(s): Ajava seeds, Ajowan caraway, Ajowan seed, Ajowanj, Ajwain, Bishop's weed, Carum, Omum., Yavani
Medically reviewed by Drugs.com. Last updated on Dec 30, 2020.
High quality clinical trials are very limited. The medical literature documents numerous pharmacological activities including analgesia (neuropathic), antifungal, antimicrobial, hypolipidemic, antihypertensive, antilithiasis, abortifacient, antitussive, nematicidal, anthelmintic, and antifilarial.
Bishop's weed is commercially available as a single entity or herbal blend in numerous dosage forms including capsules, liquids, powders, and cream. Internet sources list the product as being primarily marketed as "ajwain" and as an overall panacea. One herbal blend prescribes 1 or 2 capsules (200 mg/capsule) with a full glass of water for GI discomfort. The prescription drug methoxsalen, as documented by various Internet resources, was developed from bishop's weed (Ammi majus Linn) and is used to treat several skin conditions. Use of a 10% topical cream twice daily has been supported by a clinical trial in adults with neuropathic pain.
Hypersensitivity to any of the components of bishop's weed. Avoid use during pregnancy and lactation due to documented adverse effects.
Avoid use. Documented adverse effects. Bishop's weed was listed as 1 of 14 indigenous medicinal plants used for abortion in some districts of India in 1987, and it may also cause congenital defects. The same review article also documents a risk of human fetotoxicity as observed in rat teratogenicity studies.
Data are lacking concerning specific drug interactions. Potentiation of the effects of antibiotics and antiplatelet medications could be theorized.
Caution may be warranted in patients taking nonsteroidal anti-inflammatory drugs (NSAIDs) or antiplatelet medications due to platelet aggregation inhibition by bishop's weed.
Bishop's weed is toxic in high doses and can result in fatal poisoning. Avoid use during pregnancy due to documented adverse effects.
- Apiaceae (carrot)
Bishop's weed is a smooth, or slightly hairy, branched annual growing 60 to 90 cm tall. The stem is striated, containing up to 16 small, white flowers, and the leaves are pinnately divided with a terminal and 7 pairs of adjacent leaflets. The grayish-brown, ovoid, aromatic fruit is 2 mm long and 1.7 mm wide. The fruit is harvested from February to March and is separated when dried. The plant is indigenous to India, Iran, Egypt, Afghanistan, and Ethiopia. It is widely grown in arid and semiarid areas, particularly where the soil contains high levels of salt.1, 2, 3 The scientific name is synonymous with Carum copticum (L.) Benth., Ammi copticum L. and Hook. f. and Trachyspermum copticum (L.) Link.1
Bishop's weed has been used for curing numerous diseases in humans and animals,2 and it is used in Ayurvedic and Unani medical systems.4, 5, 6, 7 Ayurvedic use of bishop's weed includes treatment of atrophy, cachexia, spasms, and rheumatism. Patients diagnosed with fever and lung ailments, including bronchitis, the common cold, cough, consumption, and emphysema have also benefited from treatment with bishop's weed. To treat asthma, a paste of crushed fruit is applied on the chest. The paste is also used for colic. Bishop's weed may be helpful in treating several GI disorders, including diarrhea, gastrosis, atonic dyspepsia, cholera, flatulence, and indigestion. In the Unani system, the plant is used to enhance the body's immune system.2, 5 The fruit has stimulant, antispasmodic, and carminative properties.6 The plant has also been used to treat abdominal tumors and hemorrhoids.2 The seeds are bitter and pungent, and have carminative and laxative properties. They have been used in folk medicine to remove systemic helminth infections in humans and domestic animals.8
Traditionally, bishop's weed has been used as a spice and as a preservative. It is used as a commercial product in the food and flavoring industries.9 The fruits are used to flavor curries, pickles, biscuits, confections, and beverages.10, 11 The plant is used in soaps and perfumes and has several applications in aromatherapy dating to ancient times.4, 12 Ajwain oil, which is found in the seeds, is used in India as an antiseptic to treat nasal catarrh and as an antifungal for skin diseases. It is also used as a mouthwash, gargle, or toothpaste preparation in dentistry. Bishop's weed has been used as an insecticide and anthelmintic.4 The plant has been made into solutions, ointments, lotions, powders, and deodorants.
The seeds of bishop's weed contain 2% to 4.4% brownish-colored oil, which is known as ajwain oil.2 The major constituent of the oil is thymol (35% to 60%).13 It crystallizes easily and is sold in India as "flowers of Ajowan."4 The seeds also contain fiber (11.9%), carbohydrates (38.6%), tannins, glycosides, moisture (8.9%), protein (15.4%), fat (18.1%), saponins, flavone, and mineral matter (7.1%) containing calcium, phosphorous, iron, and nicotinic acid.2, 13 The nonthymol fraction (thymene) contains para-cymene, gamma-terpenine, alpha- and beta-pinenes, dipentene, alpha-terpinene, and carvacrol.4 Minute amounts of caphene, myrcene, and alpha-3-carene also have been found in the plant. Alcoholic extracts 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-beta-glucopyranosyloxythymol, a glucoside.10 Several other chemical studies have reported 69% carvacrol in bishop's weed14 and a yield of 25% oleoresin containing 12% volatile oil (thymol, gamma-terpinene, para-cymene, and alpha- and beta-pinene).10 The principal oil constituents of bishop's weed are carvone (46%), limonene (38%), and dillapiole (9%).15 The essential oil obtained by steam distillation of the fruits of Trachyspermum copticum yielded thymol (61%), para-cymene (15%), and gamma-terpinene (12%).16
Uses and Pharmacology
Clinical studies are limited. However, the medical literature documents numerous pharmacological activities for bishop's weed including antifungal,17 antimicrobial,18 hypolipidemic,2 antihypertensive,19, 20 antilithiasis,21 abortifacient,2 antitussive,22 nematicidal,23, 24 anthelmintic,2 and antifilarial.2
In a double-blind, randomized, placebo-controlled trial (n=92), the effect of topical T. ammi 10% cream on neuropathic pain was investigated in adults with moderate to severe neuropathic pain. Burning feet was the main complaint and diagnoses included diabetic neuropathy, postsurgical or posttraumatic neuropathic pain, or neuropathic pain for at least 6 months. The essential oil of Ajwain seeds was extracted and compounded into a 10% cream that was applied twice daily for 28 days. The mean changes in absolute pain scores for feet burning (−3.55 vs −0.76), numbness (−0.58 vs −0.11), allodynia (−0.64 vs −0.06), and tingling (−1.69 vs −0.16) were all significantly greater in the Ajwain group versus placebo, respectively (P<0.001, P=0.011, P=0.023, P<0.001, respectively). No adverse effects were reported by patients in either group.48
Dietary administration of 2%, 4%, and 6% bishop's weed reduced skin tumor multiplicity, but not the incidence of skin tumors, in an induced skin papillomagenesis model.34 However, dietary administration of 2%, 4%, and 6% bishop's weed inhibited both tumor multiplicity and incidence in an induced forestomach papillomagenesis model. The difference in the anticancer activity may be related to bioavailability and the actual dose.
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.7
Bishop's weed fruit methanolic extracts exhibited significant in vitro activity against worm motility in adult bovine Setaria digitata worms. The active chemical component is believed to be thymol. The extracts exhibited significant in vivo activity for adult worm mortality and female worm sterility for the human filarial worm Brugia malayi.35 The antiparasitic activity of bishop's weed fruit essential oils at a concentration of 5 mg/mL (60 min) or 10 mg/mL (10 min) was comparable with 20% hypertonic saline (15 min), 20% silver nitrate (20 min), 0.5% to 1% cetrimide (10 min), and 95% ethyl alcohol (15 min).36
One review article documents activity against Ascaris lumbricoides in humans and Haemonchus contortus in sheep.2
Animal studies have shown thymol (the active principle of bishop's weed) exerting a blood pressure–lowering action, suggesting a channel-blocking mechanism and possibly explaining the hypotensive and bradycardic effects observed in in vivo studies.19 The mechanism of action may be associated with a calcium channel blockade.20
Alcohol and aqueous extracts of bishop's weed demonstrated anti-inflammatory effects in rats comparable with aspirin and phenylbutazone.6 Competitive antagonism of histamine H1 receptors has been demonstrated in guinea pig tracheal chains.37 The mechanism of action is associated with carvacrol and not due to anticholinergic or beta-adrenergic stimulatory effects.38
In vitro data
Antimicrobial properties of the essential oil demonstrated in vitro activity against gram-positive and gram-negative bacteria as well as against yeast,25 while in another study an in vitro activity greater than 7 antibacterial drugs against clinically relevant pathogens (including Pseudomonas aeruginosa, Escherichia coli, Corynebacterium diphtheriae, and Staphylococcus aureus).18 Another study documents antibacterial activity for hot water and acetone bishop's seed extracts against several gram-positive and -negative bacteria, except for Klebsiella pneumonia and 1 strain of P. aeruginosa.26, 27 The seeds inhibited dental caries by reducing the biofilm properties of S. mutans.9 The anticariogenic activity may be associated with the sterols, terpenes, fatty acids, and their derivatives in the petroleum ether fraction.
Another investigation revealed antifungal properties.28 The antifungal activity for bishop's seed on 10 fungi (Acrophialophora fusispora, Curvularia lunata, Fusarium chlamydosporum, Fusarium poae, Myrothecium roridum, Papulaspora sp., Alternaria grisea, Alternatia tenuissima, Drechslera tetramera, and Rhizoctonia solani) was tested and resulted in 72% to 90% growth inhibition of all test fungi.2 The essential oil exhibited a broad spectrum of antifungal activity against all tested fungi including Aspergillus niger, Aspergillus flavus, Aspergillus oryzae, Aspergillus ochraceus, Fusarium monoliforme, Fusarium graminearum, Pencillium citrium, Penicillium viridicatum, Pencillium madriti, and Curvularia lunata.17 Bishop's weed essential oil exhibited no inhibition or antifungal activity against Trichosporon ovoides, which may cause a fungal infection of the hair shaft.29
Several studies examine the antimicrobial actions of the essential oils and extracts of bishop's weed against food-borne and spoilage bacteria.12, 30, 31 Bishop's weed fruit oil exhibited potential antimicrobial activity against S. aureus, Bacillus subtilis, P. aeruginosa, Salmonella typhimurium, E. coli, Enterobacter aerogenes, and Salmonella enteritidis.12 The thymol (49.64%), b-cymene (16.33%), eugenol (3.04%), and b-pinene (2.51%) content in the oil may contribute to the antimicrobial activity. A bishop's seed extract versus tea leaf extract showed greater antimicrobial activity against the growth of food-borne Salmonella isolates.30
The inhibitory effects of extracts32 on hepatitis C viral (HCV) protease have been reported and an aqueous extract of bishop's weed was demonstrated to have potent activity against Helicobacter pylori, even against metronidazole- and tinidazole-resistant isolates.33
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 B2 formation. The same study showed antiaggregatory effects and alteration of arachidonic acid metabolism by the extract.39
The antitussive effects of aerosols using 2 different concentrations of aqueous and macerated bishop's weed extracts and carvacrol, codeine, and saline were tested in guinea pigs. The results documented a reduction in the number of coughs obtained with both concentrations of aqueous and macerated bishop's weed extracts and codeine (P < 0.001 for extracts and P < 0.01 for codeine). The antitussive effect was not associated with the main constituent carvacrol.22
Detoxification of aflatoxins
The seed extract of bishop's weed degraded and detoxified aflatoxin G1 up to 65%.40 The dialyzed extract was more effective degrading more than 90% of the toxin. Aflatoxins are highly toxic and carcinogenic to several animal species.
A C. copticum seed extract given at 500 mg/kg orally for 2 days at 12-hour intervals protected rats from paracetamol 640 mg/kg and carbon tetrachloride or CCl4 150 mL/kg–induced rise in serum alkaline phosphatase and aminotransferases. The hepatoprotective activity was confirmed in mice with the same dose of seed extract preventing CCl4–induced prolongation in pentobarbital-induced sleeping time.20 Antioxidant activity may be a mechanism of action as documented by the protective effects of bishop's weed extract on hexachlorocyclohexane-induced oxidative stress and toxicity in rats.41
A review article documents how a dose of bishop's weed 2 g/kg powder and its equivalent methanol extract reduced total cholesterol, LDL-cholesterol, triglycerides, and total lipids in albino rabbits.2
The pinewood nematode Bursaphelenchus xylophilus, which is responsible for pine wilt disease, causes substantial ecological and economical damage in Korean forests. Bishop's weed essential oils have nematicidal activities against the pinewood nematode. The exact mechanism of action is unclear.23, 24
A combination preparation containing bishop's weed was evaluated for efficacy and adverse reactions in ophthalmic conditions. The preparation was effective in acute conjunctivitis and dacrocystitis, as well as in postcataract surgery and conjunctival xerosis, with no adverse reactions reported.5
Bishop's weed essential oils have insecticidal activity against Japanese termites.45
A combined herbal extract containing bishop's weed seeds inhibited the developmental stages of Rhipicephalus (Boophilus) microplus, the common cattle tick, which is capable of transmitting viral diseases and can cause anemia in cattle.46
Bishop's weed contains an anticalcifying protein that helped maintain renal function, reduced renal injury by inhibiting calcium oxalate monohydrate crystal size and adhesion, and decreased crystal excretion in urine in rats.21
Bishop's weed is commercially available as a single entity or herbal blend in numerous dosage forms including capsules, liquids, and powders. Internet sources list the product primarily marketed as "ajwain" and as an overall panacea. One herbal blend prescribes 1 or 2 capsules (200 mg/capsule) with a full glass of water for GI discomfort. The prescription drug methoxsalen, as documented by various Internet resources, was developed from bishop's weed (Ammi majus Linn) and is used to treat several skin conditions. Use of a 10% topical cream twice daily has been supported by a clinical trial in adults with neuropathic pain.48
Pregnancy / Lactation
Avoid use. Documented adverse effects. Avoid use. Bishop's weed was listed as 1 of 14 indigenous medicinal plants used for abortion in some districts of India in 1987 and it may also cause congenital defects. A risk of human fetotoxicity was documented as observed in rat teratogenicity studies.2
Data are lacking concerning specific drug interactions. Potentiation of the effects of antibiotics and antiplatelet medications39 could be theorized.
Caution may be warranted in patients taking NSAIDS or antiplatelet medications due to platelet aggregation inhibition by bishop's weed.39
Bishop's weed is toxic in high doses and can result in fatal poisoning.10 The essential oils isolated from bishop's weed seeds showed cytotoxic activity against P388 mouse leukemia cells.47 Avoid use during pregnancy due to documented adverse effects.2
- Ammi copticum L. and Hook. f.
- Carum copticum (L.) Benth.
- Trachyspermum copticum (L.) Link.
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