Scientific Name(s): Syzygium aromaticum (L.) Merr. and L.M. Perry.
Common Name(s): Caryophyllus, Clove
Clove has historically been used for its antiseptic and analgesic effects. Clove and clove oils are used safely in foods, beverages, and toothpastes. Clove oil cream has been used in the treatment of anal fissures and an extract has exhibited aphrodisiac action in rats; however, there are limited studies supporting clinical applications for clove oil.
There are limited studies to support therapeutic dosing for clove oil.
Contraindications have not been identified.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Contact dermatitis has been noted.
Toxicity has been observed following ingestion of the oil, but is rare and poorly documented.
- Myrtaceae (Myrtle)
The clove plant grows in warm climates and is cultivated commercially in Tanzania, Sumatra, the Maluku (Molucca) Islands, and South America. The tall evergreen plant grows up to 20 m and has leathery leaves. The strongly aromatic clove spice is the dried flower bud; essential oils are obtained from the buds, stems, and leaves. The dark brown buds are 12 to 22 mm in length and have 4 projecting calyx lobes. The 4 petals above the lobes fold over to form a hood, which hides numerous stamens.1, 2 Synonyms are Eugenia caryophyllata, Eugenia caryophyllus, and Caryophyllus aromaticus.
Clove has a long history of culinary and medicinal use. The oil has been used as an expectorant and antiemetic with inconsistent clinical results. Clove tea was used to relieve nausea. Use of the oil in dentistry as an analgesic and local antiseptic continues today. It also has been used topically as a counterirritant.3
Clove buds yield approximately 15% to 20% of a volatile oil that is responsible for the characteristic aroma and flavor. The stems yield approximately 5% of the oil, and the leaves yield approximately 2%. In addition, the bud contains a tannin complex, gum and resin, and a number of glucosides of sterols.
The principal constituents of distilled clove bud oil (60% to 90%) are the phenylpropanoids, including primarily eugenol (4-allyl-2-methoxyphenol) and carvacrol, thymol, and cinnamaldehyde. The oil also contains approximately 10% acetyleugenol and small quantities of gallic acid, sesquiterpenes, furfural, vanillin, and methyl-n-amyl ketone. Other constituents include flavonoids, carbohydrates, lipids, oleanolic acid, rhamnetin, and vitamins.3, 4, 5, 6, 7 Essential oil of the leaf has also been described, similarly containing eugenol, caryophyllene, humulene, and eugenyl acetate.8 Flavonoid triglycosides have been identified in the seeds, and rapid high-performance chromatographic techniques have been developed for determining phenolic acid content.9, 10
Uses and Pharmacology
Eugenol has been used extensively in dentistry for its anesthetic and antianaerobic bacteria activity.3, 11 The short duration of effect has been used in anesthesia of fish, such as the rainbow trout, channel catfish, and zebra fish.3, 12
Clove oil gel (2:3 vol/vol with glycerin) performed as well as benzocaine gel in an experiment evaluating effect on induced pain in the buccal mucosa.13
In vitro studies demonstrate activity of clove oil against gram-positive and gram-negative bacteria pathogenic to humans, including multiresistant strains.3, 14, 15, 16 Activity against listeria in pasteurized milk has been demonstrated17 as well as antifungal action in vitro against Candida, Aspergillus, and Trichophyton species.15, 16, 18, 19 The leaf extract was found to have a minimal inhibitory concentration (MIC) of 50 mcg/mL against Helicobacter pylori. Amoxicillin (MIC range, 0.0039 to 0.25 mcg/mL) and metronidazole (MIC range, 64 to 124 mcg/mL) were used as controls.49 Experimentation in H. pylori-infected gastric epithelial cells with 24 medicinal plants indigenous to Pakistan was conducted to evaluate their effect on secretion of interleukin (IL)-8 and generation of reactive oxygen species (ROS) in order to assess anti-inflammatory and cytoprotective effects. Although no significant direct cytotoxic effects on the gastric cells or bactericidal effects on H. pylori were found, clove was observed to have strong inhibitory activity on IL-8 at 50 and 100 mcg/mL in H. pylori-infected gastric cells.50 Antiviral activity against herpes simplex and hepatitis C virus has also occurred.3
Mice with induced pneumonia showed a decrease in bacterial colonization when fed clove oil for 15 days.20 Clove oil has been proposed for use in cat and dog ear infections based on in vitro studies.21
In vitro studies have shown antibacterial action against gram-negative anaerobes responsible for acne.22
Whole cloves were chemoprotective against liver and bone marrow toxicity in mice.25 In mice with induced lung cancer, an oral aqueous preparation of whole clove decreased cell proliferation and increased apoptosis.26
There are no clinical evaluations of clove; however, activity against human cancer cell lines has been demonstrated.3
The use of 1% clove oil cream resulted in significantly greater healing rates than 5% lignocaine in a small study of anal fissures.27
Clove oil possesses mosquito repellant and other insecticidal activity.3, 32 Eugenol possesses marked antipyretic activity in animals, similar to that of acetaminophen. Enhanced transdermal delivery of ibuprofen by clove oil has been demonstrated in rabbits.33 Anti-inflammatory activity has been demonstrated in macrophages of mice fed aqueous clove extract.34, 35
There are limited studies supporting clinical applications for clove oil.
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. In a toxicological experiment, clove added to the diet of pregnant mice for 2 weeks resulted in increases in cell death. No effects on pregnant adult mice were noted.36
Clove has been reported to have antiplatelet effects; however, case reports are lacking.37, 38, 39 The following are possible based on pharmacologic activity of clove or its ingredients: additive effects of analgesics; anticoagulant medications (including warfarin), aspirin or aspirin-containing products, NSAIDs, or antiplatelet agents (eg, ticlopidine, clopidogrel, dipyridamole).
Clove oil can be a skin and mucous membrane irritant and sensitizer; contact dermatitis has been noted.7, 40 A woman 24 years of age reported permanent local anesthesia and anhidrosis following clove oil spillage onto the facial area.41 Use eugenol, a constituent of clove, with caution in individuals with a history of bleeding, hemostatic disorders, or drug-related hemostatic problems.42, 43
Clove and clove oils are used safely in foods, beverages, and toothpastes. In general, the level of clove used in foods does not exceed 0.24%; the oil is not used in amounts greater than 0.06%. Toxicity has been observed following ingestion of the oil but is rare and poorly documented.44, 45 There is no documentation of toxicity in the bud, leaf, or stem of the plant.7
In rats, the oral median lethal dose (LD50) of eugenol is 2,680 mg/kg; however, the toxicity of the compound increases almost 200-fold when administered intratracheally (LD50 11 mg/kg).46
Increased toxicity by the pulmonary route has been reported among people who have smoked clove cigarettes. Clove cigarettes, called "kreteks," generally contain about 60% tobacco and 40% ground cloves.47, 48
- Caryophyllus aromaticus
- Eugenia caryophyllata
- Eugenia caryophyllus
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