Syzygium – Clove (Caryophylii flos)
|Latin name of the genus:||Syzygium|
|Latin name of herbal substance:||Caryophylii flos|
|Botanical name of plant:||Syzygium aromaticum (l.) merill et l. m. perry|
|English common name of herbal substance:||Clove|
Latin name of the genus: Syzygium
Latin name of herbal substance: Caryophylii flos
Botanical name of plant: Syzygium aromaticum (L.) Merill et L. M. Perry
English common name of herbal substance: Clove
- 1. Introduction
- 2. Historical data on medicinal use
- 3. Non-Clinical Data
- 3.1. Overview of available pharmacological data regarding the herbal substance(s), herbal preparation(s) and relevant constituents thereof
- 3.2. Overview of available pharmacokinetic data regarding the herbal substance(s), herbal preparation(s) and relevant constituents thereof
- 3.3. Overview of available toxicological data regarding the herbal substance(s)/herbal preparation(s) and constituents thereof
- 3.4. Overall conclusions on non-clinical data
- 4. Clinical Data
- 4.1. Clinical Pharmacology
- 4.1.1. Overview of pharmacodynamic data regarding the herbal substance(s)/preparation(s) including data on relevant constituents
- 4.1.2. Overview of pharmacokinetic data regarding the herbal substance(s)/preparation(s) including data on relevant constituents
- 4.2. Clinical Efficacy
- 4.2.1. Dose response studies
- 4.2.2. Clinical studies (case studies and clinical trials)
- 4.2.3. Clinical studies in special populations (e.g. elderly and children)
- 4.3. Overall conclusions on clinical pharmacology and efficacy
- 5. Clinical Safety/Pharmacovigilance
- 6. Overall conclusions
1.1. Description of the herbal substance(s), herbal preparation(s) or combinations thereof
According to the European Pharmacopoeia (1/2008: 1091), Caryophylli flos consists of the whole flower buds of Syzygium aromaticum (L.) Merill et L.M. Perry (Syn. Eugenia caryophyllus (C. Spreng.) Bull. et Harr.) which were dried until they become
According to the International Plant Names Index, which is the electronic version of the Index Kewensis, the correct spelling of the author should be ‘Merrill’ (abbr. Merr.) after Elmer Drew Merrill
Constituents (according to Blaschek et al 2008):
Further components: chavicol, (Z)- and
Alcohols: benzyl alcohol.
Flavones: quercetin, kaempferol, kaempferid, rhamnetin,
Tannins: ellagitannins, including eugeniine.
Phenolic acids: gallic- and ellagic acid, 3- and
Triterpenes: oleanolic acid, crataegolic acid.
Sugars: glucose, xylose, arabinose.
According to the European Pharmacopoeia (1/2008: 1091) Caryophylli floris aetheroleum is obtained by steam distillation from the dried flower buds of Syzygium aromaticum (L.) Merill et L.M. Perry.
Composition (according to Blaschek et al 2008, Chaieb et al 2007):
Three main components account for nearly 99% of the essential oil: eugenol
Further components: chavicol, (Z)- and
Methyleugenol is not reported for clove oil (De Vincenzi et al 2000).
Combinations of herbal substance(s) and/or herbal preparation(s) including a description of vitamin(s) and/or mineral(s) as ingredients of traditional combination herbal medicinal products assessed, where applicable.
This assessment refers only to Caryophylli flos and Caryophylli floris aetheroleum.
1.2. Information about products on the market in the Member States
Regulatory status overview
This regulatory overview is not legally binding and does not necessarily reflect the legal status of the products in the MSs concerned.
1.3. Search and assessment methodology
Search terms: Syzygium aromaticum, Gewürznelke, Caryophylli flos, eugenol.
Databases: Pubmed and Toxnet.
Libraries: University Vienna, centre of pharmacy; Medical University Vienna, central library.
2. Historical data on medicinal use
2.1. Information on period of medicinal use in the Community
The medicinal use of Caryophylli flos can be traced in literature back to the 13th century (cited in Benedum et al 2006), it is also mentioned by Matthiolus and Lonicerus in the 17th century (cited in Benedum et al 2006).
Caryophylli flos has been in therapeutic use for many decades. However, there are no reports of any medicinal product containing cloves. Other information available on the medicinal use is considered insufficient to establish a Community herbal monograph.
The medicinal use of Caryophylli floris aetheroleum can be traced in literature back to the 15th century (according to Gildemeister & Hoffmann 1899). It is also mentioned by Schröder and Vietz in the 17th and 18th century (cited in Benedum et al 2006). The essential oil is the only active substance of several authorised medicinal products in UK. Although the SmPCs of these medicinal products state authorisation dates back to 1988, most of them were in medicinal use prior to 1980, according to information provided by the UK national authority MHRA. Moreover, the evidence on traditional medicinal use is supported by a large number of publications providing consistent information.
Therefore for Caryophylli floris aetheroleum, a period of at least 30 years in medicinal use as requested by Directive 2004/24 EC for qualification as a traditional herbal medicinal product is fulfilled.
Type of tradition: European.
2.2. Information on traditional/current indications and specified substances/preparations
Caryophylli flos is traditionally used as spice such as for gingerbread flavouring. Many spice blends, including curry contain powdered cloves, most herb liqueurs and bitter liqueurs contain clove macerates (Blaschek et al 2008).
Clove has been traditionally used in dyspeptic complaints, flatulence and diarrhoea as a decoction (Blaschek et al 2008).
Caryophylli floris aetheroleum has been traditionally used externally or locally for the treatment of toothache and minor infections of the mouth and skin, dressing of minor wounds, sore throats and coughs associated with the common cold, myalgia, rheumatic complaints, insect bites, flatulent colic or nausea (Blaschek et al 2008, WHO Monographs 2002, Koch 1953, Dingermann et al 2004, Barnes et al 2002, Frerichs et al 1938).
The German commission E proposes the use of the essential oil for treatment of inflammations of the oral and pharyngeal mucosa and in dentistry for topical anaesthesia (German commission E in Blumenthal et al 1998).
Caryophylli floris aetheroleum or eugenol alone is widely used in dentistry mixed with zinc oxide as temporary filling material (Blaschek et al 2008).
The high content of eugenol makes the medicinal use in the proposed indication plausible.
2.3. Specified strength/posology/route of administration/duration of use for relevant preparations and indications
Children between 1 and 4 years of age: a strength of
Children between 4 and 12 years of age and adolescents: a strength of
Duration of use
According to the SmPCs of UK medicinal products: The relief of toothache by clove essential oil is only a provisional measure. Dental attention should be sought as soon as possible. Repeat administration after 20 minutes, then every 2 hours thereafter if necessary.
Method of administration
According to the SmPCs of UK medicinal products: A small piece of cotton wool should be soaked in the undiluted oil or in a diluted solution; semisolid dosage forms should be placed on a cotton bud. Cotton bud or cotton wool should be accurately directed to the decayed part of the tooth. Avoid contact with gums.
Assessor’s comment on data on traditional use
Traditional use of Caryophylli flos:
Although there are consistent data on a traditional use of cloves for the short term suppression of toothache, the development of a community monograph does not seem appropriate because clove for such use will be taken from food and not from medicinal products. Moreover, there are no reports on medicinal products containing cloves as an only active ingredient.
Traditional use of Caryophylli aetheroleum:
The analgesic and antimicrobial properties of clove oil, as described below, make the dental and oromucosal use plausible. Traditional use for more than 30 years is documented. Adequate tests on reproductive toxicity, genotoxicity and carcinogenicity of clove oil have not been performed, however experimental data on genotoxicity suggest that the main constituent of clove oil, eugenol, might be harmful.
Use of eugenol in dentistry:
Eugenol can be part of temporary pulp fillings in dentistry. Eugenol is mixed with zinc oxide, giving a paste which hardens quickly when coming into contact with saliva. This special application is not within the scope of a Community herbal monograph and will therefore not be further discussed.
3.1. Overview of available pharmacological data regarding the herbal substance(s), herbal preparation(s) and relevant constituents thereof
Effects of Caryophylli flos
Antiseptic, antibacterial, antifungal, antiviral, local anaesthetic and spasmolytic effects are attributed to the drug. This information is only partially covered by experimental work (Blaschek et al 2008).
The addition of 1 g clove powder to 9 ml culture medium inhibited the growth of Aspergillus flavus, A. ocharceus and A. versicolor totally (Hikoto et al 1980 cited in Blaschek et al 2008). A methanolic extract from cloves demonstrated preferential antimicrobial activity against the periodontal pathogens
Prevotella intermedia and Porphyromonas gingivalis with MICs of 156 and 625 µg/ml (Cai & Wu 1996). An extract prepared with methanol 70% showed antibacterial activity against 32 strains of S. aureus (Betoni et al 2006).
Taguchi et al (2005) studied the effect of a suspension of clove powder in water on oral and intestinal candidiasis in mice. When the preparation was administered into the oral cavity, the oral symptoms improved and the number of viable Candida cells in the cavity was reduced. After intragastric administration, the oral symptoms did not improve, but viable Candida cells in the stomach and faeces were decreased.
Eugeniine isolated from cloves by solvent distribution and multiple column chromatography (yield 82 mg/50g drug) inhibits in vitro in
Kurokawa et al (1998) studied the effects of eugeniine on Herpes simplex
The combination of hot water clove extract with acyclovir had a stronger anti
The effect of clove aqueus infusion was very pronounced (p < 0.01) on the incidence of Carcinoma in situ (CIS). The infusion was administered at a dose of 100 µl/mouse/day. While 70% of benzopyrene- exposed animals (Newborn Strain A mice) had CIS, after treatment with clove infusion, only 10% animals showed CIS, indicating 85.71% inhibition after such treatment. Incidence of hyperplasia and dysplasia evident in the carcinogen control group were effectively reduced after treatment with clove infusion. Significant reduction in the number of proliferating cells and an increased number of apoptotic cells was also noted in these
The toxicity of
Two different polysaccharides with rhamnogalacturan backbone and arabinan side chain were isolated which exhibit antithrombotic activity. After intravenous application of the low molecular weight polysaccharide (MW 34.000) in doses up to 1000 mg/kg body weight in mice, no signs of acute toxicity were observed, while the high molecular weight polysaccharide (MW 103.000) exhibited approximately half the toxicity of heparin (LD50 322 mg/kg) (Lee et al 2001).
Kim et al (1998) investigated the effect of a hot water extract (DER app. 14:1) of clove on the immediate hypersensitivity in rats. The extract inhibited the compound
17.78 mg/kg, i.v., IC50 = 19.81 mg/kg, p.o.). The extract also inhibited
A decoction (0.1%) of clove reduced NO levels by 57.2%, in comparison with the control value at a concentration of 250 µg/ml. The scavenging effects were
A decoction (10%) of clove exhibited antioxidative effects on the lipid peroxidation and protein oxidative modification of mice brain homogenate produced by copper in vitro (Toda 2001, Toda 2003).
Effects on the
Agbaje (2008) investigated a hot aqueous extract using selected doses in the various study models. The effect of the decoction on intestinal propulsion was studied by administering 300 and 700 mg/kg extract to groups of overnight fasted mice, while using charcoal meal as a marker. The effect of the herbal drug was compared with other standard drugs and antagonists. In an identical design the same doses of the extract were administered orally to groups of overnight fasted rats prior to challenge with different necrotizing
Tajuddin et al (2003, 2004) studied the effect of an extract of clove prepared with ethanol 50% on the sexual behaviour of male rats. After oral administration of 100, 250 and 500 mg/kg extract, a
significant and sustained increase in sexual activity was observed. The highest effect was achieved with the dose of 500 mg/kg.
Male 7 to 8 weeks old
A methanol extract from cloves is said to induce the differentiation of
The toxic effect of cloves on Culex pipiens larvae, the common European mosquito, was investigated by El Hag et al (1999). The LC50 for the methanol extract was 824.7 ppm (assay time: 6 days) and the LC50 for the ethanol extract was 921.3 ppm (assay time: 6 days). The highest mortality (70%) was obtained in the 1000 ppm concentration after 10 days.
Effects of Caryophylli floris aetheroleum
Due to a high content of eugenol in Caryophylli floris aetheroleum, the effects of eugenol are often extrapolated to the entire essential oil.
Intrathecal treatment of mice with eugenol (12.5 to 50 µg) for 24 hours,
Eugenol inhibited the NO production in a
1 µg/ml lipopolysaccharide for 24 hours. Isoeugenol was more effective.
Mice received 20 mg of isolated sesquiterpenes once every 2 days. The sesquiterpenes ß-
The majority of publications on pharmacological effects of clove, clove essential oil and eugenol deal with the antimicrobial effects. Only some selected references are cited below:
Eugenol (1 mg/ml) showed pronounced antibacterial properties against Gram+ as well as against Gram- microorganisms comparable with 500 µg/ml neomycin (Laekeman et al 1990). Growth inhibition was even more pronounced for Candida species in comparison with nystatin (5000 U/ml).
0.4% clove oil in 63% sugar syrup inactivated after
The effect of
Clove oil was superior to rosemary oil when tested against several
In an investigation of various aromatic waters, clove
Mycobacterium phlei 1:640 and for Staphylococcus aureus 1:160 or 1:320. The minimal fungicidal dilution was 1:320 in case of Aspergillus niger, for Penicillium chrysogenum 1:40 and for Mucor,
Rhizopus and Candida albicans for each 1:20. The results in the agar diffusion test differ in part from that in the serial dilution test (Yousef & Tawil 1980).
Ali et al (2005) found that eugenol inhibits the growth of 30 Helicobacter pylori strains tested, at a concentration of 2µ/ml after 9 and 12 h of incubation. A lower
Dorman & Deans (2000) tested the antibacterial activity of the essential oil of S. aromaticum in 25 bacteria. The results suggest that the essential oil is equally effective against both
Saini et al (2009) investigated the effect of orally administered essential oil on respiratory tract infections with Klebsiella pneumoniae in rats. The daily oral supplementation was 0.5 ml of a 1% w/v solution. The comparison of short term (15 days) and long term (30 days) treatment resulted in a significantly lower bacterial load in the lungs of mice fed clove oil for 30 days. The authors stated also a significant decrease of bacterial colonization already after 15 days.
Khan et al (2009) studied the influence of clove oil and of eugenol on quorum sensing (QS = mechanism by which bacterial populations coordinate the expression according to the density of the
local population) regulated functions in bacteria. The production of violacein by Chromobacterium violaceum is
The swarming motility in Pseudomonas aeruginosa which is also
The antibacterial activity of eugenol may be due to an interaction of eugenol with the bacterial cell membrane (Devi et al 2010). The membrane is disrupted and macromolecules of the membrane are deformed.
The antifungal activity of clove essential oil against Aspergillus section Flavi was evaluated in sterile maize grain. The effect of the essential oil added to maize grains on growth rate, lag phase and aflatoxin B1 (AFB1) accumulation of Aspergillus section Flavi were evaluated at different water activity conditions (a measure for water content; 0.982; 0.955; and 0.90). The essential oil had an inhibitory effect on Aspergillus section Flavi growth rate; the efficacy depended mainly on the water activity and concentration. Clove essential oil showed a considerable inhibitory effect on the AFB1 accumulation. When the water activity was 0.982, the AFB1 inhibition percentage for all aflatoxigenic strains exceeded 98% at all clove essential oil concentrations (Bluma & Etcheverry 2008).
The antifungal effect of clove oil was tested against several dermatophytes using the agar diffusion method (Park et al 2007). Hyphal growth was completely inhibited in Trichophyton mentagrophytes, T. rubrum and Microsporum gypseum in concentrations of 0.2 mg clove oil per ml. Eugenol was found to be the most effective compound against T mentagrophytes and M. canis.
The composition and antifungal activity of clove essential oil were tested by Pinto et al (2009). MICs, determined according to Clinical and Laboratory Standards Institute protocols, and minimum fungicidal concentration were used to evaluate the antifungal activity of the clove oil and its main component eugenol, against Candida, Aspergillus clinical isolates (e.g. American Type Culture Collection strains). The essential oil and eugenol showed inhibitory activity against all the tested strains. Propidium iodide rapidly penetrated the majority of the yeast cells when the cells were treated with concentrations just over the MICs. Therefore the fungicidal effect may result from extensive lesions of the cell membrane. Clove oil and eugenol also caused a considerable reduction in the quantity of ergosterol, a specific fungal cell membrane component. Germ tube formation by Candida albicans was completely or almost completely inhibited by the essential oil and eugenol concentrations below the MIC values. The authors conclude that the results indicate that clove oil and eugenol have considerable antifungal activity against clinically relevant fungi, including
Eugenol significantly reduced the number of colony forming units sampled from the oral cavity of immunosuppressed rats treated for 8 days. Eugenol was used in a concentration of 24 mM (= double MIC) in agar solution. Nystatin was used as a poisitive control in a concentration of 58 µM (= tenfold MIC). Eugenol and nystatin gave similar results. Only few zones were occupied by hyphae with eugenol, while under nystatin hyphae were found in the folds of the tongue mucosa (Chami et al 2004).
There was a significant reduction of colony counts in a prophylactic approach and a treatment approach in cases of vaginal candidiasis in an immunosuppressed rat model. The rats received 10 mg/kg/day eugenol via an intravaginal route (Chami et al 2004a).
Lee et al (2007) evaluated the antifungal effect of eugenol against skin lesions in guinea pigs infected with Microsporum gypseum. Eugenol was adjusted to 10% concentration with a base of vaseline petroleum jelly and was applied topically to the skin lesions daily for 3 weeks. Eugenol was clinically active.
For eugenol no significant antiviral activity against herpes simplex virus type 1 was found in vitro using the plaque reduction assay (Astani et al 2009).
A saturated aqueous solution of clove oil was active in vitro on isolated organs against various spasmogenes: rat/duodenum/acetylcholine: 20 to 40% inhibition; rat/duodenum/barium chloride: 40 to 60% inhibition;
Clove oil antagonized in vitro the
Eugenol relaxes the rabbit thoracic aorta while suppressing the Ca2+ sensitivity and both the uptake and extrusion mechanisms for Ca2+ (Nishijima et al 1999).
Effect on coagulation:
Clove oil inhibited in vitro the platelet aggregation which was induced by arachidonic acid, epinephrine and collagen. The formation of thromboxane B2 induced by arachidonic acid was inhibited in intact and in lysed platelet preparations. The effect, which exceeds the in vitro effect of acetylsalicylic acid, might be attributed to eugenol and eugenyl acetate. The combination of these compounds inhibits the platelet aggregation in a superadditive manner (Srivastava 1987, 1993).
The IC50 of eugenol (3.0
Eugenol and isoeugenol inhibit the arachidonic acid (1 x
Effect on prostaglandin synthesis:
The addition of 37 µM clove oil to in vitro preparations from sheep seminal vesicles inhibits (based on average molecular weight of 200) the prostaglandin synthesis from
Eugenol and its derivatives are inhibitors of
Wagner & Sprinkmeyer (1973 cited in Blaschek et al 2008) investigated the sedative effect of clove essential oil. Mice received 1 to 100 mg/kg p. o. The motility in the photocell cage was compared with the results of the day before (without treatment). The authors observed a non
Clove oil inactivated in vitro Trichomonas vaginalis in a dose- and
Treatment of epimastigotes of Trypanosoma cruzi with different concentrations of clove essential oil resulted in a
Effect as repellent:
In a study by Eamsobhana et al (2009) commercially produced essential oils of 13 plant species and ethanol (control) were tested for repellent activity against
Miyazawa & Hisama (2003) identified dehydrodieugenol and
Antigenotoxic effects of eugenol were assessed in the mouse bone marrow micronucleus test by Abraham (2001). The test doses of eugenol were administered to mice by gavage 2 and 20 hours before exposure to the genotoxic agent. A
High doses (0.05% clove oil; 2.50 mM eugenol) of the essential oil and its components into culture media already markedly increased the percentage of both necrotic and apoptotic cells after 1 hour (clove oil: 18.04%; eugenol: 21.64%). The medium doses (0.01% clove oil; 0.52 mM eugenol) did not cause significant damage to the
Hepatoprotective effects: eugenol may protect the liver from damage by certain chemicals, including iron overload. The mechanism may involve eugenol acting both as an antioxidant to prevent lipid peroxidation and by scavenging free radicals. In an animal study, eugenol reduced the hepatic injury caused by iron overload. Eugenol lowered liver lipid peroxidation by 38% and serum lipid peroxidation by 30% in
Clove essential oil increased the total white blood cell count and enhanced the
Eugenol attenuates the reduction of dopamine. Eugenol administration 3 days before and 7 days after one intracerebroventricular injection of
Eugenol depressed cell respiration in homogenates of human dental pulp and in mouse fibroblast monolayers. The authors conclude that the irritant effect of zinc oxide eugenol when applied directly to soft tissue is due to the fact that concentrations of eugenol are achieved which are sufficient to inhibit respiration and thus kills cells (Hume 1984).
Molluscicidal activity: treatment with 20% and 60% of the
Allen & Cornforth (2009) demonstrated the iron chelating ability of eugenol. In presence of iron, type I antioxidants like eugenol had a significant prooxidant effect.
The aim of the study by Khan et al (2009) was to evaluate quorum sensing (QS) inhibitory activity of plant essential oils using strains of Chromobacterium violaceum (CV12472 and CV026) and Pseudomonas aeroginosa (PAO1). Significant inhibition of pigment production was detected in clove oil with 19 and 17 mm zone of pigment inhibition against CV12472 and CV026 strains. Clove oil, at lower concentration (2 µl) showed no activity, but at higher concentration (20 µl) antibacterial activity was observed along with
Clove oil is active against the eggs and
Mild hypertension has resulted in dogs after receiving 0.05 ml of eugenol (Gruenwald et al 2004).
3.2. Overview of available pharmacokinetic data regarding the herbal substance(s), herbal preparation(s) and relevant constituents thereof
No specific data are available on Caryophylli flos, Caryophylli floris aetheroleum.
After oral administration of 40 mg/kg in rats, eugenol reaches maximal concentrations in the plasma and blood within 0.25 hour and 2.13 hours, respectively. The terminal elimination
Glucuronide and sulphate conjugates of eugenol were identified in the urine (Guenette et al 2006).
Some allylbenzenes like methyleugenol are metabolised in the liver by several CYP 450 enzymes at least partially into reactive 1’
3.3. Overview of available toxicological data regarding the herbal substance(s)/herbal preparation(s) and constituents thereof
Toxicity of Caryophylli flos
The acute toxicity of a decoction of clove was studied in 30 overnight fasted mice. Doses of 100-
520 mg/kg body weight were administered intraperitoneally, larger doses of
The LD50 was interpolated as 263 mg/kg (i.p.) and 2500 mg/kg (oral) (Agbaje et al 2009).
Tajuddin et al (2003) studied the acute toxicity of an ethanolic extract (DER app. 10:1, ethanol 50%). 6 mice received 500 mg/kg extract p.o. No signs of mortality or gross behavioural changes were observed.
Swiss albino mice received for 10, 20 and 30 days 0.5%, 1% and 2% w/w clove powder in the diet. Enhanced
After 90 days of administration of a decoction of clove at doses of 300 mg/kg and 700 mg/kg in rats significant alterations in liver enzymes and haematological parameters were observed. Even in the lower dose histopathological modifications could be found in body organs. The authors conclude that a prolonged use of decoctions of clove should be avoided (Agbaje et al 2009).
The dry residue of aqueous and methanolic extracts showed mutagenic effects in the rec assay in Bacillus subtilis. The mutagenic activity in the Ames test on Salmonella typhimurium TA98 and TA100 was not assessable due to the antimicrobial action (Morimoto et al 1982).
After administration of a decoction (1:100) of cloves to Drosophila melanogaster no genotoxic effects were observed (Schulz & Herrmann 1980).
An in vivo bone marrow micronucleus assay demonstrated that the administration of 0.5% and 2% of cloves in the diet of mice for 10 days neither significantly induced micronuclei nor could effectively modulate the 7,
Data from Caryophylli flos are not available. However, the herbal substance contains up to 2% oleanolic acid. For oleanolic acid isolated from Syzygium jambos flowers a possible
30 mg/kg body weight olenolic acid daily over a period of 60 days. This dosage is equivalent to approximately 0.8 to 3 g clove per kg body weight. A histological examination of the testes showed a
Mishra & Singh (2008) investigated a hexane extract of cloves in doses of
increased. At doses of 30 mg and 60 mg/kg body weight these parameters were inhibited. Additionally
Toxicity of Caryophylli floris aetheroleum and of eugenol
Essential oil (Blaschek et al 2008):
Rat: p.o., LD50
Rabbit: cutaneous application, LD50 5 g/kg
Eugenol (Blaschek et al 2008):
Rat: p.o., LD50 2.68 g/kg; i.p. LD50 800 mg/kg
Mouse: p.o., LD50 3 g/kg; i.p. LD50 500 mg/kg
Acute toxicity (essential oil):
After oral administration of 5000 mg/kg of the essential oil in rats, all animals died within 24 hours. The autopsy showed bleeding in the stomach and intestines, and pleural effusion (Blaschek et al 2008).
A single oral dose of 140 mg/animal killed rats within a short time. Undiluted clove oil applied on the dorsal skin of hairless mice did not cause irritation. On intact or shaved rabbit skin clove essential oil acted under occlusive conditions as a weak irritant. Phototoxic effects were not observed with undiluted clove oil on hairless mice and pigs (Opdyke 1975 cited in Blaschek et al 2008).
Acute toxicity (eugenol):
On the isolated rabbit lung, the addition of 1 mM eugenol resulted in oedema, as measured by the increase in lung weight and wet/dry weight of the lung. The addition of catalase (1000 U/ml) or dimethylthiourea (30 mM) decreased the response. Dimethylurea, superoxide dismutase or heat inactivated catalase had no influence (McDonald & Heffner 1991).
Chronic toxicity (essential oil):
Clove essential oil in oral dosages of 35 or 70 mg per animal (rat) over 8 weeks was tolerated without signs of toxicity. Higher doses led to inactivity and weight loss. 105 mg/animal p.o. daily for 2 to 3 weeks led to serious liver and kidney damage and death of the animals (Opdyke 1975 cited in Blaschek et al 2008).
Clove oil is allowed as food additive and therefore an administration to
Chronic toxicity (eugenol):
Within the US National Toxicology Program (National Toxicology Program 1983) eugenol was tested over a period of 13 weeks in F344 rats and B6C3F1 mice. In concentrations up to 12,500 ppm (rats) and 6,000 ppm (mice) of eugenol in the diet no
Genotoxicity (entire clove oil):
No signs of a mutagenic effect could be observed in the in vitro chromosomal aberration test in fibroblasts from Chinese hamsters at concentrations up to 0.04 mg/ml of clove oil (Ishidate et al 1984).
No evidence of a mutagenic activity could be detected in clove oil (10 to 250 µl) in vitro in Salmonella typhimurium TA1530 and G46 without metabolic activation (Blaschek et al 2008).
The National Toxicology Program (NTP) performed a mutagenic study on eugenol. The study was finished in 1980. Outcome was the following:
Ames test (TA1535, TA100, TA98, TA1537 strains with metabolic activation): negative; Mouse lymphoma: positive, Sister chromatide exchange: positive; Chromosome aberrations: positive; Micronucleus: negative; Drosophila: negative; in vivo sister chromatid exchange: positive; in vivo chromosome aberrations: equivocal (National Toxicology Program 1983).
Eugenol was tested for mutagenic activity in the
Eugenol induces chromosome aberrations in Chinese hamster lung cells and exerts a
Maralhas et al (2006) demonstrated that eugenol induces chromosome aberrations, including exchanges in V79 cells, in particular in the presence of rat liver S9 mix, which suggests biotransformation to reactive metabolites. Eugenol induced chromosomal aberrations significantly (3.5% aberrant cells) at 2500 µM, demonstrating cytotoxicity in higher doses. S9 increases the number of aberrant cells to 15% with a high frequency of chromatid exchanges. Additionally an increase in endoreduplicated cells was observed. The authors suggest that eugenol exhibits topoisomerase II inhibiting activity.
Eugenol was also tested by Ellahuene et al (1994) in the mouse bone marrow micronucleus assay. Single doses of 400 and 600 mg/kg eugenol i.p. induced a statistically significant increase in the induction of
Munerato et al (2005) investigated the phenolic compounds eugenol, isoeugenol and safrole for genotoxicity in the wing spot test of Drosophila melanogaster. The assay was applied in its standard version with normal bioactivation and in its variant with increased cytochrome
Burkey et al (2000) investigated the cytotoxicity and genotoxicity of several allylbenzenes. Cytotoxicity was determined by measuring lactate dehydrogenase release, while genotoxicity was determined by using the unscheduled
The results of this study correspond with the opinion of the authors that methyleugenol and safrole cause UDS in rat and mouse hepatocytes over a range of concentrations, while isoeugenol and eugenol do not. The difference in the genotoxicity of the two groups of compounds may be related to the biotransformation of the compounds. Both safrole and methyleugenol lack free hydroxy groups on their rings that are present on isoeugenol and eugenol. The lack of these freely available hydroxyl groups may allow both methyleugenol and safrole to avoid immediate conjugation and elimination, providing a greater opportunity for metabolism to take place on the allyl side chain.
The authors conclude that methyleugenol is minimally cytotoxic to hepatocytes isolated from rats and mice while causing UDS in both species. Safrole showed similar patterns of toxicities. In contrast, isoeugenol and eugenol showed significant cytotoxicity at extremely high concentrations in rodent- derived hepatocytes but did not cause UDS. It seems likely that extensive glucuronidation and sulfation of the
Guenthner & Luo (2001) demonstrated that potentially genotoxic 2’, 3’ epoxide metabolites occur readily in vivo using the isolated perfused rat liver, but these metabolites are rapidly further metabolised to less toxic dihydrodiol or glutathione conjugates. The authors conclude that the epoxide formation at the allylic double bond represents, therefore, a potentially genotoxic bioactivation pathway for allylbenzene analogs. However, comparison of the relative kinetics of epoxide metabolism and epoxide formation suggests that a wide margin of protection from DNA covalent adduct formation exists in the rat liver, thus preventing genotoxicity resulting from this pathway to any significant degree. The authors also observed that the general rate of epoxide hydrolysis is much greater in human liver than in rat liver. It is therefore suggested that while the epoxidation pathway poses a potential genotoxic threat to humans, no actual genotoxicity occurs as a result of this metabolic pathway.
Rompelberg et al (1996) however found only limited support for the suspected antigenotoxic potential of eugenol in vivo. The effects of eugenol in rats were investigated in the unscheduled DNA synthesis (UDS) assay with established mutagens and the Salmonella typhimurium mutagenicity assay. In addition, the effect of in vivo treatment with eugenol on benzo[a]pyrene
Reproductive and developmental toxicity:
Domaracky et al (2007) investigated the effects of clove essential oil on the growth and development of mouse
to 177 mg/kg body weight (6 to 10 of gestation, foetuses at day 14) and in rabbits by 1.72 to 172 mg/kg body weight (6 to 18 of gestation, foetuses at day 29) (Blaschek et al 2008).
Within the US National Toxicology Program (National Toxicology Program 1983) eugenol was tested over a period of two years in F344 rats and B6C3F1 mice.
Rats: eugenol was administered in the diet in a concentration of up to 6000 ppm. Considering the mean diet consumption per day the daily uptake of eugenol was for male rats about 1100 mg/kg body weight at the beginning to 245 mg/kg body weight at the end of the study; for female rats about
790 mg/kg body weight at the beginning to 237 mg/kg body weight at the end of the study. The study outcome was negative in both sexes.
Mice: Considering the mean diet consumption per day, the daily uptake of eugenol was for male mice about 1160 mg/kg body weight at the beginning to 564 mg/kg body weight at the end of the study; for female mice about 1440 mg/kg body weight at the beginning to 718 mg/kg body weight at the end of the study. Eugenol caused increased incidences of both carcinomas and adenomas of the liver in male mice and eugenol was associated with an increase in the combined incidences of hepatocellular carcinomas or adenomas in female mice. These findings were judged to be statistically significant at concentrations from 3000 ppm upwards in the diet. However, the study outcome was considered to be equivocal.
Recently, Auerbach et al (2010) classified eugenol as a
Undiluted eugenol (no data on amount of eugenol) was applied to a circumscribed area 3 mm in diameter of rat labial mucosa for one minute. Reaction periods of 15 minutes, 1, 2, 4 and 6 hours were then permitted. Using routine histological procedures for processing the experimental tissues it was observed that eugenol caused denaturation of cytoplasmatic proteins and loss of staining capacity of epithelium, loss of cell boundaries, swelling and cell necrosis. In addition, vesicle formation, oedema in the corium, and striated muscle dissolution were observed (Kozam & Mantell 1978).
3.4. Overall conclusions on
The published data concerning the special indications and preparations is very limited, but on the basis of existing data the pharmacological activities support the traditional use of Caryophylli aetheroleum and preparations thereof in the proposed indication: For the temporary relief of toothache due to a dental cavity and for the symptomatic treatment of minor inflammations in the mouth or the throat.
The efficacy of traditional herbal medicinal products is only plausible but not based on clinical data. Nevertheless, the safety must be guaranteed. In the case of Caryophylli aetheroleum the main component eugenol gives reason for safety concerns. Natural compounds with a similar allylbenzene structure like safrole and methyleugenol are known as genotoxic carcinogens. Available data regarding genotoxicity and carcinogenicity of eugenol are inconsistent and equivocal. In general the toxicity of eugenol is estimated to be considerably lower compared to methyleugenol. In human liver the rate of detoxification reactions of the 2’, 3’ epoxidemetabolites appears to be considerably higher compared to rat liver. Due to the presence of a free
Therefore, from the potential toxicity point of view, the short term local use of clove oil for the temporary relief of toothache due to a dental cavity and for the symptomatic treatment of minor inflammations in the mouth or the throat in traditional herbal medicinal products can be supported.
Because available data regarding genotoxicity and carcinogenicity are inconsistent and equivocal the establishment of a Community list entry is not recommended.
4. Clinical Data
4.1. Clinical Pharmacology
4.1.1. Overview of pharmacodynamic data regarding the herbal substance(s)/preparation(s) including data on relevant constituents
Eugenol caused a ‘comfortable feeling’ in the 13 female subjects. Alpha 1 of EEG significantly decreased after inhalation. Suppression of alpha 1 indicates the neural activity around the brain regions. There is a possible positive correlation between alpha 1 activity and subjective evaluation (Masago et al 2000).
4.1.2. Overview of pharmacokinetic data regarding the herbal substance(s)/preparation(s) including data on relevant constituents
No data available for the entire essential oil.
The metabolism of eugenol was investigated in male and female healthy volunteers by Fischer et al (1990). Eugenol was rapidly absorbed and metabolized after oral administration and was almost completely excreted in the urine within 24 hours. Unmetabolized eugenol was found in the urine less than 0.1% of the dose. The urine contained conjugates of eugenol and of nine metabolites. The authors could identify
4.2. Clinical Efficacy
4.2.1. Dose response studies
No data available.
4.2.2. Clinical studies (case studies and clinical trials)
Alqareer (2006) compared the anesthetic properties of cloves, benzocaine and placebo in 73 adult volunteers. The volunteers received either 2 g of a gel containing 40% clove powder and 60% glycerine or 2 g of a gel containing 20% benzocaine on one side of the canine buccal mucosa and placebo on the other side. Five minutes after the administration each participant received two needle sticks. The pain response was registered using a visual analogue pain scale. Both clove and benzocaine lowered the pain score significantly (p = 0.005), no difference was found between benzocaine and the clove preparation.
Clinical studies in the proposed indication: no data available.
Other clinical studies:
Central effects: The influence of clove oil on psychometric parameters such as mood, affective reaction, memory and cognitive abilities in 21 male and 51 female probands was studied in a crossover trial. The concentration in the room air conditioning was corresponding to
4.2.3. Clinical studies in special populations (e.g. elderly and children)
No data available.
4.3. Overall conclusions on clinical pharmacology and efficacy
No clinical data are available for Caryophylli flos and Caryophylli aetheroleum in order to support well- established use. The traditional use in the proposed indications is made plausible by pharmacological data.
Therefore the medicinal use has to be regarded as traditional.
5. Clinical Safety/Pharmacovigilance
5.1. Overview of toxicological/safety data from clinical trials in humans
No data available.
5.2. Patient exposure
No data available.
5.3. Adverse events and serious adverse events and deaths
Skin and mucosal irritations:
In concentrated form, oil of clove may be irritating to mucosal tissues (Gruenwald et al 2004).
In contrast to this Anton et al (2001) report that there is no skin irritation (undiluted oil) on hairless mice. Under occlusion the undiluted clove oil was moderately irritating in rabbits.
In patients sensitized to Peru balsam, a hexane extract of clove, caused, in concentrations higher than 0.12% in petrolatum, local reactions. In a concentration of 1% in petrolatum, in two of four patients, a moderate reaction was observed, in the other two, an intense reaction occurred (large, infiltrated, dark spots with numerous vesicles) (Bouhlal et al 1989).
In an epicutaneous test with clove powder (on filter paper moistened with water), out of 78 patients with allergy against Peru balsam, 36 reacted positive. In a control group of 156 probands lacking Peru balsam allergy, nobody responded positively (Niinimäki).
A 22 years old patient with eczema on the hands reacted to a p.o. stress test 2 times 100 mg clove powder in gelatine capsules) with blisters on palms and fingers (Niinimäki 1984).
Clove cigarettes have been reported to cause acute respiratory problems in humans that rapidly progress to hemorrhagic pulmonary oedema or pneumonia (Blaschek et al 2008, Gruenwald et al 2004).
In a patch test study a 10% ethanol extract of Caryophylli flos was investigated among other herbal preparations used in the Traditional Chinese Medicine. Out of 30 patients 8 reacted positively to clove extract (Chen et al 2003).
Clove oil, 20% incorporated in petrolatum, produced in 2 of 25 healthy subjects an erythema. In concentrations of 2% and 0.2% in petrolatum, no reactions were observed (Opdyke 1975).
When trying to administer clove essential oil onto an aching tooth, a 24 year old woman disposed accidentally the oil on the upper lip and cheek. Although she tried to remove the essential oil, a sensation of burning and inflammation occurred, which disappeared within a few hours. Subsequently, local anaesthesia and reduced sweat production in the affected areas were observed. The medical examination after 11 months revealed a dry, slightly erythematous skin with reduced pressure sensitivity. During the following 9 months the situation remained unchanged (Isaacs 1983).
Data from root canal fillings with eugenol cement:
When eugenol cement is applied near the pulpa (intact dentin layer) no toxicity is observed. However, when applied directly to the exposed pulp, pulp necrosis and inflammation appeared (Reichl et al 2007).
A root canal filling with eugenol cement resulted in a patient with a generalized urticaria. In the skin test, the patient responded positively to Peru balsam and cloves. A distributed oral provocation test with 0.1 to 0.5 ml of eugenol, in water, resulted in urticaria which persisted for several weeks (Grade & Martens 1989).
During 1984 and 1985, the Centers for Disease Control received 11 case reports of clove cigarette
The medicinal use of clove essential oil should be contraindicated in cases of hypersensitivity to clove essential oil as well hypersensitivity to Peru balsam (Blaschek et al 2008).
5.4. Laboratory findings
No data available.
5.5. Safety in special populations and situations
The antiplatelet effect of clove oil may increase the risk of bleeding if taken with these medications. Clove may result in a false increase in phenytoin levels (Gruenwald et al 2004).
Assessor’s comment: The proposed routes of administration are the oromucosal and dental use; the duration of use is limited. Therefore these mentioned theoretical drug interactions are not relevant for
the traditional use of clove oil for the short term treatment of toothache or as an antiseptic mouthwash.
Pregnancy and lactation:
No data are available. In the absence of sufficient data, the use during pregnancy and lactation is not recommended.
A 2 year old boy drank 5 to 10 ml of clove oil. After 1 hour only mild drowsiness was observed. Within the next 3 hours, a drastic deterioration occurred with deep coma and severe acidosis. 8.5 hours after the ingestion, generalized cramps occurred which were treated with diazepam. The patient had an unrecordable blood glucose level which was treated with intravenous dextrose. 24 hours after ingestion, the patient was unconscious. A severely impaired liver function and disseminated intravascular coagulopathy (therapy with plasma, heparin, antithrombin III, protein C, factor VII) was observed. The liver function deteriorated further in the following days. During the 5th day, the patient awoke and on day 6, he was fully conscious. From this time point, the symptoms gradually disappeared, the patient fully recovered (Hartnoll et al 1993).
A very similar case – ingestion of about 10 ml of clove oil by a 2 year old boy resulting in convulsions, unconsciousness and severe coagulation – is described by Brown et al (1992). The patient was treated with heparin and fresh frozen plasma, and, following specific haemostasis assays, with appropriate coagulation factor and inhibitor concentrates.
A 3 month old girl developed a fulminant hepatic failure after ingestion of less than 8 ml of clove oil (exact amount not documented). She was successfully treated with
A similar case is reported by Janes et al (2005): a 15 month old boy developed a fulminant hepatic failure after ingestion of 10 ml of clove oil. After 24 h, the ALT level was in excess of 13,000 U/l, with blood urea and creatinine of 11.8 mmol and 134 µmol/l respectively. The hepatic impairment resolved after intravenous administration of
5.6. Overall conclusions on clinical safety
Clove essential oil acts in high concentrations as local irritant, allergic reactions may also be possible. However, when applied in diluted form, no reports on severe adverse events are published. When applied correctly in the proposed routes of administration, clove essential oil can be considered as clinically safe.
6. Overall conclusions
The positive effects of Caryophylli flos and Caryophylli floris aetheroleum and preparations thereof on inflammatory changes of the oral and pharyngeal mucosa and for topical anaesthesia have long been recognised empirically. The use is made plausible by pharmacological data. There is a lack of controlled clinical studies, using herbal preparations, containing the herbal substance Caryophylli flos or Caryophylli floris aetheroleum.
In conclusion, Caryopyhlli flos and Caryophylli floris aetheroleum and its preparations can be regarded as traditionally used, in the following indications: temporary relief of toothache due to a dental cavity and symptomatic treatment of minor inflammations in the mouth or the throat.
There is no documented use of medicinal products containing Caryophylli flos as the only active ingredient. Therefore no monograph for Caryophylli flos has been developed, which is communicated in a public statement.
In Caryophylli aetheroleum, the main component eugenol gives reason for safety concerns. Natural compounds with a similar allylbenzene structure, like safrole and methyleugenol, are known as genotoxic carcinogens. Available data regarding genotoxicity of eugenol are inconsistent and equivocal. In general the toxicity of eugenol is estimated to be considerably lower compared to methyleugenol. In the human liver, the rate of detoxification reactions of the 2’, 3’ epoxide metabolites appears to be considerably higher compared to rat liver. Due to the presence of a free
Therefore, from the potential toxicity point of view, the short term local use of clove oil for the temporary relief of toothache due to a dental cavity and for the symptomatic treatment of minor inflammations in the mouth or the throat in traditional herbal medicinal products can be supported.
The safety concerns do not allow the establishment of a Community list entry.