Table of contents
1. Introduction ............................................................................................ 3
1.3. Search and assessment methodology....................................................................
6
2. Historical data on medicinal use .............................................................. 6
2.1. Information on period of medicinal use in the Community ........................................
6
preparations and indications.......................................................................................
7
3. Non-Clinical Data..................................................................................... 8
preparation(s) and relevant constituents thereof ...........................................................
8
preparation(s) and relevant constituents thereof ......................................................... 1
6
preparation(s) and constituents thereof ..................................................................... 1
6
3.4. Overall conclusions on non-clinical data............................................................... 2
1
4. Clinical Data .......................................................................................... 22
4.1. Clinical Pharmacology ....................................................................................... 2
2
including data on relevant constituents ...................................................................... 2
2
including data on relevant constituents ...................................................................... 2
2
4.2. Clinical Efficacy ................................................................................................ 2
2
4.2.1. Dose response studies.................................................................................... 2
2
4.2.2. Clinical studies (case studies and clinical trials).................................................. 2
2
4.2.3. Clinical studies in special populations (e.g. elderly and children)........................... 2
2
4.3. Overall conclusions on clinical pharmacology and efficacy ...................................... 2
3
5.1. Overview of toxicological/safety data from clinical trials in humans.......................... 2
3
5.2. Patient exposure .............................................................................................. 2
3
5.3. Adverse events and serious adverse events and deaths ......................................... 2
3
5.4. Laboratory findings .......................................................................................... 2
4
5.5. Safety in special populations and situations ......................................................... 2
4
5.6. Overall conclusions on clinical safety ................................................................... 2
5
Assessment report on Syzygium aromaticum (L.) Merill et L.M. Perry, flos and
Syzygium aromaticum (L.) Merill et L.M. Perry, floris aetheroleum
EMA/HMPC/534946/2010
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1.
Introduction
1.1.
Description of the herbal substance(s), herbal preparation(s) or
combinations thereof
Herbal substance(s)
According to the European Pharmacopoeia 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 reddish-brown. They contain not less than 150 ml/kg essential oil.
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
(1876–1956).
Constituents (according to Blaschek et al 2008):
Essential oil: 15–17%, three main components account for nearly 99% of the essential oil: eugenol
(75–88%), acetyl eugenol (4–15%), β-caryophyllene (5–14%).
Further components: chavicol, (Z)- and (E)-isoeugenol, benzylacetate, α- and β-pinene, limonene; α-
ylangene, γ- and α-caryophyllene (= humulene), caryophyllene epoxid, caryophyllenoxide,
caryophylla-3(12),7(13)-dien-6 α-ol and caryophylla-3(12),6-dien-4-ol [39] as well as 4,4-
dimethyltricyclo[6.3.2.02.5]trideca-8-en-1-ol, caryophylla-4(12),8(13)-dien-5β-ol, caryophylla-
3,8(13)-dien-5 α-ol and caryophylla-3,8(13)-dien-5β-ol, α-copaen, α-cubeben, farnesol.
Aldehydes: benzaldehyde, m-methoxybenzaldehyde.
Alcohols: benzyl alcohol.
Ketones: the flavorings heptan-2-one (= methyl-n-amylketone) and octan-2-one
(= methylheptylketone).
Hydrocarbons: naphthalene.
Acetophenonderivates: 2,6-dihydroxy-4-methoxyacetophenone, methylxanthoxylin.
Flavones: quercetin, kaempferol, kaempferid, rhamnetin, kaempferol-3-O-β-D-glucoside, quercetin-3-
O-β-D-glucoside, quercetin-3-O-β-D-galactoside, quercetin-3,4′-O-β-D-diglucoside.
Tannins: ellagitannins, including eugeniin.
Phenolic acids: gallic- and ellagic acid, 3- and 4-caffeoyl-, 3-p-cumaroyl- and 3-feruloylchina acid,
ferulic acid, p-hydroxybenzoic acid, caffeic acid, salicylic acid, syringa acid, vanillic acid, gentisic acid,
protocatechuic acid and p-coumaric acid.
Triterpenes: oleanolic acid, crataegolic acid.
Phytosterols: β-sitosterol, stigmasterol, campesterol.
Sugars: glucose, xylose, arabinose.
Herbal preparation(s)
According to the European Pharmacopoeia 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):
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Three main components account for nearly 99% of the essential oil: eugenol (75–88%), acetyl eugenol
(4-15%), β-caryophyllene (5–14%).
Further components: chavicol, (Z)- and (E)-isoeugenol, benzylacetate, α- and β-pinene, limonene; α-
ylangene, γ- and α-caryophyllene (= humulene), caryophyllene epoxid, caryophyllenoxide,
caryophylla-3(12),7(13)-dien-6 α-ol and caryophylla-3(12),6-dien-4-ol [39] as well as 4,4-
dimethyltricyclo[6.3.2.02.5]trideca-8-en-1-ol, caryophylla-4(12),8(13)-dien-5β-ol, caryophylla-
3,8(13)-dien-5 α-ol and caryophylla-3,8(13)-dien-5β-ol, α-copaen, α-cubeben, farnesol.
OH
CH
3
OCH
3
H
2
C
H
H
CH
3
H
3
C
eugenol
-Caryophyllene
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.
Assessment report on Syzygium aromaticum (L.) Merill et L.M. Perry, flos and
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1.2.
Information about products on the market in the Member States
Regulatory status overview
Member State
Regulatory Status
Comments (not
mandatory field)
Austria
MA
TRAD
Other TRAD
Other Specify: Combinations only
Belgium
MA
TRAD
Other TRAD
Other Specify: Food supplements
Bulgaria
MA
TRAD
Other TRAD
Other Specify:
Cyprus
MA
TRAD
Other TRAD
Other Specify:
Czech Republic
MA
TRAD
Other TRAD
Other Specify:
Denmark
MA
TRAD
Other TRAD
Other Specify:
Estonia
MA
TRAD
Other TRAD
Other Specify:
Finland
MA
TRAD
Other TRAD
Other Specify:
France
MA
TRAD
Other TRAD
Other Specify:
Germany
MA
TRAD
Other TRAD
Other Specify:
Greece
MA
TRAD
Other TRAD
Other Specify:
Hungary
MA
TRAD
Other TRAD
Other Specify: Combinations only
Iceland
MA
TRAD
Other TRAD
Other Specify:
Ireland
MA
TRAD
Other TRAD
Other Specify:
Italy
MA
TRAD
Other TRAD
Other Specify:
Latvia
MA
TRAD
Other TRAD
Other Specify: Food supplements
Liechtenstein
MA
TRAD
Other TRAD
Other Specify:
Lithuania
MA
TRAD
Other TRAD
Other Specify:
Luxemburg
MA
TRAD
Other TRAD
Other Specify:
Malta
MA
TRAD
Other TRAD
Other Specify:
The Netherlands
MA
TRAD
Other TRAD
Other Specify:
Norway
MA
TRAD
Other TRAD
Other Specify:
Poland
MA
TRAD
Other TRAD
Other Specify:
Portugal
MA
TRAD
Other TRAD
Other Specify:
Romania
MA
TRAD
Other TRAD
Other Specify:
Slovak Republic
MA
TRAD
Other TRAD
Other Specify: Combinations only
Slovenia
MA
TRAD
Other TRAD
Other Specify:
Spain
MA
TRAD
Other TRAD
Other Specify: No product
Sweden
MA
TRAD
Other TRAD
Other Specify:
United Kingdom
MA
TRAD
Other TRAD
Other Specify:
MA: Marketing Authorisation
TRAD: Traditional Use Registration
Other TRAD: Other national Traditional systems of registration
Other: If known, it should be specified or otherwise add ’Not Known’
Assessment report on Syzygium aromaticum (L.) Merill et L.M. Perry, flos and
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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, Medline 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 17
th
century (cited in
Benedum et al 2006).
In fact Caryophylli flos has been in therapeutic use for many decades. However, there are no reports of
any medicinal product containing cloves. Therefore the criteria for traditional use as defined by
Directive 2004/24 EC are considered not to be fulfilled.
The medicinal use of Caryophylli floris aetheroleum can be traced in literature back to the 15
th
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 easily 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 herbs 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 is traditionally used for
external or local applications 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).
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Caryophylli floris aetheroleum or eugenol alone is widely used in dentistry mixed with zinc oxide as
temporary filling material.
The high content of eugenol makes the medicinal use in the proposed indication plausible.
Indication
Herbal substance (Caryophylli flos)
Indication
A
Herbal substance
Traditionally as decoction for treatment of
dyspeptic complaints, flatulence or diarrhoea
(Blaschek et al 2008)
Herbal preparation (Caryophylli floris
aetheroleum)
Indication
A
Mouth washes
Inflammations of the oral and pharyngeal
mucosa (German commission E in Blumenthal
et al 1998)
B
Undiluted essential oil or solutions in a
strength of minimum 50% or gels in a
strength of 20%
Authorised products in UK: temporary relief of
toothache due to dental cavity
2.3.
Specified strength/posology/route of administration/duration of use
for relevant preparations and indications
Posology/Strength
Herbal substance (Caryophylli flos)
Posology
A
Herbal substance
One piece when necessary in case of toothache
(Blaschek et al 2008)
Decoction: no information (Blaschek et al 2008)
Herbal preparation (Caryophylli floris
aetheroleum)
Posology
A
Inflammations of the oral and pharyngeal
mucosa
Mouth washes corresponding to 1–5% essential
oil (German commission E in Blumenthal et al
1998)
B
Temporary relief of toothache due to dental
cavity
Authorised products in UK: undiluted essential
oil or solutions in a strength of minimum 50%
or gels in a strength of 20%
Apply directly to the tooth cavities
Traditional use in children and adolescents:
Oromucosal use:
Children between 1 and 4 years of age: a strength of 1–2% of the essential oil is proposed (Dorsch et
al 2002).
Children between 4 and 12 years of age and adolescents: a strength of 1–5% of the essential oil is
proposed (Dorsch et al 2002).
Assessment report on Syzygium aromaticum (L.) Merill et L.M. Perry, flos and
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Duration of use
Dental use:
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
Dental use:
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.
Oromucosal use.
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 cloves 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. A traditional use for more than 30 years is documented. Experimental data
on genotoxicity suggest that clove oil might be harmful. The development of a community monograph
depends on the outcome of the discussions on the safety of clove oil.
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.
Non-Clinical Data
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).
Antimicrobial effects:
The additive 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).
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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.
Antiviral effect:
Eugeniin isolated from cloves by solvent distribution and multiple column chromatography (yield
82 mg/50g drug) inhibits
in vitro
in FL-cell cultures at a concentration of 10 µg/ml the replication of
Herpes simplex virus (HSV). When eugeniin was added one hour after virus seeding, no giant cells
could be observed after 24 hours of incubation (Takechi & Tanaka 1981 cited in Blaschek et al 2008).
The combination of hot water clove extract with acyclovir had a stronger anti HSV-1 activity compared
to the sum of the single compounds (Kurokawa et al 1995). When acyclovir and/or the herbal extract
were orally administered at doses corresponding to human use (250 mg/kg extract, 5 mg/kg
acyclovir), the combination significantly limited the development of skin lesions and/or prolonged the
mean survival times of infected mice compared to acyclovir or the extract alone. The combination was
not toxic to the mice.
Anti-Hepatitis C Virus Protease-activity was caused by
Syzygium aromaticum
. The methanol extract
exhibited significant inhibitory activity (≥ 90% inhibition). The IC
50
was 33 µg/ml (Hussein et al 2000).
Anticarcinogenic effects:
Dimethylbenzanthracen-croton oil treated mice had a visible rough granular surface on the shaved skin
with varying degrees of erythema and sometimes with white plaque like lesion. Treatment with an
aqueous infusion of clove delayed the onset of papillomas in the treated groups. Treatment was most
effective in the group which received the clove infusion orally. At the dose of 100 µl the onset of
papillomas was delayed by two weeks. 200 µl clove infusion also delayed the onset of papillomas but
not to the extent seen with 100 µl. 50 µl of clove infusion were not effective (Banerjee & Das 2005).
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 benzopyrene-induced lung lesions following clove treatment (Banjeree et
al 2006).
Molluscicidal effect:
The toxicity of flower-bud powder of
Syzygium aromaticum
L. and its organic solvent extracted
fractions against the snail
Lymnaea acuminata
were time and concentration dependent. The LC
50
of the
flower-bud powder was at 24 hours 172.75 mg/l and at 96 hours 51.98 mg/l, respectively. The ethanol
extract was more toxic than other organic extracts. The 24 hours LC
50
of ethanol extract of the flower-
bud powder against
L. acuminata
was 83.53 mg/l. The 24 hours LC
50
of the column purified fractions of
S. aromaticum
flower-bud powder was 20.73 mg/l; 96 hours LC
50
7.87 mg/l; 24 hours LC
50
of eugenol
was 11.03 mg/l (Kumar & Singh 2006).
Antithrombotic effects
:
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
Assessment report on Syzygium aromaticum (L.) Merill et L.M. Perry, flos and
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were observed, while the high molecular weight polysaccharide (MW 103.000) exhibited approximately
half the toxicity of heparin (LD
50
322 mg/kg) (Lee et al 2001).
Antiallergic effects
:
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 48/80-induced systemic
anaphylaxis in rats with an IC
50
of 31.25 mg/kg when administered intraperitoneally. The extract also
inhibited the local immunoglobulin E-mediated passive cutaneous anaphylactic reaction (IC
50
=
17.78 mg/kg, i.v., IC50 = 19.81 mg/kg, p.o.). The extract also inhibited dose-dependently the induced
histamine release from rat peritoneal mast cells.
Effect on NO-formation
:
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 concentration-dependent (Yokozawa et al
2000).
Antioxidative effects
:
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 gastro-intestinal tract:
Agbaje (2008) investigated a hot aqueous extract using selected doses in the various study models.
Effect of the decoction on intestinal propulsion was studied by administering 300 and 700 mg/kg hot
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 agents-absolute ethanol (1 ml/rat), indomethacin (30 mg/kg) and 70% ethanol in
150 mM HCl (1 ml/rat). Both negative and positive controls were similarly treated simultaneously with
distilled water (10 ml/kg) and standard antiulcer drugs (omeprazole 20 mg/kg, cimetidine 100 mg/kg
and misoprostol 0.2 mg/kg), respectively. Lastly, the effect of the clove decoction was investigated on
a segment of isolated rabbit ileum and subsequently compared with acetylcholine 5.5 x 10(-5) M. The
extract was found to increase the gut muscle propulsion similar to the standard drugs, carbachol and
metoclopramide. When used together with atropine, the herbal preparation produced a reduction in
intestinal propulsion which suggested the involvement of cholinergic mechanisms in the action of the
extract. In the ulcer models, the decoction reduced the ulcer number and ulcer area in the ethanol and
HCl-ethanol models, with significant respective ulcer indices of 2.80 +/- 3.51 and 11.4 +/- 3.79
compared with controls (p < 0.05). In the indomethacin model, the extract, 700 mg/kg, compared
favourably with misoprostol with an index of 0.20 +/- 0.11 which was also found to be significant
compared with the control. In the
in vitro
investigation on the rabbit ileum, the decoction (200-6400
mcg/ml) contracted the tissue in a dose-dependent fashion, but it was found to be less effective than
acetylcholine (5.5 x 10(-5) M). Atropine sulphate 3.4 x 10(-6) M and 3.4 x 10(-5) M reduced gut
contractility induced by clove decoction, similar to the
in vivo
observation. The author concludes that
the herbal drug exerts its effect via a cholinergic mechanism.
Aphrodisiac activity:
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.
Other effects:
Male 7 to 8 weeks old Swiss-albino mice were given over 10, 20 or 30 days a feed containing 0.5%,
Assessment report on Syzygium aromaticum (L.) Merill et L.M. Perry, flos and
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1% and 2% (m/m) clove powder. The content of acid-soluble, free SH-groups in the liver homogenates
increased significantly dose- and time-dependent compared to untreated controls. After 30 days 27.79
or 30.01 or 33.10 µmol/g tissue (control 19.89 µg/g; p < 0.005) were found. The formation of
malondiealdehyde was reduced after γ–irradiation: 30 days, 1.90 (p < 0.01), 1.01 or 0.89 (p <
0.0005) nmol/mg protein; control 2.29 nmol/mg protein. The glutathion-S-transferase activity and the
cytochrome-
b5
-content increased significantly in all groups (with the exception 0.5%, 10 days)
compared with controls (p < 0.0005 to p < 0.01). The cytochrom-P
450
-content fell significantly in all
dose groups after 30 days. The activity of arylhydrocarbonhydroxylase was unaffected. A possible
protective effect of the drug against chemical pollutants is discussed (Kumari 1991 cited in Blaschek et
al 2008).
A methanol extract from cloves is said to induce the differentiation of M1-cells (myelotic leukemia of
mouse) in macrophage
in vitro
. The fractionation of the extract yielded oleanolic acid and crategolic
acid as active ingredients, which induce at a concentration of 5 × 10
–5
or 2 × 10
–5
M a differentiation.
Oleanolic acid resulted at a concentration of 5 × 10
–6
M also in a differentiation of HL-60 cells
(promyelotic human leukemia) while the effect of crategolic acid was overlaid by cytotoxic effects
(Umehara et al 1992 cited in Blaschek et al 2008).
Clove infusion reduced the COX-2 level on the 17
th
and 26
th
weeks but not on the 8
th
week (Banjeree
et al 2006).
The toxic effect of cloves on
Culex pipiens
larvae
, the common European mosquito, was investigated
by El Hag et al (1999). The LC
50
for the methanol extract was 824.7 ppm (assay time: 6 days) and the
LC
50
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 claimed
for the essential oil as such.
Analgesic effects
:
Patch-clamp experiments showed that eugenol reversibly activates calcium ion channels and chloride
ion channels in dorsal root ganglion cells from rats. Eugenol concentrations used were from 0.125 to
1 mmol/l. These effects may be responsible for the analgesic activity (Gruenwald et al 2004).
Natrium and Calcium channels act as molecular targets for eugenol for its analgesic effect. Eugenol
inhibits ATP-induced P2X currents in trigeminal ganglion neurons, which contributes to the analgesic
effect (Li et al 2008).
Intrathecal treatment of mice with eugenol (12.5 to 50 µg) for 24 hours, dose-dependently inhibited
the formalin-induced nociceptive response. Capsazepine shifted the dose-response curves in parallel to
the right. Eugenol may exert its antinociceptive effect via the capsaicin receptor located on sensory
terminals in the spinal cord. These results indicate that eugenol act as a capsaicin-like substance
(Ohkubo & Shibata 1997)
Anti-inflammatory effects:
Eugenol inhibited the NO production in a dose-dependent manner in the RAW264.7 cells treated with
1 µg/ml Lipopolysaccharide for 24 hours. Isoeugenol was more effective. LPS-dependent expression of
COX-2 was also inhibited by isoeugenol and less effectively by eugenol (Li et al 2006).
Anticarcinogenic effects:
Mice received 20 mg of isolated sesquiterpenes once every 2 days. The sesquiterpenes ß-
caryophyllene, ß-caryophyllene oxide, alpha-humulene, alpha-humulene epoxide and eugenol induced
the detoxifying enzyme glutathione S-transferase in the mouse liver and intestine (Zheng et al 1992).
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Eugenol showed chemopreventive effects. Eugenol, but not its isomer isoeugenol, was found to be a
potent inhibitor of melanoma cell proliferation. It inhibits the growth of melanoma cells in culture (50%
inhibition by 0.5 µM). Eugenol causes significant tumour growth delay, decrease of tumour size and
prevents tumour metastasis in mice (125 mg/kg) (Ghosh et al 2005).
Antimicrobial effects:
The majority of publications on pharmacological effects of clove or clove essential oil deal with the
antimicrobial effects. Only some selected references are cited below:
0.4% clove oil in 63% sugar syrup inactivated after 2–7 min
Candida albicans, Clostridium perfringens,
Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa
and
Staphylococcus aureus
. The
effect was not affected by addition of serum. Added sugar is not needed for an effect; however, it
stabilizes the dispersion of the essential oil (Briozzo et al 1989 cited in Blaschek et al 2008).
The effect of 0–300 ppm clove oil on the growth and synthesis of aflatoxins from
Aspergillus parasiticus
was studied in submerged culture. 0–250 ppm led to a slower growth, but had no influence on the
weight of the mycelium after 21 days. 300 ppm completely inhibited the growth. The production of
aflatoxins was dose-dependent delayed (Bullerman et al 1977 cited in Blaschek et al 2008).
Clove oil was superior to rosemary oil when tested against several gram-positive and gram-negative
bacteria as well as against two fungi. A synergistic effect was observed against
Candida albicans
, an
antagonism for
Aspergillus niger
(Fu et al 2007).
In an investigation of various aromatic waters, clove oil–water had no sustainable growth-inhibiting
effect on
Pseudomonas
. Clove oil exhibited in the serial dilution test and agar diffusion test only a weak
antimicrobial effect. The MHC in the serial dilution test was in the case of
Bacillus subtilis
,
Escherichia
coli
and
Pseudomonas aeruginosa
for each 1:20, for
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 cited in Blaschek et al 2008).
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 pH-value increased the activity. The
bacteria did not develop any resistance even after 10 passages grown at sub-inhibitory concentrations.
The authors conclude that eugenol may prevent the growth of
H. pylori
.
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 gram-positive and
gram-negative microorganisms. A different sensitivity of the bacteria tested was observed.
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 regulated
functions in bacteria. The production of violacein by
Chromobacterium violaceum
is QS-controlled.
Clove oil reduces at sub-MICs this production up to 78% compared to control.
The swarming motility in
Pseudomonas aeruginosa
which is also QS-controlled was reduced up to 78%.
Eugenol was not responsible for these effects.
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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 B
1
(AFB
1
) 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 AFB
1
accumulation.
When the water activity was 0.982, the AFB
1
inhibition percentage for all aflatoxigenic strains
exceeded 98% at all clove essential oil concentrations (Bluma & Etcheverry 2008).
Eugenol was found to be the most effective compound out of clove oil against several dermatophytes
(Park et al 2007).
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
and dermatophyte clinical and 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 fluconazole-resistant strains.
Eugenol significantly reduced the number of colony forming units sampled from the oral cavity or
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
Microsporum gypseum
. Eugenol was
adjusted to 10% concentration with a base of Vaseline petroleum jelly and was applied topically to the
infected skin lesions daily for 3 weeks. Eugenol was clinically active.
Antiviral effect:
Eugeniin, which was found at a concentration of 0.1% in cloves, inhibited
in vitro
in FL-cell cultures at
a concentration of 10 µg/ml, the replication of Herpes simplex virus (Takechi & Tanaka 1981 cited in
Blaschek et al 2008).
Kurokawa et al (1998) studied the effects of eugeniin on Herpes simplex virus-1. The effective
concentration for 50% plaque reduction for HSV-1 on Vero cells was 5 µg/ml, which is approximately
14 fold lower than the 50% cytotoxic concentration. The viral DNA synthesis was found to be one of
the major target sites of the inhibitory action.
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For eugenol no significant antiviral activity against herpes simplex virus type 1 was found (Astani et al
2009).
Spasmolytic effect
:
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/bariumchlorid: 40 to
60% inhibition; guinea-pig/ileum/histamine: >60% inhibition; rabbit/jejunum/nicotin: >60%
inhibition. No further details on the methodology are available (Debelmas & Rochat 1967 cited in
Blaschek et al 2008).
Clove oil antagonized
in vitro
the carbachol-induced spasm of the muscles of the trachea of the guinea-
pig and the electrically stimulated contraction of the longitudinal muscles of the ileum of the guinea-
pig. The EC
50
was 3.8 mg/ml (trachea; isoprenaline EC
50
= 3.9 nmol/l) or 6.8 mg/ml (ileum;
papaverine EC
50
= 3.7 µmol/l) (Reiter & Brandt 1985).
Eugenol relaxes the rabbit thoracic aorta while suppressing the Ca
2+
sensitivity and both the uptake
and extrusion mechanisms for Ca
2+
(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 cited in Blaschek et al 2008).
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 1-14C-arachidonic acid by 84.1%
compared to a control without the essential oil. The IC
50
of eugenol was 11 µM; the IC
50
of
indomethacin was 1.2 µM (Wagner et al 1986).
Eugenol and its derivatives are inhibitors of LOX-5 and COX-2 (Hübner 2008).
Sedative effect:
Wagner & Sprinkmeyer (1973 cited in Blaschek et al 2008) investigated the sedative effect of clove
essential oil. Mice received 1 to 100 mg/kg 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 dose-dependent
reduction of motility.
Antiprotozoal effects
:
Clove oil inactivated
in vitro Trichomonas vaginalis
in a dose-and time-depending manner. After
addition of 4, 2, 1, 0.5 and 0.25 mg/ml to the culture medium no surviving Trichomonads were
detectable after an incubation period of 5 min to 8 hours. Concentrations of 1 and 0.05 mg/ml were
not effective. With eugenol comparable effects were achieved. With 4–0.05 mg/ml of the reference
substance metronidazol the effect was achieved after 30 min to 2 hours (Salem 1980 cited in Blaschek
et al 2008).
Treatment of epimastigotes of
Trypanosoma cruzi
with different concentrations of clove essential oil
resulted in a dose-dependent growth inhibition with IC
50
/24 hours of about 99.5 µg/ml; IC
50
/24 hours
values obtained after treatment of bloodstream trypomastigotes were about 57.5 µg/ml. The values
obtained for epimastigotes treated with eugenol were 246 µg/ml, while treatment of bloodstream
trypomastigotes resulted in IC
50
/24 hours values of 76 µg/ml for eugenol (Santoro et al 2007).
Effect as repellent:
In a study by Eamsobhana et al (2009) commercially produced essential oils of 13 plant species and
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ethanol (control) were tested for repellent activity against host-seeking larvae of
Leptotrombidium
imphalum
. Dilutions of each essential oil were prepared in absolute ethanol. Clove essential oil
exhibited 100% repellent activity at 5% concentration.
Antimutagenic activity:
Miyazawa & Hisama (2003) identified dehydrodieugenol and trans-coniferyl aldehyde as the
antimutagenic compounds in clove. These compounds showed suppressive effects on umu gene
expression of the SOS response in
S. typhimurium
TA1535/pSK10002 against furylfuramide, 4NQO,
and MNNG, which do not require liver-metabolizing enzymes, and AFB
1
and Trp-P-1, which require
liver-metabolizing enzymes and UV irradiation. Dehydrodieugenol had stronger suppressive potencies.
Antigenotoxicity
:
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 pre-treatment with 50-500 mg/kg body weight eugenol
resulted in significant reductions with cyclophosphamide, procarbazine, methylnitronitrosoguanidine
and urethane. The administration of eugenol alone did not exert genotoxicity.
Cytotoxicity:
An
in-vitro
study demonstrates cytotoxic properties of both the essential oil and eugenol towards
human fibroblasts and endothelial cells. Clove oil was found to be highly cytotoxic at concentrations as
low as 0.03% (v/v) with up to 73% of this effect attributable to eugenol. ß-Caryophyllene did not
exhibit any cytotoxic activity, indicating that other cytotoxic components may also exist within the
essential oil. The viability of all cell types dropped by 60–90% when the concentration of the oil was
increased from 0.01% to 0.03% (Prashar et al 2006).
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 Caco-2 population after 1 hour culture when compared with the
control (Fabian et al 2006).
Other effects:
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 by conjugating with glutathione. 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 iron-treated rats (Gruenwald et al 2004).
Clove essential oil increased the total white blood cell count and enhanced the delayed-type
hypersensitivity response in mice. Moreover, it restored cellular and humoral immune responses in
cyclophosphamide-immunosuppressed mice in a dose-dependent manner. The immunostimulatory
activity found in mice treated with clove essential oil is due to improvement in humor- and cell-
mediated immune response mechanisms (Carrasco et al 2009).
Eugenol attenuates the reduction of dopamin. Eugenol administration 3 days before and 7 days after
one intracerebroventricular injection of 6-hydroxydopamine prevented the reduction of striatal
dopamine and its metabolites. This effect suggests it possible usefulness for the treatment of Morbus
Parkinson (Kabuto et al 2007).
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).
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Molluscicidal activity: Treatment with 20% and 60% of the 96 hours LC50 of eugenol caused in the test
animals of the snail
Lymnaea acuminata
significant inhibition of the alkaline phosphatase and
acetylcholinesterase activities (Kumar et al 2009).
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 = mechanism by which
bacterial population coordinate the expression according to the density of the local population)
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 (2µl) showed no activity, but at higher concentration (20 µl)
antibacterial activity was observed along with anti-QS activity (zone of inhibition 21 mm). Eugenol
does not seem to be responsible for these effects.
Eugenol fulfils all points of a narcotic for commercial fish. Clove oil is allowed as food additive and
therefore an administration to food-producing animals is possible. The allowed daily intake for the
United States is reported with 2.5 mg/kg (Oetinger 2003).
Clove oil is active against the eggs and second-stage juveniles of the parasitic nematode Meloidogyne
incognita (Meyer et al 2008).
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 in the plasma maximal concentrations
within 0.25 hours in the blood and within 2.13 hours. The terminal elimination half-life was determined
with 18.3 hours (blood) and 14 hours (plasma) which indicates that after repeated oral administration
accumulation may occur (Guenette et al 2007).
Glucuronide and sulphate conjugates were identified in the urine (Guenette et al 2006).
Other allylbenzenes like methyleugenol are metabolised in the liver by several CYP 450 enzymes at
least partially into reactive 1’ hydroxy-derivatives or 2’, 3’-(allylic) epoxide derivatives (Jeurissen et al
2006, Guenthner & Luo 2001). The metabolism of eugenol via the same bioactivation pathway has
been alluded to, but not directly demonstrated. It seems probable that the formation of the ultimate
genotoxicant and carcinogen from eugenol is insignificant as compared to methyleugenol.
3.3.
Overview of available toxicological data regarding the herbal
substance(s)/herbal preparation(s) and constituents thereof
Toxicity of Caryophylli flos
Acute Toxicity:
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 500-5000 mg/kg body
weight by oral gavage. The animals were observed for respiratory, GIT, CNS symptoms, behavioural
patterns and mortality. The only toxic manifestation was abdominal cramps.
The LD
50
was interpolated as 263 mg/kg (i.p.) and 2500 mg/kg (oral) (Agbaje et al 2009).
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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.
Subchronic toxicity:
Swiss albino mice received for 10, 20 and 30 days 0.5%, 1% and 2% w/w clove powder in the diet.
Enhanced glutathione-S-transferase, cytochrome
b5
and sulphydryl enzyme levels were observed in all
the treatment groups, except those maintained on a 0.5% diet for 10 days. A significant reduction in
P450 and malondialdehyde levels was observed in all groups at 30 days duration (Kumari (1991).
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).
Mutagenicity:
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 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, 12-dimethylbenz[a]anthracene genotoxicity in mice (Kumari 1991).
Reproduction toxicity:
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 anti-estrogenic
effect is documented (Rajasekaran et al 1988). Rats received orally 15 mg/kg body weight or
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
dose-dependent reduction in the number of spermatides and spermatocytes from 2.69 (control) to
1.73 and 0.93. The number of fertilized females was reduced from 20/20 (control) to 7/20 or 2/20.
The number of implants also decreased from 8.80 to 5.43 and 2.55.
Mishra & Singh (2008) investigated a hexane extract of cloves in doses of 15-60 mg/kg body weight
per os
in mice over 35 days. The treatment did not induce systemic toxicity at the doses tested. At
15 mg/kg body weight the activities of testicular enzymes and serum levels of testosterone were
increased. At doses of 30 mg and 60 mg/kg body weight these parameters were inhibited. Additionally
non-uniform degenerative changes in the seminiferous tubules associated with a decrease in daily
sperm production were observed.
Toxicity of Caryophylli floris aetheroleum and of eugenol
Toxicity:
Essential oil (Blaschek et al 2008):
Rat: p.o., LD
50
1.8–3.72 g/kg
Rabbit: cutaneous application, LD
50
5 g/kg
Eugenol (Blaschek et al 2008):
Rat: p.o., LD
50
2.68 g/kg; i.p. LD
50
800 mg/kg
Mouse: p.o., LD
50
3 g/kg; i.p. LD
50
500 mg/kg
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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).
Chronic toxicity (eugenol):
Within the US National Toxicology Program (NTP 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 compound-related histopathological effects were observed.
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
cited in Blaschek et al 2008).
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).
Genotoxicity (eugenol):
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 mebabolic 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 (NTP 1980).
Eugenol was tested for mutagenic activity in the AMES-test using
S. typhimurium
TA 1535, TA 100 and
TA 98. For TA 100 and TA 98 strains no mutagenicity was detected, but in case of TA 1535 dose-
dependent mutagenicity was observed (Swanson et al 1979).
Eugenol induces chromosome aberrations in Chinese hamster lung cells and exerts a cell-transforming
activity in Syrian hamster embryo cells (Hikiba et al 2005).
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
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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 micronucleus-polychromatic erythrocytes compared to the negative control. No signs of
genotoxicity were observed at a dose of 100 mg/kg.
Munerato et al (2005) investigated the phenolic compounds eugenol, isoeugenol and safrole for
genotoxicity in the wing spot test of
Drosophila melanogaster
. The SMART was applied in its standard
version with normal bioactivation and in its variant with increased cytochrome P450-dependent
biotransformation capacity. Eugenol produced in concentrations up to 15 mM a positive
recombinagenic response only in the improved assay, which was related to a high CYP450-dependent
activation capacity. This suggests the involvement of this family of enzymes in the activation of
eugenol rather than in its detoxification. On the contrary, isoeugenol was clearly non-genotoxic at the
same millimolar concentrations as used for eugenol in both the crosses. The responsiveness of SMART
assays to recombinagenic compounds, as well as the reactive metabolites from eugenol and safrole
were considered responsible for the genotoxicity observed.
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 DNA-synthesis (UDS) assay. Isoeugenol and eugenol were more cytotoxic to the
hepatocytes than methyleugenol or safrole. Isoeugenol and eugenol had LC
50
values of 300 mM for rat
hepatocytes and 200 mM for mice, with both compounds showing relatively steep dose–response
curves.
The results of this study indicate in 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 para-hydroxy groups of isoeugenol and eugenol greatly reduce bioactivation on the alkenyl side
chain. Safrole and methyleugenol, which lack this structural feature, undergo hydroxylation at C-1, and
thus produce the precursor of a genotoxic metabolite in greater amounts.
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
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potential genotoxic threat to humans, no actual genotoxicity occurs as a result of this metabolic
pathway.
Anti-genotoxic 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 pre-treatment with 50-500 mg/kg body weight eugenol
resulted in significant reductions with cyclophosphamide, procarbazine, methylnitronitrosoguanidine
and urethane. The administration of eugenol alone did not exert genotoxicity.
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 (B[a]P)-induced genotoxicity
in human hepatoma cell line Hep G2 was investigated in the single-cell gel electrophoresis assay. The
mutagenicity of B[a]P in the
S. typhimurium
assay was lower in liver S-9 fractions from control rats.
Incubation of liver S-9 fractions from eugenol-treated rats with dimethylbenzanthracene (DMBA) had
no antimutagenic effect. Eugenol did not modify UDS activity in hepatocytes isolated from rats
pretreated with eugenol orally, after exposure of these cells
in vitro
to DMBA and aflatoxin B1. Four
different treatment schemes of combinations of B[a]P and eugenol were examined in Hep G2 cells:
pre-treatment with eugenol; simultaneous treatment with eugenol and B[a]P; a combination of these
(pretreatment/simultaneous treatment); and post-treatment with eugenol. An increase in the
genotoxicity of B[a]P was found in Hep G2 cells. No effect of eugenol on the genotoxicity of B[a]P was
found with the pre- and post-treatments. It is concluded that the effect of eugenol on genotoxicity
induced by established mutagens is not unequivocal;
in vivo
treatment of rats with eugenol resulted in
a reduction of the mutagenicity of B[a]P in the
S. typhimurium
mutagenicity assay, while in the UDS
assay no effect of eugenol was found.
In vitro
treatment of cultured cells with eugenol resulted in an
increase in genotoxicity of B[a]P.
Reproductive and developmental toxicity:
Domaracky et al (2007) investigated the effects of clove essential oil on the growth and development
of mouse pre-implantation embryos
in vivo
. The animals received 0.25% essential oil in the
commercial diet (= 375 mg/kg per day). Treatment with clove essential oil induced a significantly
higher percentage of dead cells compared to the control group.
Female CD-1 mice were given clove oil from day 6 to day 15 of gestation p. o. 2.2 to 215 mg/kg body
weight daily. The foetuses were obtained on day 17. The use of clove oil had no apparent toxic effect
on the implantation and survival of the mother and foetus. The number of malformations of the soft
tissues and the skeletal system was not different from that in the control group spontaneously
occurring. Similar results were obtained in female Wistar rats following daily p. o. administration of 2.8
to 280 mg/kg body weight (6 to 15 of gestation, foetuses at day 20), to golden hamsters after p.o. 1.8
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) achieved (Blaschek et al 2008).
Carcinogenicity (eugenol):
Within the US National Toxicology Program (NTP 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
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about 1160 mg/kg body weight at the beginning to 564 mg/kg body weight at the end of the study; for
female rats 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 non-hepatocarcinogen allylbenzene,
while methyleugenol, safrole and estragol are classified as hepatocarcinogens. This classification was
supported by several vector machine classification models.
Local toxicity:
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 non-clinical data
The published data referred to the 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 para-hydroxyl group, eugenol is much more easily conjugated
with sulphate and glucuronide resulting in a reduced probability of the formation of reactive
metabolites like in methyleugenol. Additionally, when considering the relatively high concentrations of
eugenol used in the carcinogenicity studies the actual risk for short term use seems to be relatively
low.
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.
Due to safety concerns the establishment of a Community list entry is not recommended.
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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.
Eugenol:
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 which were
identified as: eugenol, 4-hydroxy-3-methoxyphenyl-propane, cis- and trans-isoeugenol, 3-(4-hydroxy-
3-methoxyphenyl)-propylene-1,2-oxide, 3-(4-hydroxy-3-methoxyphenyl)-propane-1,2-diol, and 3-(4-
hydroxy-3-methoxyphenyl)-propionic acid. 95% of the dose was recovered in the urine, most of which
(greater than 99%) consisted of phenolic conjugates; 50% of the conjugated metabolites were
eugenol-glucuronide and sulphate.
4.2.
Clinical Efficacy
4.2.1.
Dose response studies
No data available.
4.2.2.
Clinical studies (case studies and clinical trials)
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 cross-
over trial. The concentration in the room air conditioning was corresponding to 0.0057–0.0167 g/m
3
.
No differences in the examined parameters could be observed (Wagner & Sprinkmeyer 1973 cited in
Blaschek et al 2008).
4.2.3.
Clinical studies in special populations (e.g. elderly and children)
No data available.
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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.
With direct application to the exposed pulp, pulp necrosis and inflammation appeared (Reichl et al
2007).
Allergic effects:
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 cited in Blaschek et al 2008).
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 1984 cited in Blaschek et al 2008).
A 22 years old patient with eczema on the hands reacted to a p.o. stress test, with 2 times 100 mg
clove powder in gelatine capsules, with blisters on palms and fingers (Niinimäki 1984 cited in Blaschek
et al 2008).
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).
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 cited in Blaschek et al 2008).
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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 cited in
Blschek et al 2008).
Systemic effects (case report):
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 cited in
Blaschek et al 2008).
Serious events:
A 17-year-old male high-school student died of rapidly progressive inflammatory lung disease that
developed hours after smoking a clove cigarette. The student was recovering from a lower respiratory
infection at the time. The California Department of Health Service and Centers for Disease Control
collected 110 cases of clove cigarette toxicity by 1984, two of which were fatal (Gruenwald et al 2004).
During 1984 and 1985, the Centers for Disease Control received 11 case reports of clove cigarette
smoking-associated acute respiratory system injury in adolescents and young adults; two deaths were
also reported. The reported respiratory adverse effects included hemoptysis, bronchospasm,
hemorrhagic and nonhemorrhagic pulmonary oedema, pleural effusion, respiratory insufficiency,
respiratory infection and aspiration of foreign material. Clove affects cellular respiration as well.
Eugenol inhibits cytochrome oxidase, thus poisoning the mitochondria (Gruenwald et al 2004).
Contraindications:
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
Interactions:
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.
Overdose:
Case reports:
A 7-month-old boy received 1 teaspoon of clove oil. The dose corresponds to about 500 mg/kg
eugenol. On admission to hospital, an attenuation of the CNS (awake, but without a direct response to
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environment), leukocytosis, proteinuria and ketonuria were observed. The also observed metabolic
acidosis was attributed to the already existing diarrhoea. 3 hours after ingestion, gastric lavage was
performed with the addition of activated carbon. An endoscopy the next morning showed no evidence
of mucosal damage in the stomach or oesophagus. After 48 hours acidosis and leukocytosis were no
longer detectable. The patient recovered completely and was released from hospital after 4 days (Lane
et al 1991 cited in Blaschek et al 2008).
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 (cited in Blaschek et al
2008). The patient was treated with heparin and fresh frozen plasma, and, following specific
haemostasis assays, with appropriate coagulation factor and inhibitor concentrates.
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, 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, Caryophylli
floris aetheroleum.
In conclusion, Caryopyhlli flos, Caryophylli floris aetheroleum and its preparations can be regarded as
traditional herbal medicinal products in the indications: 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.
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 will be
communicated in a draft 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’ epoxidemetabolites appears to be
considerably higher compared to rat liver. Due to the presence of a free para-hydroxyl group, eugenol
is much more easily conjugated with sulphate and glucuronide resulting in a reduced probability of the
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formation of reactive metabolites like in methyleugenol. Additionally, when considering the relatively
high concentrations of eugenol used in the carcinogenicity studies the actual risk for short term use
seems to be relatively low.
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.
Annex
List of references
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Source: European Medicines Agency
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