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Potential of clove of Syzygium aromaticum in development of a therapeutic agent for periodontal disease. A review
Abstract
Introduction: Clove (Syzygium aromaticum) is a plantderived
spice that has been traditionally used as a natural
medicine for the treatment for various ailments including
dental diseases.
Aim and objective: To present a comprehensive report
on the properties of clove based on an analysis of contemporary
scientific and professional literature in order to
explore the prospects for its application in the treatment
of plaque-induced periodontal diseases.
Methods: An online search was performed in PubMed
and Google Scholar using a combination of key words
which included clove buds, clove essential oil, eugenol,
Eugenia caryophyllata, spices, medicinal plant, chemical
composition, biological effect, therapeutic use, anti-bacterial,
anti-fungal, anti-viral, anti-oxidant, anti-inflammatory,
anaesthetic, periodontal, dental, and periodontitis.
Results: In vitro studies have shown Syzygium aromaticum
to have bacteriostatic, bactericidal, anti-viral, antimycotic,
anti-oxidant, anti-carcinogenic, anaesthetic and
analgesic properties. Clove oil has a specific anti- inflammatory
property as it inhibits the cyclo-oxygenase-2 and
lipo-oxygenase enzymes.
Conclusion: Clove and its derivatives have a definite potential
to be used as specific anti-plaque and anti-inflammatory agents
for the treatment of periodontal disease. Future research should
concentrate on designing new formulations based on clove
derivatives in the form of local drug delivery system or topical
agents for the treatment of periodontal diseases.
According to data in the literature, natural products and essential oils are often used in dental practice. To develop a new oromucosal spray for the treatment of infectious and inflammatory diseases of the oral cavity, clove CO2 extract and essential oils of lavender and grapefruit were used as active pharmaceutical ingredients. Clove extract was obtained by the method of subcritical extraction from various raw materials, the choice of which was based on the yield of the CO2 extract and the study of its phytochemical and microbiological properties. Based on the results of microscopic and diffraction analyses, the rational time of ultrasonic exposure for the emulsion of active pharmaceutical ingredients was established. Mucoadhesive polymers were used as stabilizers of the two-phase system and prolongators. This article discusses the impact of the type and concentration of mucoadhesive polymers on the stability of the emulsion system; the viscous, textural, adhesive, and film characteristics of oromucosal spray; and the parameters determining sprayability.
The transfer of gram-positive bacteria, particularly multiresistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), among patients is a growing concern. One critical aspect of bacterial transfer is the ability of the microorganism to survive on various common hospital surfaces, The purpose of this study was to determine the survival of 22 gram-positive bacteria (vancomycin-sensitive and -resistant enterococci and methicillin-sensitive and -resistant staphylococci) on five common hospital materials: smooth 100% cotton (clothing), 100% cotton terry (towels), 60% cotton-40% polyester blend (scrub suits and lab coats), 100% polyester (privacy drapes), and 100% polypropylene plastic (splash aprons), Swatches were inoculated with 10(4) to 10(5) CFU of a microorganism, assayed daily be placing the swatches in nutritive media, and examining for growth after 48 h, All isolates survived for at least 1 day, and some survived for more than 90 days on the various materials. Smaller inocula (10(2)) survived for shorter times but still generally for days, Antibiotic sensitivity had no consistent effect on survival, The long survival of these bacteria, including MRSA and VRE, on commonly used hospital fabrics, such as scrub suits, lab coats, and hospital privacy drapes, underscores the need for meticulous contact control procedures and careful disinfection to limit the spread of these bacteria.
Background:
To evaluate the antibacterial activity of 21 plant essential oils against six bacterial species.
Methods:
The selected essential oils were screened against four gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris) and two gram-positive bacteria Bacillus subtilis and Staphylococcus aureus at four different concentrations (1:1, 1:5, 1:10 and 1:20) using disc diffusion method. The MIC of the active essential oils were tested using two fold agar dilution method at concentrations ranging from 0.2 to 25.6 mg/ml.
Results:
Out of 21 essential oils tested, 19 oils showed antibacterial activity against one or more strains. Cinnamon, clove, geranium, lemon, lime, orange and rosemary oils exhibited significant inhibitory effect. Cinnamon oil showed promising inhibitory activity even at low concentration, whereas aniseed, eucalyptus and camphor oils were least active against the tested bacteria. In general, B. subtilis was the most susceptible. On the other hand, K. pneumoniae exhibited low degree of sensitivity.
Conclusion:
Majority of the oils showed antibacterial activity against the tested strains. However Cinnamon, clove and lime oils were found to be inhibiting both gram-positive and gram-negative bacteria. Cinnamon oil can be a good source of antibacterial agents.
Eugenol, obtained from clove oil (Eugenia caryophyllata), possess several biological activities. It is anti-inflammatory, analgesic, anaesthesic, antipyretic, antiplatelet, anti-anaphylactic, anticonvulsant, anti-oxidant, antibacterial, antidepressant, antifungal and antiviral. The anti-oxidant activity of eugenol have already been proven. From this perspective testing, a series of planned structural derivatives of eugenol were screened to perform structural optimization and consequent increase of the potency of these biological activities.
In an attempt to increase structural variability, 16 compounds were synthesized by acylation and alkylation of the phenolic hydroxyl group. Anti-oxidant activity capacity was based on the capture of DPPH radical (2,2-diphenyl-1-picryl-hydrazyl), ABTS radical 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), measure of TBARS (thiobarbituric acid-reactive species), total sulfhydryl and carbonyl content (eugenol derivatives final concentrations range from 50 to 200 μm).
Four derivatives presented an efficient concentration to decrease 50% of the DPPH radical (EC50 ) < 100 μm, which has a good potential as a free-radical scavenger. Three of these compounds also showed reduction of ABTS radical. Eugenol derivatives presenting alkyl or aryl (alkylic or arylic) groups substituting hydroxyl 1 of eugenol were effective in reducing lipid peroxidation, protein oxidative damage by carbonyl formation and increase total thiol content in cerebral cortex homogenates. In liver, the eugenol derivatives evaluated had no effect.
Our results suggest that these molecules are promising anti-oxidants agents.
Eugenia caryophyllata, popular name "clove", is grown naturally in Indonesia and cultivated in many parts of the world, including Brazil. Clove is used in cooking, food processing, pharmacy; perfumery, cosmetics and the clove oil (eugenol) have been used in folk medicine for manifold conditions include use in dental care, as an antiseptic and analgesic. The objective of this study was evaluated the anti-inflammatory and antinociceptive activity of eugenol used for dentistry purposes following oral administration in animal models in vivo. The anti-inflammatory activity of eugenol was evaluated by inflammatory exudates volume and leukocytes migration in carrageenan-induced pleurisy and carrageenan-induced paw edema tests in rats. The antinociceptive activity was evaluated using the acetic acid-induced writhing and hot-plate tests in mice. Eugenol (200 and 400 mg/kg) reduced the volume of pleural exudates without changing the total blood leukocyte counts. At dose of 200 mg/kg, eugenol significantly inhibited carrageenan-induced edema, 2-4 h after injection of the flogistic agent. In the hot-plate test, eugenol administration (100 mg/kg) showed unremarkable activity against the time-to-discomfort reaction, recorded as response latency, which is blocked by meperidine. Eugenol at doses of 50, 75 and 100 mg/kg had a significant antinociceptive effect in the test of acetic-acid-induced abdominal writhing, compared to the control animals. The data suggest that eugenol possesses anti-inflammatory and peripheral antinociceptive activities.
The aim of the study was to evaluate the effect of a toothpaste containing high concentrations of Aloe vera on the reduction of plaque and gingivitis in patients attending regular dental care by a dental hygienist. Fifteen subjects participated in this randomized, double-blind, intra-individual and controlled clinical study. Participants were non-smokers, with signs of gingivitis (bleeding index 30%) and no signs of periodontitis. Subjects were followed for three 6-month periods during which they used either their own toothpaste, or an Aloe vera or a control toothpaste. Plaque and gingival indices were recorded atthe start and end of each period. There was a statistically and clinically significant reduction of about 20% of the plaque and gingivitis indices at the end of the clinical trial compared to baseline values, but no differences between the Aloe vera and the control toothpaste. It may be concluded that in patients motivated to improve their oral hygiene habits, the use of a toothpaste containing Aloe Vera showed no additional effect on plaque and gingivitis compared to a control toothpaste.
The anaesthetic effects of clove-oil-derived eugenol were studied in juvenile rainbow trout, Oncorhynchus mykiss (Walbaum). Acute lethality and the effects of multiple exposures to eugenol were measured. The estimated 8-96 h LC50 for eugenol was found to be approximately 9 p.p.m. Times to induction and recovery from anaesthesia were measured and compared with MS-222 under similar conditions. Eugenol generally induced anaesthesia faster and at lower concentrations than MS-222. The recovery times for fish exposed to eugenol were six to 10 times longer than in those exposed to similar concentrations of MS-222. Clove oil eugenol was determined to be an acceptable anaesthetic with potential for use in aquaculture and aquatic research. Doses of 40-60 p.p.m. eugenol were found to induce rapid anaesthesia with a relatively short time for recovery in juvenile trout.
A comparative study was carried out between cinnamon oil and clove oil on the oral micro-biota causing dental caries. Cinnamon oil was found to be more effective than clove oil exhibiting broad spectrum of antibacterial activity inhibiting all the ten test bacterial species involved in dental caries. Cinnamon oil produced maximum inhibition zone of diameter (IZD) of 24.0 mm against Streptococcus mutans (major causative bacteria of dental plaque) as compared to clove oil (IZD = 13.0mm). This is contrary to the popular belief that clove oil is effective in tooth decay and dental plaque. This study shows the potential of cinnamon oil over clove oil in the treatment of dental caries. (www.actabiomedica.it).
Eugenol is a major volatile constituent of clove essential oil obtained through hydrodistillation of mainly Eugenia caryophyllata (=Syzygium aromaticum) buds and leaves. It is a remarkably versatile molecule incorporated as a functional ingredient in numerous products and has found application in the pharmaceutical, agricultural, fragrance, flavour, cosmetic and various other industries. Its vast range of pharmacological activities has been well-researched and includes antimicrobial, anti-inflammatory, analgesic, anti-oxidant and anticancer activities, amongst others. In addition, it is widely used in agricultural applications to protect foods from micro-organisms during storage, which might have an effect on human health, and as a pesticide and fumigant. As a functional ingredient, it is included in many dental preparations and it has also been shown to enhance skin permeation of various drugs. Eugenol is considered safe as a food additive but due to the wide range of different applications, extensive use and availability of clove oil, it is pertinent to discuss the general toxicity with special reference to contact dermatitis. This review summarises the pharmacological, agricultural and other applications of eugenol with specific emphasis on mechanism of action as well as toxicity data.
Aroma extract from dried clove buds [Syzygium aromaticum (L.) Merr. et Perry] was obtained by using steam-distillation under mild conditions (55°C and 95 mm Hg). The antioxidant property of the aroma extract was evaluated in two different assays. The aroma extract isolated from clove buds inhibited the oxidation of hexanal for 30 days at a level of 50 μg/ml. Clove bud extract inhibited malonaldehyde formation from cod liver oil by 93% at the 160 μg/ml level. Twenty-two compounds were identified in the extracts of clove buds by gas chromatography and gas chromatography/mass spectrometry. The major aroma constituents of clove buds were eugenol (24.371 mg/g) and eugenyl acetate (2.354 mg/g). Eugenol, eugenyl acetate, and benzyl alcohol inhibited the oxidation of hexanal by 99, 99, and 82%, respectively, for a period of 30 days at 500 μg/ml. Eugenol, eugenyl acetate, and benzyl alcohol inhibited malonaldehyde formation from cod liver oil by 88, 79, and 63%, respectively, at 160 μg/ml. The antioxidant activity of clove bud extract and its major aroma components, eugenol and eugenyl acetate, were comparable to that of the natural antioxidant, α-tocopherol (vitamin E).
Candida-associated denture stomatitis is a frequent infectious disease. Treatment of this oral condition is difficult because failures and recurrences are common. The aim of this study was to test the in vitro antifungal activity of pure constituents of essentials oils.
Eight terpenic derivatives (carvacrol, farnesol, geraniol, linalool, menthol, menthone, terpinen-4-ol, and α-terpineol), a phenylpropanoid (eugenol), a phenethyl alcohol (tyrosol) and fluconazole were evaluated against 38 Candida isolated from denture-wearers and 10 collection Candida strains by the CLSI M27-A3 broth microdilution method.
Almost all the tested compounds showed antifungal activity with MIC ranges of 0.03-0.25% for eugenol and linalool, 0.03-0.12% for geraniol, 0.06-0.5% for menthol, α-terpineol and terpinen-4-ol, 0.03-0.5% for carvacrol, and 0.06-4% for menthone. These compounds, with the exception of farnesol, menthone and tyrosol, showed important in vitro activities against the fluconazole-resistant and susceptible-dose dependent Candida isolates.
Carvacrol, eugenol, geraniol, linalool and terpinen-4-ol were very active in vitro against oral Candida isolates. Their fungistatic and fungicidal activities might convert them into promising alternatives for the topic treatment of oral candidiasis and denture stomatitis.
To investigate three tropical plant materials - clove seeds [Syzygium aromaticum (S. aromaticum)], bitter kola fruits [Garcinia kola (G. kola)] and tobacco leaves (Nicotiana species) as potential targeted killers of Streptococcus mutans (S. mutans), a cavity-causing bacterium (gram-positive, facultative anaerobe) that resides in a multispecies microbial community (dental plaque) for the treatment of dental caries (tooth decay).
Thirty one (31) teeth samples were collected from patients with obvious signs of tooth decay (swollen gum, weak or fallen tooth, etc.) using sterile swab sticks. These samples were collected from two major dental clinics in Nsukka, Enugu State, Nigeria and investigated by spread inoculation onto sterile blood agar and Mueller Hinton agar (MHA) respectively and incubated at 37 °C for 24 h. The discrete colonies obtained were further re-inoculated onto sterile Mitis salivarius agar (MSA) plates and incubated as above. The isolates were characterized by gram staining and catalase test. Tobacco leaves, clove seeds and bitter kola fruits were ground into powder, extracted with three different solvents (n-hexane, hot water and ethanol), filtered, dried and stored in clean containers, corked and kept until used. The plant extracts were investigated for phytochemistry, minimum inhibitory concentration (MIC), minimum cidal concentration (MCC) and compared with some conventional antibiotics commonly used against tooth decay. Antibiotic sensitivity test was also carried out. The results were statistically analyzed.
The extracts showed varied phytochemical composition but most abundantly the flavonoids. Our result also shows that females (16) have more tooth decay than males (15) and that 16 samples were very bloody while 15 were slightly bloody. The microbial characterization showed that 18 samples were catalase-positive indicating the presence of S. mutans while 13 were catalase-negative suspected to be Staphylococcus spp. The Gram reaction confirmed 13 Gram-negative and 18 Gram-positive organisms. The n-hexane extract had the best antimicrobial activity followed by the ethanol and lastly hot water. MIC showed that n-hexane clove extract had the largest inhibition zone diameter, followed by bitter kola extract and lastly tobacco extract. The antibiotic sensitivity test credited ciprofloxacin the best because it exhibited broad spectrum of action.
Since the n-hexane extract of clove seeds demonstrated preferential growth-inhibitory activity against the causal cariogenic pathogens (S. mutans) in dental caries, we therefore, report here that clove extract be henceforth considered as a potential ingredient in toothpaste preparation.
The antimicrobial activities of the ethyl acetate, acetone and methanol extract of 12 plant species were studied. The extract of Capsicum annuum (red pepper) (fruit) Zingiber officinale (ginger) (root), Cuminum cyminum (cumin), Alpinia ficinarum (galingale), Coriandrum sativum (coriander), Cinnamomun zeylanicum Nees (cinnamomun), Origanum onites L. (thyme), Folium sennae (senna), Eugenia caryophyllata (cloves), Flos tiliae (lime), Folium menthae crispae (peppermint) and Piper nigrum (blackpepper) were tested in vitro against 2 fungi and 8 bacterial species by the disc diffusion method. Klebsiella pneumonia 13883, Bacillus megaterium NRS, Pseudomonas aeroginosa ATCC 27859, Staphylococcus aureus 6538 P, Escherichia coil ATCC 8739, Enterobacter cloaca ATCC 13047, Corynebacterium xerosis UC 9165, Streptococcus faecalis DC 74, Kluyveromyces marxianus, Rhodotorula rubra were used in this investigation. The results indicated that extracts of different spices has shown antibacterial activity in the range of 7-24 mm 30 microl(-1) inhibition zone Eugenia caryophyllata (clove), 7-20 mm 30microl(-1) inhibition zone Capsicum annum (red pepper) and Cinnamomun zeylanicum (cinnamon) bark, 7-18 mm 30microl(-1) inhibition zone Folium sennae (senna) leaves, 7-16 mm 30 microl(-1) inhibition zone Zingiber officinale (ginger) root, 7-15 mm 30microl(-1) inhibition zone Cuminum cyminum (cumin) seed, 7-14 mm 30 microl(-1) inhibition zone Folium menthae crispae (peppermint), Origanum onites (thyme) leaves and Alpinia ficinarum (galingale) root, 7-12 mm 30 microl(-1) inhibiton zone Piper nigrum (blackpepper), 7-11 mm 30microl(-1) inhibition zone Flos tiliae (lime) leaves, 7-8 mm 30microl(-1) inhibition zone Coriandrum sativum (coriander) to the microorganisms tested.
Therapy for candidiasis is becoming problematic due to the toxicities of currently available antifungal agents and the increasing
prevalence of resistance among the etiologic agents. Therefore, new antifungals and alternative approaches are needed. In
this study, 20 fluconazole-resistant strains of Candida albicans were found to have varying levels of resistance to other azoles, i.e., itraconazole (MIC of 4–128 μg/ml) and ketoconazole
(2–256 μg/ml). In addition, 13 of these isolates appeared resistant to amphotericin B (32–128 μg/ml). A total of 21 plant
essential oils were screened for their antifungal activity against these multi-drug resistant isolates. The oils of Cymbopogon martini, i.e., citral and cinnamaldehyde, exhibited strong inhibitory activity with minimum inhibitory concentrations (MIC50) ranging from 90–100 μg/ml. The test oils were more effective than fluconazole and amphotericin B in inhibiting azole- and
amphotericin B-resistant, as well as amphotericin B-susceptible isolates. The test oils and especially eugenol, exhibited
significant synergy with fluconazole or amphotericin B against the test isolates. These findings suggest the possible effective
use of certain oils alone or in combination with fluconazole or amphotericin B, against multi-drug resistant isolates of C. albicans.
This study examined the efficacy of hydroalcoholic extract of dried clove buds, which is rich in phenolic compounds namely eugenol and eugenol derivatives (precursors of flavones, isoflavones and flavonoids), on different primary and secondary osteoporotic marker changes in an ovariectomised (OVX) rat model of osteoporosis. Female Wistar rats were randomly divided into three groups: sham-operated control (A), OVX (B) and OVX plus 50% hydroalcoholic extract of dried clove buds for 4 weeks (C). Results indicated that, compared to control, serum alkaline phosphatase (AP; 48.25%, p < 0.01), serum tartrate-resistant acid phosphatase (TRAP; 63.48%, p < 0.01), urinary calcium (14.70%, p < 0.01), urinary phosphate (50.30%, p < 0.01) and urinary creatinine (122.44%, p < 0.01) were significantly altered in OVX rats. All these altered responses were significantly restored (AP: 27.53%, p < 0.01; TRAP: 33.51%, p < 0.01; calcium: 53.15%, p < 0.01; phosphate: 27.49%, p < 0.01; creatinine: 46.40%, p < 0.01) by supplementation with hydroalcoholic extract of dried clove buds. Results of bone density, bone mineral content, bone tensile strength and histological analysis also showed similar trend of results, which supported initial observations of this study. It is proposed that hydroalcoholic extract of dried clove buds has bone-preserving efficacy against hypogonadal osteoporosis.
Eugenol, the major constituent of clove oil, has been widely used for its anesthetic and analgesic action in dentistry. Eugenol exhibits pharmacological effects on almost all systems and our aim is to review the research work that has identified these pharmacological actions. Eugenol possesses significant antioxidant, anti-inflammatory and cardiovascular properties, in addition to analgesic and local anesthetic activity. The metabolism and pharmacokinetics of the compound in humans have been studied. Eugenol has also been used as a penetration enhancer. The compound is a very promising candidate for versatile applications, and the design of new drugs based on the pharmacological effects of eugenol could be beneficial.
Nineteen Thai medicinal plants used in Thai traditional medicine preparation to treat colds, asthma and fever were studied for their antioxidant and NO inhibitory activities. Three extracts were obtained from each plant. First extract obtained by macerating the plant part in 95% ethanol (Et) residue was boiled in water, where water extract (EW) was obtained. The third extract (HW) was obtained by boiling each plant in water similar to that of Thai traditional medicine practice. These extracts were tested for their antioxidant activity using DPPH assay, and anti-inflammatory activity by determination of inhibitory activity on lipopolysaccharide (LPS) induced nitric oxide (NO) production in RAW 264.7 cell lines using Griess reagent. Results indicated that Et, EW and HW of Syzygium aromaticum showed the highest antioxidant activity (EC50 = 6.56, 4.73 and 5.30 microg/ml, respectively). Et of Atractylodes lancea exhibited the most potent inhibitory activity on lipopolysaccharide (LPS) induced nitric oxide (NO) production in RAW 264.7 cells, with IC50 value of 9.70 microg/ml, followed by Et of Angelica sinensis and Cuminum cyminum (IC50 = 12.52 and 13.56 microg/ml, respectively) but water extract (EW, HW) of all plants were apparently inactive. These results of anti-inflammatory activity of these plants correspond with the traditional use for fever; cold, allergic-related diseases and inflammatory-related diseases.
In this study, the antibacterial activities of eugenol, cinnamaldehyde, thymol, carvacrol, and their combinations against E. coli were investigated separately. First, broth macro-dilution assay was adopted to determine the minimal inhibitory concentration (MIC) of the 4 components. Second, the combination testing was performed using chequerboard method. Finally, the combined effects were evaluated with an improved method, which was based on the indices of fractional inhibitory concentration (FIC) and Effect of the Combination (EC) jointly. The results indicated that MICs of the 4 components were 1600, 400, 400, and 400 mg/L, respectively; treatments with cinnamaldehyde/eugenol, thymol/eugenol, carvacrol/eugenol, and thymol/carvacrol revealed synergistic effects according to the 2 indices. By means of combination, MICs of eugenol, cinnamaldehyde, thymol, and carvacrol decreased to 400, 100, 100, and 100 mg/L, respectively. Consequently, the negative impacts of unpleasant smell of these 4 components could be minimized, making it possible to add them to foods as preservatives. In addition, this improved evaluation method provided a more accurate and comprehensive way to evaluate combined effects.
To evaluate quorum sensing (QS) inhibitory activity of plant essential oils using strains of Chromobacterium violaceum (CV12472 and CVO26) and Pseudomonas aeruginosa (PAO1).
Inhibition of QS-controlled violacein production in C. violaceum was assayed using disc diffusion and agar well diffusion method. Of the 21 essential oils, four oils showed varying levels of anti-QS activity. Syzygium aromaticum (Clove) oil showed promising anti-QS activity on both wild and mutant strains with zones of pigment inhibition 19 and 17 mm, respectively, followed by activity in cinnamon, lavender and peppermint oils. The effect of clove oil on the extent of violacein production was estimated photometrically and found to be concentration dependent. At sub-MICs of clove oil, 78.4% reduction in violacein production over control and up to 78% reduction in swarming motility in PAO1 over control were recorded. Gas chromatography-mass spectrometry analysis of clove oil indicated presence of many phytocompounds. Eugenol, the major constituent of clove oil could not exhibit anti-QS activity.
Presence of anti-QS activity in clove oil and other essential oils has indicated new anti-infective activity. The identification of anti-QS phytoconstituents is needed to assess the mechanism of action against both C. violaceum and Ps. aeruginosa.
Essential oils having new antipathogenic drugs principle because of its anti-QS activity might be important in reducing virulence and pathogenicity of drug-resistant bacteria in vivo.
The effect of temperature, concentration and contact time on the fungicidal effect of clove oleoresin dispersed in a concentrated sugar solution at 21 and 37ºC, and clove oleoresin at 0.2 to 0.8% (v/v) was studied. The test microorganisms were Candida albicans, Penicillium citrinum, Aspergillus niger and Trichophyton mentagrophytes. The fungicidal effect was enhanced at 37ºC; at this temperature short contact times (e.g. 1 min.) were enough to eliminate a microbial inoculum of 10(6) c.f.u./ml of C. albicans. Although clove oleoresin caused important lethal effect, P. citrinum and A. niger were more resistant. After 60 minutes, clove oleoresin dispersed (0.4% v/v) in concentrated sugar solution caused a 99.6% reduction of the initial population (10(6) c.f.u./ml) of Trichophyton mentagrophytes. The fungicidal activity of clove-sugar on C. albicans, after 2 min contact, was similar to that presented by disinfectants commonly used in hospitals, such as povidone-iodine and chloroxylenol.
The essential oils of the leaves of Eugenia brasiliensis, Eugenia beaurepaireana, and Eugenia umbelliflora were analyzed by GC-MS. The major compounds found in the oil of E. brasiliensis were spathulenol (12.6%) and tau-cadinol (8.7%), of E. beaurepaireana were beta-caryophyllene (8.0%) and bicyclogermacrene (7.2%), and of E. umbelliflora were viridiflorol (17.7%) and beta-pinene (13.2%). These oils were assayed to determine their antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. All of the oils analyzed showed antibacterial activity, ranging from moderate to strong, which was most accentuated for the E. umbelliflora and E. brasiliensis oils, which strongly inhibited the growth of S. aureus giving values of MIC = 119.2 and 156.2 microg/mL, respectively.
The compositional profile of the essential oils isolated from Eugenia uniflora L. revealed the occurrence of an unusual sesquiterpene as the major compound. The volatile oils were characterized by the abundance of curzerene (19.7%), selina-1,3,7(11)-trien-8-one (17.8%), atractylone (16.9%) and furanodiene (9.6%) in the leaves; and germacrone (27.5%), selina-1,3,7(11)-trien-8-one (19.2%) curzerene (11.3%) and oxidoselina-1,3,7(11)-trien-8-one (11.0%) in the fruits. The two oils exhibited potent cytotoxic activity and varying antibacterial effects.
The ability of Listeria monocytogenes to survive and grow at refrigeration temperature in some ready to eat (RTE) poultry products is a public health concern. The inhibitory effect of clove oil (1% and 2%, v/w) applied to the surface of RTE chicken frankfurters was determined on seven strains of L. monocytogenes inoculated at low (102–103cfu/g) or high cell numbers (104–106cfu/g), and stored at 5°C for 2 weeks or at 15°C for 1week. All strains of L. monocytogenes survived and grew on control frankfurters at 5°C and 15°C but growth was inhibited under both storage conditions in the presence of either 1% or 2% clove oil. Depending on the sensory considerations, the addition of clove oil to frankfurters may be an effective strategy to control L. monocytogenes in chicken frankfurters.
We recently reported that eugenol exerted comparable cytotoxicity towards human normal and tumor cells. In the present study, we investigated the effect of eugenol on interleukin-8 (IL-8) production by IL-1β-stimulated oral cells.
The viable cell number was determined by direct cell counting with a hemocytometer after trypsinization. IL-8 released into the culture medium was determined by enzyme-linked immunosorbent assay (ELISA).
IL-1β (5 ng/ml) induced two orders of magnitude higher production of IL-8 by human cultured cells than unstimulated cells. Upon IL-1β stimulation, both gingival fibroblasts (HGF) and periodontal ligament fibroblasts (HPLF) produced the greatest amounts of IL-8 (approximately 200-300 ng/ml), followed by pulp cells (HPCs) (approximately 40-50 ng/ml), whereas skin keratinocyte (HaCat) and oral squamous cell carcinoma cells (HSC-2, HSC-4) produced much less IL-8 (less than 15 ng/ml). The production of IL-8 depended on growth factor(s), since the omission of fetal bovine serum from the culture medium resulted in an approximately 90% decline of IL-8 production. Eugenol (5-500 μM) significantly stimulated IL-8 production in HGF cells, but had bi-modal effects on HPCs, causing slight stimulation at lower concentration (5 μM) and a significant inhibition at higher concentration (500 μM), regardless of the presence or absence of serum. Eugenol exerted similar effects on lipopolysaccharide-stimulated HGFs and HPCs.
These results demonstrate that an anti-inflammatory effect of eugenol is observed in HPCs, but not in HGFs. The narrow therapeutic range of eugenol suggests the importance of careful usage of this compound for dental treatment.
Periodontal diseases are common inflammatory conditions of the supporting apparatus of the teeth which lead to early tooth loss. This review discusses the evidence for a role of reactive oxygen species in inducing periodontal tissue damage and focuses on recent evidence showing increased local and systemic alterations in the redox balance of periodontitis. An appraisal of the methods for analysis of oxidative stress in periodontal disease research is provided, showing an increase in oxidative stress measures and oxidative damage fingerprints detected in studies investigating periodontitis cases compared to healthy controls. Hypotheses on the relationships between oxidative stress and inflammatory responses and on the role of redox status in periodontal medicine are discussed. Finally, the review provides an overview of possible intervention pathways for the use of antioxidants as adjuncts to mechanical biofilm removal for the treatment of periodontitis.
To investigate the effects of the clove oil constituents β-caryophyllene oxide and eugenol on the heart muscle, experiments were performed on isolated papillary muscles and on ventricular myocytes of the guinea-pig. The results were compared with those obtained with the dihydropyridine, nifedipine.
All three substances exerted negative inotropic effects in heart muscle although with different potencies and different influences on the time course of the contraction curve.
They all reduced rested-state contractions (RSCs) in the presence of isoprenaline which are thought to be due to the Ca2+ current (ICa).
β-Caryophyllene oxide, eugenol and nifedipine inhibited the ICa in single cells from the guinea-pig ventricle in a concentration-dependent, reversible way, but with different potencies.
In addition to the ICa-inhibiting effect, β-caryophyllene oxide strongly inhibited and eugenol slightly inhibited the potassium current.
The action potential of papillary muscles at a 1 Hz contraction frequency was greatly shortened by nifedipine, slightly shortened by eugenol, but not changed by β-caryophyllene oxide.
The inhibition of the potassium current by β-caryophyllene oxide obviously prevents a shortening of the action potential due to the diminution of the ICa. Accordingly, the negative inotropic effect of β-caryophyllene oxide is closely related to the inhibition of ICa. In contrast, eugenol and nifedipine, which shorten the action potential, exert stronger negative inotropic effects than expected from their influence on ICa.
The results show that the negative inotropic effect of a calcium channel blocker can be attenuated by an additional inhibition of potassium channels.
British Journal of Pharmacology (2000) 131, 1089–1096; doi:10.1038/sj.bjp.0703673
The extract and essential oil of clove (Syzygium aromaticum) are widely used because of their medicinal properties. Eugenol is the most important component of clove, showing several biological properties. Herein we have analysed the immunomodulatory/anti-inflammatory effect of clove and eugenol on cytokine production (interleukin (IL)-1β, IL-6 and IL-10) in vitro.
Macrophages were incubated with clove or eugenol (5, 10, 25, 50 or 100µg/well) for 24h. Concentrations that inhibited the production of cytokines were used before or after incubation with lipopolysaccharide (LPS), to verify a preventive or therapeutic effect. Culture supernatants were harvested for measurement of cytokines by enzyme-linked immunosorbent assay.
Clove (100µg/well) inhibited IL-1β, IL-6 and IL-10 production and exerted an efficient action either before or after LPS challenge for all cytokines. Eugenol did not affect IL-1β production but inhibited IL-6 and IL-10 production. The action of eugenol (50 or 100µg/well) on IL-6 production prevented efficiently effects of LPS either before or after its addition, whereas on IL-10 production it counteracted significantly LPS action when added after LPS incubation.
Clove exerted immunomodulatory/anti-inflammatory effects by inhibiting LPS action. A possible mechanism of action probably involved the suppression of the nuclear factor-κB pathway by eugenol, since it was the major compound found in clove extract.
Many essential oils have been advocated for use in complementary medicine for bacterial and fungal infections. However, few of the many claims of therapeutic efficacy have been validated adequately by either in vitro testing or in vivo clinical trials.
To study the antibacterial activity of nine commercially available essential oils against Streptococcus mutans in vitro and to compare the antibacterial activity between each material.
Nine pure essential oils; wintergreen oil, lime oil, cinnamon oil, spearmint oil, peppermint oil, lemongrass oil, cedarwood oil, clove oil and eucalyptus oil were selected for the study. Streptococcus mutans was inoculated at 37ºC and seeded on blood agar medium. Agar well diffusion assay was used to measure antibacterial activity. Zone of inhibition was measured around the filter paper in millimeters with vernier caliper. Results: Cinnamon oil showed highest activity against Streptococcus mutans followed by lemongrass oil and cedarwood oil. Wintergreen oil, lime oil, peppermint oil and spearmint oil showed no antibacterial activity.
Cinnamon oil, lemongrass oil, cedarwood oil, clove oil and eucalyptus oil exhibit antibacterial property against S. mutans.
The use of these essential oils against S. mutans can be a viable alternative to other antibacterial agents as these are an effective module used in the control of both bacteria and yeasts responsible for oral infections.
In the present study eugenol loaded solid lipid nanoparticles (SLN) was prepared and characterized for particle size, polydispersity index, zeta potential, encapsulation efficiency, in vitro release and in vivo antifungal activity. Effect of addition of liquid lipid (caprylic triglyceride) to solid lipid (stearic acid) on crystallinity of lipid matrix of SLN was determined by using Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. Transmission electron microscopy (TEM) was carried out to determine the morphology of SLN. In vivo antifungal activity of eugenol loaded lipid nanoparticles was evaluated by using a model of oral candidiasis in immunosuppressed rats. Particle size results showed that d90 of SLN1 (single lipid matrix) and SLN2 (binary lipid matrix) was 332±14.2nm and 87.8±3.8nm, respectively. Polydispersity index was found to be in the range of 0.27-0.4 which indicate moderate size distribution. Encapsulation efficiency of SLN2 (98.52%) was found to be more than that of SLN1 (91.80%) at same lipid concentration (2%, w/v). Increasing of the solid lipid concentration from 2% (w/v) to 4% (w/v) resulted in increase in encapsulation efficiency and the particle size. SLN2 shows faster release of eugenol than that of SLN1 due to smaller size and presence of liquid lipid which provide less barriers to the diffusion of drug from matrix. TEM study reveals the spherical shape of SLN. FT-IR, DSC and XRD results indicate less crystallinity of SLN2 than that of SLN1. In vivo studies show no significant difference in log cfu value of all the groups at 0 day. At 8th day, log cfu value of group treated with saline (control), standard antifungal agent, eugenol solution, SLN1 and SLN2 was found to be 3.89±.032, 2.69, 3.39±.088, 3.19±.028 and 3.08±0.124, respectively. The in vivo study results indicate improvement in the antifungal activity of eugenol when administrated in the form of SLN.
Essential oils have been found to be antibacterial, antifungal, spasmolytic, and antiplasmodial activity and therapeutic effect in cancer treatment.
In this study, clove oil and its major compounds, eugenol and β-caryophyllene were evaluated against oral bacteria, either alone or in combination with ampicillin or gentamicin, via checkerboard and time kill assay.
The antibacterial activity of the clove oil was higher than β-caryophyllene but was similar to eugenol against all tested oral bacteria. Furthermore, the MIC and MBC were reduced to one half-one sixteenth as a result of the combination of clove oil or eugenol with antibiotics. The synergistic interaction was verified by time kill studies using the clove oil or eugenol with antibiotics. 60 min of treatment with MIC of the clove oil or eugenol with ampicillin or gentamicin resulted in an increase in the rate of killing in units of CFU/mL to a greater degree than was observed with alone.
The results suggest that the clove oil and eugenol could be employed as a natural antibacterial agent against cariogenic and periodontopathogenic bacteria.
Objective: To investigate the antinociceptive potential of eugenol on different pain models in mice. Materials and Methods : Eugenol was evaluated (1-100 mg/kg, i.p.) in various experimentally induced pain models like, formalin induced hyperalgesia, acetic acid induced abdominal constrictions, and thermal pain experiment using Eddy's hot plate. Results : Eugenol significantly inhibited acetic acid induced abdominal constrictions, with the maximal effect (92.73% inhibition) at 100 mg/kg. In formalin induced paw licking pain model, eugenol exhibited more pronounced antinociceptive effect in the inflammatory phase than the neurogenic phase (maximal effect was 70.33% and 42.22%, respectively, at 100 mg/kg, i.p). A mild reduction in the pain response latency at 100 mg/kg, i.p. dose of eugenol was observed in the hotplate thermal pain studies in mice. In the rotarod motor coordination experiment eugenol reduced the endurance time at the dose of 100 mg/kg, i.p. Conclusion: The data suggest that eugenol exerts antinociceptive activity in different experimental models of pain in mice.
To evaluate the antibacterial activity of eugenol and its mechanism of bactericidal action against Salmonella typhi.
The antibacterial activity was checked by disc-diffusion method, MIC, MBC, time course assay and pH sensitivity assay. The chemo-attractant property of eugenol was verified by chemotaxis assay. The mode of action of eugenol was determined by crystal violet assay, measurement of release of 260 nm absorbing material, SDS-PAGE, FT-IR spectroscopy, AFM and SEM.
Treatment with eugenol at their MIC (0.0125%) and MBC (0.025%) reduced the viability and resulted in complete inhibition of the organism. Eugenol inactivated Salmonella typhi within 60 min exposure. The chemo-attractant property of eugenol combined with the observed high antibacterial activity at alkaline pH favors the fact that the compound can work more efficiently when given in vivo. Eugenol increased the permeability of the membrane, as evidenced by crystal violet assay. The measurement of release of 260 nm absorbing intracellular materials, SDS-PAGE, SEM and AFM analysis confirmed the disruptive action of eugenol on cytoplasmic membrane. The deformation of macromolecules in the membrane, upon treatment with eugenol was verified by FT-IR spectroscopy.
The results suggest that the antibacterial activity of eugenol against Salmonella typhi is due to the interaction of eugenol on bacterial cell membrane.
The comparison of the efficacy of surgical and nonsurgical procedures revealed that scaling and root planing alone or in combination with flap procedures are effective methods for the treatment of chronic periodontitis. Also, the consistent message is that in treating deep pockets, open-flap debridement results in greater probing pocket depth reduction and clinical attachment gain than nonsurgical modalities. Nonsurgical modalities in shallower pockets consistently involve less post-therapy recession and are clearly recognized as being more conservative. Research is still needed on the clinical benefit of the granulation tissue removal that is a feature of periodontal surgical therapy and, to a lesser extent, occurs through indirect trauma in nonsurgical therapy.
The present study was designed to investigate the protective efficacy of eugenol against skin cancer and probe into the mechanistic aspects. Skin tumors were initiated by applying 160 nmol DMBA and promoted by twice weekly applications of 8.5 nmol TPA for 28 wk. All mice developed tumors by 13 wk of promotion. However, in mice pretreated with 30 microL eugenol, no tumors were detected until 8 wk (following anti-initiation protocol) and until 14 wk (following antipromotion protocol) of tumor promotion. PCNA and TUNEL immunohistochemistry of tumors revealed eugenol to ameliorate cell proliferation and elevate apoptosis respectively. The effect of eugenol was assessed on specific stages of carcinogenesis. Initiation with DMBA led to a significant upregulation of p53 expression with a concomitant increase in p21(WAF1) levels in epidermal cells indicating induction of damage to the DNA. However, pretreatment with eugenol led to overexpression of these genes, which probably helped stimulate apoptosis of the initiated cells. To ascertain the molecular mechanisms implicated in the antitumor promoting activity of eugenol, its effect was investigated on markers of tumor promotion and inflammation: ODC activity and iNOS and COX-2 expression, and on levels of proinflammatory cytokines (IL-6, TNF-alpha, and PGE(2)). Eugenol markedly inhibited all. Eugenol also inhibited the upstream signaling molecule: NF-kappaB, which regulates the expression of these genes. TPA-induced depletion of cutaneous GSH and antioxidant enzymes armory was also precluded by eugenol. From these results, it could be concluded that eugenol markedly protects against chemically induced skin cancer and acts possibly by virtue of its antiproliferative, anti-inflammatory, and antioxidant activities.
Periodontal diseases, if left unchecked, can lead to major health problems. There are a number of traditional herbal remedies for the treatment and management of diseases related to teeth, gum and oral hygiene. Use of clove oil is an age old remedy still practiced for periodontal problems. Our aim is to present an overall view of the current strategies adopted for the formulation and application of traditional herbal remedies. The article provides a review of the patents obtained on herbal remedies for the treatment of periodontal diseases. In addition, it also provides an overall view of potent herbal remedies widely used for periodontal diseases.
The impact of diet and specific food groups on respiratory tract infections has been widely recognized in recent years. This study was conducted to study the effect of tulsi (Ocimum sanctum) oil and clove (Syzgium aromaticum) oil on the susceptibility of experimental mice to respiratory tract infection.
The effect of 2 different regimens of short-term (15 days) and long-term (30 days) feeding with tulsi oil and clove oil on the course of Klebsiella pneumoniae American Type Culture Collection 43816 infection in the lungs of mice was analyzed. The operative mechanisms of lipid peroxidation/nitrite production were studied by estimating their levels in bronchoalveolar lavage fluid (BALF). Bacterial colonization, malondialdehyde (MDA) and nitrite production in BALF, and tumor necrosis factor-alpha level in serum were assessed.
The results showed that there was a significant decrease in bacterial colonization after short-term feeding with clove oil compared with the controls (p < 0.05). For tulsi oil-fed mice, the decrease in bacterial load was significant with long-term feeding (p < 0.01). The maximum decrease in MDA levels and increase in nitrite levels were noted with long-term feeding.
Dietary supplementation with tulsi and clove oils protects against bacterial colonization of the lungs.
The composition and antifungal activity of clove essential oil (EO), obtained from Syzygium aromaticum, were studied. Clove oil was obtained commercially and analysed by GC and GC-MS. The EO analysed showed a high content of eugenol (85.3 %). 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 EO and eugenol showed inhibitory activity against all the tested strains. To clarify its mechanism of action on yeasts and filamentous fungi, flow cytometric and inhibition of ergosterol synthesis studies were performed. Propidium iodide rapidly penetrated the majority of the yeast cells when the cells were treated with concentrations just over the MICs, meaning that the fungicidal effect resulted from an extensive lesion 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 oil and eugenol concentrations below the MIC values. The present study indicates that clove oil and eugenol have considerable antifungal activity against clinically relevant fungi, including fluconazole-resistant strains, deserving further investigation for clinical application in the treatment of fungal infections.
In this study, clove bud oil, which was cultivated in the Mediterranean region of Turkey, was provided from a private essential oil company in Turkey. Essential oil from clove (Syzygium aromaticum L.) was obtained from steam-distillation method, and its chemical composition was analyzed by GC and GC-MS. The results showed that the essential oils mainly contained about 87.00% eugenol, 8.01% eugenyl acetate and 3.56% β-Caryophyllene. The chemical composition of the Turkish clove bud oil was comparable to those of trees naturally grown in their native regions.
To compare the bacteriostatic and bactericidal activity of 13 chemotyped essential oils (EO) on 65 bacteria with varying sensitivity to antibiotics.
Fifty-five bacterial strains were tested with two methods used for evaluation of antimicrobial activity (CLSI recommendations): the agar dilution method and the time-killing curve method. EO containing aldehydes (Cinnamomum verum bark and Cymbopogon citratus), phenols (Origanum compactum, Trachyspermum ammi, Thymus satureioides, Eugenia caryophyllus and Cinnamomum verum leaf) showed the highest antimicrobial activity with minimum inhibitory concentration (MIC) <2% (v/v) against all strains except Pseudomonas aeruginosa. Alcohol-based EO (Melaleuca alternifolia, Cymbopogon martinii and Lavandula angustifolia) exhibited varying degrees of activity depending on Gram status. EO containing 1.8-cineole and hydrocarbons (Eucalyptus globulus, Melaleuca cajeputii and Citrus sinensis) had MIC(90%) > or = 10% (v/v). Against P. aeruginosa, only C. verum bark and O. compactum presented MIC < or =2% (v/v). Cinnamomum verum bark, O. compactum, T. satureioides, C. verum leaf and M. alternifolia were bactericidal against Staphylococcus aureus and Escherichia coli at concentrations ranging from to 0.31% to 10% (v/v) after 1 h of contact. Cinnamomum verum bark and O. compactum were bactericidal against P. aeruginosa within 5 min at concentrations <2% (v/v).
Cinnamomum verum bark had the highest antimicrobial activity, particularly against resistant strains.
Bacteriostatic and bactericidal activity of EO on nosocomial antibiotic-resistant strains.
Eugenol, the principal chemical component of clove oil from Eugenia aromatica has been long known for its analgesic, local anesthetic, anti-inflammatory, and antibacterial effects. The interaction of the eugenol with ten different hydrophobic and hydrophilic antibiotics was studied against five different Gram negative bacteria. The MIC of the combination was found to decrease by a factor of 5-1000 with respect to their individual MIC. This synergy is because of the membrane damaging nature of eugenol, where 1mM of its concentration is able to damage nearly 50% of the bacterial membrane. Eugenol was also able to enhance the activities of lysozyme, Triton X-100 and SDS in damaging the bacterial cell membrane. The hydrophilic antibiotics such as vancomycin and beta-lactam antibiotics which have a marginal activity on these gram negative bacteria exhibit an enhanced antibacterial activity when pretreated with eugenol. Reduced usage of antibiotics could be employed as a treatment strategy to slow down the onset of antibiotic resistance as well as decrease its toxicity. Experiments performed with human blood cells indicated that the concentration of eugenol used for the combination studies were below its cytotoxic values. Pharmacodynamic studies of the combinations need to be performed to decide on the effective dosage.
Hospital-acquired infections and antibiotic-resistant bacteria continue to be major health concerns worldwide. Particularly problematic is methicillin-resistant Staphylococcus aureus (MRSA) and its ability to cause severe soft tissue, bone or implant infections. First used by the Australian Aborigines, Tea tree oil and Eucalyptus oil (and several other essential oils) have each demonstrated promising efficacy against several bacteria and have been used clinically against multi-resistant strains. Several common and hospital-acquired bacterial and yeast isolates (6 Staphylococcus strains including MRSA, 4 Streptococcus strains and 3 Candida strains including Candida krusei) were tested for their susceptibility for Eucalyptus, Tea tree, Thyme white, Lavender, Lemon, Lemongrass, Cinnamon, Grapefruit, Clove Bud, Sandalwood, Peppermint, Kunzea and Sage oil with the agar diffusion test. Olive oil, Paraffin oil, Ethanol (70%), Povidone iodine, Chlorhexidine and hydrogen peroxide (H(2)O(2)) served as controls. Large prevailing effective zones of inhibition were observed for Thyme white, Lemon, Lemongrass and Cinnamon oil. The other oils also showed considerable efficacy. Remarkably, almost all tested oils demonstrated efficacy against hospital-acquired isolates and reference strains, whereas Olive and Paraffin oil from the control group produced no inhibition. As proven in vitro, essential oils represent a cheap and effective antiseptic topical treatment option even for antibiotic-resistant strains as MRSA and antimycotic-resistant Candida species.
Food constituents are the major source of various phytochemicals and micronutrients. The importance of these dietary constituents has been stressed in recent years due to their antioxidant and anticarcinogenic potential. Spices used in Indian foods such as cloves (Syzygium aromaticum), licorice (Glycyrrhiza glabra), mace (aril of Myristica fragans), and greater cardamom (Amomum subulatum) were tested for their antioxidant properties in vitro. The metal chelating activity, bleomycin dependent DNA oxidation, diphenyl-p-picryl hydrazyl (DPPH) radical scavenging activity and the ferric reducing /antioxidant power (FRAP) were measured in rat liver homogenate in presence of spices. Metal chelating activity was significantly high with all the spice extracts except mace. The spices due to higher reducing potential (in presence of bleomycin-FeCl_{3}) showed increased DNA oxidation. Cloves showed the highest DPPH radical scavenging activity, followed by licorice, mace and cardamom. FRAP values for cloves were also the highest, while other spices showed comparatively lesser FRAP values. The results show that the spices tested are strong antioxidants and may have beneficial effects on human health.
Eugenol-containing dental materials are frequently used in clinical dentistry. When zinc oxide-eugenol (ZOE) is applied to a dentinal cavity, small quantities of eugenol diffuse through the dentin to the pulp. Low concentrations of eugenol exert anti-inflammatory and local anesthetic effects on the dental pulp. Thus use of ZOE temporary filling may facilitate pulpal healing; on the other hand, high eugenol concentrations are cytotoxic. Direct application of eugenol to pulp tissue may result in extensive tissue damage. The ability of ZOE-based endodontic sealers to influence periapical tissue healing is considered in view of eugenol's anti-inflammatory and toxic properties.
The mechanism of inhibition of prostaglandin H synthase (PHS) by eugenol was investigated using purified apoenzyme reconstituted with either manganese protoporphyrin IX (Mn-PHS) or hematin (Fe-PHS). Eugenol stimulated Fe-PHS activity at low concentrations and inhibited at higher concentrations, an activity typical of many phenolic compounds. Eugenol was also an excellent reducing cosubstrate for the peroxidase, being cooxidized to a reactive quinone methide in the process. Higher concentrations of eugenol were required to inhibit Fe-PHS than Mn-PHS (which retains cyclooxygenase activity but not peroxidase activity). Inhibition by eugenol was highly dependent on arachidonic acid concentration. In experiments using Mn-PHS, eugenol increased the time required for the initiation of O2 consumption after addition of arachidonic acid and also inhibited the rate of O2 uptake. Eugenol did not, however, affect the total amount of O2 consumed. The addition of 10 microM hydroperoxide (prostaglandin G2) to these incubations did not prevent the inhibitory effects of eugenol. Other phenolic compounds, including guaiacol, butylated hydroxyanisole, and acetaminophen inhibited Mn-PHS in a manner similar to eugenol. These results demonstrate that eugenol and other phenolic compounds specifically inhibit the cyclooxygenase component of PHS and that this inhibition occurs in addition to, or independent of, the effect of these compounds on peroxide tone or their peroxidative metabolism. We suggest that this inhibition is due to competition with arachidonic acid for the active site of PHS.
This chapter discusses the role of flavonoids and iron chelation in antioxidant action. The potential of flavonoids to inhibit lipid peroxidation in biological models is supposed to reside mainly in their free radical scavenging capacity rather than in their iron chelating activity. This property is considered as a minor mechanism in the antioxidant action, because it has not been clearly established in biological systems. The assessment of a relationship between the antioxidant effect and the iron chelating capacity of flavonoids is subsequently of interest. For this purpose, rat is used hepatocyte cultures as a biological model where lipid peroxidation is induced by iron [Fe(III)] in its complexed form with nitrilotriacetic acid (NTA). The Fe-NTA complex is known to induce a rapid accumulation of iron inside the cells. Nitrilotriacetic acid (NTA) is used to maintain ferric iron in a soluble state; it is a low-affinity iron chelator.
A case of ingestion of oil of cloves is presented, which resulted in coma, fits, a coagulopathy, and acute liver damage. This is not unlike the syndrome produced in the late stages of a substantial paracetamol overdose, and a similar treatment regimen is proposed.