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At least 127 records · Page 7Linked to original sources
PubMed1998

Postischemic hypothermia induced by eugenol protects hippocampal neurons from global ischemia in gerbils.

We studied whether eugenol provides neuroprotection against delayed neuronal death in the hippocampal CA1 region following a 5 min occlusion of the common carotid arteries bilaterally under either free-regulating temperature (TF) or maintained temperature (TM, 37 degrees C) conditions in gerbils. Right after occlusion of the carotid arteries, we injected eugenol intraperitoneally at concentrations of either 50, 100, or 200 mg/kg. There was significant preservation of neuronal cells in the CA1 region in the eugenol-treated groups 7 days after the ischemic insult in the TF condition, with respective survival values of 26, 43, and 68%. In the TM condition, however, significant neuroprotection was only seen with eugenol concentrations of 100 and 200 mg/kg (32% and 52%, respectively). When the rectal temperature was maintained at 38 degrees C for 30 min after occlusion of the carotid arteries, no reduction in CA1 damage was observed with any dose of eugenol. These results suggest that eugenol may provide neuroprotection against ischemic damage by its hypothermic action.

Animals↗
PubMedDate not supplied

Oxidation of eugenol by purified human term placental peroxidase.

The oxidation of eugenol by purified human term placental peroxidase (HTPP) was examined. Spectral analyses indicated that, similar to horseradish peroxidase, HTPP is capable of catalyzing the oxidation of eugenol. The accumulated stable product in the reaction medium due to eugenol oxidation by HTPP was tentatively identified as quinone methide of eugenol (EQM). The EQM formation exhibited a pH optimum of 8.0 and was dependent on incubation time, amount of HTPP and the concentration of both eugenol and hydrogen peroxide. The specific activity of approx 2.8 micromoles of EQM/min/mg protein was observed with different preparations of HTPP. The EQM formation was significantly suppressed by glutathione and ascorbic acid. The classical peroxidase inhibitors viz. potassium cyanide and sodium azide blocked the reaction in a concentration manner. Collectively, the results suggest that eugenol may undergo peroxidative metabolism in human placenta.

Eugenol↗
PubMed2006

Effects of eugenol on nerve and vascular dysfunction in streptozotocin-diabetic rats.

Hyperglycaemia in diabetes mellitus results in oxidative stress and pro-inflammatory changes which contribute to vascular complications including endothelial dysfunction and peripheral neuropathy. The aim of this study was to examine whether treatment with the dominant ingredient of clove oil, eugenol, which has antioxidant and anti-inflammatory properties, could improve diabetic vascular and nerve function in streptozotocin-induced diabetic rats. Intervention treatment was given for 2 weeks following 6 weeks of untreated diabetes. Dose-ranging studies on diabetic deficits in sciatic nerve motor and saphenous nerve sensory nerve conduction velocities gave ED50 values of 28 mg/kg and 9 mg/kg, respectively, conduction velocity being within the non-diabetic range at a dose of 200 mg/kg. Sciatic nerve endoneurial blood flow was 49% reduced by diabetes and this was completely corrected by 200 mg/kg eugenol treatment. Gastric fundus maximum nitrergic nerve-mediated relaxation was 44% reduced by diabetes; eugenol corrected this deficit by 69%. For renal artery rings, maximum endothelium-dependent relaxation to acetylcholine was 51% reduced by diabetes; eugenol corrected this deficit by 60%, with improvements in both nitric oxide and endothelium-derived hyperpolarising factor (EDHF)-mediated vasorelaxation components. Diabetes increased renal artery sensitivity to phenylephrine-mediated contraction, however, this was unaffected by eugenol treatment. Thus, aspects of both vascular and neural complications in experimental diabetes are improved by eugenol, which could have potential therapeutic implications for diabetic neuropathy and vasculopathy.

Animals↗
PubMed1999

Basic emotions evoked by eugenol odor differ according to the dental experience. A neurovegetative analysis.

Subjective individual experiences seem to indicate that odors may form strong connections with memories, especially those charged with emotional significance. In the dental field, this could be the case with the odorant eugenol, responsible for the typical clinging odor impregnating the dental office. The odor of eugenol could evoke memories of unpleasant dental experiences and, therefore, negative feelings such as anxiety and fear, since eugenates (cements containing eugenol) are used in potentially painful restorative dentistry. This hypothesis was tested by evaluating the emotional impact of the odor of eugenol through autonomic nervous system (ANS) analysis. The simultaneous variations of six ANS parameters (two electrodermal, two thermovascular and two cardiorespiratory), induced by the inhalation of this odorant, were recorded on volunteer subjects. Vanillin (a pleasant odorant) and propionic acid (an unpleasant one) served as controls. After the experiment, subjects were asked to rate the pleasantness versus unpleasantness of each odorant on an 11-point hedonic scale. The patterns of autonomic responses, obtained for each odorant and each subject, were transcribed into one of the six basic emotions defined by Ekman et al. (happiness, surprise, sadness, fear, anger and disgust). Results were compared between two groups of subjects divided according to their dental experience (fearful and non-fearful dental care subjects) and showed significant differences only for eugenol. This odorant was rated as pleasant by non-fearful dental subjects but unpleasant by fearful dental subjects. The evoked autonomic responses were mainly associated with positive basic emotions (happiness and surprise) in non-fearful dental subjects and with negative basic emotions (fear, anger, disgust) in fearful dental subjects. These results suggest that eugenol can be responsible for different emotional states depending on the subjects' dental experience, which seems to confirm the potential role of odors as elicitors of emotional memories. This study also supports the possible influence of the ambient odor impregnating the dental office, strengthening a negative conditioning toward dental care in some anxious patients.

Adult↗
PubMed2004

Eugenol stimulates lactate accumulation yet inhibits volatile fatty acid production and eliminates coliform bacteria in cattle and swine waste.

AIM: To determine how eugenol affects fermentation parameters and faecal coliforms in cattle and swine waste slurries stored anaerobically. METHODS AND RESULTS: Waste slurries (faeces:urine:water, 50:35:15) were blended with and without additives and aliquoted to triplicate 1-l flasks. Faecal coliforms were eliminated in cattle and swine waste slurries within 1 or 2 days with additions of eugenol at 10.05 mm (0.15%) and 16.75 mm (0.25%). At these concentrations volatile fatty acids (VFA) were reduced ca 70 and 50% in cattle and swine waste, respectively, over 6-8 weeks. Additionally, in cattle waste, eugenol stimulated the accumulation of lactate (>180 mm) when compared with thymol treatment (20 mm lactate). In swine waste, lactate accumulation did not occur without additives; eugenol and thymol stimulated lactate accumulation to concentrations of 22 and 32 mm, respectively. CONCLUSIONS: Eugenol added to cattle waste may be more beneficial than thymol because not only does it effectively control faecal coliforms and odour (VFA production), it also stimulates lactate accumulation. This in turn, causes the pH to drop more rapidly, further inhibiting microbial activity and nutrient emissions. SIGNIFICANCE AND IMPACT OF THE STUDY: Plant essential oils have the potential to solve some of the environmental problems associated with consolidated animal feeding operations. Thymol and eugenol reduce fermentative activity, thus, have the potential to reduce emissions of greenhouse gases and odour, and curtail transmission of pathogens in cattle and swine wastes.

Animals↗
PubMed2006

Pharmacokinetics and anesthetic activity of eugenol in male Sprague-Dawley rats.

Eugenol, the principle chemical constituent of clove oil, has recently been evaluated for its anesthetic and analgesic properties in fish and amphibians. The objective of this study was to determine the pharmacokinetic (PK) and anesthetic activity of eugenol in rats. Male Sprague-Dawley rats received single i.v. doses of eugenol (0, 5, 10, 20, 40 and 60 mg/kg) and anesthetic level was evaluated with the withdrawal reflex. For the 20 mg/kg dose level, blood and urinary samples were collected over 1 h for the PK assessment. Plasma and blood concentrations of eugenol, as well as metabolite identification in urine, were determined using a novel dansyl chloride derivatization method with liquid chromatography mass spectrometry (LC/MS/MS). PK parameters were calculated using noncompartmental methods. Eugenol-induced loss of consciousness in a dose-dependent manner, with mean (+/-SEM) recovery in reflex time of 167 +/- 42 sec observed at the highest dose level. Mean systemic clearance (Cl) in plasma and blood were 157 and 204 mL/min/kg, respectively. Glucuronide and sulfate conjugates were identified in urine. Overall, eugenol produced a reversible, dose-dependent anesthesia in male Sprague-Dawley rats.

Anesthesia↗
PubMed2005

Study of anticandidal activity of carvacrol and eugenol in vitro and in vivo.

BACKGROUND/AIMS: The mechanism of the anticandidal action of the major phenolic components of oregano and clove essential oils - carvacrol and eugenol - was studied. This activity was also evaluated for the therapeutic efficacy in the treatment of the experimental oral candidiasis induced by Candida albicans in immunosuppressed rats. METHODS: In vitro, the addition of carvacrol at 0.1% or eugenol at 0.2% during the exponential growth of C. albicans was evaluated. The release of substances absorbing at 280 nm by cells treated with these two components was also measured spectrophotometrically. In vivo, oral candidiasis in immunosuppressed rats was established by inoculating 3 x 10(8) cells of C. albicans with a cotton swab on three alternate days. The number of colony counts was evaluated from the oral cavity of rats treated for eight consecutive days with carvacrol, eugenol or nystatin and compared to untreated controls. RESULTS: Carvacrol and eugenol were fungicidal in exponentially growing C. albicans. Interestingly, this fungicidal effect was accompanied by the release of substances absorbing at 280 nm. In an immunosuppressed rat model of oral candidiasis, carvacrol or eugenol treatment significantly (P < 0.05) reduced the number of colony counts sampled from the oral cavity of rats treated for eight consecutive days compared to untreated control rats. Similar results were obtained with nystatin used as a reference treatment. CONCLUSION: The in vitro results indicated that both carvacrol and eugenol exerted an anticandidal effect by a mechanism implicating an important envelope damage. Their in vivo efficacy on experimental oral candidiasis leads us to consider them as possible antifungal agents.

Analysis of Variance↗
PubMed1997

The effect of eugenol-containing temporary cement on the bond strength of two resin composite core materials to dentin.

PURPOSE: This study investigated the effect of eugenol-containing temporary cement on the bond strength of two resin composite core materials (FluoroCore and Ti-Core) to dentin. MATERIALS AND METHODS: Dentin was exposed in three groups of extracted teeth (20 specimens each). In group one, dentin was covered with eugenol-containing temporary cement; the second group was covered with eugenol-free temporary cement; and the third group was left uncovered and served as a control group. All specimens were stored for 1 week at 37 degrees C and 100% humidity. The dentin surfaces were cleaned and treated using the GLUMA adhesive system, followed by placement of composite core build-ups. Debonding of the core material was accomplished using the Accuforce Elite test system. RESULTS: There was a significant reduction in bond strength for the specimens covered with eugenol temporary cement (p < .0001), but no significant difference was found between the control group and the group treated with eugenol-free temporary cement. Bond strength of the Ti-Core material to dentin was significantly higher than that of FluoroCore (p < .0001). CONCLUSION: Pretreatment of the dentin with eugenol-based temporary cement adversely affects the bond strength of resin composite core material to dentin.

Analysis of Variance↗
PubMed2002

Biotransformation of eugenol to ferulic acid by a recombinant strain of Ralstonia eutropha H16.

The gene loci ehyAB, calA, and calB, encoding eugenol hydroxylase, coniferyl alcohol dehydrogenase, and coniferyl aldehyde dehydrogenase, respectively, which are involved in the first steps of eugenol catabolism in Pseudomonas sp. strain HR199, were amplified by PCR and combined to construct a catabolic gene cassette. This gene cassette was cloned in the newly designed broad-host-range vector pBBR1-JO2 (pBBR1-JO2ehyABcalAcalB) and transferred to Ralstonia eutropha H16. A recombinant strain of R. eutropha H16 harboring this plasmid expressed functionally active eugenol hydroxylase, coniferyl alcohol dehydrogenase, and coniferyl aldehyde dehydrogenase. Cells of R. eutropha H16(pBBR1-JO2ehyABcalAcalB) from the late-exponential growth phase were used as biocatalysts for the biotransformation of eugenol to ferulic acid. A maximum conversion rate of 2.9 mmol of eugenol per h per liter of culture was achieved with a yield of 93.8 mol% of ferulic acid from eugenol within 20 h, without further optimization.

Bacterial Proteins↗
PubMed2003

Highly efficient biotransformation of eugenol to ferulic acid and further conversion to vanillin in recombinant strains of Escherichia coli.

The vaoA gene from Penicillium simplicissimum CBS 170.90, encoding vanillyl alcohol oxidase, which also catalyzes the conversion of eugenol to coniferyl alcohol, was expressed in Escherichia coli XL1-Blue under the control of the lac promoter, together with the genes calA and calB, encoding coniferyl alcohol dehydrogenase and coniferyl aldehyde dehydrogenase of Pseudomonas sp. strain HR199, respectively. Resting cells of the corresponding recombinant strain E. coli XL1-Blue(pSKvaomPcalAmcalB) converted eugenol to ferulic acid with a molar yield of 91% within 15 h on a 50-ml scale, reaching a ferulic acid concentration of 8.6 g liter(-1). This biotransformation was scaled up to a 30-liter fermentation volume. The maximum production rate for ferulic acid at that scale was 14.4 mmol per h per liter of culture. The maximum concentration of ferulic acid obtained was 14.7 g liter(-1) after a total fermentation time of 30 h, which corresponded to a molar yield of 93.3% with respect to the added amount of eugenol. In a two-step biotransformation, E. coli XL1-Blue(pSKvaomPcalAmcalB) was used to produce ferulic acid from eugenol and, subsequently, E. coli(pSKechE/Hfcs) was used to convert ferulic acid to vanillin (J. Overhage, H. Priefert, and A. Steinbüchel, Appl. Environ. Microbiol. 65:4837-4847, 1999). This process led to 0.3 g of vanillin liter(-1), besides 0.1 g of vanillyl alcohol and 4.6 g of ferulic acid liter(-1). The genes ehyAB, encoding eugenol hydroxylase of Pseudomonas sp. strain HR199, and azu, encoding the potential physiological electron acceptor of this enzyme, were shown to be unsuitable for establishing eugenol bioconversion in E. coli XL1-Blue.

Alcohol Oxidoreductases↗
PubMed2002

Inhibitory actions of eugenol on rat isolated ileum.

The effects of eugenol (1-2000 microM) on rat isolated ileum were studied. Eugenol relaxed the basal tonus (IC50 83 microM) and the ileum precontracted with 60 mM KCl (IC50 162 microM), an action unaltered by 0.5 microM tetrodotoxin, 0.2 mM N(G)-nitro-L-arginine methyl ester, 0.5 mM hexamethonium, and 1 microM indomethacin. Eugenol did not alter the resting transmembrane potential (Em) of the longitudinal muscle layer under normal conditions (5.0 mM K+) or in depolarised tissues. Eugenol reversibly inhibited contractions induced by submaximal concentrations of acetylcholine (ACh) and K+ (40 mM) with IC50 values of approximately 228 and 237 microM, respectively. Eugenol blocked the component of ACh-induced contraction obtained in Ca(2+)-free solution (0.2 mM EGTA) or in the presence of nifedipine (1 microM). Our results suggest that eugenol induces relaxation of rat ileum by a direct action on smooth muscle via a mechanism largely independent of alterations of Em and extracellular Ca2+ influx.

Animals↗
PubMed2003

Activation of vanilloid receptor 1 (VR1) by eugenol.

The structural similarity of eugenol with capsaicin suggests that these two agents may share molecular mechanisms to produce their effects. We investigated the effects of eugenol in comparison with those of capsaicin using whole-cell patch clamp and Fura-2-based calcium-imaging techniques in a heterologous expression system and with sensory neurons. In vanilloid receptor 1 (VR1)-expressing human embryonic kidney (HEK) 293 cells and trigeminal ganglion (TG) neurons, eugenol activated inward currents, whereas capsazepine, a competitive VR antagonist, and ruthenium red (RR), a functional VR antagonist, completely blocked eugenol-induced inward currents. Moreover, eugenol caused elevation of [Ca(2+)](i), and this was completely abolished by both capsazepine and ruthenium red in VR1-expressing HEK 293 cells and TG neurons. Our results provide strong evidence that eugenol produces its effects, at least in part, via VR1 expressed by the sensory nerve endings in the teeth.

Animals↗
PubMed2000

Antioxidant activity of eugenol and related monomeric and dimeric compounds.

Since the inhibitory effect of eugenol (a), which was isolated as an antioxidative component from plant, Caryopylli flos, on lipid peroxidation was less than that of alpha-tocopherol, we synthesized the eugenol-related compounds dieugenol (b), tetrahydrodieugenol (c), and dihydroeugenol (d), to find new strong antioxidants and assessed them for their inhibitory effect on lipid peroxidation and scavenging ability for superoxide and hydroxyl radicals. The antioxidative activities were in the order: (b)>(c)>(d)>(a) for the thiobarbituric acid reactive substance (TBARS) formation. These results suggest that the dimerized compounds have higher antioxidant activities than that of the monomers. Electron spin resonance (ESR) spin trapping experiments revealed that eugenol and its dimer, having allyl groups in the structure, scavenged superoxide, and that only eugenol trapped hydroxyl radicals under the conditions used. These finding suggest that eugenol and dieugenol have a different mechanism of antioxidation, i.e. eugenol may inhibit lipid peroxidation at the level of initiation, however, the related dimeric compounds may inhibit lipid peroxidation at the level of propagation of free radical chain reaction like alpha-tocopherol.

Antioxidants↗
PubMed2004

Modification of thymocytes membrane radiooxidative damage and apoptosis by eugenol.

Radiation-induced membrane oxidative damage, generation of reactive oxygen species (ROS), and cellular apoptosis, as well as their modification by a natural antioxidant from plant source, eugenol, have been investigated in mouse thymocytes. Thymocyte suspension was irradiated by gamma-rays, and the malondialdehyde (MDA) formation was measured with the thiobarbituric acid reactive species (TBARS) method. The results showed an increase in MDA in irradiated (2 Gy) thymocytes, which was inhibited in samples treated with increasing concentrations of eugenol (10-200 microM) prior to irradiation. The concentration of eugenol required to inhibit half of the MDA formation (IC(50)) in irradiated thymocytes was 100 microM. A dose-dependent increase in the generation of ROS was observed in irradiated thymocytes (0.5-200 cGy) as measured by 2,7-dichlorodihydro fluorescein diacetate (DCH-FDA), which was, however, inhibited by eugenol administered before irradiation. Furthermore, experiments showed a significant decrease in thymocytes apoptosis by antioxidant as measured by annexin-V labeling protocol. The inhibition of apoptosis by membrane-localized antioxidants such as eugenol, isoeugenol, and alpha-tocopherol acetate was more effective than a cytosolic antioxidant such as ascorbic acid. The results suggest an effective prevention of membrane and cellular damage in irradiated thymocytes by eugenol. It is inferred that damage to membrane played a significant role in radiation-induced cellular apoptotic death, which was markedly modified by membrane-specific antioxidants.

Animals↗
PubMed1996

Horseradish peroxidase-catalyzed conjugation of eugenol with basic amino acids.

L-Lysine is shown to yield an adduct with the quinone methide intermediate formed during the horseradish peroxidase (HRP)-catalyzed aerobic oxidation of eugenol (4-allyl-2-methoxyphenol). Adduct formation is evidenced by (i) lysine quenching of the characteristic quinone methide absorption band measured at 350 nm; arginine and gamma-aminobutyric acid, but not alanine or propionic acid showed similar behaviour (ii) lysine-promoted a 400 mV decrease of the eugenol oxidation voltammetric wave (1.00 V), concomitantly with an increase in current intensity and (iii) reverse phase HPLC isolation of the lysine eugenol adduct, followed by GC-MS analysis. The MS spectrum is consistent with a 2:1 lysine:eugenol adduct (MW = 455). If operative in vivo, binding of lysine to eugenol might lead to protein inactivation and possibly be involved in eugenol toxicity.

Amino Acids↗
PubMed1997

Dentinal adhesion and histomorphology of two dentinal bonding agents under the influence of eugenol.

This study examined the influence of eugenol on the dentinal adhesion of an enamel-dentin bonding agent that removes the smear layer (total-etch technique) and a system that partially dissolves the smear layer (self-conditioning adhesive system). The tensile bond strength was measured on flat, dentinal surfaces after application and removal of pure eugenol for 15 minutes and a eugenol-containing temporary luting agent for 24 hours. In addition, the resin-dentin interface was evaluated with confocal laser scanning microscopy. Dentinal adhesion was found to be significantly reduced after the application of eugenol when a dentin bonding agent that dissolves the smear layer was used. Under confocal laser scanning microscopy, the resin-dentin interdiffusion zone of both adhesive was found to be changed, not only after application of eugenol but also after application of a eugenol-containing temporary luting agent.

Adhesiveness↗
PubMed2003

Dentin permeability and eugenol diffusion after full crown preparation.

PURPOSE: To compare teeth prepared to receive a metallic versus a metal-ceramic crown with respect to (1) in vitro dentin permeability before and after using a desensitizing agent and (2) pulpal eugenol concentration after sealing a temporary crown with a zinc oxide-eugenol based cement. MATERIALS AND METHODS: The roots of 20 human mandibular molars were separated and the crowns were prepared to receive a metallic crown. The hydraulic conductance was recorded before and after using Protect dentin desensitizer. The crowns were then further reduced to receive a metal-ceramic crown and the hydraulic conductance was recorded under the same conditions, on deeper dentin, before and after using the desensitizing agent. Twenty additional teeth were prepared: 10 to receive a metallic crown and 10 teeth to receive a metal-ceramic crown. A tube filled with 1 mL phosphate buffered saline (PBS) was sealed to the cementoenamel junction. A temporary crown was sealed onto the preparation with Temp Bond. The amount of eugenol that diffused across dentin into PBS was spectrofluorimetrically measured at Day 1 and Day 7. The crown preparations were vertically sectioned and the dentin remaining thickness was recorded. RESULTS: The hydraulic conductance of teeth prepared for a metal-ceramic crown was twice as high as teeth prepared for a metallic crown (P < 0.001). The desensitizing agent reduced the hydraulic conductance in both groups (P< 0.001). The two groups showed the same hydraulic conductance after using Protect (ns). No significant difference was found in the amount of eugenol diffusion between the two groups of teeth although eugenol diffusion decreased with time (P < 0.01). No correlation was found between eugenol diffusion and remaining dentin thickness.

Analysis of Variance↗
PubMed1991

Hepatotoxicity of eugenol in mice depleted of glutathione by treatment with DL-buthionine sulfoximine.

Eugenol is widely used as a food flavoring agent and a dental analgesic. Mice treated with eugenol (400-600 mg/kg, po) in combination with an inhibitor of glutathione (GSH) synthesis, buthionine sulfoximine (BSO; 1 hr before eugenol, 4 mmol/kg, ip) developed hepatotoxicity characterized by increases in relative liver weight and serum GPT, hepatic congestion, and centrilobular necrosis of hepatocytes. Eugenol (up to 600 mg/kg) alone produced no hepatotoxicity. Drug metabolism inhibitors such as carbon disulfide, methoxsalen, and piperonyl butoxide prevented or significantly reduced the hepatotoxic effect of eugenol given in combination with BSO. On the other hand, pretreatment with phenobarbital (PB) increased the hepatotoxicity. These results suggest that eugenol is activated by a cytochrome-P-450-dependent metabolic reaction and that the liver injury is caused by inadequate rates of detoxification of the resulting metabolite in mice depleted of hepatic GSH by BSO treatment.

Alanine Transaminase↗