Antibacterial; anthelmintic; antioxidant; Pesticide active substance; Flavoring Agents

O. Eugenol and gratissimum essential oil both work well to prevent H from changing into another species. contortus eggs, indicating possible application in the management of small ruminant gastrointestinal helminthiasis. Eugenol and essential oils had the strongest inhibitory impact at a concentration of 0.50% [1]. Eugenol inhibits the xanthine-xanthine oxidase system's ability to produce superoxide anions by 50% at a dose of 250 μM. Additionally, ethanol can reduce the synthesis of hydroxyl free radicals by 70%. The measurement of OH radical generation involves hydroxylating salicylate to 2,3-dihydroxybenzoate, and 46% of OH radical formation is inhibited by 250 μM eugenol [2]. Eugenol has antioxidant properties, but it also modulates the brain's monoaminergic pathways and HPA axis, which may help avoid gastrointestinal dysfunction similar to IBS that is brought on by RS. Like ondansetron, eugenol (50 mg/kg) decreased the rise in fecal particles brought on by RS by 80%. Eugenol affects the PFC and amygdala's serotonin pathway and reduces stress-induced increases in plasma corticosterone by 80%. Eugenol strengthens antioxidant defense mechanisms throughout the brain and reduces norepinephrine alterations brought on by stress [3].

Eugenol (33 mg/kg) given orally for two days considerably reduced knee edema, which persisted to do so at the conclusion of the treatment. After two days, rats with mycobacterial arthritis treated with eugenol showed a considerable reduction in paw swelling [4].

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Eugenol (50 mg/kg) reduced 80% of RS-induced increase in fecal pellets similar to that of ondansetron. Eugenol attenuated 80% of stress-induced increase in plasma corticosterone and modulated the serotonergic system in the PFC and amygdala. Eugenol attenuated stress-induced changes in norepinephrine and potentiated the antioxidant defense system in all brain regions. Conclusion: Eugenol protected against RS-induced development of IBS-like gastrointestinal dysfunction through modulation of HPA-axis and brain monoaminergic pathways apart from its antioxidant effect.[3]

The spice principles curcumin (from turmeric) and eugenol (from cloves) are good inhibitors of lipid peroxidation. Lipid peroxidation is known to be initiated by reactive oxygen species. The effect of curcumin and eugenol on the generation of reactive oxygen species in model systems were investigated. Both curcumin and eugenol inhibited superoxide anion generation in xanthine-xanthine oxidase system to an extent of 40% and 50% at concentrations of 75 microM and 250 microM respectively. Curcumin and eugenol also inhibited the generation of hydroxyl radicals (.OH) to an extent of 76% and 70% as measured by deoxyribose degradation. The .OH-radical formation measured by the hydroxylation of salicylate to 2,3-dihydroxy benzoate was inhibited to an extent of 66% and 46%, respectively, by curcumin and eugenol at 50 microM and 250 microM. These spice principles also prevented the oxidation of Fe2+ in Fentons reaction which generates .OH radicals.[2]

Preparation of tested materials[1]
The essential oil and eugenol were diluted in aqueous solution of Tween 20 (0.5%) in the following concentrations: 0.0625, 0.12, 0.25, 0.5 and 1.0% to be used in the egg hatch test.

Evaluation of anthelmintic activity[1]
The egg hatching test in vitro to evaluate the ovicidal activity was based on the method described by Coles et al. (1992). A suspension of 300 μl containing approximately 250 fresh eggs, recovered from feces of goats and sheep experimentally infected with H. contortus, were distributed and mixed with the same volume of the essential oil in different concentrations. These tests had three controls: distilled water, Tween 20 (0.5% aqueous solution) and thiabendazole (0.5% aqueous solution). The eggs were incubated for 48 h at room temperature. After 48 h, lugol was added to stop the egg hatch. All the eggs and first-stage larvae (L1) were counted. The test was repeated five times for each treatment and control. The values obtained were analyzed using ANOVA and the Duncan test at the 0.05% significance level.

Eugenol (12.5, 25, and 50 mg/kg), ondansetron (4.0 mg/kg, p.o.), and vehicle were administered to rats for 7 consecutive days before exposure to 1 h RS. One control group was not exposed to RS-induction. The effect of eugenol (50 mg/kg) with and without RS exposure was evaluated for mechanism of action and per se effect, respectively. The hypothalamic-pituitary-adrenal cortex (HPA)-axis function was evaluated by estimating the plasma corticosterone level. The levels of brain monoamines, namely serotonin, norepinephrine, dopamine, and their metabolites were estimated in stress-responsive regions such as hippocampus, hypothalamus, pre-frontal cortex (PFC), and amygdala. Oxidative damage and antioxidant defenses were also assessed in brain regions.[3]

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This study examined the effect of eugenol and ginger oil on severe chronic adjuvant arthritis in rats. Severe arthritis was induced in the right knee and right paw of male Sprague-Dawley rats by injecting 0.05 ml of a fine suspension of dead Mycobacterium tuberculosis bacilli in liquid paraffin (5 mg/ml). Eugenol (33 mg/kg) and ginger oil (33 mg/kg), given orally for 26 days, caused a significant suppression of both paw and joint swelling. These findings suggest that eugenol and ginger oil have potent antiinflammatory and/or antirheumatic properties.[4]

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The ovicidal activity of the essential oil of Ocimum gratissimum Linn. (Labideae) and its main component eugenol was evaluated against Haemonchus contortus, gastrointestinal parasite of small ruminants. The oil and eugenol were diluted in Tween 20 (0.5%) at five different concentrations. In the egg hatch test, H. contortus eggs were obtained from feces of goats experimentally infected. At 0.50% concentration, the essential oil and eugenol showed a maximum eclodibility inhibition. These results suggest a possible utilization of the essential oil of O. gratissimum as an aid to the control of gastrointestinal helmintosis of small ruminants.[1]

Absorption, Distribution and Excretion
Following a single intraperitoneal injection of 450 mg/kg of 14C-methoxy-labeled eugenol, eugenol rapidly distributed to all organs. Both ether-soluble and water-soluble components were recovered from most tissues and excreta. Only 0.2–1.0% of the dose was excreted as 14C CO₂. More than 70% of the lethal dose of eugenol was recovered from the urine of rabbits after death. Eugenol did not penetrate mouse skin after percutaneous application. Metabolism/Metabolites The presence of 14C CO₂ in the exhaled breath of rats following intraperitoneal injection of 14C-eugenol indicates that eugenol underwent demethylation. The metabolism and toxicity of eugenol were investigated in isolated rat hepatocytes. Upon incubation of hepatocytes with eugenol, eugenol forms conjugates with sulfate, glucuronic acid, and glutathione. The main metabolite is the glucuronic acid conjugate. Covalent binding of eugenol to cellular proteins was observed using 3H-labeled eugenol. During these incubations, intracellular glutathione loss and cell death were also observed. A 1 mM eugenol concentration resulted in over 90% loss of intracellular glutathione and approximately 85% cell death within a 5-hour incubation period. Most of the glutathione loss occurred before cell death (2 hours). The effect of eugenol is concentration-dependent. Adding 1 mM N-acetylcysteine to an incubation system containing 1 mM eugenol completely prevented glutathione loss and cell death and inhibited the covalent binding of eugenol metabolites to proteins. Conversely, pretreatment of hepatocytes with diethyl maleate to deplete intracellular glutathione enhanced the cytotoxic effects of eugenol. These results indicate that eugenol is actively metabolized in hepatocytes, suggesting that its cytotoxic effects are due to the formation of an active intermediate, which may be a quinone methylation. Two metabolites of eugenol have been isolated from rat urine: 3-piperidinyl-1-(3'-methoxy-4'-hydroxyphenyl)-1-propanone and 3-pyrrolidinyl-1-(3'-methoxy-4'-hydroxyphenyl)-1-propanone. It has been reported that rat hepatocyte cultures can undergo epoxidation of eugenol. The dihydrodiol metabolite of eugenol has been isolated from liver homogenates and urine of rats pretreated with eugenol. For more complete metabolite/metabolite data on eugenol (9 metabolites in total), please visit the HSDB record page. Eugenol's known human metabolites include hydroxychavone and (2S,3S,4S,5R)-3,4,5-trihydroxy-6-(2-methoxy-4-prop-2-enylphenoxy)oxacyclohexane-2-carboxylic acid.

Hepatotoxicity
Low concentrations of eugenol and clove extract used in topical and herbal products have not been definitively linked to liver injury (whether elevated serum enzymes or clinically apparent liver damage). However, high doses of eugenol appear to be a direct cytotoxic agent, and there have been several reports of severe acute liver and kidney injury due to accidental overdose of eugenol-containing herbal products (primarily in children). Overdose typically presents as agitation, decreased consciousness, and coma within hours of ingestion (10-30 ml of clove oil). It is usually accompanied by acidosis, respiratory depression, and severe hypoglycemia, requiring mechanical ventilation and intravenous glucose. Liver injury appears 12 to 24 hours after ingestion, manifested by significantly elevated serum transaminase levels and early coagulation abnormalities. Signs of liver failure develop rapidly, and jaundice may develop and worsen. The overall clinical presentation is consistent with the typical features of acute hepatic necrosis, similar to symptoms caused by overdose of acetaminophen, iron, or copper. Liver damage typically worsens within days but then improves rapidly, eventually healing within 1 to 3 weeks. Renal dysfunction may also occur, but rarely requires intervention or dialysis. No long-term damage or sequelae have been reported. All cases described in the literature involve infants accidentally ingesting clove oil used by their parents. Probability Score: C[H] (Clinically significant cause of liver damage in case of overdose). Toxicity Data: LC50 > 2,580 mg/m3/4hr Interactions: Hepatotoxicity was observed in mice after oral administration of eugenol (400-600 mg/kg) in combination with the glutathione synthesis inhibitor sulfoxide (4 mmol/kg intraperitoneally, 1 hour before eugenol administration). This hepatotoxicity was characterized by elevated relative liver weight and serum alanine aminotransferase, hepatic congestion, and central lobular necrosis of hepatocytes. Eugenol alone (at doses up to 600 mg/kg) did not produce hepatotoxicity. Drug metabolism inhibitors, such as carbon disulfide, methoxsalen, and piperonyl butyl ether, can prevent or significantly reduce the hepatotoxicity of eugenol in combination with sulfoxide butyl sulfoxide. This study aimed to evaluate the chemopreventive potential of eugenol alone and in combination with chemotherapeutic agents such as gemcitabine. Compared with normal cells, eugenol exhibited dose-dependent selective cytotoxicity in HeLa cells, indicating good cytotoxicity. Compared with eugenol or gemcitabine alone, the combination induced cell growth inhibition and apoptosis at lower concentrations. Analysis of the data using the combination index showed a combination index value <1, indicating a significant synergistic effect. Therefore, this combination therapy may enhance the efficacy of gemcitabine at lower doses and minimize its toxicity to normal cells. Furthermore, gene expression analysis involving apoptosis and inflammation showed that the expression of Bcl-2, COX-2, and IL-1β was significantly downregulated after eugenol treatment. Therefore, the results indicate that eugenol exerts its anticancer activity through inducing apoptosis and anti-inflammatory properties, and for the first time, a synergistic effect between eugenol and gemcitabine has been demonstrated, which may enhance the efficacy of cervical cancer prevention and/or treatment. This study also explored the biochemical mechanisms underlying the enhanced toxicity of several plant essential oils (thymol, eugenol, menthol, terpineol, and citronellol) to fourth-instar larvae of Aedes aegypti when co-exposed to piperityl butyl ether (PBO). This study measured the activities of biotransformation enzymes in larvae, including cytochrome P450-mediated oxidases (ethoxylated halogen O-deethylase (EROD)), glutathione S-transferase (GST), and β-esterase, in the control group, the essential oil-only group (single chemical), and the essential oil + PBO (10 mg/L) group. At high concentrations, EROD activity decreased by 5-25% after 16 hours of exposure to thymol, eugenol, menthol, and citronellol alone. At a terpineol concentration of 10 mg/L, EROD activity increased by 5 ± 1.8% compared to the control group. Exposure to essential oils alone reduced GST activity by 3-20%, but exposure to PBO alone had no significant effect on the activity of any of the enzymes measured. When all essential oils were combined with PBO, EROD activity decreased by 58-76% and GST activity decreased by 3-85% at 16 hours post-exposure. This study indicates a synergistic effect between essential oils and PBO in inhibiting Aedes aegypti cytochrome P450 and GST detoxification enzymes. …Swiss albino mice were injected with different doses of eugenol (75, 150, and 300 mg/kg) before exposure to 1.5 Gy γ-rays. Micronucleus assays were performed to determine genetic damage in the bone marrow. The results showed that all three doses of eugenol significantly reduced the frequency of micronucleated polychromatic erythrocytes (MnPCEs). Eugenol (150 mg/kg) was also tested against different doses of radiation (0.5, 1, 1.5, and 2 Gy) and showed significant radiation protection. A decrease in the incidence of MnPCE was observed within 72 hours after irradiation (1.5 Gy). Furthermore, compared to untreated mice, mice treated with eugenol for 7 days showed increased levels of oxidative damage and higher specific activities of lactate dehydrogenase (LDH) and methylglyoxalase I (Gly I) in their livers. For more complete data on interactions of eugenol (7 items in total), please visit the HSDB record page.

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Non-human toxicity values
Guinea pig oral LD50: 2130 mg/kg
Mouse intraperitoneal LD50: 1109 mg/kg (7.5% eugenol saline)
Rat oral LD50: 1930 mg/kg
Mouse intraperitoneal LD50: 500 mg/kg
For more complete non-human toxicity data (6 values in total), please visit the HSDB record page.

[1]. Anthelmintic activity of essential oil of Ocimum gratissimum Linn. and eugenol against Haemonchus contortus. Vet Parasitol. 2002 Oct 16;109(1-2):59-63.

[2]. Studies on the inhibitory effects of curcumin and eugenol on the formation of reactive oxygenspecies and the oxidation of ferrous iron. Mol Cell Biochem. 1994 Aug 17;137(1):1-8.

[3]. Protective effect of eugenol against restraint stress-induced gastrointestinal dysfunction: Potential use in irritable bowel syndrome. Pharm Biol. 2015 Jul;53(7):968-74.

[4]. Suppressive effects of eugenol and ginger oil on arthritic rats. Pharmacology. 1994 Nov;49(5):314-8.

Therapeutic Uses
…It has been used as an antipyretic, but with relatively poor efficacy. Eugenol has been used in medical research, such as in mucus secretion and gastric cytology, without the need for gastrectomy or gastrointestinal anastomosis. It has been shown to have anthelmintic effects. /SRP: Previous Uses/
Over-the-counter toothache medications often contain eugenol, and some oral ulcer products may also contain it.
Eugenol is an ingredient in many dental materials, such as dental cements, impression pastes, and surgical pastes. These products are primarily composed of zinc oxide and eugenol in varying proportions. They are reportedly widely used in dentistry as temporary filling materials, cavity liners for pulp protection, pulp capping materials, temporary cements for fixed restorations, impression materials, and as a major component of root canal sealants. Additionally, eugenol is also used in dentistry for root canal disinfection.
Analgesics (Dental)

C10H12O2

164.2011

164.083

C, 73.15; H, 7.37; O, 19.49

97-53-0

Eugenol-d3;1335401-17-6

3314

Colorless to light yellow liquid

1.1±0.1 g/cm3

255.0±0.0 °C at 760 mmHg

−12-−10 °C(lit.)

119.8±8.1 °C

0.0±0.5 mmHg at 25°C

1.536

2.2

1

2

3

12

145

0

OC1C(OC)=CC(CC=C)=CC=1

OC1=CC=C(CC=C)C=C1OC

InChI=1S/C10H12O2/c1-3-4-8-5-6-9(11)10(7-8)12-2/h3,5-7,11H,1,4H2,2H3

Phenol, 2-methoxy-4-(2-propen-1-yl)-; 2-methoxy-4-prop-2-enylphenol

4-Allyl-2-methoxyphenol; 4-Allylguaiacol; Eugenic acid; Allylguaiacol; p-Eugenol; Caryophyllic acid;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ≥ 100 mg/mL (~609.01 mM)

Solubility in Formulation 1: ≥ 3.25 mg/mL (19.79 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 32.5 mg/mL clear DMSO stock solution to 400 μL of PEG300 and mix evenly; then add 50 μL of Tween-80 to the above solution and mix evenly; then add 450 μL of normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 3.25 mg/mL (19.79 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 32.5 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 3.25 mg/mL (19.79 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 32.5 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)