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

Effect of Intrathecal Eugenol on Cerebral Vasospasm in an Experimental Subarachnoid Hemorrhage Model

BACKGROUND

Eugenol has various curative properties. It affects the dilatation of cerebral arteries through voltage-dependent Ca2+ channel inhibition. This study is the first to explore the impact of eugenol on neuroprotection and vasospasm in an experimental subarachnoid hemorrhage (SAH) model.

METHODS

Twenty-four adult male Sprague-Dawley rats were indiscriminately separated into 3 groups: the control group (n = 8), the SAH group (n = 8), and the eugenol group (n = 8). A double-bleeding method was used. The eugenol group received intracisternal eugenol (Sigma-Aldrich, St. Louis, MO, USA) at 30 μg/20 μl after induction of SAH. On the day 7, all groups were euthanized. Measurements were taken for basilar artery wall thickness, lumen diameter, serum endothelin-1 (ET-1), and caspase-3 levels.

RESULTS

The eugenol group exhibited significantly lower wall thickness, ET-1, oxidative stress index, and caspase-3 levels compared to the SAH group. In comparison to the control group, the eugenol group showed a higher oxidative stress index along with higher ET-1 and caspase-3 levels, but these differences were not statistically significant. Wall thickness was significantly higher in the eugenol group than in the control group.

CONCLUSIONS

This study represents the first literature exploration of intrathecal eugenol's impact on vasospasm induced after experimental SAH. Administration of intrathecal eugenol demonstrates a positive effect on the treatment of experimental vasospasm as well as on the reduction of oxidative stress and apoptosis.

Study on mechanism of transdermal administration of eugenol for pain treatment by network pharmacology and molecular docking technology

The objective of this study was to explore the pharmacological mechanism of transdermal administration of eugenol (EUG) for pain treatment. Firstly, network pharmacology techniques were employed to identify the potential targets responsible for the analgesic effect of EUG. Subsequently, molecular docking technology was used to validate interactions between EUG and the crystal structure of the core target protein. Finally, the impact of EUG on the expression and activation of TRPV1 receptors in HaCaT cells was evaluated through in vitro experiments, thus confirming the analysis of network pharmacology. The study suggested that the transdermal administration of EUG for pain treatment might target the TRPV1 receptor. Molecular docking revealed that EUG could spontaneously bind to the TRPV1 receptor with a high binding ability. The analysis of Western blot (WB) and intracellular Ca2+ levels demonstrated that EUG could increase the expression of TRPV1 in HaCaT cells, activating TRPV1 to induce intracellular Ca2+ influx (P < 0.05). These findings suggested that the initial application of EUG would cause a brief stimulation of TRPV1 receptors and upregulation of TRPV1 expression. Upon continued exposure, EUG would act as a TRPV1 agonist, increasing intracellular Ca2+ levels that might be associated with desensitization of pain sensations.

Pharmacodynamic, pharmacokinetic, toxicity, and recent advances in Eugenol's potential benefits against natural and chemical noxious agents: A mechanistic review

The active biological phytochemicals, crucial compounds employed in creating hundreds of medications, are derived from valuable and medicinally significant plants. These phytochemicals offer excellent protection from various illnesses, including inflammatory disorders and chronic conditions caused by oxidative stress. A phenolic monoterpenoid known as eugenol (EUG), it is typically found in the essential oils of many plant species from the Myristicaceae, Myrtaceae, Lamiaceae, and Lauraceae families. One of the main ingredients of clove oil (Syzygium aromaticum (L.), Myrtaceae), it has several applications in industry, including flavoring food, pharmaceutics, dentistry, agriculture, and cosmeceuticals. Due to its excellent potential for avoiding many chronic illnesses, it has lately attracted attention. EUG has been classified as a nonmutant, generally acknowledged as a safe (GRAS) chemical by the World Health Organization (WHO). According to the existing research, EUG possesses notable anti-inflammatory, antioxidant, analgesic, antibacterial, antispasmodic, and apoptosis-promoting properties, which have lately gained attention for its ability to control chronic inflammation, oxidative stress, and mitochondrial malfunction and dramatically impact human wellness. The purpose of this review is to evaluate the scientific evidence from the most significant research studies that have been published regarding the protective role and detoxifying effects of EUG against a wide range of toxins, including biological and chemical toxins, as well as different drugs and pesticides that produce a variety of toxicities, throughout view of the possible advantages of EUG.

Targeting cardiovascular risk factors with eugenol: an anti-inflammatory perspective

Inflammation is a multifaceted biological reaction to a wide range of stimuli, and it has been linked to the onset and progression of chronic diseases such as heart disease, cancer, and diabetes. Inflammatory markers found in the blood, including C-reactive protein, serum amyloid A, fibrinogen, plasma viscosity, erythrocyte sedimentation rate, interleukin-6, and soluble adhesion molecules (like intercellular adhesion molecule-1 and vascular cell adhesion molecule-1), are risk factors for cardiovascular diseases such as coronary heart disease, stroke, and peripheral arterial disease. These markers play a crucial role in understanding and assessing cardiovascular health. Due to this complicated relationship between inflammation and cardiovascular disease, anti-inflammatory agents of natural origin have been the subject of many preclinical and clinical studies in recent years. Eugenol is a natural phenolic compound found in clove oil, nutmeg oil, cinnamon oil, and bay leaf oil, as well as other essential oils. Eugenol has been shown to have anti-inflammatory properties in many forms of experimental inflammation. It may scavenge free radicals, which contribute to inflammation and tissue damage. Various studies also suggest that eugenol can limit the production of inflammatory mediators such as prostaglandins, cytokines, and chemokines. Animal models of arthritis, colitis, and lung damage, as well as human clinical studies, have shown that eugenol has phenomenal anti-inflammatory properties. These properties suggest that eugenol may be able to reduce the risk of cardiovascular diseases.

Cannflavins isolated from Cannabis sativa impede Caenorhabditis elegans response to noxious heat

Cannflavins, flavonoids abundantly present in Cannabis sativa, possess a distinct chemical structure comprising a vanillyl group. Notably, the capsaicin structure also contains a vanillyl group, which is considered essential for interacting with the vanilloid receptor. The vanilloid receptor plays a crucial role in the perception of pain, heat, and inflammation and mediates the analgesic effects of capsaicin. Therefore, we postulated that prolonged exposure to cannflavin A (Can A) and cannflavin B (Can B) would provoke vanilloid receptor desensitization and hinder nocifensive responses to noxious thermal stimuli. C. elegans wild-type (N2) and mutants were exposed to Can A and Can B solutions for 60 min and then aliquoted on Petri dishes divided into quadrants for thermal stimulation. We then determined the thermal avoidance index for each C. elegans experimental group. Proteomics was performed to identify proteins and pathways associated with Can A or B treatment. Prolonged exposure to Can A and Can B hindered heat avoidance (32-35 °C) in C. elegans. No antinociceptive effect was observed 6 h post Can A or B exposure. Proteomics and Reactome pathway enrichment analyses identified hierarchical differences between Can A- and B-treated nematodes. However, both treatments were related to eukaryotic translation initiation (R-CEL-72613) and metabolic processes strongly associated with pain development. Our study aids in characterizing the pharmacological activity of cannflavins isolated from Cannabis sativa and outlines a possible application as pain therapy.

Eugenol Reduced ΜPO, CD45 and HMGB1 Expression and Attenuated the Expression of Leukocyte Infiltration Markers in the Intestinal Tissue in Biliopancreatic Duct Ligation-Induced Pancreatitis in Rats

Background and Objectives: Inflammation and dysregulation in the intestinal barrier function in acute pancreatitis (AP) trigger pancreatic lesions, systemic inflammatory response, and multiple organ dysfunction. Eugenol, as the main component of clove (Syzygium aromaticum), is known for its antioxidant and anti-inflammatory properties. We studied the potentially beneficial effect of eugenol in a rodent model of biliopancreatic duct ligation-induced AP. Materials and Methods: Rats were randomly divided into three groups: Sham, AP, and AP + eugenol (15 mg/kg/day). Serum TNFα, IL-6, IL-18, and resistin levels, as well as IL-6, TNFα, MPO, HMGB1, and CD45 tissue expression, were determined at various timepoints after the induction of AP. Results: Eugenol attenuated hyperemia and inflammatory cell infiltration in the intestinal mucosal, submucosal, and muscular layers. IL-6 and resistin serum levels were significantly reduced in the AP + eugenol group, while serum TNFα and IL-18 levels remained unaffected overall. TNFα pancreatic and intestinal expression was attenuated by eugenol at 72 h, while IL-6 expression was affected only in the pancreas. MPO, CD45, and HMGB1 intestinal expression was significantly reduced in eugenol-treated rats. Conclusions: Eugenol managed to attenuate the inflammatory response in the intestine in duct ligation-induced AP in rats.

Pharmacological Evaluation of the Anesthetic and Analgesic Potential of Injection Harsha 22: A Novel Polyherbal Local Anesthetic Formulation Intended for Parenteral Administration in Wistar Albino Rats

Background

Local anaesthetics are medications that cause numbness that can be reversed by applying them topically. Local anaesthetics are clinically used to control pain during minor surgeries or to treat other acute and chronic pain. The present investigation intended to investigate the anesthetic as well as analgesic potential of Injection Harsha 22, a novel polyherbal formulation in Wistar albino rats.

Methods

The anesthetic potential of Injection Harsha 22 was evaluated by a heat tail-flick latency (TFL) test, whereas the analgesic effect was elevated by electrical stimulation testing. Here, lignocaine (2%) was used as the standard anesthetic drug.

Results

In TFL, Injection Harsha 22 showed anesthetic effects up to 90 minutes after application. Also, the duration of anesthesia in rats that were administered subcutaneously with Injection Harsha 22 was comparable to that of the rats treated with commercial lignocaine (2%). In an electrical stimulation test, single administration of Injection Harsha 22 to rats significantly prolonged analgesia compared with the normal control group. The median duration of analgesia in rats administered subcutaneously with Injection Harsha 22 and lignocaine solution was 40 minutes and 35 minutes, respectively. Furthermore, Injection Harsha 22 does not interfere with the hematopoietic system of the experiment animals.

Conclusion

Thus, the present investigation established the in vivo anesthetic and analgesic potential of Injection Harsha 22 in experimental animals. Hence, it can be concluded that Injection Harsha 22 can become a prominent substitute for lignocaine as a local anaesthetic agent after establishing its efficacy through stringent clinical trials in humans.

Integrative network pharmacology and in silico analyses identify the anti-omicron SARS-CoV-2 potential of eugenol

Eugenol as a natural product is the source of isoniazid, and purified eugenol is extensively used in the cosmetics industry and the productive processes of edible spices. Accumulating evidence suggested that eugenol exerted potent anti-microorganism and anti-inflammation effects. Application of eugenol effectively reduced the risk of atherosclerosis, arterial embolism, and Type 2 diabetes. A previous study confirmed that treatment with eugenol attenuated lung inflammation and improved heart functions in SARS-CoV-2 spike S1-intoxicated mice. In addition to the study, based on a series of public datasets, computational analyses were conducted to characterize the acting targets of eugenol and the functional roles of these targets in COVID-19. The binding capacities of eugenol to conservative sites of SARS-CoV-2 like RNA-dependent RNA polymerase (RdRp) and mutable site as spike (S) protein, were calculated by using molecular docking following the molecular dynamics simulation with RMSD, RMSF, and MM-GBSA methods. The results of network pharmacology indicated that six targets, including PLAT, HMOX1, NUP88, CTSL, ITGB1 andTMPRSS2 were eugenol-SARS-CoV-2 interacting proteins. The omics results of in-silico study further implicated that eugenol increased the expression of SCARB1, HMOX1 and GDF15, especially HMOX1, which were confirmed the potential interacting targets between eugenol and SARS-CoV-2 antigens. Enrichment analyses indicated that eugenol exerted extensive biological effects such as regulating immune infiltration of macrophage, lipid localization, monooxyenase activity, iron ion binding and PPAR signaling. The results of the integrated analysis of eugenol targets and immunotranscription profile of COVID-19 cases shows that eugenol also plays an important role in strengthen of immunologic functions and regulating cytokine signaling. As a complement to the integrated analysis, the results of molecular docking indicated the potential binding interactions between eugenol and four proteins relating to cytokine production/release and the function of T type lymphocytes, including human TLR-4, TCR, NF-κB, JNK and AP-1. Furthermore, results of molecular docking and molecular dynamics (100ns) simulations implicated that stimulated modification of eugenol to the SARS-CoV-2 Omicron Spike-ACE2 complex, especially for human ACE2, and the molecular interaction of eugenol to SARS-CoV-2 RdRp, were no less favorable than two positive controls, molnupiravir and nilotinib. Dynamics (200ns) simulations indicated that the binding capacities and stabilities of eugenol to finger subdomain of RdRp is no less than molnupiravir. However, the simulated binding capacity of eugenol to SARS-CoV-2 wild type RBD and Omicron mutant RBD were less than nilotinib. Eugenol was predicted to have more favor LD50 value and lower cytotoxicity than two positive controls, and eugenol can pass through the blood-brain barrier (BBB). In a brief, eugenol is helpful for attenuating systemic inflammation induced by SARS-CoV-2 infection, due to the direct interaction of eugenol to SARS-CoV-2 proteins and extensive bio-manipulation of pro-inflammatory factors. This study carefully suggests eugenol is a candidate compound of developing drugs and supplement agents against SARS-CoV-2 and its Omicron variants.

Pharmacokinetic and Permeation Studies in Rat Brain of Natural Compounds Led to Investigate Eugenol as Direct Activator of Dopamine Release in PC12 Cells

Eugenol, cinnamaldehyde and D-limonene, the main components of natural essential oils, are endowed with antioxidant and anti-inflammatory properties which allow them to induce beneficial effects on intestinal, cardiac and neuronal levels. In order to characterize their pharmacokinetic profiles and aptitude to permeate in the central nervous system after intravenous and oral administration to rats, new analytical procedures, easily achievable with HPLC-UV techniques, were developed. The terminal half-lives of these compounds range from 12.4 ± 0.9 (D-limonene) and 23.1 ± 1.6 min (cinnamaldehyde); their oral bioavailability appears relatively poor, ranging from 4.25 ± 0.11% (eugenol) to 7.33 ± 0.37% (cinnamaldehyde). Eugenol evidences a marked aptitude to permeate in the cerebrospinal fluid (CSF) of rats following both intravenous and oral administrations, whereas cinnamaldehyde appears able to reach the CSF only after intravenous administration; limonene is totally unable to permeate in the CSF. Eugenol was therefore recruited for in vitro studies of viability and time-/dose-dependent dopamine release in neuronal differentiated PC12 cells (a recognized cellular model mimicking dopaminergic neurons), evidencing its ability to increase cell viability and to induce dopamine release according to a U-shaped time-course curve. Moreover, concentration-response data suggest that eugenol may induce beneficial effects against Parkinson's disease after oral administration.

Liposomal Formulations Loaded with a Eugenol Derivative for Application as Insecticides: Encapsulation Studies and In Silico Identification of Protein Targets

A recently synthesized new eugenol derivative, ethyl 4-(2-methoxy-4-(oxiran-2-ylmethyl)phenoxy)butanoate, with a high insecticidal activity against Sf9 (Spodoptera frugiperda) insect cells, was encapsulated in the liposomal formulations of egg-phosphatidylcholine/cholesterol (Egg-PC:Ch) 70:30 and 100% dioleoylphosphatidylglycerol (DOPG), aiming at the future application as insecticides. Compound-loaded DOPG liposomes have sizes of 274 ± 12 nm, while Egg-PC:Ch liposomes exhibit smaller hydrodynamic diameters (69.5 ± 7 nm), high encapsulation efficiency (88.8 ± 2.7%), higher stability, and a more efficient compound release, thus, they were chosen for assays in Sf9 insect cells. The compound elicited a loss of cell viability up to 80% after 72 h of incubation. Relevantly, nanoencapsulation maintained the toxicity of the compound toward insect cells while lowering the toxicity toward human cells, thus showing the selectivity of the system. Structure-based inverted virtual screening was used to predict the most likely targets and molecular dynamics simulations and free energy calculations were used to demonstrate that this molecule can form a stable complex with insect odorant binding proteins and/or acetylcholinesterase. The results are promising for the future application of compound-loaded nanoliposome formulations as crop insecticides.

Phytochemical study: molecular docking of eugenol derivatives as antioxidant and antimicrobial agents

Abstract:

Eugenol (4-allyl-2-methoxyphenol) is a natural phenolic compound present in certain aromatic plants; however, it is generally extracted from essential oil of Eugenia caryophyllata (Syzygiumaromaticum) (L.) Merr. and L.M. Perry. This bioactive natural compound has generated considerable biological interest with well-known antimicrobial and antioxidant actions. The authors have aimed to the evaluations of eugenol derivatives and their as antimicrobial and antioxidant agent with the aid of molecular dynamic simulation. The starting material was extracted from cloves using hydrodistillation. Two eugenol derivatives, acetyleugenol (4-allyl-2-methoxyphenylacetate) and epoxyeugenol (4-allyl-2-methoxyphenol) were prepared and tested against two strains Escherichia coli (E. Coli) and Staphylococcus aureus (S. Aureus). The results have revealed that the three compounds (Eugenol, acetyleugenol and epoxyeugenol) possess important potentials of inhibition against E. coli and S. Aureus. The antioxidant activity of eugenol derivatives was evaluated by the reaction with DPPH (1,1-diphenyl-2-picrylhydrazyl), showed that the epoxyeugenol was the most active compound. The molecular docking scores of three compounds and the amino acids in the active site pockets of the selected proteins of the two bacteria have approved and explain the biological experimental outcomes.

Differential effects of aquatic anaesthetics on the pharmacokinetics of antibiotics: Examples using florfenicol in Nile tilapia (Oreochromis niloticus)

Anaesthetics are commonly applied in pharmacokinetic (PK) studies to assure smooth handling of experimental procedures or to promote animal welfare. However, the influence of anaesthetics on the PK of co-administered drug is generally unknown but assumes ignorable. The goal of the study was to investigate the effect of tricaine methanesulfonate (MS-222), 2-phenoxyethanol (2-PE) and eugenol (EUG) on the PK of florfenicol (FF) in Nile tilapia. Twenty-eight fish were repeatedly exposed to 90 ppm EUG, 300 ppm MS-222 or 900 ppm 2-PE before FF oral administration (15 mg/kg) and each successive blood sampling. The serum concentration-time profiles were analysed by a 2-compartmental model, and the generated parameters in the control (without anaesthetic) and anaesthetic groups were statistically compared. The results demonstrated that the serum concentrations of each anaesthetic were similar at every FF sampling times (70 μg/ml for MS-222; 277 μg/ml for 2-PE; and 61 μg/ml for EUG). In comparison with the control group, the repeated use of MS-222 did not result in a statistical difference in most of the PK parameters. In contrast, the elimination half-lives of the 2-PE and EUG groups were significantly longer whereas the absorption and distribution half-lives of the 2-PE group were significantly shorter than the control, resulting in altered optimal dosages in the simulation modelling. Whether or not the numbers and extent of PK parameters change mitigate subsequent estimations of other PK-derived secondary values such as dosing regimen and withdrawal time remains to be elucidated, but the auxiliary use of anaesthetics in PK studies should not assume uninfluential.

Pharmacological Properties and Health Benefits of Eugenol: A Comprehensive Review

The biologically active phytochemicals are sourced from edible and medicinally important plants and are important molecules being used for the formulation of thousands of drugs. These phytochemicals have great benefits against many ailments particularly the inflammatory diseases or oxidative stress-mediated chronic diseases. Eugenol (EUG) is a versatile naturally occurring molecule as phenolic monoterpenoid and frequently found in essential oils in a wide range of plant species. EUG bears huge industrial applications particularly in pharmaceutics, dentistry, flavoring of foods, agriculture, and cosmeceutics. It is being focused recently due to its great potential in preventing several chronic conditions. The World Health Organization (WHO) has declared EUG as a nonmutant and generally recognized as safe (GRAS) molecule. The available literature about pharmacological activities of EUG shows remarkable anti-inflammatory, antioxidant, analgesic, and antimicrobial properties and has a significant effect on human health. The current manuscript summarizes the pharmacological characteristics of EUG and its potential health benefits.

Nociceptive Threshold of Calves and Goat Kids Undergoing Injection of Clove Oil or Isoeugenol for Disbudding

Simple Summary

Hot-iron disbudding in calves and goat kids is a widespread husbandry procedure involving pain and, especially in goats, the risk of brain damage. The injection of clove oil under the horn bud is a potential alternative disbudding method. Clove oil, with its active substance eugenol, is cytotoxic but has anaesthetic effects, and the injection of clove oil, or the pure substance isoeugenol, under the horn bud to stop horn growth may have potential welfare benefits compared to hot-iron disbudding. We compared the injection of clove oil with the injection of isoeugenol under the horn bud with respect to pain sensitivity in this area in the first 24 h after injection. Compared to before injection, the pain sensitivity of goats kids was higher 24 h after injection of clove oil and up to at least 6 h after isoeugenol injection, while, in calves, pain sensitivity was highest after 9 h. Future studies should compare the welfare effects of isoeugenol injection with hot-iron disbudding.

Abstract

In this preliminary study, we compared changes in mechanical nociceptive thresholds (MNT) of calves and goat kids injected with clove oil or isoeugenol under the horn bud as a potential, more welfare-friendly alternative to hot-iron disbudding. Twenty male calves and goat kids were randomly allocated to clove oil (n = 10 per species) or isoeugenol (n = 10 per species) injection under the horn buds. MNT was measured via a pressure algometer in calves and kids at several locations around the horn buds at several time points before and up to 24 h after injection. In kids, von Frey filaments were used additionally at the same time points. In calves, linear mixed models revealed an effect on MNT of time point (p = 0.010) and side (p = 0.007), but not of injection (p = 0.298), nor of the interaction ‘injection*time point’, MNT waslowest 9 h post-injection. In goats, there was an effect of injection depending on time point (interaction injection*time point, p = 0.03) with MNT being lowest 24 h post-injection for clove oil, while MNT was similar to pre-injection in isoeugenol. In both species, variation in the individual response post-injection was very high. Our results suggest that clove oil and isoeugenol induced hypersensitivity, which was higher for clove oil, in goat kids, but they also suggest a transient anaesthetic effect in some animals and locations.

Eugenol and its association with levodopa in 6-hydroxydopamine-induced hemiparkinsonian rats: Behavioural and neurochemical alterations

Parkinson's disease is a neurodegenerative disorder that affects the central nervous system and is mainly characterized by the loss of dopaminergic neurons and pro-oxidant mechanisms. Eugenol has been widely studied due to its anti-inflammatory and antioxidant activities, making it a promising neuroprotective agent. This study aimed to investigate the effects of eugenol and its combined action with levodopa in the 6-hydroxydopamine-induced Parkinson's disease model. Wistar rats were subjected to intrastriatal injection of 6-hydroxydopamine (21 μg) and then treated with eugenol (0.1, 1, or 10 mg/kg), levodopa (25 mg/kg) or their combination (eugenol 10 mg/kg + levodopa 12.5 mg/kg) orally for 14 days. On the 14th day, the animals were subjected to behavioural tests, and after euthanization and dissection of the brain areas, neurochemical analyses were performed. The results showed that eugenol reduced the oxidative stress and behavioural disturbances induced by 6-hydroxydopamine. The eugenol and levodopa combination was more effective in some behavioural parameters and body-weight gain in addition to promoting an increase in reduced glutathione levels compared to levodopa alone. Thus, the neuroprotective activity of eugenol was observed against motor and neurochemical disorders. Additionally, the eugenol and levodopa combination was promising when compared to conventional treatment.

An aromatic substance, eugenol induces distinct depressant effects on respiratory activity in different postnatal developmental stages of the rat

Eugenol modulates neuronal activity through actions on voltage-gated ionic channels and/or transient receptor potential channels. We previously suggested that eugenol inhibited cellular (and/or network) mechanisms essential for the maintenance of the respiratory burst activity in a brainstem-spinal cord preparation from newborn rat (postnatal day 0-3). Study of the distinct effects of eugenol in neonatal and later developmental stage rats may offer new information about postnatal developmental changes of respiratory neuron networks. In the present study, therefore, we compared effects of eugenol in an in vitro newborn rat preparation with those in an arterially perfused in situ preparation from juvenile rat (postnatal day 12-15). In the former preparation, application of 1 mM eugenol decreased respiratory rate and inspiratory burst duration. In contrast, in the latter preparation, 1 mM eugenol induced a gradual decrease in the amplitude of integrated phrenic nerve activity. Phrenic nerve activity gradually recovered at 25-30 min after washout with a burst duration similar to control values. We hypothesized that the depressant effects of eugenol were caused by inhibition of cell excitability in the neonatal rat in vitro preparation but by a reduction of synaptic interactions in the juvenile rat in situ preparation.

Neurotoxicity of fragrance compounds: A review

Fragrance compounds are chemicals belonging to one of several families, which are used frequently and globally in cosmetics, household products, foods and beverages. A complete list of such compounds is rarely found on the ingredients-list of such products, as "fragrance mixtures" are defined as "trade secrets" and thus protected by law. While some information regarding the general toxicity of some of these compounds is available, their neurotoxicity is known to a lesser extent. Here, we discuss the prevalence and neurotoxicity of fragrance compounds belonging to the three most common groups: phthalates, synthetic musks and chemical sensitizers.

Effects of eugenol on respiratory burst generation in newborn rat brainstem-spinal cord preparations

Eugenol is contained in several plants including clove and is used as an analgesic drug. In the peripheral and central nervous systems, this compound modulates neuronal activity through action on voltage-gated ionic channels and/or transient receptor potential channels. However, it is unknown whether eugenol exerts any effects on the respiratory center neurons in the medulla. We examined the effects of eugenol on respiratory rhythm generation in the brainstem-spinal cord preparation from newborn rat (P0-P3). The preparations were superfused by artificial cerebrospinal fluid at 25-26 °C, and inspiratory C4 ventral root activity was monitored. Membrane potentials of respiratory neurons were recorded in the parafacial region of the rostral ventrolateral medulla. Bath application of eugenol (0.5-1 mM) decreased respiratory rhythm accompanied by strong inhibition of the burst activity of pre-inspiratory neurons. After washout, respiratory rhythm partly recovered, but the inspiratory burst duration was extremely shortened, and this continued for more than 60 min after washout. The shortening of C4 inspiratory burst by eugenol was not reversed by capsazepine (TRPV1 antagonist) or HC-030031 (TRPA1 antagonist), whereas the depression was partially blocked by GABA_A antagonist bicuculline and glycine antagonist strychnine or GABA_B antagonist phaclofen. A spike train of action potentials in respiratory neurons induced by depolarizing current pulse was depressed by application of eugenol. Eugenol decreased the negative slope conductance of pre-inspiratory neurons, suggesting blockade of persistent Na⁺ current. These results suggest that changes in both membrane excitability and synaptic connections are involved in the shortening of respiratory neuron bursts by eugenol.

Pharmacological and Toxicological Properties of Eugenol

Eugenol is a volatile phenolic constituent of clove essential oil obtained from Eugenia caryophyllata buds and leaves. It is a functional ingredient of numerous products which have been used in the pharmaceutical, food and cosmetic industry in restricted concentrations. Its derivatives have been used in medicine as a local antiseptic and anesthetic. The wide range of eugenol activities includes antimicrobial, anti-inflammatory, analgesic and antioxidant. Although eugenol is considered safe as a product, due to the vast range of different applications and extensive use, there has been a great concern about its toxicity in recent years. However, studies about cytotoxicity and genotoxicity of eugenol are very limited and controversial. The pharmacological and toxicological properties of eugenol will be discussed in this review.

Influence of clove oil and eugenol on muscle contraction of silkworm (Bombyx mori)

Clove oil is used in fish anesthesia and expected to have a mechanism via glutamic receptor. The present study explores the activities of clove oil and its major compound, eugenol, in comparison with L-glutamic acid on glutamic receptor of silkworm muscle and fish anesthesia. It was found that clove oil and eugenol had similar effects to L-glutamic acid on inhibition of silkworm muscle contraction after treated with D-glutamic acid and kainic acid. Anesthetic activity of the test samples was investigated in goldfish. The results demonstrated that L-glutamic acid at 20 and 40 mM could induce the fish to stage 3 of anesthesia that the fish exhibited total loss of equilibrium and muscle tone, whereas clove oil and eugenol at 60 ppm could induce the fish to stage 4 of anesthesia that the reflex activity of the fish was lost. These results suggest that clove oil and eugenol have similar functional activities and mechanism to L-glutamic acid on muscle contraction and fish anesthesia.

Kampo Medicine: Evaluation of the Pharmacological Activity of 121 Herbal Drugs on GABAA and 5-HT3A Receptors

Kampo medicine is a form of Japanese phytotherapy originating from traditional Chinese medicine (TCM). During the last several decades, much attention has been paid to the pharmacological effects of these medical plants and their constituents. However, in many cases, a systematic screening of Kampo remedies to determine pharmacologically relevant targets is still lacking. In this study, a broad screening of Kampo remedies was performed to look for pharmacologically relevant 5-HT_3A and GABA_A receptor ligands. Several of the Kampo remedies are currently used for symptoms such as nausea, emesis, gastrointestinal motility disorders, anxiety, restlessness, or insomnia. Therefore, the pharmacological effects of 121 herbal drugs from Kampo medicine were analyzed as ethanol tinctures on heterologously expressed 5-HT_3A and GABA_A receptors, due to the involvement of these receptors in such pathophysiological processes. The tinctures of Lindera aggregata (radix) and Leonurus japonicus (herba) were the most effective inhibitory compounds on the 5-HT_3A receptor. Further investigation of known ingredients in these compounds led to the identification of leonurine from Leonurus as a new natural 5-HT_3A receptor antagonist. Several potentiating herbs (e.g., Magnolia officinalis (cortex), Syzygium aromaticum (flos), and Panax ginseng (radix)) were also identified for the GABA_A receptor, which are all traditionally used for their sedative or anxiolytic effects. A variety of tinctures with antagonistic effects Salvia miltiorrhiza (radix) were also detected. Therefore, this study reveals new insights into the pharmacological action of a broad spectrum of herbal drugs from Kampo, allowing for a better understanding of their physiological effects and clinical applications.

The Role of Eugenol in the Prevention of Acute Pancreatitis-Induced Acute Kidney Injury: Experimental Study

Aim. Acute pancreatitis is an inflammatory intra-abdominal disease, which takes a severe form in 15–20% of patients and can result in high mortality especially when complicated by acute renal failure. The aim of this study is to assess the possible reduction in the extent of acute kidney injury after administration of eugenol in an experimental model of acute pancreatitis. Materials and Methods. 106 male Wistar rats weighing 220–350 g were divided into 3 groups: (1) Sham, with sham surgery; (2) Control, with induction of acute pancreatitis, through ligation of the biliopancreatic duct; and (3) Eugenol, with induction of acute pancreatitis and eugenol administration at a dose of 15 mg/kg. Serum urea and creatinine, histopathological changes, TNF-α, IL-6, and MPO activity in the kidneys were evaluated at predetermined time intervals. Results. The group that was administered eugenol showed milder histopathological changes than the Control group, TNF-α activity was milder in the Eugenol group, and there was no difference in activity for MPO and IL-6. Serum urea and creatinine levels were lower in the Eugenol group than in the Control group. Conclusions. Eugenol administration was protective for the kidneys in an experimental model of acute pancreatitis in rats.

Neurorestorative effects of eugenol, a spice bioactive: Evidence in cell model and its efficacy as an intervention molecule to abrogate brain oxidative dysfunctions in the streptozotocin diabetic rat

Eugenol (EU), an active principle of cloves, is also widely distributed in various other plants (eg. basil, cinnamon, etc). While its antioxidant and anti-inflammatory properties are well established, biochemical insights related to its neuromodulatory potential in diabetic conditions are not clear. In the present study, initially we investigated its potential to modulate specific biochemical responses in SHSY5Y cells under experimentally -induced hyperglycemic condition. Co-exposure of cells with EU (5-10 μM) not only enhanced the cell viability, but significantly offset glucose -associated oxidative stress (as evidenced by diminished levels of reactive oxygen species and hydroperoxides). Further EU enhanced the reduced glutathione (GSH) levels and also ameliorated the levels of 3 - nitrotyrosine and expression of HSP70. We subsequently examined its efficacy to attenuate biochemical aberrations in brain regions of a streptozotocin (STZ) diabetic rat employing an intervention approach. Brain regions of EU treated (10 mg/kg bw/d, post 6 weeks of STZ) diabetic rats showed diminished levels of oxidative markers and protein carbonyls in both cytosolic and mitochondrial fractions. EU treatment caused enhanced activities of enzymic antioxidants and diminished both GSH and total thiols. Further, activities of complex I - III, succinate dehydrogenase and citrate synthase in brain regions were also significantly restored. Interestingly, EU treatment differentially attenuated the elevated activity of acetylcholinesterase and levels of calcium in brain regions. Collectively, based on the data obtained in in vitro and in vivo models, we hypothesize that EU may be employed as an adjuvant therapeutic molecule to alleviate complications under diabetic conditions.

Antioxidant activity and kinetics studies of eugenol and 6-bromoeugenol

In this work, we report the antioxidant and free radical scavenging activity of 6-bromoeugenol and eugenol. EC50, the concentration providing 50% inhibition, is calculated and the antioxidant activity index (AAI) is evaluated. The antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging method. EC50 values of 6-bromoeugenol, ascorbic acid and eugenol were 34.270 μg/mL, 54.888 μg/mL and 130.485 μg/mL, respectively. 6-Bromoeugenol showed higher AAI value (1.122) followed by ascorbic acid (0.700), then by eugenol (0.295). We also investigate the kinetics of DPPH radical scavenging activity of our products to determine the useful parameter TEC50 to evaluate their antiradical efficiency (ARE). Our results have shown high ARE. This study has provided the following ARE ( × 10(-3)) order for the tested antioxidants: ascorbic acid (70.119)>6-bromoeugenol (34.842) > eugenol (21.313). Finally, we classify ascorbic acid and eugenol as fast kinetics reaction (TEC50 8.82 and 11.38 min, respectively) and 6-bromoeugenol as medium kinetics reaction (TEC50 39.24 min).

GABAergic pharmacological activity of propofol related compounds as possible enhancers of general anesthetics and interaction with membranes

Phenol compounds, such as propofol and thymol, have been shown to act on the GABAA receptor through interaction with specific sites of this receptor. In addition, considering the high lipophilicity of phenols, it is possible that their pharmacological activity may also be the result of the interaction of phenol molecules with the surrounding lipid molecules, modulating the supramolecular organization of the receptor environment. Thus, in the present study, we study the pharmacological activity of some propofol- and thymol-related phenols on the native GABAA receptor using primary cultures of cortical neurons and investigate the effects of these compounds on the micro viscosity of artificial membranes by means of fluorescence anisotropy. The phenol compounds analyzed in this article are carvacrol, chlorothymol, and eugenol. All compounds were able to enhance the binding of [(3)H]flunitrazepam with EC50 values in the micromolar range and to increase the GABA-evoked Cl(-) influx in a concentration-dependent manner, both effects being inhibited by the competitive GABAA antagonist bicuculline. These results strongly suggest that the phenols studied are positive allosteric modulators of this receptor. Chlorothymol showed a bell-type effect, reducing its positive effect at concentrations >100 μM. The concentrations necessary to induce positive allosteric modulation of GABAA receptor were not cytotoxic. Although all compounds were able to decrease the micro viscosity of artificial membranes, chlorothymol displayed a larger effect which could explain its effects on [(3)H]flunitrazepam binding and on cell viability at high concentrations. Finally, it is suggested that these compounds may exert depressant activity on the central nervous system and potentiate the effects of general anesthetics.

Identification and analysis of absorbed components and their metabolites in rat plasma and tissues after oral administration of 'Ershiwuwei Shanhu' pill extracts by UPLC-DAD/Q-TOF-MS

ETHNOPHARMACOLOGICAL RELEVANCE

'Ershiwuwei Shanhu' pill (ESP), a classical and famous prescription of traditional Tibetan medicine, has a long history of empirical clinical use for the treatment of cerebrovascular and neurological diseases, but the absence of scientific evidence for its effect restricted its clinical application and further development.

MATERIALS AND METHODS

The methodology of plasma pharmacochemistry was adopted to analyze the potentially bioactive components in ESP extracts. A method based on UPLC-DAD/Q-TOF-MS was established to identify herb components in ESP extracts and analyze the absorbed components of ESP and their metabolites in rat plasma, brain, heart, liver and kidney samples after oral administration of ESP extracts.

RESULTS

A total of 61 herb components were detected and identified in ESP extracts, while 35 absorbed components-including 19 prototype compounds and 16 metabolites-were discovered as potentially bioactive components in rat plasma and tissues by comparative analysis of the UV and MS chromatograms of ESP extracts, blank biosamples and dosed biosamples.

CONCLUSIONS

The potentially bioactive components of ESP extracts identified from rat plasma and tissues provide useful information for further study of the pharmacology and mechanism of action of ESP.

Fractionation of a herbal antidiarrheal medicine reveals eugenol as an inhibitor of Ca2+-Activated Cl- channel TMEM16A

The Ca²⁺-activated Cl⁻ channel TMEM16A is involved in epithelial fluid secretion, smooth muscle contraction and neurosensory signaling. We identified a Thai herbal antidiarrheal formulation that inhibited TMEM16A Cl⁻ conductance. C18-reversed-phase HPLC fractionation of the herbal formulation revealed >98% of TMEM16A inhibition activity in one out of approximately 20 distinct peaks. The purified, active compound was identified as eugenol (4-allyl-2-methoxyphenol), the major component of clove oil. Eugenol fully inhibited TMEM16A Cl⁻ conductance with single-site IC₅₀∼150 µM. Eugenol inhibition of TMEM16A in interstitial cells of Cajal produced strong inhibition of intestinal contraction in mouse ileal segments. TMEM16A Cl⁻ channel inhibition adds to the list of eugenol molecular targets and may account for some of its biological activities.

Presynaptic enhancement by eugenol of spontaneous excitatory transmission in rat spinal substantia gelatinosa neurons is mediated by transient receptor potential A1 channels

Eugenol, which is contained in several plants including clove, has been widely used as an analgesic and anti-inflammatory drug in the dental clinic. Eugenol also has anesthetic effects and produces sedation and the reduction of convulsion threshold. These benefits have been partly attributed to the effects of eugenol on neural tissues, such as inhibition of voltage-gated ion channels. As expected from the fact that eugenol is a vanilloid compound, this drug activates transient receptor potential (TRP) V1 channels in the peripheral nervous system (PNS). Although eugenol affects synaptic transmission in the central nervous system (CNS), this has not yet been fully examined. We investigated how eugenol affects spontaneous glutamatergic excitatory transmission in substantia gelatinosa (SG; lamina II of Rexed) neurons of adult rat spinal cord slices by use of the blind whole-cell patch-clamp technique. Bath-applied eugenol reversibly enhanced spontaneous excitatory transmission and produced an outward current at -70 mV in SG neurons. The former action was due to a large increase in the frequency of spontaneous excitatory postsynaptic current (sEPSC) with a small increase in the amplitude. These actions of eugenol were seen by its repeated application and resistant to a voltage-gated Na(+) channel blocker tetrodotoxin. The effect of eugenol on sEPSC frequency was concentration-dependent with an EC(50) value of 3.8 mM and unaffected by a TRPV1 antagonist capsazepine, whereas inhibited by a nonspecific TRP antagonist ruthenium red and a TRPA1 antagonist HC-030031. On the other hand, the eugenol-induced outward current was not affected by these TRP antagonists. It is concluded that eugenol activates TRPA1 channels in the SG, leading to an increase in the spontaneous release of L-glutamate to SG neurons, and that eugenol also produces a membrane hyperpolarization that is not mediated by TRP channels. Eugenol is suggested to activate different types of TRP channel between the PNS and CNS.

Enhancement of the capabilities of liquid chromatography-mass spectrometry with derivatization: general principles and applications

The integration of liquid chromatography-mass spectrometry (LC-MS) with derivatization is a relatively new and unique strategy that could add value and could enhance the capabilities of LC-MS-based technologies. The derivatization process could be carried out in various analytical steps, for example, sampling, storage, sample preparation, HPLC separation, and MS detection. This review presents an overview of derivatization-based LC-MS strategy over the past 10 years and covers both the general principles and applications in the fields of pharmaceutical and biomedical analysis, biomarker and metabolomic research, environmental analysis, and food-safety evaluation. The underlying mechanisms and theories for derivative reagent selection are summarized and highlighted to guide future studies.

Feasibility Assessment of Micro-Electrode Chip Assay as a Method of Detecting Neurotoxicity in vitro

Detection and characterization of chemically induced toxic effects in the nervous system represent a challenge for the hazard assessment of chemicals. In vivo, neurotoxicological assessments exploit the fact that the activity of neurons in the central and peripheral nervous system has functional consequences. And so far, no in vitro method for evaluating the neurotoxic hazard has yet been validated and accepted for regulatory purpose. The micro-electrode array (MEA) assay consists of a culture chamber into which an integrated array of micro-electrodes is capable of measuring extracellular electrophysiology (spikes and bursts) from electro-active tissues. A wide variety of electrically excitable biological tissues may be placed onto the chips including primary cultures of nervous system tissue. Recordings from this type of in vitro cultured system are non-invasive, give label free evaluations and provide a higher throughput than conventional electrophysiological techniques. In this paper, 20 substances were tested in a blinded study for their toxicity and dose-response curves were obtained from fetal rat cortical neuronal networks coupled to MEAs. The experimental procedure consisted of evaluating the firing activity (spiking rate) and modification/reduction in response to chemical administration. Native/reference activity, 30 min of activity recording per dilution, plus the recovery points (after 24 h) were recorded. The preliminary data, using a set of chemicals with different mode-of-actions (13 known to be neurotoxic, 2 non-neuroactive and not toxic, and 5 non-neuroactive but toxic) show good predictivity (sensitivity: 0.77; specificity: 0.86; accuracy: 0.85). Thus, the MEA with a neuronal network has the potency to become an effective tool to evaluate the neurotoxicity of substances in vitro.

Eugenol: A Natural Compound with Versatile Pharmacological Actions

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.

Quantitative determination of capsaicin, a transient receptor potential channel vanilloid 1 agonist, by liquid chromatography quadrupole ion trap mass spectrometry: evaluation of in vitro metabolic stability

Capsaicin is the most abundant pungent molecule present in red peppers and it is widely used for food flavoring, in pepper spray in self-defense devices and more recently in ointments for the relief of neuropathic pain. Capsaicin is a selective agonist of transient receptor potential channel, vanilloid subfamily member 1. A selective and sensitive quantitative method for the determination of capsaicin by LC-ESI/MS/MS was developed. The method consisted of a protein precipitation extraction followed by analysis using liquid chromatography electrospray quadrupole ion trap mass spectrometry. The chromatographic separation was achieved using a 100 x 2 mm C(18) Waters Symmetry column combined with a gradient mobile phase composed of acetonitrile and 0.1% formic acid aqueous solution at a flow rate of 220 microL/min. The mass spectrometer was operating in full-scan MS/MS mode using two-segment analysis. An analytical range of 10-5000 ng/mL was used in the calibration curve constructed in rat plasma. The interbatch precision and accuracy observed were 6.5, 6.7, 5.3 and 101.2, 102.7, 103.5% at 50, 500 and 5000 ng/mL, respectively. An in vitro metabolic stability study was performed in rat, dog and mouse liver microsomes and the novel analytical method was adapted and used to determine intrinsic clearance of capsaicin. Results suggest very rapid degradation with T(1/2) ranging from 2.3 to 4.1 min and high clearance values suggesting that drug bioavailability will be considerably reduced, consequently affecting drug response and efficacy.

Molecular mechanism for local anesthetic action of eugenol in the rat trigeminal system

Eugenol is widely used in dentistry as a local analgesic agent, because of its ability to allay tooth pain. Interestingly, eugenol shares several pharmacological actions with local anesthetics which include inhibition of voltage-gated sodium channel (VGSC) and activation of transient receptor potential vanilloid subtype 1 (TRPV1). In the present study, we investigated the effects of eugenol on pain behaviors in orofacial area, and as an attempt to elucidate its mechanism we characterized inhibitory effects of eugenol on VGSCs in trigeminal ganglion (TG) neurons. TG neurons were classified into four types on the basis of their neurochemical and electrophysiological properties such as cell size, shapes of action potential (AP), isolectin-B(4) (IB(4)) binding, and were analyzed for the association of their distinctive electrophysiological properties and mRNA expression of Na(v)1.8 and TRPV1 by using single-cell RT-PCR following whole-cell recordings. Subcutaneous injection of eugenol reduced the thermal nociception and capsaicin-induced thermal hyperalgesia in a dose-dependent manner. Eugenol also diminished digastric electromyogram evoked by noxious electrical stimulation to anterior tooth pulp, which was attributable to the blockade of AP conduction on inferior alveolar nerve. At cellular level, eugenol reversibly inhibited APs and VGSCs in IB(4)+/TRPV1+/Na(v)1.8+ nociceptive TG neurons (Type I-Type III) and IB(4)-/TRPV1-/Na(v)1.8- nociceptive TG neurons (Type IV). Both TTX-resistant I(Na) in Type I-Type III neurons and TTX-sensitive I(Na) in Type IV neurons were sensitive to eugenol. Taken together, these results suggest that eugenol may serve as local anesthetics for other pathological pain conditions in addition to its wide use in dental clinic.

Effects of eugenol on Na+ currents in rat dorsal root ganglion neurons

Eugenol is an aromatic molecule found in several plants and widely used in dentistry for analgesic and antiseptic purposes. It inhibits pro-inflammatory mediators including nitric oxide synthase, cyclooxygenase and lipoxygenase. It also regulates ion channels involved in pain signaling, such as TRPV1 receptor, high-voltage-activated Ca(2+) channels, NMDA receptor and GABA(A) receptor. The expression and functional properties of voltage-gated Na(+) channels in primary sensory neurons are altered following inflammation or nerve injury. To elucidate an involvement of Na(+) channels in the eugenol-induced analgesia we investigated the effects of eugenol on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) Na(+) currents in acutely dissociated rat dorsal root ganglion neurons. Eugenol inhibited TTX-S and TTX-R Na(+) currents in a concentration-dependent manner. The K(d) values were 308 muM and 543 muM, respectively. Eugenol did not influence the activation voltage of either type of Na(+) current. However, eugenol moved the steady-state inactivation curves of both Na(+) currents to a hyperpolarizing direction and reduced the maximal Na(+) current. Thus eugenol appears to inhibit Na(+) currents through its interaction with both resting and inactivated Na(+) channels. The recovery from inactivation of both Na(+) currents was slowed by eugenol. The eugenol inhibition of Na(+) currents was not dependent on the stimulus frequency. The inhibition of Na(+) currents is considered as one of the mechanisms by which eugenol exerts analgesia.

Pharmacokinetics of eugenol and its effects on thermal hypersensitivity in rats

Neuropathic pain is a type of chronic pain following central or peripheral nervous system lesions that cause allodynia (pain initiated by a non-painful stimulus) and hyperalgesia (increased pain sensation following a painful stimulus). The first objective of the study was to evaluate the pharmacokinetics of eugenol, the principle chemical constituent of clove oil, following a gavage administration (40 mg/kg) in male Sprague-Dawley rats. The second objective was to evaluate the effect of repeated oral administrations of eugenol on hyperalgesia and allodynia using an experimental model of neuropathic pain in rats. Thermal and mechanical sensitivity (Hargreave's test and von Frey filaments) were determined in sciatic nerve cuff-implanted rats. Sensitivities were assessed following repeated oral administrations of 40 mg/kg of eugenol or saline for 5 days (n=6 per group). Pharmacokinetic parameters were calculated using noncompartmental methods. Serial blood samples were collected over 24 h. Concentrations of eugenol in blood and plasma peaked rapidly following oral administration. Mean T(1/2) values of eugenol in plasma and blood were long (14.0 and 18.3 h, respectively), suggesting a potential accumulation of the drug following repeated administrations. Reaction time to thermal stimuli appeared to increase constantly following repeated administrations of eugenol. On the last day of treatment, eugenol treatments resulted in a statistically significant prolongation of the reaction time to thermal stimuli in rats compared to the saline group (Mean+/-S.E.M.: 11.4+/-1.23 vs. 6.1+/-0.53 s, P<0.01). These results support the hypothesis that eugenol may alleviate neuropathic pain and that the cumulative effect of the drug may be in part responsible for this effect following repeated daily administrations.