Mechanisms mediating the vasorelaxing action of eugenol, a pungent oil, on rabbit arterial tissue

The vasodilator effect of Eugenol on uterine artery - potential therapeutic applications in pregnancy-associated hypertension

Preeclampsia, a gestational associated hypertension, has been reported in 6-8% of pregnant women worldwide leading to premature delivery and low birth weight of newborn due to reduced blood flow to placenta. Although several vasodilators (Methyl dopa, hydralazine, β-blockers and diuretics) are currently in use to treat preeclampsia, still there is a search for safer drugs with better efficacy. Lately, antihypertensive vasodilators from natural sources are gaining importance in treating preeclampsia. Eugenol (Eug), a natural essential oil, has been traditionally used in health and food products without any risk. In the present study, ex vivo experiments were designed to examine the vasorelaxation effect of Eug and its signaling pathways in a middle uterine artery (MUA) of pregnant Capra hircus (Ch). In presence of different blockers (L-NAME, indomethacin, ODQ, Ouabain, glibenclamide, 4-AP, Ba2, Carbenoxolone and 18β Glycyrrhetinic acid), Eug-induced concentration-dependent vasorelaxation response was elicited. The results showed that Eug caused a greater vasorelaxation effect in the MU of pregnant animals, which is mediated by potential activation of eNOS, KATP channels, and Kir channels with moderate activation of Na+- K+- ATPase and sGC and MEGJ. These findings provide a strong basis for developing Eug as a therapeutic candidate in the treatment of pregnancy-associated hypertension.

Ocimum sanctum [Tulsi] as a Potential Immunomodulator for the Treatment of Ischemic Injury in the Brain

Stroke causes brain damage and is one of the main reasons for death. Most survivors of stroke face long-term physical disabilities and cognitive dysfunctions. In addition, they also have persistent emotional and behavioral changes. The two main treatments that are effective are reperfusion with recombinant tissue plasminogen activator and recanalization of penumbra using mechanical thrombectomy. However, these treatments are suitable only for a few patients due to limitations such as susceptibility to hemorrhage and the requirement for administering tissue plasminogen activators within the short therapeutic window during the early hours following a stroke. The paucity of interventions and treatments could be because of the multiple pathological mechanisms induced in the brain by stroke. The ongoing immune response following stroke has been attributed to the worsening brain injury. Hence, novel compounds with immunomodulatory properties that could improve the outcome of stroke patients are required. Natural compounds and medicinal herbs with anti-inflammatory activities and having minimal or no adverse systemic effect could be beneficial in treating stroke. Ocimum sanctum is a medicinal herb that can be considered an effective therapeutic option for ischemic brain injury. Ocimum sanctum, commonly known as holy basil or "Tulsi," is mentioned as the "Elixir of Life" for its healing powers. Since antiquity, Tulsi has been used in the Ayurvedic and Siddha medical systems to treat several diseases. It possesses immuno-modulatory activity, which can alter cellular and humoral immune responses. Tulsi can be considered a potential option as an immuno-modulator for treating various diseases, including brain stroke. In this review, we will focus on the immunomodulatory properties of Tulsi, specifically its effect on both innate and adaptive immunity, as well as its antioxidant and antiinflammatory properties, which could potentially be effective in treating ongoing immune reactions following ischemic brain injury.

Eugenol delays the onset of ouabain-induced ventricular cardiac arrhythmias in guinea pigs

Eugenol is an aromatic compound used in the manufacture of medicines, perfumes, cosmetics and as an anaesthetic due to the ability of the drug to block the neuronal isoform of voltage-gated Na+ channels (NaV ). Some arrhythmias are associated with gain of function in the sodium current (INa ) found in cardiomyocytes, and antiarrhythmic sodium channel blockers are commonly used in the clinical practice. This study sought to elucidate the potential mechanisms of eugenol's protection in the arrhythmic model of ouabain-induced arrhythmias in guinea pig heart. Ex vivo arrhythmias were induced using 50 μM of ouabain. The antiarrhythmic properties of eugenol were evaluated in the ex vivo heart preparation and isolated ventricular cardiomyocytes. The compound's effects on cardiac sodium current and action potential using the patch-clamp technique were evaluated. In all, eugenol decreased the ex vivo cardiac arrhythmias induced by ouabain. Furthermore, eugenol showed concentration dependent effect upon peak INa , left-shifted the stationary inactivation curve and delayed the recovery from inactivation of the INa . All these aspects are considered to be antiarrhythmic. Our findings demonstrate that eugenol has antiarrhythmic activity, which may be partially explained by the ability of eugenol to change de biophysical properties of INa of cardiomyocytes.

Chinese herbal medicine for the treatment of cardiovascular diseases ─ targeting cardiac ion channels

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality, imposing an increasing global health burden. Cardiac ion channels (voltage-gated Na_V, Ca_V, K_Vs, and others) synergistically shape the cardiac action potential (AP) and control the heartbeat. Dysfunction of these channels, due to genetic mutations, transcriptional or post-translational modifications, may disturb the AP and lead to arrhythmia, a major risk for CVD patients. Although there are five classes of anti-arrhythmic drugs available, they can have varying levels of efficacies and side effects on patients, possibly due to the complex pathogenesis of arrhythmias. As an alternative treatment option, Chinese herbal remedies have shown promise in regulating cardiac ion channels and providing anti-arrhythmic effects. In this review, we first discuss the role of cardiac ion channels in maintaining normal heart function and the pathogenesis of CVD, then summarize the classification of Chinese herbal compounds, and elaborate detailed mechanisms of their efficacy in regulating cardiac ion channels and in alleviating arrhythmia and CVD. We also address current limitations and opportunities for developing new anti-CVD drugs based on Chinese herbal medicines.

Potential of natural products in combination with arsenic trioxide: Investigating cardioprotective effects and mechanisms

Over the past few decades, clinical trials conducted worldwide have demonstrated the efficacy of arsenic trioxide (ATO) in the treatment of relapsed acute promyelocytic leukemia (APL). Currently, ATO has become the frontline treatments for patients with APL. However, its therapeutic applicability is severely constrained by ATO-induced cardiac side effects. Any cardioprotective agents that can ameliorate the cardiac side effects and allow exploiting the full therapeutic potential of ATO, undoubtedly gain significant attention. The knowledge and use of natural products for evidence-based therapy have grown rapidly in recent years. Here we discussed the potential mechanism of ATO-induced cardiac side effects and reviewed the studies on cardiac side effects as well as the research history of ATO in the treatment of APL. Then, We summarized the protective effects and underlying mechanisms of natural products in the treatment of ATO-induced cardiac side effects. Based on the efficacy and safety of the natural product, it has a promising future in the development of cardioprotective agents against ATO-induced cardiac side effects.

Pharmacological Screening of Species from the Lippia genus, Content in Terpenes and Phenylpropanoids, and their Vasorelaxing Effects on Human Umbilical Artery

BACKGROUND

Naturally occurring bioactive compounds have a plethora of biological effects.

OBJECTIVE

In this study, we examined a pharmacological screening of natural products on the human umbilical artery (HUA).

METHODS

HUA preparations were used to follow contractions by KCl (60 mM) and tested at different concentrations (1-5000 μg/mL and μM) of the Lippia alba (EOLa) and Lippia origanoides (EOLo) essential oils, terpenes (citral, limonene perilic alcohol) and phenylpropanoids (eugenol, methyl eugenol). Discussion/Results: The reduction corresponded to approximately 100%, except for limonene (80±1.2 %). When evaluating the concentration of the natural product that promotes 50 % relaxation of the HUA contracted by KCL, EC50 values were: 424.3 μg/mL (EOLa); 468.7±6.7 μg/mL (EOLo); 264.2 ± 8.2 μM (citral); 677.8±5.4 μM (limonene); 186.3±6.4 μM (peryl alcohol); 986.4±7.9 μM (eugenol); and 279.1±4.4 μM (methyl-eugenol). Perillyl alcohol had a lower EC50 (consequently it has a higher pharmacological potency).

CONCLUSION

The plant extracts have a promising vasorelaxing effect in HUAs, paving the way for future investigations: as applications in diseases related to these vessels, such as preeclampsia.

Eugenol interacts with cardiac sodium channel and reduces heart excitability and arrhythmias

AIMS

Eugenol is a natural compound found in the essential oils of many aromatic plants. The compound is used as a local anesthetic because of its inhibitory effect on the voltage-gated Na⁺ channels (Na_v), which are expressed in the nociceptive neurons. Eugenol has shown wide range of activities in the cardiovascular system; most of these activities are attributed to the modulation of voltage-sensitive Ca²⁺ channels. However, its action on Na_v1.5, the main subtype of Na_v expressed in the mammalian myocardium, is unknown. The interaction of eugenol with Na_v1.5 could also contribute to its antiarrhythmic properties in vitro and ex vivo. We investigated the compound's effect on sodium current (I_Na) and its possible cardiac antiarrhythmic activity.

METHODS

The effect of eugenol on cardiac contractility was investigated using isolated atrium from guinea pig (for isometric force measurements). The compound's effect on I_Na was evaluated using human embryonic cell transiently expressing human Nav1.5 and patch-clamp technique.

KEY FINDINGS

Eugenol caused negative inotropic and chronotropic effects in the atria. In the ex vivo arrhythmia model, eugenol decreased atrial pacing disturbance induced by ouabain. Eugenol reduced the I_Na in a concentration-dependent manner. Furthermore, the compound left-shifted the stationary inactivation curve, delayed recovery from inactivation of the I_Na, and preferentially blocked the channel in the inactivated state. Importantly, eugenol was able to attenuate the late sodium current. All these aspects are considered to be antiarrhythmic.

SIGNIFICANCE

Overall, our findings demonstrate that eugenol has antiarrhythmic activity due, at least in part, to its interaction with Na_v1.5.

Strengthening antioxidant defense & cardio protection by Piper betle: An in-vitro study

Introduction

The purpose of this research work was to evaluate Piper betle ethyl acetate extract (PBEA) for its free radical scavenging, antioxidant, anti-apoptotic activities and its role in protecting against oxidative cardiac cell injury.

Methods

The Free radical scavenging activity and antioxidant potential of PBEA were evaluated using various non-cellular methods (1,1-Diphenyl-2-picrylhydrazyl, β-carotene bleaching, superoxide anion, hydroxyl radical, hydrogen peroxide_, Reducing power, Total phenolics and Total flavonoids). PBEA was standardized with Eugenol by GC-FID analysis. Furthermore, PBEA was also assessed for its cytotoprotective effect against 100μM H₂O₂ in H9c2 cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Intracellular reactive oxygen species scavenging and anti-apoptoic activity of PBEA was assessed by using 2′, 7′-Dichlorofluorescein diacetate and Annexin- Propidium Iodide, respectively.

Results

PBEA exhibited radical scavenging and antioxidant defense response at different magnitudes of potency. Eugenol, a cardiac protective bioactive molecule in PBEA was found to be 43.43 ± 1.46 mg/g of PBEA extract. Further, pre-incubation of H9c2 cells with 10 μg/ml PBEA for 24 h exhibited remarkable cytoprotective effect against H₂O₂ induced oxidative stress. PBEA at 10 μg/ml dose with 24 h contact with H9c2 cells significantly enhanced the activity of cellular defense system and significantly decreased intracellular ROS (P < 0.001) and apoptosis (P < 0.01) thereby protecting against the cytotoxic effects of H₂O₂.

Conclusion

These outcomes indicated that PBEA could shield against oxidative and apoptotic cardiac cell injury in invitro studies. Thus, PBEA might be a desirable antioxidant of natural origin that has future clinical implications in both health care and food industry.

Vasorelaxation Caused by Eugenol, Curcumin and Nanocurcumin is Partially Mediated by Activation of Aminoguanidine-sensitive iNOS in the Middle Uterine Artery of Non-pregnant and Pregnant Capra hircus

Natural products like eugenol and curcumin have been reported to control hypertension. The purpose of our study was to examine the role of iNOS in eugenol/curcumin/nanocurcumin–induced vasorelaxation in the middle uterine artery (MUA) obtained from non-pregnant (NP) and pregnant (P) Capra hircus ( Ch). The MUA rings were mounted in an automatic organ bath attached to a powerlab data acquisition system. Vasorelaxation was induced by eugenol/curcumin/nanocurcumin in either the absence or presence of aminoguanidine in phenylephrine precontracted MUA rings. The vasorelaxation response was recorded isometrically by a highly sensitive isometric force transducer automatic organ bath connected to powerlab and analysed using Labchart 7.1.3 software. The maximal vasorelaxation (Rmax) obtained from eugenol, curcumin and nanocurcumin -induced concentration related contractile response elicited in PE- precontracted ED+ MUA rings was 49.5%, 42.6%, and 40.4% in NP, and 79.5%, 55.5%, and 44.1% in P Ch. Aminoguanidine attenuated the Rmax of eugenol, curcumin and nanocurcumin to 28.2%, 28.5%, and 16.4% in MUA of NP, and 57.2%, 57.4%, and 38.0% in MUA of P Ch, respectively. The results demonstrated that vasorelaxation to (i) Eugenol is partly mediated by partial activation of aminoguanidine-sensitive iNOS in the uterine artery and this pathway is augmented in pregnancy, (ii) Nanocurcumin is mediated by activation of aminoguanidine-sensitive iNOS in the uterine artery of NP, but not in P Ch and (iii) Curcumin is mediated by minimal activation of aminoguanidine sensitive iNOS only in the uterine artery of NP, but not in P Ch. In conclusion, eugenol and nanocurcumin possess a greater potential than curcumin in the control of hypertension due to partial activation of iNOS. These nutraceuticals could be useful to improve blood flow to the uterus to maintain oestrus cycle, maternal and fetal health.

The effects of food essential oils on cardiovascular diseases: A review

Essential oils (EO) are complex secondary metabolites, which are produced by aromatic plants and identified by their powerful odors. Present studies on EO and their isolated ingredients have drawn the attention of researchers to screen these natural products and evaluate their effect on the cardiovascular system. Some EO, and their active ingredients, have been reported to improve the cardiovascular system significantly by affecting vaso-relaxation, and decreasing the heart rate and exert a hypotension activity. Several mechanisms have been proposed for the role of EO and their main active components in promoting the health of the cardiovascular system. The objective of this review is to highlight the current state of knowledge on the functional role of EO extracted from plants for reducing the risk of cardiovascular diseases and their mechanisms of action. Research on EO has the potential to identify new bioactive compounds and formulate new functional products for the treatment of cardiovascular diseases such as arterial hypertension, angina pectoris, heart failure, and myocardial infarction.

Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels

Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca) currents, when using Ba as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca currents involved pore block, a hyperpolarizing shift (∼-10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivation rate. In summary, our data indicate that eugenol dilates cerebral arteries by means of multimodal inhibition of voltage-dependent Ca channels.

Vanillin and vanillin analogs relax porcine coronary and basilar arteries by inhibiting L-type Ca2+ channels

Vanillin (VA) and vanillyl alcohol (VAA), components of natural vanilla, and ethyl vanillin (EtVA; synthetic analog) are used as flavoring agents and/or as additives by the food, cosmetic, or pharmaceutic industries. VA, VAA, and EtVA possess antioxidant and anti-inflammatory properties, but their vascular effects have not been determined. Therefore, we compared in isolated porcine coronary and basilar arteries the changes in isometric tension caused by VA, VAA, and EtVA. VA and its analogs caused concentration-dependent relaxations of both preparations during contractions from U46619 (9,11-dideoxy-11α,9α-epoxymethanoprostaglandin F2α, a thromboxane A2 receptor agonist), and of coronary arteries contracted with KCl or endothelin-1. The order of potency was VAA < VA < EtVA. The relaxations were not inhibited by endothelium removal, by inhibitors of NO synthases (N(ω)-nitro-l-arginine methyl ester hydrochloride), cyclooxygenases (indomethacin), soluble guanylyl cyclase (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one [ODQ]), KCa (1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole [TRAM-34], 6,12,19,20,25,26-hexahydro-5,27:13,18:21,24-trietheno-11,7-metheno-7H-dibenzo[b,n][1,5,12,16]tetraazacyclotricosine-5,13-diium ditrifluoroacetate hydrate [UCL-1684], or iberiotoxin), by KATP (glibenclamide), by Kir (BaCl2), by transient receptor potential receptor vanilloid 3 (TRPV3) channels (ruthenium red), or by antioxidants (catalase, apocynin, tempol, N-acetylcysteine, tiron). VA and its analogs inhibited contractions induced by Ca(2+) reintroduction in coronary arteries, and by an opener of L-type Ca(2+)-channels (methyl 2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]-1,4-dihydropyridine-3-carboxylate [Bay K8644]) in coronary and basilar arteries. They inhibited contractions of coronary rings induced by the protein kinase C activator phorbol 12,13-dibutyrate to the same extent as the removal of extracellular Ca(2+) or incubation with nifedipine. Thus, in porcine arteries, relaxation from VA (and its analogs) is due to inhibition of L-type Ca(2+) channels. Hence, these compounds could be used to relieve coronary or cerebral vasospasms due to exaggerated Ca(2+) influx, but therapeutic efficacy would require exposures that far exceed the current levels obtained by the use of vanillin additives.

Ocimum sanctum leaf extracts attenuate human monocytic (THP-1) cell activation

ETHNOPHARMACOLOGICAL RELEVANCE

Ocimum sanctum (OS), commonly known as Holy basil/Tulsi, has been traditionally used to treat cardiovascular diseases (CVD) and manage general cardiac health. The present study is designed to evaluate the antiinflammatory effect of O. sanctum and its phenolic compound and eugenol (EUG) in human monocytic (THP-1) cells and validate its traditional use for treating cardiovascular diseases.

MATERIALS AND METHODS

The phytochemical analysis of alcoholic and water extracts of OS-dry leaves (OSAE and OSWE) was done using LC-QTOF-MS. A phenolic compound, EUG was quantified in both OSAE and OSWE by an LC-MS technique using a mass hunter work station software quantitative analysis system. The effect of both OSAE, OSWE, pure compound EUG and positive control imatinib (IMT) was investigated in THP-1 cells by studying the following markers: lipopolysaccharide (LPS) induced tumor necrosis factor alpha (TNF-α) secretion by ELISA, gene expression of inflammatory markers (TNF-α, IL-6, MIP-1α and MCP-1) by real time PCR and translocation of nuclear factor kappa B (NF-κB) by confocol microscopy. Furthermore, the effect of the extracts, EUG and IMT, was studied on phorbol-12-myristate-13-acetate (PMA) induced monocyte to macrophage differentiation and gene expression of CD14, TLR2 and TLR4.

RESULTS

The LC-MS analysis of OSAE and OSWE revealed the presence of several bioactive compounds including eugenol. Quantitative analysis revealed that OSAE and OSWE had EUG of 12 ng/mgdwt and 19 ng/mgdwt respectively. OSAE, OSWE (1 mg dwt/mL) pure compound EUG (60 µg/mL) and positive control IMT (20 µg/mL) showed marked inhibition on LPS induced TNF-α secretion by THP-1 cells. At the selected concentration, the plant extracts, EUG and IMT inhibited gene expression of cytokines and chemokines (IL-6, TNF-α, MIP-1α, MCP-1) and translocation of NF-κB-p65 to the nuclei. In addition, they showed significant inhibition on PMA induced monocyte to macrophage differentiation and the gene expression of CD14, TLR2 and TLR4 markers.

CONCLUSION

The result of the present study validated traditional use of Ocimum sanctum for treating cardiovascular disease for the first time by testing antiinflammatory activity of Ocimum sanctum in acute inflammatory model, LPS induced THP-1 cells. The plant extracts showed significant antiinflammatory activity, however, further to be evaluated using chronic inflammatory animal models like diabetic or apolipoprotein E-deficient mice to make it evidence based medicine. The phenolic compound eugenol (60 µg/mL) showed significant antiinflammatory activity. However the amount of eugenol present in 1mg of OSAE and OSWE (12 ng/mg and 19 ng/mg dwt respectively) used for cell based assays was very low. It suggests that several other metabolites along with eugenol are responsible for the efficacy of the extracts.

Protective effect of clove oil and eugenol microemulsions on fatty liver and dyslipidemia as components of metabolic syndrome

In the present research, the effect of clove essential oil (CO) and its major constituent, eugenol, formulated in water-based microemulsions, was studied on fatty liver and dyslipidemia in high-fructose-fed rats. Plasma and liver lipids, oxidative stress, inflammatory biomarker, and liver function were the assessed criteria. CO dispersed in water as conventional cloudy emulsion was also subjected to the same biological evaluations for comparison with the microemulsified form of this oil. Results showed that the particle size of CO microemulsion (COM) and eugenol microemulsion (EM) was 8.0 nm and 8.9 nm, respectively. Excess dilution and incubation of these microemulsions in 1.2 N HCl, that mimic stomach juice (without lipase), for 5 hours at 37 °C lead to the establishment of second population of larger particles with average diameter>100.0 nm. Biological evaluation revealed that rats of high fructose control group exhibited significant dyslipidemia, high plasma tumor necrosis factor-α, and elevated malondialdehyde. The same group of rats showed significant high liver total fat, triglycerides and cholesterol, and liver dysfunction compared to control normal rats fed balanced diet. Daily oral administration of CO conventional emulsion, COM, and EM produced significant improvement of all studied parameters. No significant change in all biochemical parameters was noticed when the groups given the different formulations were compared with each other. The study concluded that administration of CO conventional emulsion, COM, or EM produced significant improvement in fatty liver and dyslipidemia with consequent expected protection from cardiovascular diseases and other complications of fatty liver. Formulation of CO in microemulsion having particle size ∼ 8.0 nm did not enhance the protective effect compared with the same dose of CO dispersed in water as conventional macroemulsion, probably due to the ease of absorption of these bioactives in their native states. However, formulation in microemulsion provides a delivery system for oral administration of CO or eugenol in homogeneous, water-based, and thermodynamically stable dosage form during storage.

Autonomic Nervous System Mediates the Hypotensive Effects of Aqueous and Residual Methanolic Extracts of Syzygium polyanthum (Wight) Walp. var. polyanthum Leaves in Anaesthetized Rats

Syzygium polyanthum (Wight) Walp. var. polyanthum leaves are consumed as a traditional Malay treatment of hypertension. This study investigates hypotensive potential of aqueous (AESP) and residual methanolic (met-AESP) extracts of S. polyanthum leaves and possible involvement of autonomic receptors. AESP and met-AESP (20 to 100 mg/kg) were intravenously administered into anaesthetized Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Blood pressure and heart were monitored for 20 min. AESP and met-AESP induced significant dose-dependent hypotension, but only 100 mg/kg AESP caused mild bradycardia (n = 5). AESP-induced hypotension was more potent than that of met-AESP in WKY. AESP has a faster onset time than that of met-AESP in both WKY and SHR. However, met-AESP-induced hypotension was more sustained than that of AESP in SHR. Blockages of autonomic ganglion and α-adrenergic receptors using hexamethonium and phentolamine (n = 5 for each group) partially attenuated AESP-induced hypotension, suggesting involvement of α-adrenergic receptors. Blockages of autonomic ganglion, β-adrenergic, cholinergic receptors, and nitric oxide production using hexamethonium, propranolol, atropine, and N-ω-nitro-l arginine methyl ester (L-NAME) (n = 5 for each group) partially attenuated met-AESP-induced hypotension, suggesting involvement of β-adrenergic and cholinergic receptors via nitric oxide production.

Effects of different extracts of Eugenia caryophyllata on pentylenetetrazole-induced seizures in mice

OBJECTIVE

To investigate the possible anticonvulsant effect of different extracts of Eugenia caryophyllata (clove) on pentylenetetrazole (PTZ)-induced seizures in mice.

METHODS

The animals were divided into saline, 50, 100, 250 and 500 mg/kg of aqueous extract, 50, 100, 250 and 500 mg/kg of ethanolic extract, and 50, 100, 250 and 500 mg/kg of chloroformic extract of clove groups. The extracts or saline were injected 60 min before each PTZ injection. Latency to the first minimal clonic seizure (MCS) and generalized tonic-clonic seizure (GTCS) and the percent of mortality were recorded.

RESULTS

Aqueous extract of clove at doses of 50, 100, 250 and 500 mg/kg significantly extended the MCS and GTCS latency (P<0.05). The MCS latency in mice treated with 50, 100 and 250 mg/kg of the ethanolic extract was significantly increased (P<0.05). The GTCS latency in mice treated with 50, 100, 250 and 500 mg/kg of ethanolic extract was significantly higher than that of the saline-treated group (P<0.05). There were no significant differences in MCS and GTCS latency between mice treated with different chloroformic extract of clove or saline.

CONCLUSION

The aqueous and ethanolic extracts of clove could inhibit the PTZ-induced convulsion, and this plant has the potential to be used as a new therapeutic agent for control of seizures. The exact mechanisms and the active compounds that are responsible for the anticonvulsive effect need to be clarified in future studies.

The role of endothelium in the vasorelaxant effects of the essential oil of Ocimum gratissimum in aorta and mesenteric vascular bed of rats

This study investigated the endothelium-dependent vasorelaxant effects of the essential oil of Ocimum gratissimum (EOOG) in aortas and mesenteric vascular beds isolated from rats. EOOG (3-300 µg/mL) relaxed the tonic contractions induced by phenylephrine (0.1 µmol/L) in isolated aortas in a concentration-dependent manner in both endothelium-containing and endothelium-denuded preparations. This effect was partially reversed by L-NAME (100 µmol/L) but not by indomethacin (10 µmol/L) or TEA (5 mmol/L). In mesenteric vascular beds, bolus injections of EOOG (30, 50, 100, and 300 ng) decreased the perfusion pressure induced by noradrenaline (6 µmol/L) in endothelium-intact preparations but not in those treated with deoxycholate. L-NAME (300 µmol/L) but not TEA (1 mmol/L) or indomethacin (3 µmol/L) significantly reduced the vasodilatory response to EOOG at all of the doses tested. Our data showed that EOOG exerts a dose-dependent vasodilatory response in the resistance blood vessels of rat mesenteric vascular beds and in the capacitance blood vessel, the rat aorta. This action is completely dependent on endothelial nitric oxide (NO) release in the mesenteric vascular beds but only partially dependent on NO in the aorta. These novel effects of EOOG highlight interesting differences between resistance and capacitance blood vessels.

Pharmacological evidence of calcium-channel blockade by essential oil of Ocimum gratissimum and its main constituent, eugenol, in isolated aortic rings from DOCA-salt hypertensive rats

Intravenous (i.v.) treatment of conscious DOCA-salt hypertensive rats with the essential oil of Ocimum gratissimum L. (Labiatae) (EOOG) induced a hypotensive effect that seems related to an active vascular relaxation rather than withdrawal of sympathetic tone. To corroborate this hypothesis, the present study examined the vascular effects of EOOG and its main constituent, eugenol (EUG) and the putative mechanisms underlying these effects. Additionally, the role of the vascular beta(2)-adrenergic mechanism in the mediation of EOOG-induced hypotension has also been investigated. In conscious DOCA-salt hypertensive rats, the EOOG-induced hypotension was reversible and remained unchanged by i.v. pretreatment with propranolol (2 mg/kg). In isolated aorta preparations with intact endothelium from DOCA-salt hypertensive rats, EOOG (1-1000 microg/mL) and EUG (0.006-6 mM) relaxed the phenylephrine-induced contraction similarly with IC(50) [geometric mean (95% confidence interval)] values of 226.9 (147.8-348.3) microg/mL and 1.2 (0.6-2.1) mm, respectively. Vasorelaxant effects of EOOG were significantly altered by removal of the vascular endothelium [IC(50) = 417.2 (349.5-497.8) microg/mL]. In a calcium-free medium, the CaCl(2)-induced contractions were significantly reduced and even abolished by EOOG at 300 and 1000 microg/mL, respectively, whereas EOOG (1000 microg/mL) did not have any significant effect on caffeine-induced contractions. Similar results were obtained with EUG (1.8 and 6 mM) on both CaCl(2)- and caffeine-induced contractions, respectively. The data suggest that hypotensive responses to EOOG in DOCA-salt hypertensive rats are due to an active vascular relaxation, which is partly dependent upon the integrity of the vascular endothelium and seems predominantly mediated through an inhibition of plasmalemmal Ca(2+) influx rather than Ca(2+)-induced Ca(2+) release from the sarcoplasmic reticulum.

Effects of anethole and structural analogues on the contractility of rat isolated aorta: Involvement of voltage-dependent Ca2+-channels

Anethole is a naturally occurring aromatic oxidant, present in a variety of medicinal plant extracts, which is commonly used by the food and beverage industry. Despite its widespread occurrence and commercial use, there is currently little information regarding effects of this compound on the vasculature. Therefore the actions of anethole on the contractility of rat isolated aorta were compared with those of eugenol, and their respective isomeric forms, estragole and isoeugenol. In aortic rings precontracted with phenylephrine (PE; 1 microM), anethole (10(-6) M-10(-4) M) induced contraction in preparations possessing an intact endothelium, but not in endothelium-denuded tissues. At higher concentrations (10(-3) M-10(-2) M), anethole-induced concentration-dependent and complete relaxation of all precontracted preparations, irrespective of whether the endothelium was intact or not, an action shared by eugenol, estragole and isoeugenol. The contractile and relaxant effects of anethole in PE-precontracted preparations were not altered by L-NAME (10 microM) or indomethacin (10 microM), indicating that neither nitric oxide nor prostaglandins were involved in these actions. The mixed profile of effects was not confined to PE-mediated contraction, since similar responses were obtained to anethole when tissues were precontracted with 25 mM KCl. Anethole and estragole (10(-6)-10(-4) M), but not eugenol or isoeugenol, increased the basal tonus of endothelium-denuded aortic rings, an action that was abolished by VDCC blockers nifedipine (1 microM) and diltiazem (1 microM), or by withdrawal of extracellular Ca(2+). Our data suggest complex effects of anethole on isolated blood vessels, inducing contraction at lower doses, mediated via opening of voltage-dependent Ca(2+)-channels, and relaxant effects at higher concentrations that are shared by structural analogues.

Clove oil cream: a new effective treatment for chronic anal fissure

OBJECTIVE

Anal fissure is a common painful condition affecting the anal canal and causes considerable morbidity and reduction in quality of life. Surgical treatment has been associated with a degree of incontinence in up to 30% of patients. This study discussed the results of clove oil 1% cream in healing of chronic anal fissure.

METHOD

A single-blind randomized comparative trial was setup to compare traditional treatment with stool softeners and lignocaine cream 5% against clove oil 1% cream for 6 weeks.

RESULTS

55 patients were included in this study, 30 patients in clove oil group and 25 patients in control group. Healing had occurred in 60% of patients in clove oil group and in 12% of patients in the control group after 3-month follow up (P < 0.001). Patients in clove oil group showed significant reduction in resting anal pressure and almost all other anorectal manometric pressures compared with patients in control group.

CONCLUSION

Topical application of clove oil cream demonstrated a significant beneficial effect when applied to patients suffering from chronic anal fissure.

Temporal variation of chemical composition and relaxant action of the essential oil of Ocimum gratissimum L. (Labiatae) on guinea-pig ileum

The medicinal plant Ocimum gratissimum L. (Labiatae) is widely encountered in the Northeast of Brasil where it is used to treat digestive problems. Its leaves have an essential oil (EOOG) content whose chemical composition varies according to the time of plant collection. We have compared the effects of the EOOG, collected at 08:00 a.m. (EOOG8) and at 12:00 a.m. (EOOG12), on the relaxation of guinea-pig isolated ileum. Both EOOG8 and EOOG12 (30-300 microg/ml) reversibly relaxed the spontaneous tonus of the guinea-pig ileum in a concentration-dependent manner, with similar IC50 values (49.3 and 23.8 microg/ml, respectively). The magnitude of the decrease in resting tonus was similar to that of the recognised smooth muscle relaxant papaverine. EOOG8 and EOOG12 relaxed 60 mM KCl-precontracted preparations similarly (38.33 +/- 9.91 microg/ml and 35.53 +/- 6.70), whereas a significantly more potent relaxant effect of EOOG12 compared to EOOG8 was observed when tissues were contracted using 10 microM acetylcholine (IC50 values of 69.55 +/- 4.93 and 128.16 +/- 15.70 microg/ml, respectively; p < 0.05). The principal constituents of the essential oil, eugenol and cineole, also relaxed KCl-precontracted preparations, although they were less potent than EOOG, suggesting that they alone were not responsible for EOOG-induced relaxations. Our results show that the essential oil extracted from the leaves of O. gratissimum L., collected at different time periods, exerts significant relaxant effects on isolated guinea-pig ileum which may underlie the therapeutic action of the plant.

Eucalyptol, an essential oil, reduces contractile activity in rat cardiac muscle

Eucalyptol is an essential oil that relaxes bronchial and vascular smooth muscle although its direct actions on isolated myocardium have not been reported. We investigated a putative negative inotropic effect of the oil on left ventricular papillary muscles from male Wistar rats weighing 250 to 300 g, as well as its effects on isometric force, rate of force development, time parameters, post-rest potentiation, positive inotropic interventions produced by Ca2+ and isoproterenol, and on tetanic tension. The effects of 0.3 mM eucalyptol on myosin ATPase activity were also investigated. Eucalyptol (0.003 to 0.3 mM) reduced isometric tension, the rate of force development and time parameters. The oil reduced the force developed by steady-state contractions (50% at 0.3 mM) but did not alter sarcoplasmic reticulum function or post-rest contractions and produced a progressive increase in relative potentiation. Increased extracellular Ca2+ concentration (0.62 to 5 mM) and isoproterenol (20 nM) administration counteracted the negative inotropic effects of the oil. The activity of the contractile machinery evaluated by tetanic force development was reduced by 30 to 50% but myosin ATPase activity was not affected by eucalyptol (0.3 mM), supporting the idea of a reduction of sarcolemmal Ca2+ influx. The present results suggest that eucalyptol depresses force development, probably acting as a calcium channel blocker.

Effects of eugenol, an essential oil, on the mechanical and electrical activities of cardiac muscle

Eugenol (EUG) acts as a calcium antagonist but effects on the contractile proteins could also occur. We investigated inotropic effects of EUG in rat left ventricular papillary muscles, measuring isometric force, time variables, and post rest potentiation and EUG actions on the effects of Ca2+ (0.62 to 2.5 mM) and isoproterenol (5 ng/ml), on myosin ATPase activity and on the calcium currents in single ventricular myocytes. EUG reduced tension and time variables without altering the sarcoplasmic reticulum activity increasing post-pause relative potentiation. Isoproterenol and Ca2+ counteract these negative inotropic effects. Tetanic tension diminished, but not the myosin ATPase activity suggesting an isolated sarcolemmal effect. EUG 0.1 mM decreased the Ca2+ current amplitude in the entire potential range tested and 0.5 mM almost completely blocked this inward current. Results suggested that EUG depresses force without affecting the contractile machinery and its action is the only dependent blockade of the calcium inward current.

Cardiovascular effects of the essential oil of Ocimum gratissimum leaves in rats: role of the autonomic nervous system

1. The cardiovascular effects of intravenous (i.v.) administration of the essential oil of Ocimum gratissimum (EOOG) were investigated in rats. In addition, the present study examined: (i) whether the autonomic nervous system is involved in the mediation of EOOG-induced changes in mean aortic pressure (MAP) and heart rate (HR); and (ii) whether these changes could be attributed, at least in part, to the actions of eugenol, the major constituent of EOOG. 2. In both pentobarbitone-anaesthetized and conscious rats, i.v. bolus injections of EOOG (1-20 mg/kg) elicited immediate and dose-dependent decreases in MAP and HR. These responses to EOOG were of the same order of magnitude irrespective of whether the animal was under general anaesthesia. 3. Pretreatment of anaesthetized rats with bilateral vagotomy did not significantly modify the EOOG-induced dose-dependent hypotension, whereas it significantly reduced the bradycardia at the highest dose used. 4. In conscious rats, i.v. injections of bolus doses (1-10 mg/kg) of eugenol also elicited immediate and dose-dependent decreases in MAP and HR. Intravenous pretreatment of conscious rats with either methylatropine (1 mg/kg) or hexamethonium (30 mg/kg) significantly reduced the EOOG-induced dose-dependent bradycardia without affecting the hypotension. 5. These data show, for the first time, that i.v. administration of EOOG to either anaesthetized or conscious rats induces an immediate and significant hypotension and bradycardia, which appear to be due, at least in part, to the actions of the major constituent of EOOG, eugenol. These cardiovascular effects appear to be mediated by different pathways because only EOOG-induced hypotension appears to be independent of the presence of an operational autonomic nervous system. This may suggest that the hypotensive activity of EOOG results from its vasodilatory effects directly upon vascular smooth muscle.

Cardiovascular effects of eugenol, a phenolic compound present in many plant essential oils, in normotensive rats

Cardiovascular effects of intravenous (i.v.) treatment with eugenol (Eug), a natural pungent present in many plant essential oils, were investigated in normotensive rats. In either anesthetized or conscious rats, i.v. bolus injections of Eug (1 to 10 mg/kg) elicited immediate and dose-dependent hypotension and bradycardia. Magnitude of Eug-induced hypotension was similar in both groups. Pretreatment of anesthetized rats with bilateral vagotomy almost abolished the bradycardic responses to Eug without affecting the hypotension. Likewise, i.v. pretreatment of conscious rats with methylatropine (1 mg/kg) or hexamethonium (30 mg/kg) significantly reduced the Eug-induced bradycardia without affecting the hypotension. However, i.v. pretreatment with the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl (L-NAME, 20 mg/kg), affected neither the hypotension nor the bradycardia elicited by Eug. In rat mesenteric bed preparations precontracted with potassium (60 mM), Eug (0.1-2 mM) induced a reversible and concentration-dependent vasodilator effect, which remained unaffected by atropine (1 microM). These results show that i.v. treatment of rats with Eug induces dose-dependent hypotension and bradycardia, which occurred independently. The bradycardia appears dependent upon the presence of an intact and functional parasympathetic nerve drive to the heart while the hypotension is due to an active vascular relaxation rather than withdrawal of sympathetic tone. Released nitric oxide from vascular endothelial cells seems to be not involved in the mediation of Eug-induced hypotension.

Endothelium-dependent and -independent vasodilator effects of eugenol in the rat mesenteric vascular bed

The possible involvement of the endothelium in the vasodilator action of eugenol was investigated in the mesenteric vascular bed (MVB) of the rat. Bolus injections of eugenol (0.2, 2 and 20 micromol) and acetylcholine (ACh; 10, 30 and 100 pmol) induced dose-dependent vasodilator responses in noradrenaline-precontracted beds that were partially inhibited by pretreatment of the MVB with deoxycholate (1 mg mL(-1)) to remove the endothelium (approximately 14% and approximately 30% of the control response remaining at the lowest doses of ACh and eugenol, respectively). The vasodilator effect of glyceryl trinitrate (1 micromol) was unaltered by deoxycholate. In the presence of either N(omega)-nitro-L-arginine methyl ester (300 microM) or tetraethylammonium (1 mM)the response to ACh was partially reduced, whereas eugenol-induced vasodilation was unaffected. Similarly the vasodilator effect of eugenol was not inhibited by indometacin (3 microM). Under calcium-free conditions the vasoconstrictor response elicited by bolus injections of noradrenaline (10 nmol) was dose-dependently and completely inhibited by eugenol (0.1-1 mM). Additionally, the pressor effects of bolus injections of calcium chloride in potassium-depolarized MVBs were greatly reduced in the presence of eugenol (0.1 mM), with a maximal reduction of approximately 71% of the control response. Our data showed that eugenol induced dose-dependent, reversible vasodilator responses in the rat MVB, that were partially dependent on the endothelium, although apparently independent of nitric oxide, endothelium-derived hyperpolarizing factor or prostacyclin. Furthermore, an endothelium-independent intracellular site of action seemed likely to participate in its smooth muscle relaxant properties.

Vasorelaxant effects of eugenol on rat thoracic aorta

Eugenol is a natural pungent substance and the main component of clove oil, with vasorelaxant action. To elucidate some of the possible mechanisms involved in this action isometric tension was measured in aortic rings from male Wistar rats precontracted with phenylephrine (PHE, 10(-7) M) or KCl (75 mM). Responses to increasing concentrations of eugenol (10(-6)-10(-2) M) were obtained in the presence and absence of endothelium. In the presence of eugenol, dose-response curves to PHE (10(-9) to 10(-4) M) and KCl (5-125 mM) were displaced downwards. Concentration-dependent relaxation was observed in rings precontracted with PHE (10(-7) M) and KCl (75 mM). The tension increment produced by increasing external calcium concentration (0.25-3 mM) was also reduced by eugenol (300 microM) treatment. The inhibitory effects of eugenol (300 microM) were compared to those induced by nifedipine (0.01 microM), a selective Ca(2+) channel blocker, producing similar relaxant effects. Two other protocols were performed. After precontraction with PHE (10(-7) M), increasing concentrations of eugenol (10(-6)-10(-2) M) were used before and after N(w)-nitro-L-arginine (L-NAME, 10(-4) M) and methylene blue (10(-5) M) treatment. Eugenol-induced relaxation was reduced by endothelial damage (rubbing), L-NAME and methylene blue treatments. Results suggested that eugenol produces smooth muscle relaxation resulting from the blockade of both voltage-sensitive and receptor-operated channels that are modulated by endothelial-generated nitric oxide.

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.

The presence of cholinomimetic and calcium channel antagonist constituents in Piper betle Linn

The crude aqueous extract of Piper betle leaves (Pb.Cr) was studied for the possible presence of cholinomimetic and calcium channel antagonist constituents. Pb.Cr at doses of 1-10 mg/mL caused a moderate spasmogenic effect in isolated guinea-pig ileum and this activity was concentrated in the aqueous fraction, which was found to be about 5 times more potent. Pretreatment of the tissue with atropine (1 microM) but not hexamethonium (100 microM) completely abolished the contractile effect of the aqueous fraction indicating a cholinergic (muscarinic) mechanism. In isolated rabbit jejunum preparations Pb.Cr did not produce a significant increase in the spontaneous contractions, but instead produced a dose-dependent (0.03-3.0 mg/mL) inhibition of spontaneous activity. Activity-directed fractionation revealed that the spasmolytic action was concentrated in the ethyl acetate fraction. When tested against K(+)-induced contractions, both Pb.Cr and its ethyl acetate fraction (Pb.EtAc) caused a dose-dependent inhibition, suggesting calcium channel blockade (CCB). The potent CCB effect of the crude extract and its ethyl acetate fraction was confirmed when pretreatment of the tissue with Pb.Cr or Pb.EtAc shifted the Ca(++) dose-response curves to the right in a dose-dependent manner. These data indicate that the plant contains cholinomimetic and possible calcium channel antagonist constituents, which are concentrated in the aqueous and ethyl acetate fractions respectively. It is suggested that some of the traditional uses of this plant may be explained on the basis of these activities.