Involvement of Cholinergic and Opioid System in γ-Terpinene-Mediated Antinociception

Chemical Profiling and Assessment of Analgesic and Anti-Inflammatory Activity of Ammoides verticillata Essential Oil: In Vitro, In Vivo, and In Silico Studies

Background/Objectives: Essential oils are increasingly recognized for their therapeutic potential, yet Ammoides verticillata essential oil (AVEO) remains relatively unexplored, particularly for its anti-inflammatory and analgesic properties. This study aimed to profile AVEO's chemical composition and evaluate its antioxidant, anti-inflammatory, and analgesic effects, with a focus on its novel pharmacological actions. Methods: The chemical composition of AVEO was determined using GC-MS analysis, and antioxidant capacity was assessed through in vitro assays. Furthermore, the anti-inflammatory potential was investigated using a carrageenan-induced paw edema model in rats, complemented by the inhibition assays of cyclooxygenase (COX) enzymes. The analgesic effects were evaluated through acetic acid-induced writhing and tail immersion tests. Additionally, a computational study was performed to explore the binding affinity of AVEO's major constituents to COX-2. Results: GC-MS analysis revealed a rich monoterpene profile dominated by carvacrol (32.51%). It was found that AVEO exhibited significant antioxidant activity. Similarly, in vivo, AVEO showed significant anti-inflammatory effects, achieving a percentage inhibition of 52.23% at 200 mg/kg, comparable to diclofenac, along with potent COX-2 inhibition observed (IC50 = 1.51 ± 0.20, SI = 5.56). Moreover, analgesic tests demonstrated dose-dependent pain relief, in which the dose of 200 mg/kg significantly prolonged tail latency to 14.00 ± 1.45 s and markedly reduced abdominal constriction to 21.17 ± 1.62. Computational analysis further corroborated the high binding affinity of carvacrol and thymol with COX-2 (-7.381 and -6.939 Kcal/mol, respectively). Conclusions: These findings underscore AVEO's potential as a promising therapeutic agent for managing inflammation and pain.

Non-clinical investigations about cytotoxic and anti-platelet activities of gamma-terpinene

Gamma-terpinene (γ-TPN) is a cyclohexane monoterpene isolated from plant essential oils, such as tea tree (Melaleuca alternifolia), oregano (Origanum vulgare), rosemary (Rosmarinus officinalis L.), thyme (Thymus vulgaris Marchand), and eucalyptus (Eucalyptus sp.). Terpenes are widely studied molecules pharmacologically active on the cardiovascular system, hemostasis, and antioxidant actions. Herein, it was investigated the cytotoxic and antiplatelet activity of γ-TPN using different non-clinical laboratory models. For in silico evaluation, the PreADMET, SwissADME, and SwissTargetPrediction softwares were used. Molecular docking was performed using the AutoDockVina and BIOVIA Discovery Studio databases. The cytotoxicity of γ-TPN was analyzed by the MTT assay upon normal murine endothelial SVEC4-10 and fibroblast L-929 cells. Platelet aggregation was evaluated with platelet-rich (PRP) and platelet-poor (PPP) plasma from spontaneously hypertensive rats (SHR), in addition to SVEC4-10 cells pre-incubated with γ-TPN (50, 100, and 200 µM) for 24 h. SHR animals were pre-treated by gavage with γ-TPN for 7 days and divided into four groups (negative control, 25, 50, and 100 mg/kg). Blood samples were collected to measure nitrite using the Griess reagent. Gamma-TPN proved to be quite lipid-soluble (Log P = +4.50), with a qualified profile of similarity to the drug, good bioavailability, and adequate pharmacokinetics. It exhibited affinity mainly for the P2Y12 receptor (6.450 ± 0.232 Kcal/mol), moderate cytotoxicity for L-929 (CC50 = 333.3 µM) and SVEC 4-10 (CC50 = 366.7 µM) cells. The presence of γ-TPN in SVEC 4-10 cells was also able to reduce platelet aggregation by 51.57 and 44.20% at lower concentrations (50 and 100 µM, respectively). Then, γ-TPN has good affinity with purinergic receptors and an effect on the reversal of platelet aggregation and oxidative stress, being promising and safe for therapeutic targets and subsequent studies on the control of thromboembolic diseases.

Antihyperalgesic effect of γ-terpinene complexed in β-cyclodextrin on neuropathic pain model induced by tumor cells

Neuropathic pain is a high-intensity pain that can be caused by compression, transection, injury, nerve infiltration and drug treatment of cancer. Furthermore, drug therapy has low clinical efficacy, many adverse effects and remission of painful symptoms. In this way, natural products derived from plants constitute a promising therapeutic alternative. Therefore, the aim of this study was to evaluate the antihyperalgesic effect of γ-terpinene (γ-TPN) e γ-terpinene in β-cyclodextrin inclusion complexes (TPN/CD) on neuropathic pain induced by tumor cells. Complexation extended the effect time for another 5 h and daily treatment for six days with γ-TPN (50 mg/kg, p.o.) and γ-TPN/β-CD (50 mg/kg, p.o.) significantly reduced (p < 0.001) the mechanical hyperalgesia induced by the administration of 2x106 sarcoma cells 180 in the around the sciatic nerve. In addition, the Grip and Rota-rod techniques demonstrated that there was no interference on the muscle strength and motor coordination of the animals, suggesting that the compound under study does not have central nervous system depressant effects at the doses used. Molecular docking studies demonstrate favorable binding energies between γ-TPN and β-CD, and alpha-2 adrenergic, glutamatergic, opioid and cholinergic receptors. Thus, this study demonstrates the potential of terpinene complexation in controlling neuropathic pain induced by tumor cells.

Chemical composition, antioxidant, antimicrobial, and wound healing effects of Trachyspermum roxburghianum (DC.) H. Wolff essential oil: An in vivo and in silico approach

ETHNOPHARMACOLOGICAL RELEVANCE

Trachyspermum roxburghianum (DC.) H. Wolff, commonly known as 'Ajamoda,' is a neglected Indian spice highly used in Ayurveda and folklore remedies as an antimicrobial for chronic wounds and discharges, along with many other disease conditions.

AIM OF THE STUDY

The objective of the study was to explore chemical composition and to investigate the antioxidant, antimicrobial, analgesic, and wound healing activities of T. roxburghianum fruit essential oil from India.

MATERIALS AND METHODS

The phytochemical characterization of the oil was determined through standard qualitative procedures and the gas chromatography-mass spectrometry (GC-MS) technique. The in vitro antioxidant aptitude was assessed by scavenging DPPH and ABTS radicals. The antimicrobial potential of the oil was investigated using the disc diffusion method, followed by the determination of minimum inhibitory concentration against Gram-positive and Gram-negative bacterial and fungal strains. The analgesic potential was evaluated using thermal and chemically induced pain models in Swiss albino mice. Wound healing was assessed in vivo, including determining wound contraction rates, histopathology, and hydroxyproline estimation, using the excision wound model in Swiss albino mice.

RESULTS

GC-MS analysis identified 55 compounds with major terpenoids, including thymol (13.8%), limonene (11.5%), and others. Substantial radical-scavenging activity was exhibited by T. roxburghianum fruit essential oil (TREO) (IC50 94.41 ± 2.00 μg/mL in DPPH assay and 91.28 ± 1.94 μg/mL in ABTS assay). Microorganisms were inhibited with low MIC (2 μL/mL for the inhibition of Staphylococcus aureus and Bacillus subtilis; 4 μL/mL against Salmonella typhi and 16 μL/mL against Candida albicans). In the cytotoxicity study, no cytotoxicity was observed on the Monkey Normal Kidney Cell line (Vero). Significant antinociceptive effects were observed (25.47 ± 1.10 % of inhibition at 100 mg/kg and 44.31 ± 1.69 % at 200 mg/kg). A remarkable rate of wound closure and epithelization, along with a marked increase in hydroxyproline content, were observed for the oil during wound healing in mice.

CONCLUSIONS

The results suggested that oil could be utilized as a potential source of wound healing therapeutics.

Promising Effects of Casearins in Tumor-Bearing Mice and Antinociceptive Action against Oncologic Pain: Molecular Docking and In Vivo Findings

Safer analgesic drugs remain a hard challenge because of cardiovascular and/or gastrointestinal toxicity, mainly. So, this study evaluated in vivo the antiproliferative actions of a fraction with casearins (FC) from Casearia sylvestris leaves against human colorectal carcinomas and antihyperalgesic effects on inflammatory- or opiate-based pain relief and oncologic pain in Sarcoma 180 (S180)-bearing mice. Moreover, docking investigations evaluated the binding among Casearin X and NMDA(N-methyl-D-aspartate)-type glutamate receptors. HCT-116 colorectal carcinoma-xenografted mice were treated with FC for 15 days. Antinociceptive assays included chemically induced algesia and investigated mechanisms by pharmacological blockade. Intraplantar region S180-bearing animals received a single dose of FC and were examined for mechanical allodynia and behavior alterations. AutoDock Vina determined molecular interactions among Cas X and NMDA receptor subunits. FC reduced tumor growth at i.p. (5 and 10 mg/kg) and oral (25 mg/kg/day) doses (31.12-39.27%). FC reduced abdominal pain, as confirmed by formalin and glutamate protocols, whose antinociception activity was blocked by naloxone and L-NAME (neurogenic phase) and naloxone, atropine, and flumazenil (inflammatory phase). Meanwhile, glibenclamide potentiated the FC analgesic effects. FC increased the paw withdrawal threshold without producing changes in exploratory parameters or motor coordination. Cas X generated a more stable complex with active sites of the NMDA receptor GluN2B subunits. FC is a promising antitumor agent against colorectal carcinomas, has peripheral analgesic effects by desensitizing secondary afferent neurons, and inhibits glutamate release from presynaptic neurons and/or their action on cognate receptors. These findings emphasize the use of clerodane diterpenes against cancer-related pain conditions.

A Review of the Ethnobotanical Use, Chemistry and Pharmacological Activities of Constituents Derived from the Plant Genus Geijera (Rutaceae)

Geijera Schott is a plant genus of the Rutaceae Juss. (rue and citrus) family, comprising six species which are all native to Oceania. Of the plants belonging to this genus, the most significant species that has a customary use is Geijera parviflora, which was used by Indigenous Australians, primarily as a pain reliever. Herein, a comprehensive review of the literature published on the genus Geijera from 1930 to 2023 was conducted. This is the first review for this plant genus, and it highlights the chemical constituents reported to date, together with the range of pharmacological properties described from the various species and different parts of the plant. These properties include anti-inflammatory, anti-microbial, anti-parasitic, insect repellent, analgesic, neuroactive, and anti-cancer activities. Finally, a reflection on some of the important areas for future focused studies of this plant genus is provided.

Growth inhibitory, immunosuppressive, cytotoxic, and genotoxic effects of γ-terpinene on Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae)

γ-Terpinene, a monoterpene widely present in essential oils of many medicinal and aromatic plants with numerous biological properties, was evaluated for its insecticidal activity against melon fruit fly, Zeugodacus cucurbitae (Coquillett). Different concentrations (5, 25, 125, 625, and 3125 ppm) of γ-terpinene along with control were fed to larvae of melon fly. The number of pupae formed and adults emerged declined significantly after treatment. Morphologically deformed adults and pupae were also observed. The developmental duration too prolonged in treated larvae. Food assimilated, mean relative growth rate, larval weight gain, and pupal weight also declined. In the larvae treated with LC30 and LC50 concentrations, there was a decline in the titers of phenoloxidase and total hemocyte count, and variations were observed in the differential hemocyte count, suggesting an immunosuppressive effect of γ-terpinene on melon fly. Both concentrations also led to an increase in the apoptotic and necrotic cells as well as decrease in the viable hemocytes in the circulating hemolymph of treated larvae. Comet parameters (tail length, % tail DNA, tail moment, and olive tail moment) of γ-terpinene fed larvae increased significantly. Given the observed effects of γ-terpinene on normal developmental and nutritional physiology, its immunosuppressive properties, and its potential for genome damage, it can be considered for incorporation into integrated pest management strategies for controlling Z. cucurbitae.

TNF-α and IL-1β in Diabetes-Induced Liver Damage: The Relationship between Trachyspermum ammi Seeds Methanol Extract and Inflammatory Cytokine Inhibition

The objective of this study was to determine the effect of Trachyspermum ammi (T. ammi) on the liver of streptozotocin (STZ)-induced diabetic rats. This study began by identifying the methanolic composition of T. ammi. The presence of three compounds was determined using gas chromatography-mass spectrometry (GC-MS), with Thymol (60.705%), ϒ-Terpinene (22.216%), and P-cymene (17.078%) being the most prevalent. Afterwards, diabetic rats were treated with T. ammi (200–500 mg/kg) or losartan (20 mg/kg) daily for 60 days. In the diabetic rats treated with T. ammi, levels of hepatic indicators, lipid peroxidation markers, and proinflammatory mediators decreased significantly. In the liver of T. ammi-treated diabetic rats, glutathione-S-transferase (GST), catalase (CAT), and glutathione (GSH) increased significantly. Despite the fact that proinflammatory cytokine levels were significantly increased, interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α) levels decreased in the groups administered the extract. From these results, it can be concluded that T. ammi significantly restored the liver’s antioxidant balance and inflammation caused by hyperglycemia.

γ-Terpinene complexed with β-cyclodextrin attenuates spinal neuroactivity in animals with cancer pain by Ca2+ channel block

OBJECTIVES

Considering that γ-terpinene (γ-TPN) is a monoterpene found in Cannabis oil, with high lipophilicity and limited pharmacokinetics, our objective was to evaluate whether its complexation in β-cyclodextrin (γ-TPN/β-CD) could improve its physicochemical properties and action on cancer pain, as well as verify the mechanisms of action involved.

METHODS

The γ-TPN/β-CD was prepared and submitted to physicochemical characterization. Animals with sarcoma 180 were treated (vehicle, γ-TPN 50 mg/kg, γ-TPN/β-CD 5 mg/kg or morphine) and assessed for hyperalgesia, TNF-α and IL-1β levels, iNOS and c-Fos activity. The effects of γ-TPN on calcium channels were studied by patch-clamp and molecular docking.

RESULTS

β-CD improved the physicochemical properties and prolonged the anti-hyperalgesic effect of γ-TPN. This compound also reduced the levels of IL-1β, TNF-α and iNOS in the tumour, and c-Fos protein in the spinal cord. In addition, it reduced Ca2+ current, presenting favourable chemical interactions with different voltage-dependent calcium channels.

CONCLUSION

These results indicate that the complexation of γ-TPN into β-CD increases its stability and time effect, reducing spinal neuroactivity and inflammation by blocking calcium channels.

Evaluation of the terpenes β-caryophyllene, α-terpineol, and γ-terpinene in the mouse chronic constriction injury model of neuropathic pain: possible cannabinoid receptor involvement

Pain is one of the most common reasons to seek medical attention, and chronic pain is a worldwide epidemic. Anecdotal reports suggest cannabis may be an effective analgesic. As cannabis contains the terpenes α-terpineol, β-caryophyllene, and γ-terpinene, we hypothesized these terpenes would produce analgesia in a mouse model of neuropathic pain. We used the chronic constriction injury of the sciatic nerve mouse model, which produces mechanical allodynia, assessed via the von Frey assay, as well as thermal hyperalgesia assessed via the hotplate assay. Compounds were further assessed in tests of locomotor activity, hypothermia, and acute antinociception. Each terpene produced dose-related reversal of mechanical allodynia and thermal hyperalgesia. Thermal hyperalgesia displayed higher sensitivity to the effects of each terpene than mechanical allodynia, and the rank order potency of the terpenes was α-terpineol > β-caryophyllene > γ-terpinene. To examine the involvement of cannabinoid receptors, further tests were conducted in mice lacking either functional cannabinoid type 1 receptors (CB₁R (-/-)) or cannabinoid type 2 receptors (CB₂R (-/-)). Compared to wild type mice, CB₁R (-/-) mice treated with α-terpineol displayed a 2.91-fold decrease in potency to reverse mechanical allodynia; in CB₂R (-/-) mice, the potency of α-terpineol was decreased 11.73-fold. The potency of β-caryophyllene to reverse mechanical allodynia decreased 1.80-fold in CB₂R (-/-) mice. Each terpene produced a subset of effects in tests of locomotor activity, hypothermia, and acute antinociception. These findings suggest α-terpineol, β-caryophyllene, and γ-terpinene may have differential cannabinoid receptor activity and a pharmacological profile that may yield new efficacious analgesics.

Antinociceptive effects of minor cannabinoids, terpenes and flavonoids in Cannabis

Cannabis has been used for centuries for its medicinal properties. Given the dangerous and unpleasant side effects of existing analgesics, the chemical constituents of Cannabis have garnered significant interest for their antinociceptive, anti-inflammatory and neuroprotective effects. To date, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) remain the two most widely studied constituents of Cannabis in animals. These studies have led to formulations of THC and CBD for human use; however, chronic pain patients also use different strains of Cannabis (sativa, indica and ruderalis) to alleviate their pain. These strains contain major cannabinoids, such as THC and CBD, but they also contain a wide variety of cannabinoid and noncannabinoid constituents. Although the analgesic effects of Cannabis are attributed to major cannabinoids, evidence indicates other constituents such as minor cannabinoids, terpenes and flavonoids also produce antinociception against animal models of acute, inflammatory, neuropathic, muscle and orofacial pain. In some cases, these constituents produce antinociception that is equivalent or greater compared to that produced by traditional analgesics. Thus, a better understanding of the extent to which these constituents produce antinociception alone in animals is necessary. The purposes of this review are to (1) introduce the different minor cannabinoids, terpenes, and flavonoids found in Cannabis and (2) discuss evidence of their antinociceptive properties in animals.

Analgesic Potential of Terpenes Derived from Cannabis sativa

Pain prevalence among adults in the United States has increased 25% over the past two decades, resulting in high health-care costs and impacts to patient quality of life. In the last 30 years, our understanding of pain circuits and (intra)cellular mechanisms has grown exponentially, but this understanding has not yet resulted in improved therapies. Options for pain management are limited. Many analgesics have poor efficacy and are accompanied by severe side effects such as addiction, resulting in a devastating opioid abuse and overdose epidemic. These problems have encouraged scientists to identify novel molecular targets and develop alternative pain therapeutics. Increasing preclinical and clinical evidence suggests that cannabis has several beneficial pharmacological activities, including pain relief. Cannabis sativa contains more than 500 chemical compounds, with two principle phytocannabinoids, Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD). Beyond phytocannabinoids, more than 150 terpenes have been identified in different cannabis chemovars. Although the predominant cannabinoids, Δ9-THC and CBD, are thought to be the primary medicinal compounds, terpenes including the monoterpenes β-myrcene, α-pinene, limonene, and linalool, as well as the sesquiterpenes β-caryophyllene and α-humulene may contribute to many pharmacological properties of cannabis, including anti-inflammatory and antinociceptive effects. The aim of this review is to summarize our current knowledge about terpene compounds in cannabis and to analyze the available scientific evidence for a role of cannabis-derived terpenes in modern pain management. SIGNIFICANCE STATEMENT: Decades of research have improved our knowledge of cannabis polypharmacy and contributing phytochemicals, including terpenes. Reform of the legal status for cannabis possession and increased availability (medicinal and recreational) have resulted in cannabis use to combat the increasing prevalence of pain and may help to address the opioid crisis. Better understanding of the pharmacological effects of cannabis and its active components, including terpenes, may assist in identifying new therapeutic approaches and optimizing the use of cannabis and/or terpenes as analgesic agents.

A Comparative Study of the Chemical Composition by SPME-GC/MS and Antiradical Activity of Less Common Citrus Species

Citrus secondary metabolites, such as terpene compounds, are very important for human health due to their bioactivity including anti-inflammatory, anti-cancer, and antioxidant effects. In this work, for the first time, the volatile chemical composition of peels and juices from four different Citrus species (C. junos, Citrus × aurantium, C. aurantium 'Bizzarria' and C. medica 'Florentina', commonly known as Yuzu jeune, Oni Yuzu, Bizzarria orange and Florence cedar, respectively) was investigated by Solid-Phase Microextraction-Gas Chromatography/Mass Spectrometry (SPME-GC/MS) technique and the antiradical activity was also examined. The results showed that limonene and γ-terpinene were the main volatile substances detected both in the juices and in the peels, followed by other minority compounds responsible for the phyto-complex of the unique aromas which characterize each individual analyzed Citrus species. Principal component analysis (PCA), performed on volatile compounds, showed both some correlation as well as a clear separation between the juice and the peel of each species. Among them, Oni Yuzu juice was found to be the richest in total polyphenols and flavonoids while its capacity to scavenge ABTS^•+ and DPPH^• radicals was similar to that of Yuzu Jeune and Bizzarria orange.

Possible Use of Phytochemicals for Recovery from COVID-19-Induced Anosmia and Ageusia

The year 2020 became the year of the outbreak of coronavirus, SARS-CoV-2, which escalated into a worldwide pandemic and continued into 2021. One of the unique symptoms of the SARS-CoV-2 disease, COVID-19, is the loss of chemical senses, i.e., smell and taste. Smell training is one of the methods used in facilitating recovery of the olfactory sense, and it uses essential oils of lemon, rose, clove, and eucalyptus. These essential oils were not selected based on their chemical constituents. Although scientific studies have shown that they improve recovery, there may be better combinations for facilitating recovery. Many phytochemicals have bioactive properties with anti-inflammatory and anti-viral effects. In this review, we describe the chemical compounds with anti- inflammatory and anti-viral effects, and we list the plants that contain these chemical compounds. We expand the review from terpenes to the less volatile flavonoids in order to propose a combination of essential oils and diets that can be used to develop a new taste training method, as there has been no taste training so far. Finally, we discuss the possible use of these in clinical settings.

A systematic review on ethnopharmacology, phytochemistry and pharmacological aspects of Thymus vulgaris Linn

Thymus vulgaris Linn. is a medicinal and culinary herb from the Southern European region known for its anti-infective, cardioprotective, gastroprotective, anti-inflammatory, and immunomodulatory activities since the Egyptian era. The reported pharmacological activities of T. vulgaris L. include antibacterial, antioxidant, anti-inflammatory, antiviral, and anti-cancerous activities. In this review, a comprehensive approach is put forth to scrutinize and report the available data on phytochemistry, ethnopharmacology, pharmacology, and toxicology of the plant. The different extracts and essential oil obtained from the plant have been assessed and reported to treat ailments like microbial infections, inflammation, non-communicable diseases like cancer, and sexually transmitted diseases like HIV-1 and Herpes. The literature review has also indicated the use of volatile oils, phenolic acids, terpenoids, flavonoids, saponins, steroids, tannins, alkaloids, and polysaccharides in pharmacotherapy. Applications of these compounds including antidiabetic, anti-Alzheimer's, cardio, neuro and hepatoprotective, anti-osteoporosis, sedative, immunomodulatory, antioxidant, anti-tyrosinase, antispasmodic, antinociceptive, gastroprotective, anticonvulsant, antihypertensive, antidepressant, anti-amnesia, and anti-helminthic activities have been mentioned. Further, based on research gaps, recommendations have been provided to evaluate T. vulgaris L. systematically to develop plant-based drugs, nutraceuticals, and to evaluate their clinical efficiency and safety.

Toxicity evaluation of an essential oil mixture from the Cretan herbs thyme, Greek sage and Cretan dittany

The importance of herbal extracts on health, which was initially based on ethnopharmacological and traditional knowledge, becomes increasingly well documented by numerous experimental and intervention studies. The daily use of beverages from different aromatic plants which becomes more popular nowadays, has been a tradition in Crete, and a habit that has been linked to the longevity seen in the island. Additionally, a certain combination of aromatic plants has been used against common cold and influenza. Interestingly, when such a mixture of essential oils from Cretan herbs (Cretan Aromatic Plants essential oil, CAPeo, from thyme, Greek sage, and Cretan dittany) was formulated, significant antiviral properties were observed in vitro and a significant reduction in the duration and severity of symptoms of patients with upper respiratory tract infections was found in a clinical study. However, since many plants extracts can exert toxic effects, toxicity issues should be properly addressed. In the present work we present an acute and sub-chronic toxicity evaluation for this mixture of aromatic plants' essential oils in rats. In fact, it is the only toxicity study for Cretan dittany. We report absence of toxicity, rendering the use of the mixture of essential oils from Cretan dittany, Greek sage and thyme as safe.

Antinociceptive Activity of Petroleum Ether Fraction of Clinacanthus nutans Leaves Methanolic Extract: Roles of Nonopioid Pain Modulatory Systems and Potassium Channels

Methanolic extract of Clinacanthus nutans Lindau leaves (MECN) has been reported to exert antinociceptive activity. The present study aimed to elucidate the possible antinociceptive mechanisms of a lipid-soluble fraction of MECN, which was obtained after sequential extraction in petroleum ether. The petroleum ether fraction of C. nutans (PECN), administered orally to mice, was (i) subjected to capsaicin-, glutamate-, phorbol 12-myristate 13-acetate-, bradykinin-induced nociception model; (ii) prechallenged (intraperitoneal (i.p.)) with 0.15 mg/kg yohimbine, 1 mg/kg pindolol, 3 mg/kg caffeine, 0.2 mg/kg haloperidol, or 10 mg/kg atropine, which were the respective antagonist of α 2-adrenergic, β-adrenergic, adenosinergic, dopaminergic, or muscarinic receptors; and (iii) prechallenged (i.p.) with 10 mg/kg glibenclamide, 0.04 mg/kg apamin, 0.02 mg/kg charybdotoxin, or 4 mg/kg tetraethylammonium chloride, which were the respective inhibitor of ATP sensitive-, small conductance Ca2+-activated-, large conductance Ca2+-activated-, or nonselective voltage-activated-K+ channel. Results obtained demonstrated that PECN (100, 250, and 500 mg/kg) significantly (P<0.05) inhibited all models of nociception described earlier. The antinociceptive activity of 500 mg/kg PECN was significantly (P<0.05) attenuated when prechallenged with all antagonists or K+ channel blockers. However, only pretreatment with apamin and charybdotoxin caused full inhibition of PECN-induced antinociception. The rest of the K+ channel blockers and all antagonists caused only partial inhibition of PECN antinociception, respectively. Analyses on PECN's phytoconstituents revealed the presence of antinociceptive-bearing bioactive compounds of volatile (i.e., derivatives of γ-tocopherol, α-tocopherol, and lupeol) and nonvolatile (i.e., cinnamic acid) nature. In conclusion, PECN exerts a non-opioid-mediated antinociceptive activity involving mainly activation of adenosinergic and cholinergic receptors or small- and large-conductance Ca2+-activated-K+ channels.

Effects of isopulegol in acute nociception in mice: Possible involvement of muscarinic receptors, opioid system and l-arginine/NO/cGMP pathway

Previous studies have shown that isopulegol has anxiolytic, anticonvulsant, gastro-protective and antioxidant activities in rodents, but until now there are no studies showing activity of isopulegol in animal models of nociception and inflammation. The objective of this study was to evaluate the antinociceptive effect of isopulegol and to propose possible mechanisms involved in its effects observed in mice. Groups of male and female Swiss mice (20-35 g, n = 5-8) were used in this test under the authorization of Ethics Committee on Animal Experimentation (CEEA/UFPI N° 82/2014). In order to evaluate the antinociceptive activity of isopulegol, nociception was induced using formalin test, capsaicin and glutamate in hind paw licking model, followed by the investigation of the involvement of opioid mechanisms, K + ATP channels, muscarinic, L arginine-nitric oxide and cGMP. The oral administration of isopulegol showed antinociceptive effect in both phases of the formalin test at doses from 0.78 to 25 mg/kg (first phase) and 1.56-25 mg/kg (second phase) and also produced significant results before capsaicin test at doses from 1.56 to 12.5 mg/kg and glutamate test at doses from 3.12 to 6.25 mg/kg with a dose-dependent effect. The antinociception activity of isopulegol was inhibited in the presence of naloxone (2 mg / kg, ip), glibenclamide (3 mg/kg, ip), atropine (1 mg/kg, ip), l-arginine (600 mg/kg, ip) and methylene blue (20 mg/kg, ip). The results suggested that acute antinociceptive action of opioid isopulegol seems to be related to the K + ATP channels system, through the involvement of muscarinic receptors, inhibiting nitric oxide and cGMP.

Nutmeg oil alleviates chronic inflammatory pain through inhibition of COX-2 expression and substance P release in vivo

Background

Chronic pain, or sometimes referred to as persistent pain, reduces the life quality of patients who are suffering from chronic diseases such as inflammatory diseases, cancer and diabetes. Hence, herbal medicines draw many attentions and have been shown effective in the treatment or relief of pain.

Methods and Results

Here in this study, we used the CFA-injected rats as a sustainable pain model to test the anti-inflammatory and analgesic effect of nutmeg oil, a spice flavor additive to beverages and baked goods produced from the seed of Myristica fragrans tree.

Conclusions

We have demonstrated that nutmeg oil could potentially alleviate the CFA-injection induced joint swelling, mechanical allodynia and heat hyperanalgesia of rats through inhibition of COX-2 expression and blood substance P level, which made it possible for nutmeg oil to be a potential chronic pain reliever.