Antinociceptive Activity of Chemical Components of Essential Oils That Involves Docking Studies: A Review

Almond fixed oil from Syagrus coronata (Mart.) Becc. has antinociceptive and anti-inflammatory potential, without showing oral toxicity in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Syagrus coronata, a palm tree found in northeastern Brazil, popularly known as licuri, has socioeconomic importance for the production of vegetable oil rich in fatty acids with nutritional and pharmacological effects. Licuri oil is used in traditional medicine to treat inflammation, wound healing, mycosis, back discomfort, eye irritation, and other conditions.

AIM OF THE STUDY

The study aimed to evaluate the antinociceptive, anti-inflammatory, and antipyretic effects of treatment with Syagrus coronata fixed oil (ScFO), as well as to determine the safety of use in mice.

MATERIALS AND METHODS

Initially, the chemical characterization was performed by gas chromatography-mass spectrometry. Acute single-dose oral toxicity was evaluated in mice at a dose of 2000 mg/kg. Antinociceptive activity was evaluated through abdominal writhing, formalin, and tail dipping tests, and the anti-inflammatory potential was evaluated through the model of acute inflammation of ear edema, peritonitis, and fever at concentrations of 25, 50, and 100 mg/kg from ScFO.

RESULTS

In the chemical analysis of ScFO, lauric (43.64%), caprylic (11.7%), and capric (7.2%) acids were detected as major. No mortality or behavioral abnormalities in the mice were evidenced over the 14 days of observation in the acute toxicity test. ScFO treatment decreased abdominal writhing by 27.07, 28.23, and 51.78% at 25, 50, and 100 mg/kg. ScFO demonstrated central and peripheral action in the formalin test, possibly via opioidergic and muscarinic systems. In the tail dipping test, ScFO showed action from the first hour after treatment at all concentrations. ScFO (100 mg/kg) reduced ear edema by 63.76% and leukocyte and neutrophil migration and IL-1β and TNF-α production in the peritonitis test.

CONCLUSION

Mice treated with ScFO had a reduction in fever after 60 min at all concentrations regardless of dose. Therefore, the fixed oil of S. coronata has the potential for the development of new pharmaceutical formulations for the treatment of pain, inflammation, and fever.

Synthesis, kinetic studies and in-silico investigations of novel quinolinyl-iminothiazolines as alkaline phosphatase inhibitors

Deposition of hydroxyapatite (HA) or alkaline phosphate crystals on soft tissues causes the pathological calcification diseases comprising of end-stage osteoarthritis (OA), ankylosing spondylitis (AS), medial artery calcification and tumour calcification. The pathological calcification is symbolised by increased concentration of tissue non-specific alkaline phosphatase (TNAP). An efficient therapeutic strategy to eradicate these diseases is required, and for this the alkaline phosphatase inhibitors can play a potential role. In this context a series of novel quinolinyl iminothiazolines was synthesised and evaluated for alkaline phosphatase inhibition potential. All the compounds were subjected to DFT studies where N-benzamide quinolinyl iminothiazoline (6g), N-dichlorobenzamide quinolinyl iminothiazoline (6i) and N-nitrobenzamide quinolinyl iminothiazoline (6j) were found as the most reactive compounds. Then during the in-vitro testing, the compound N-benzamide quinolinyl iminothiazoline (6g) exhibited the maximum alkaline phosphatase inhibitory effect (IC₅₀ = 0.337 ± 0.015 µM) as compared to other analogues and standard KH₂PO₄ (IC₅₀ = 5.245 ± 0.477 µM). The results were supported by the molecular docking studies, molecular dynamics simulations and kinetic analysis which also revealed the inhibitory potential of compound N-benzamide quinolinyl iminothiazoline (6g) against alkaline phosphatase. This compound can be act as lead molecule for the synthesis of more effective inhibitors and can be suggested to test at the molecular level.

Antinociceptive Effect of a p-Cymene/β-Cyclodextrin Inclusion Complex in a Murine Cancer Pain Model: Characterization Aided through a Docking Study

Pain is one of the most prevalent and difficult to manage symptoms in cancer patients, and conventional drugs present a range of adverse reactions. The development of β-cyclodextrins (β-CD) complexes has been used to avoid physicochemical and pharmacological limitations due to the lipophilicity of compounds such as p-Cymene (PC), a monoterpene with antinociceptive effects. Our aim was to obtain, characterize, and measure the effect of the complex of p-cymene and β-cyclodextrin (PC/β-CD) in a cancer pain model. Initially, molecular docking was performed to predict the viability of complex formation. Afterward, PC/β-CD was obtained by slurry complexation, characterized by HPLC and NMR. Finally, PC/β-CD was tested in a Sarcoma 180 (S180)-induced pain model. Molecular docking indicated that the occurrence of interaction between PC and β-CD is favorable. PC/β-CD showed complexation efficiency of 82.61%, and NMR demonstrated PC complexation in the β-CD cavity. In the S180 cancer pain model, PC/β-CD significantly reduced the mechanical hyperalgesia, spontaneous nociception, and nociception induced by non-noxious palpation at the doses tested (p < 0.05) when compared to vehicle differently from free PC (p > 0.05). Therefore, the complexation of PC in β-CD was shown to improve the pharmacological effect of the drug as well as reducing the required dose.

Evaluation of the antinociceptive effect generated by citronellal monoterpene isomers

Due to the complex nature of pain and the participation of physical, cognitive, psychological and behavioral aspects, pain management has several approaches. The use of medicinal plants in developing countries is quite expressive. Seeking new options for the treatment of emerging or debilitating diseases. Therefore, the present study seeks to elucidate the effects of the monoterpene, citronellal, differentiating its activity by isomers (R)-(+) and (S)-(-) citronellal. The study used several methods to evaluate the effects of citronellal isomers on motor coordination, nociceptive response, and the involvement of opioid, glutamatergic, and transient receptor pathways. The methods included rota-rod, hot-plate, and formalin tests, as well as the use of specific inhibitors and agonists. Data were analyzed using inferential statistics with a 95% confidence level. Both isomers did not significantly affect the motor coordination of the studied animals. The isomer (S)-(-) citronellal showed better results in relation to its structural counterpart, managing to have an antinociceptive effect in the formalin and hot plate tests with a lower concentration (100 mg/kg) and presenting fewer side effects, however, the this study was not able to elucidate the mechanism of action of this isomer despite having activity in studies with substances that act on specific targets such as glutamate and capsaicin, its activity was not reversed with the use of antagonists for pathways related to nociception. While the (R)-(+) citronellal isomer, despite showing total activity only at a concentration of 150 mg/kg, was able to determine its mechanism of action related to the opioid pathway by reversing its activity by the antagonist naloxone, being this is a pathway already correlated with nociception control treatments, however, it is also related to some unwanted side effects. In this way, new studies are sought to elucidate the mechanism related to the isomer (S)-(-) citronellal and a possibility of use in other areas related to the treatment of pain or inflammation.

Terpenoid Transport in Plants: How Far from the Final Picture?

Contrary to the biosynthetic pathways of many terpenoids, which are well characterized and elucidated, their transport inside subcellular compartments and the secretion of reaction intermediates and final products at the short- (cell-to-cell), medium- (tissue-to-tissue), and long-distance (organ-to-organ) levels are still poorly understood, with some limited exceptions. In this review, we aim to describe the state of the art of the transport of several terpene classes that have important physiological and ecological roles or that represent high-value bioactive molecules. Among the tens of thousands of terpenoids identified in the plant kingdom, only less than 20 have been characterized from the point of view of their transport and localization. Most terpenoids are secreted in the apoplast or stored in the vacuoles by the action of ATP-binding cassette (ABC) transporters. However, little information is available regarding the movement of terpenoid biosynthetic intermediates from plastids and the endoplasmic reticulum to the cytosol. Through a description of the transport mechanisms of cytosol- or plastid-synthesized terpenes, we attempt to provide some hypotheses, suggestions, and general schemes about the trafficking of different substrates, intermediates, and final products, which might help develop novel strategies and approaches to allow for the future identification of terpenoid transporters that are still uncharacterized.

Schinus terebinthifolia leaf lectin has central and peripheral antinociceptive action mediated by its carbohydrate-recognition domain and delta-opioid receptors

ETHNOPHARMACOLOGICAL RELEVANCE

Preparations from the bark and leaves of Schinus terebinthifolia Raddi are commonly used to treat toothaches and sore throats. The use of medications based on leaves of this plant has also been reported for pain of arthritis, toothache, and sore throat. Some evidence indicated that the lectin SteLL is an antinociceptive agent from leaves.

AIM OF THE STUDY

This study evaluated the antinociceptive activity of S. terebinthifolia leaf lectin (SteLL) using mouse models of peripheral and central nociception.

MATERIALS AND METHODS

Animals were treated intraperitoneally with SteLL at 1, 5, and 10 mg/kg. An acetic acid-induced abdominal writhing test was performed to screen for the antinociceptive effect of the lectin. Next, the formalin test was used to assess the effects of SteLL on neurogenic (first phase) and inflammatory (second phase) pain, as well as to investigate the involvement of the carbohydrate-recognition domain (CRD) of SteLL and opioid receptors in the antinociceptive effect. The tail immersion test was performed to assess the central antinociception. Additionally, a rotarod test was performed to evaluate the effects of lectin on motor coordination in mice.

RESULTS

SteLL reduced the number of acetic acid-induced writhes by 83.5-100.0%. In the first phase of the formalin test, SteLL reduced paw licking time by 49.4-50.5%, while in the second phase, SteLL reduced paw licking time by 80.5-82.6%. This antinociceptive effect was reversed by the previous incubation of the lectin with ovalbumin (indicating the possible involvement of the CRD) and by the administration of naloxone, a nonselective opioid receptor antagonist. When testing selective antagonists of opioid receptors (μ, δ, and κ), only naltrindole, a selective δ receptor antagonist, blocked the antinociceptive action of SteLL during the second phase of the formalin test. In the tail immersion test, SteLL (1, 5, and 10 mg/kg) administration reduced sensitivity to thermal stimulus, which was observed even after 2 h. SteLL (10 mg/kg) did not affect animal motor coordination in rotarod test when compared to the control group.

CONCLUSION

SteLL has peripheral and central analgesic action involving opioid receptor modulation without affecting the motor coordination of animals. These results provide new perspectives for developing analgesic agents using lectins.

Efficacy of Topical Essential Oils in Musculoskeletal Disorders: Systematic Review and Meta-Analysis of Randomized Controlled Trials

Essential oils (EOs) are widely used topically in musculoskeletal disorders (MSDs); however, their clinical efficacy is controversial. Our aim was to find evidence that topical EOs are beneficial as an add-on treatment in MSDs. We performed a systematic review and meta-analysis to summarize the evidence on the available data of randomized controlled trials (RCTs). The protocol of this work was registered on PROSPERO. We used Web of Science, EMBASE, PubMed, Central Cochrane Library and Scopus electronic databases for systematic search. Eight RCTs were included in the quantitative analysis. In conclusion, EO therapy had a favorable effect on pain intensity (primary outcome) compared to placebo. The greatest pain-relieving effect of EO therapy was calculated immediately after the intervention (MD of pain intensity = −0.87; p = 0.014). EO therapy had a slightly better analgesic effect than placebo one week after the intervention (MD of pain intensity = −0.58; p = 0.077) and at the four-week follow-up as well (MD of pain intensity = −0.52; p = 0.049). EO therapy had a beneficial effect on stiffness (a secondary outcome) compared to the no intervention group (MD = −0.77; p = 0.061). This systematic review and meta-analysis showed that topical EOs are beneficial as an add-on treatment in reducing pain and stiffness in the investigated MSDs.

Orofacial antinociceptive effects of perillyl alcohol associated with codeine and its possible modes of action

This study evaluated the orofacial antinociceptive effect of (S)-(-)-perillyl alcohol (PA) associated with codeine (C) and investigated the possible molecular anchorage mechanisms of PA. Mice (n = 5 per group) were treated with PA alone and associated with codeine and assigned to the following groups: 75.0 mg/kg PA; 75.0 mg/kg PA + C 30 mg/kg; PA 37.5 mg/kg + C 15.0 mg/kg; C 30.0 mg/kg; and control. Nociception was induced by formalin, capsaicin, and glutamate, and was quantified based on the duration (in seconds) of face grooming. The possible mechanisms of action were evaluated by molecular docking study. In the formalin test, PA75/C30 presented an effect in the neurogenic (p < 0.0001) and inflammatory (p < 0.005) phases. Mice treated with PA75 (p < 0.0001) and PA75/C30 (p < 0.0005) showed a reduced nociceptive behavior in the capsaicin test. Glutamate-induced nociception also was blocked by PA75 (p < 0.0005) and C30 (p < 0.0005). The molecular anchorage analysis indicated high negative binding energy values for the evaluated receptors, especially glutamate receptors (AMPA -79.57 Kcal/mol, mGLUR6 -71.25, and NMDA -66.33 Kcal/mol). PA associated with codeine showed orofacial antinociceptive activity, with theoretical evidence of interaction with glutamate receptors.

Identification of docosahexaenoic and eicosapentaenoic acids multiple targets facing periodontopathogens

The eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) play a substantial role in Periodontal Disease (PD) due to their antimicrobial and immunomodulatory actions. However, their antimicrobial mechanism of action against bacteria involved in PD remains unclear. We aimed to estimate the probable targets of EPA and DHA against the seven periodontopathogens. Through in silico analyses, the protein-acids interactions, protein characterization, and molecular docking were performed. We identified 165 proteins from periodontopathogens that may interact with EPA and DHA. Fusobacterium nucleatum has the highest number of predicted proteins among analyzed bacteria (n = 43, 26.06%). The EPA shows more interactions than DHA. The EPA and DHA interact mainly with proteins involved in the metabolism (n = 69, 41.81%). Also, the EPA and DHA interact with proteins located in any subcellular location. The affinities between acids and pathogenic proteins were moderate (binding energy was lower than -4.0 kcal/mol). The interactions between EPA and DHA and periodontopathogens occur in multiples proteins. There is not a predilection about the functional class of pathogenic proteins targeting EPA and DHA. However, there are moderate binding affinities between EPA or DHA and essential pathogenic proteins (TolC, CRISPR, FusA).

Activation of Drosophila melanogaster TRPA1 Isoforms by Citronellal and Menthol

BACKGROUND

The transient receptor potential ankyrin 1 (TRPA1) cation channels function as broadly-tuned sensors of noxious chemicals in many species. Recent studies identified four functional TRPA1 isoforms in Drosophila melanogaster (dTRPA1(A) to (D)), but their responses to non-electrophilic chemicals are yet to be fully characterized.

METHODS

We determined the behavioral responses of adult flies to the mammalian TRPA1 non-electrophilic activators citronellal and menthol, and characterized the effects of these compounds on all four dTRPA1 channel isoforms using intracellular Ca²⁺ imaging and whole-cell patch-clamp recordings.

RESULTS

Wild type flies avoided citronellal and menthol in an olfactory test and this behavior was reduced in dTrpA1 mutant flies. Both compounds activate all dTRPA1 isoforms in the heterologous expression system HEK293T, with the following sensitivity series: dTRPA1(C) = dTRPA1(D) > dTRPA1(A) ≫ dTRPA1(B) for citronellal and dTRPA1(A) > dTRPA1(D) > dTRPA1(C) > dTRPA1(B) for menthol.

CONCLUSIONS

dTrpA1 was required for the normal avoidance of Drosophila melanogaster towards citronellal and menthol. All dTRPA1 isoforms are activated by both compounds, but the dTRPA1(B) is consistently the least sensitive. We discuss how these findings may guide further studies on the physiological roles and the structural bases of chemical sensitivity of TRPA1 channels.

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.

Involvement of opioidergic and GABAergic systems in the anti-nociceptive activity of the methanolic extract of Cuscuta Epithymum Murr. in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Cuscuta epithymum Murr. (CE) is a parasitic plant used as a traditional medicine to treat various diseases such as muscle and joint pains and headache different parts of the world, Europe in the north, Asia in the east.

AIM OF THE STUDY

In this study, we aimed to investigate the anti-nociceptive effect of the methanolic extract of the aerial parts of CE and its probable mechanism(s) in mice.

MATERIALS AND METHODS

The anti-nociceptive activity of different doses of CE methanolic extract (2.5, 5, 10, 25, 50 and 100 mg/kg, i.p.) was assessed using tail flick, formalin and writhing tests. Morphine (5 mg/kg, s.c.) was used as positive control drug. The possible mechanisms were evaluated by using naloxone (4 mg/kg, i.p.), ondansetron (4 mg/kg, i.p.), picrotoxin (0.6 mg/kg, i.p.) and MK-801 (0.03 mg/kg, i.p.).

RESULTS

GC-MS analysis indicated that one of the main components of CE extract was terpenoid compounds. The CE extract (25-100 mg/kg), like morphine, reduced tail flick latency and nociceptive response in both phases of the formalin test. We also observed that the extract significantly decreased the number of abdominal contractions dose-dependently from 5 to 100 mg/kg. The results of tail flick and the first phase of formalin test proved that unlike ondansetron and MK-801, naloxone and picotroxin were able to reverse the anti-nociceptive effect of CE extract.

CONCLUSION

Our observations showed the anti-nociceptive potential of the CE extract, which may be mediated by opioidergic and GABAergic systems.