Anxiolytic and antidepressant-like effects of monoterpene tetrahydrolinalool and in silico approach of new potential targets

INTRODUCTION- The drugs currently available for treatment of anxiety and depression act through modulation of the neurotransmission systems involved in the neurobiology of the disorder, yet they of-ten present side effects, which can impair patient adherence to treatment. METHOD- This, has driven the search for new molecules with anxiolytic and antidepressant potential. Aromatic plants are rich in essential oils, and their chemical constituents, such as monoterpenes, are be-ing studied for these disorders. This study aims to evaluate the anxiolytic and antidepressant-like poten-tial of the monoterpene tetrahydrolinalool in in vivo animal models, and review pharmacological targets with validation through molecular docking. Male Swiss mice (Mus musculus) were treated with THL (37.5-600 mg kg-1 p.o.) and submitted to the elevated plus maze, open field, rota rod, and forced swim tests. In the elevated plus-maze, THL at doses of 37.5 and 75 mg kg-1 induced a significant increase in the percentage of entries (72.7 and 64.3% respectively), and lengths of stay (80.3 and 76.8% respective-ly) in the open arms tests. RESULT- These doses did not compromise locomotor activity or motor coordination in the animals. In the open field, rota rod tests, and the forced swimming model, treatment with THL significantly reduced immobility times at doses of 150, 300, and 600 mg kg-1, and by respective percentages of 69.3, 60.9 and 68.7%. CONCLUSION- In molecular docking assay, which investigated potential targets, THL presented sat-isfactory energy values for: nNOs, SGC, IL-6, 5-HT1A, NMDAr, and D1. These demonstrate the po-tential of THL (a derivative of natural origin) in in vivo and in silico models, making it a drug candidate.

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

INTRODUCTION

Pain is considered an unpleasant sensory and emotional experience, being considered as one of the most important causes of human suffering. Computational chemistry associated with bioinformatics has stood out in the process of developing new drugs, through natural products, to manage this condition.

OBJECTIVE

To analyze, through literature data, recent molecular coupling studies on the antinociceptive activity of essential oils and monoterpenes.

DATA SOURCE

Systematic search of the literature considering the years of publications between 2005 and December 2019, in the electronic databases PubMed and Science Direct.

ELIGIBILITY CRITERIA

Were considered as criteria of 1) Biological activity: non-clinical effects of an OE and/or monoterpenes on antinociceptive activity based on animal models and in silico analysis, 2) studies with plant material: chemically characterized essential oils and/or their constituents isolated, 3) clinical and non-clinical studies with in silico analysis to assess antinociceptive activity, 4) articles published in English. Exclusion criteria were literature review, report or case series, meta-analysis, theses, dissertations, and book chapter.

RESULTS

Of 16,006 articles, 16 articles fulfilled all the criteria. All selected studies were non-clinical. The most prominent plant families used were Asteraceae, Euphorbiaceae, Verbenaceae, Lamiaceae, and Lauraceae. Among the phytochemicals studied were α-Terpineol, 3-(5-substituted-1,3,4-oxadiazol-2-yl)-N'-[2-oxo-1,2-dihydro-3H-indol-3-ylidene] propane hydrazide, β-cyclodextrin complexed with citronellal, (-)-α-bisabolol, β-cyclodextrin complexed with farnesol, and p-Cymene. The softwares used for docking studies were Molegro Virtual Docker, Sybyl®X, Vlife MDS, AutoDock Vina, Hex Protein Docking, and AutoDock 4.2 in PyRx 0.9. The molecular targets/complexes used were Nitric Oxide Synthase, COX-2, GluR2-S1S2, TRPV1, β-CD complex, CaV1, CaV2.1, CaV2.2, and CaV2.3, 5-HT receptor, delta receptor, kappa receptor, and MU (μ) receptor, alpha adrenergic, opioid, and serotonergic receptors, muscarinic receptors and GABAA opioid and serotonin receptors, 5-HT3 and M2 receptors. Many of the covered studies used molecular coupling to investigate the mechanism of action of various compounds, as well as molecular dynamics to investigate the stability of protein-ligand complexes.

CONCLUSIONS

The studies revealed that through the advancement of more robust computational techniques that complement the experimental studies, they may allow some notes on the identification of a new candidate molecule for therapeutic use.

Comparison of behavioral, neuroprotective, and proinflammatory cytokine modulating effects exercised by (+)-cis-EC and (-)-cis-EC stereoisomers in a PTZ-induced kindling test in mice

Epoxy-carvone (EC) has chiral centers that allow generation of stereoisomers, including (+)-cis-EC and (-)-cis-EC, whose effects in the kindling tests have never been studied. Accordingly, this study aims to comparatively investigate the effect of stereoisomers (+)-cis-epoxy-carvone and (-)-cis-epoxy-carvone on behavioral changes measured in scores, in the levels of cytokines (IL-1β, IL-6, and TNFα) and neuronal protection in the face of continuous treatment with pentylenetetrazol. Swiss mice were divided into five groups (n = 10), receiving vehicle, (+) - cis-EC, (-) - cis-EC (both at the dose of 30 mg/kg), and diazepam (4 mg/kg). Thirty minutes after the respective treatment was administered to the animals one subconvulsive dose of PTZ (35 mg/kg). Seven subconvulsives treatments were made on alternate days, in which each treatment several parameters were recorded. In the eighth treatment, the animals receiving the highest dose of PTZ (75 mg/kg) and were sacrificed for quantification of cytokines and histopathologic analysis. All drugs were administered by intraperitoneal route. In the kindling test, (+)-cis-EC and (-)-cis-EC reduced the average scores. The stereoisomer (+)-cis-EC decreased levels of proinflammatory cytokines IL-1β, IL-6, and TNFα, whereas comparatively (-)-cis-EC did not reduce IL-1β levels. Histopathological analysis of the mice hippocampi undergoing this methodology showed neural protection for treated with (+)-cis-EC. The results suggest that the anticonvulsant effect of (+)-cis-EC possibly takes place due to reduction of proinflammatory cytokines involved in the epileptogenic process, besides neuronal protection, yet further investigation of the mechanisms involved is required.

Antinociceptive and anticonvulsant effects of the monoterpene linalool oxide

CONTEXT

Linalool oxide (OXL) (a monoterpene) is found in the essential oils of certain aromatic plants, or it is derived from linalool. The motivation for this work is the lack of psychopharmacological studies on this substance.

OBJECTIVE

To evaluate OXL's acute toxicity, along with its anticonvulsant and antinociceptive activities in male Swiss mice.

MATERIAL AND METHODS

OXL (50, 100 and 150 mg/kg, i.p.) was investigated for acute toxicity and in the Rota-rod test. Antinociceptive activity was evaluated by the acetic acid-induced writhing test, and by formalin testing. Anticonvulsant effects were demonstrated by testing for pentylenetetrazol (PTZ)-induced seizures and by Maximum Electroshock headset (MES) test. OXL was administered to the animals intraperitoneally 30 min before for pharmacological tests.

RESULTS

OXL showed an LD₅₀ of ∼721 (681-765) mg/kg. In the Rota-rod test, it was observed that OXL caused no damage to the animal's motor coordination. OXL significantly reduced (p < .001) the number of writhings. OXL also significantly decreased (p < .05, p < .01 or p < .001) paw-licking time in the two phases of the formalin test. OXL significantly reduced (p < .01 or p < .001) the duration of tonic seizures in the MES test, and at the dose 150 mg/kg, significantly increased (p < .01) the latency to first seizure in the PTZ test.

CONCLUSION

The tested doses of OXL were safe, with no motor impairment, and show clear antinociceptive and anticonvulsant potential. Future investigations with this monoterpene may lead to the development of a new molecule with even higher potency and selectivity.

Geraniol Induces Antinociceptive Effect in Mice Evaluated in Behavioural and Electrophysiological Models

Geraniol (GER) is a monoterpene alcohol with various biochemical and pharmacological properties present in the essential oil of more than 160 species of herbs (especially the Cymbopogon genus). In this study, we evaluated the antinociceptive activity of GER in behavioural and electrophysiological in vitro experimental models of nociception using male Swiss mice. GER (12.5, 25 or 50 mg/kg i.p. and 50 or 200 mg/kg p.o.) reduced the number of writhes induced by acetic acid. The opioid antagonist naloxone (5 mg/kg s.c.) administered in mice subsequently treated with GER (25 mg/kg i.p.) did not reverse such antinociceptive activity, suggesting a non-opioid pathway for the mechanism of action. GER (12.5, 25 and 50 mg/kg i.p.) reduced paw licking time in the second phase of the formalin test. Also, in the glutamate test, GER when administered 50 mg/kg i.p. reduced paw licking time, probably modulating glutamatergic neurotransmission. GER blocked reversibly components of the compound action potential (CAP) recorded in isolated sciatic nerve in a concentration- and drug exposure time-dependent manner: 1 mM to 120 min. for the first component and 0.6 mM to 90 min. for the second component. The IC₅₀ was calculated for the peak-to-peak amplitude (PPA) at 0.48 ± 0.04 mM. The conduction velocity was also reduced by exposure to GER starting from the concentration of 0.3 mM for both components of the CAP. In conclusion, it is suggested that GER has antinociceptive activity, especially in pain related to inflammation, and in part related to reduced peripheral nerve excitability.

Comparative Anticonvulsant Study of Epoxycarvone Stereoisomers

Stereoisomers of the monoterpene epoxycarvone (EC), namely (+)-cis-EC, (-)-cis-EC, (+)-trans-EC, and (-)-trans-EC, were comparatively evaluated for anticonvulsant activity in specific methodologies. In the pentylenetetrazole (PTZ)-induced anticonvulsant test, all of the stereoisomers (at 300 mg/kg) increased the latency to seizure onset, and afforded 100% protection against the death of the animals. In the maximal electroshock-induced seizures (MES) test, prevention of tonic seizures was also verified for all of the isomers tested. However, the isomeric forms (+) and (-)-trans-EC showed 25% and 12.5% inhibition of convulsions, respectively. In the pilocarpine-induced seizures test, all stereoisomers demonstrated an anticonvulsant profile, yet the stereoisomers (+) and (-)-trans-EC (at 300 mg/kg) showed a more pronounced effect. A strychnine-induced anticonvulsant test was performed, and none of the stereoisomers significantly increased the latency to onset of convulsions; the stereoisomers probably do not act in this pathway. However, the stereoisomers (+)-cis-EC and (+)-trans-EC greatly increased the latency to death of the animals, thus presenting some protection. The four EC stereoisomers show promise for anticonvulsant activity, an effect emphasized in the isomers (+)-cis-EC, (+)-trans-EC, and (-)-trans-EC for certain parameters of the tested methodologies. These results serve as support for further research and development of antiepileptic drugs from monoterpenes.

Antinociceptive effect of hydantoin 3-phenyl-5-(4-ethylphenyl)-imidazolidine-2,4-dione in mice

Imidazolidine derivatives, or hydantoins, are synthetic compounds with different therapeutic applications. Many imidazolidine derivatives have psychopharmacological properties, such as phenytoin, famous for its anticonvulsant efficacy, but also effective in the treatment of neuropathic pain. The hydantoin, 3-phenyl-5-(4-ethylphenyl)-imidazolidine-2,4-dione (IM-3), synthesized from the amino acid, glycine, was selected for psychopharmacological studies in mice on the basis of its chemical and structural similarity with phenytoin. The first step of this study was to define the LD₅₀, which determined the doses of 50, 100 and 200 mg/kg for subsequent tests. The results obtained from the behavioral screening indicated that IM-3 produces decreased ambulation and analgesia in mice. Motor coordination and anxiety behavior were not affected by treatment with IM-3, as observed in the rotarod and elevated plus-maze tests, respectively. Regarding its antinociceptive properties, IM-3 showed efficacy in the acetic acid-induced writhing test by increasing the latency of the first writhe and reducing the number of writhes, as well as reducing the paw licking time in the second phase of the formalin test. The behavior of treated animals exposed to the hot plate test, however, did not differ from that of the control group. These data suggest that IM-3 has antinociceptive effects in mice, which is probably mediated by anti-inflammatory mechanisms.