Inhaled Litsea glaucescens K. (Lauraceae) leaves' essential oil has anxiolytic and antidepressant-like activity in mice by BDNF pathway activation

ETHNOPHARMACOLOGICAL RELEVANCE

Litsea glaucescens K. (Lauraceae) is a small tree from the Mexican and Central American temperate forests, named as "Laurel". Its aromatic leaves are ordinarily consumed as condiments, but also are important in Mexican Traditional Medicine, and among the most important non wood forest products in this area. The leaves are currently used in a decoction for the relief of sadness by the Mazahua ethnic group. Interestingly, "Laurel" has a long history. It was named as "Ehecapahtli" (wind medicine) in pre-Columbian times and applied to heal maladies correlated to the Central Nervous System, among them depression, according to botanical texts written in the American Continent almost five centuries ago.

AIM OF THE STUDY

Depression is the first cause of incapacity in the world, and society demands alternative treatments, including aromatherapy. We have previously demonstrated the antidepressant-like activity of L. glaucescens leaves' essential oil (LEO), as well as their monoterpenes linalool, and beta-pinene by intraperitoneal route in a mice behavioral model. Here we now examined if LEO and linalool exhibit this property and anxiolytic activity when administered to mice by inhalation. We also investigated if these effects occur by BDNF pathway activation in the brain.

MATERIALS AND METHODS

The LEO was prepared by distillation with water steam and analyzed by gas chromatography-mass spectrometry (GC-MS). The monoterpenes linalool, eucalyptol and β-pinene were identified and quantified. Antidepressant type properties were determined with the Forced Swim Test (FST) on mice previously exposed to LEO or linalool in an inhalation chamber. The spontaneous locomotor activity and the sedative effect were assessed with the Open Field Test (OFT), and the Exploratory Cylinder (EC), respectively. The anxiolytic properties were investigated with the Elevated Plus Maze Apparatus (EPM) and the Hole Board Test (HBT). All experiments were video documented. The mice were subjected to euthanasia, and the brain hippocampus and prefrontal cortex were dissected.

RESULTS

The L. glaucescens essential oil (LEO) contains 31 compounds according to GC/MS, including eucalyptol, linalool and beta-pinene. The LEO has anxiolytic effect by inhalation in mice, as well as linalool, and β-pinene, as indicated by OFT and EC tests. The LEO and imipramine have antidepressant like activity in mice as revealed by the FST; however, linalool and ketamine treatments didn't modify the time of immobility. The BDNF was increased in FST in mice treated with LEO in both areas of the brain as revealed by Western blot; but did not decrease the level of corticosterone in plasma. The OFT indicated that LEO and imipramine didn't reduce the spontaneous motor activity, while linalool and ketamine caused a significant decrease.

CONCLUSION

Here we report by the first time that L. glaucescens leaves essential oil has anxiolytic effect by inhalation in mice, as well as linalool, and β-pinene. This oil also maintains its antidepressant-like activity by this administration way, similarly to the previously determined intraperitoneally. Since inhalation is a common administration route for humans, our results suggest L. glaucescens essential oil deserve future investigation due to its potential application in aromatherapy.

Central nervous system activity of a Tabernaemontana arborea alkaloid extract involves serotonergic and opioidergic neurotransmission in murine models

Tabernaemontana arborea (Apocynaceae) is a Mexican tree species known to contain ibogan type alkaloids. This study aimed at determining central nervous system-related activities of an alkaloid extract obtained from the root bark of T. arborea. A gas chromatography-mass spectrometry (GC-MS) analysis was performed to describe the alkaloid profile of the extract. A wide dosing range (0.1 to 56.2 mg/kg) of this extract was evaluated in different murine models. Electrical brain activity was examined by electroencephalography (EEG). The extract's effects on motor coordination, ambulatory activity, and memory were analyzed based on the rotarod, open field (OFT), and object recognition tests (ORT), respectively. Antidepressant and antinociceptive activities were determined using the forced swimming test (FST) and the formalin assay, respectively. In order to elucidate the underlying mechanisms of action, the 5-HT1A receptor antagonist WAY100635 (1 mg/kg) or the opioid receptor antagonist naloxone (1 mg/kg) was included in the latter experiments. GC-MS analysis (μg/mg extract) confirmed the presence of the monoterpenoid indole alkaloids (MIAs) voacangine (207.00), ibogaine (106.33), vobasine (72.81), coronaridine (30.72), and ibogamine (24.2) as principal constituents of the extract, which exhibited dose- and receptor-dependent antidepressant (0.1 to 1 mg/kg; 5-HT1A) and antinociceptive (30 and 56.2 mg/kg; opioid) effects, without altering motor coordination, ambulatory activity, and memory. EEG indicated CNS depressant activity at high doses (30 and 56.2 mg/kg). The root bark of T. arborea contains a mixture of alkaloids that may hold therapeutic value in pain relief and the treatment of psychiatric diseases without causing neurotoxic activity at effective doses.

Jacareubin inhibits FcεRI-induced extracellular calcium entry and production of reactive oxygen species required for anaphylactic degranulation of mast cells

Mast cells (MCs) are important effectors in allergic reactions since they produce a number of pre-formed and de novo synthesized pro-inflammatory compounds in response to the high affinity IgE receptor (FcεRI) crosslinking. IgE/Antigen-dependent degranulation and cytokine synthesis in MCs have been recognized as relevant pharmacological targets for the control of deleterious inflammatory reactions. Despite the relevance of allergic diseases worldwide, efficient pharmacological control of mast cell degranulation has been elusive. In this work, the xanthone jacareubin was isolated from the heartwood of the tropical tree Callophyllum brasilense, and its tridimensional structure was determined for the first time by X-ray diffraction. Also, its effects on the main activation parameters of bone marrow-derived mast cells (BMMCs) were evaluated. Jacareubin inhibited IgE/Ag-induced degranulation in a dose-response manner with an IC₅₀ = 46 nM. It also blocked extracellular calcium influx triggered by IgE/Ag complexes and by the SERCA ATPase inhibitor thapsigargin (Thap). Inhibition of calcium entry correlated with a blockage on the reactive oxygen species (ROS) accumulation. Antioxidant capacity of jacareubin was higher than the showed by α-tocopherol and caffeic acid, but similar to trolox. Jacareubin shown inhibitory actions on xanthine oxidase, but not on NADPH oxidase (NOX) activities. In vivo, jacareubin inhibited passive anaphylactic reactions and TPA-induced edema in mice. Our data demonstrate that jacareubin is a potent natural compound able to inhibit anaphylactic degranualtion in mast cells by blunting FcεRI-induced calcium flux needed for secretion of granule content, and suggest that xanthones could be efficient anti-oxidant, antiallergic, and antiinflammatory molecules.

Antidepressant activity of Litsea glaucescens essential oil: identification of β-pinene and linalool as active principles

ETHNOPHARMACOLOGICAL RELEVANCE

Litsea glaucescens (Lauraceae) has been used in Mexican Traditional Medicine to relieve illness related to central nervous system, such as epilepsy, fright and sadness. In this study, L. glaucescens essential oil properties on central nervous system were evaluated in mice using different behavioral tests.

MATERIALS AND METHODS

The essential oil was obtained by hydrodistillation and analyzed by GC/MS. Identification of major compounds was also carried out by comparison with authentic samples. The psychopharmacological profile of L. glaucescens essential oil, and some its major compounds, were evaluated in mice using several experimental models: forced swimming test (FST: Antidepressant-like activity), open field test (OFT: Spontaneous locomotor activity), elevated plus-maze (EPM: Anxiolytic-like activity), exploratory cylinder (ECT: Sedative-like activity), rotarod (motor coordination) and traction performance (myo-relaxant effect) the essential oil and active principles was administered intraperitoneally.

RESULTS

The essential oil showed antidepressant-like activity at doses of 100 and 300 mg/Kg. The monoterpenes β-pinene and linalool were identified as the two main active principles of the essential oil, and showed antidepressant-like and sedative-like activity. Eucalyptol, limonene and α-pinene they did not show antidepressant-like activity, and were not further tested.

CONCLUSIONS

L. glaucescens essential oil showed antidepressant activity, β-pinene and linalool were identified as its active principles. These results support the use of L. glaucescens in Mexican Traditional Medicine for the treatment of sadness.