Atividade analgésica do óleo essencial de Pectis elongata Kunth (asteraceae) determinada por meios de diferentes vias de inibição

Abstract

Introduction: Pectis elongata has quite a significant importance in traditional medicine of northern Brazil, where it is used for treating a wide range of ailments such as fevers, colds, hypotension, urinary and gastric disorders, and pain. Objective: To evaluate the analgesic potential of Pectis elongata essential oil (PeEO) and understand its mechanism of action by determining its possible pain inhibition pathways. Materials and Methods: Specimens of P. elongata were collected in Santarém, Pará. The plant material was dried, crushed and subjected to hydrodistillation to obtain the essential oil, which was then analyzed using gas chromatography coupled to mass spectrometry. Male Swiss mice were used to evaluate the analgesic potential of PeEO. To determine the effective dose and mechanism of action via specific blockers of the opioid, cholinergic, and nitric oxide pathways, the animals were exposed to the hot plate test. Statistical analysis was performed using ANOVA and Dunnett’s test, with significance established at p≤0.05. Results: The yield of the PeEO was determined to be 1.5%. Chemical analysis identified 23 compounds, representing 95.57% of the total, with geranial (49.61%) and neral (36.77%) as the major constituents. Together, these stereoisomers form citral. The maximum possible antinociceptive effect (EMP%) was observed with the 600 mg kg-1 dose, which was selected to evaluate the antinociceptive mechanism of action. This effect was inhibited by pre-treatments with L-NAME and naloxone, indicating the involvement of the nitric oxide and opioid pathways. Pre-treatment with atropine did not block the effect, suggesting that the cholinergic pathway is not involved in the mechanism of action of PeEO. Conclusions: PeEO showed antinociceptive activity, particularly at the 600 mg kg-1 dose. The study contributes to the understanding of the analgesic potential of PeEO. These findings demonstrate that the effects of PeEO can possibly be attributed to its high citral content. This study validates the traditional use of P. elongata for pain relief and highlights its potential as a source of novel analgesic compounds.