Aloysia oblanceolata Moldenke essential oil exhibits antinociceptive activity regulated by opioids, serotonergic, and α2-adrenergic receptors, along with low toxicity and anti-inflammatory effects.

Aloysia oblanceolata is used in traditional medicine due to its sedative properties. However, few studies prove this use or this action mechanism. This study aimed to evaluate the in vivo antinociceptive and anti-inflammatory activities, as well as the effects on the oxidative metabolism of A. oblanceolata essential oil (AoEO) in mice. The leaves' essential oil was obtained by hydrodistillation (3 h) and analyzed by gas chromatography coupled to mass spectrometry. For in vivo assays, Mus musculus/Swiss mice were used to evaluate oral acute toxicological (at 300 and 2000 mg/kg). To evaluate the analgesic potential, distinct assays were conducted: the acetic acid-induced abdominal writhing test to investigate peripheral analgesia, and the tail immersion test to assess central analgesia. The administration of carrageenan induced inflammation and oxidative stress. Oxidative stress was measured by concentration of thiobarbituric acid-reactive substances (TBARS). NO production was evaluated, and the catalase enzyme quantified. The AoEO yield was 3.15%, the higher constituents were β-pinene (22.11%), trans-pinocamphone (14.44%), trans-pinocarvyl acetate (6.62%), cis-pinocamphone (6.31%), and viridiflorol (7.67%). There were no changes in the behavior patterns or mortality of animals treated with AoEO. There was no significant difference in the concentrations of lipid peroxidation and nitrite in the kidney and liver of treated animals. There was a reduction in abdominal writhings of 23.99% (at 50 mg/kg) and 41.70% (at 100 mg/kg). However, AoEO did not increase the tail-removal latency time. In the second phase of inflammatory pain, AoEO decreased the licking time at doses of 50 mg/kg (49.52%) and 100 mg/kg (58.47%). The antinociceptive activity of AoEO is mediated by opioids, α2-adrenergic, and serotonergic receptors, explaining the high antinociception of this essential oil. AoEO at 50 and 100 mg/kg had an anti-inflammatory effect by decreasing leukocyte migration of 50.26% (at 50 mg/kg) and 42.95% (at 100 mg/kg). Nitrite concentrations in the peritoneal fluid were reduced by 74.21% (at 50 mg/kg) and 54.05% (at 100 mg/kg) in animals treated with EOAo. The essential oil of Aloysia oblanceolata demonstrated peripheral antinociceptive and anti-inflammatory effects, with no evidence of acute toxicity. The antinociceptive action was mediated through opioid, serotonergic, and α₂-adrenergic receptors. These findings indicate that A. oblanceolata essential oil is a promising natural source of bioactive compounds with potential therapeutic applications in the management of pain and inflammation.