Antinociceptive Effect and GC/MS Analysis of Rosmarinus officinalis L. Essential Oil from its Aerial Parts

The rationale of this investigation was to examine the antinociceptive properties of the essential oil obtained from Rosmarinus officinalis aerial parts, using a rat model of arthritic pain. The essential oil (100, 300 and 600 mg/kg, i.p.) produced a dose-dependent antinociceptive effect, manifested as a significant reduction in the dysfunction in the pain-induced functional impairment model in the rat (PIFIR model), mainly at high doses. Chemical constituents of the essential oil were further analyzed by gas chromatography-mass spectrometry (GC/MS). The major compounds in the essential oil were a-pinene (14.10%), camphene (11.47%), beta-pinene (12.02%), myrcene (3.31%), alpha-phellandrene (7.87%), eucalyptol (8.58%), 2-bornanone (3.42%), camphor (8.75%), isoborneol (3.48%), borneol (4.85%) and borneol acetate (6.49%). The antinociceptive effects of R. officinalis essential oil were tested in combination with 0.12 mg/kg WAY100635, s.c. (an antagonist of 5-HT1A receptors) or 1 mg/kg naloxone, i.p. (an antagonist of endogenous opioids receptors), demonstrating in both cases an inhibition of the antinociceptive response. This study suggests an involvement, at least in part, of the serotonergic system via 5-HT1A receptors and endogenous opioids in the antinociceptive effect of R. officinalis essential oil in the PIFIR model.