Evaluation of the analgesic and anti-inflammatory effects of the essential oil of Lippia gracilis leaves

The EO of Lippia gracilis leaves elicited inhibitory activity on acetic acid effect. Carrageenan-induced oedema formation and leukocyte migration into the peritoneal cavity were reduced with the EO of Lippia gracilis leaves. The analyses of the essential oil allowed the identification of Lippia gracilis as a thymol- p-cymene chemotype. The aim of the present study is to investigate the antinociceptive, anti-inflammatory, and antioxidant activities of essential oil (EO) of Lippia gracilis Schauer (Verbenaceae) leaves to support the medicinal uses claimed by folklore practitioners in the caatinga region (semi-arid) of Northeastern Brazil. The chemical composition and antinociceptive and anti-inflammatory activities of the EO of Lippia gracilis leaves (50–200 mg/kg) were investigated. Antinociceptive activity of the EO was evaluated by writhing test. Anti-inflammatory activity of the EO was evaluated using paw oedema and peritonitis methods. Oral treatment with the EO of Lippia gracilis leaves elicited inhibitory activity on acetic acid effect at 50, 100, and 200 mg/kg (30.33 ± 2.36, 25.20 ± 1.48, and 21.00 ± 1.54 abdominal writhes, respectively, P < 0.05), as compared with the control group (36.73 ± 1.92 writhes). The compound acetylsalicylic acid (ASA, 300 mg/kg) inhibited the acetic acid-induced writhing (12.67 ± 0.50 abdominal writhes, P < 0.001). Carrageenan-induced oedema formation was reduced with the EO of Lippia gracilis leaves at 200 mg/kg (0.72 ± 0.06 mL h, P < 0.001) and by the reference compound ASA (300 mg/kg, 0.85 ± 0.04 mL h, P < 0.001), as compared with the control group (1.76 ± 0.06 mL h). Leukocyte migration into the peritoneal cavity induced by carrageenan was reduced with the EO of Lippia gracilis leaves at 50, 100, and 200 mg/kg (13.81 ± 0.61, 11.77 ± 0.91, and 10.30 ± 0.60 leukocytes × 10 6/mL, respectively, P < 0.01), and by the compound dexamethasone (2 mg/kg, 5.34 ± 0.33 leukocytes × 10 6/mL, P < 0.001), as compared with the control group (16.71 ± 0.54 leukocytes × 10 6/mL). The analyses of the essential oil allowed the identification of Lippia gracilis as a thymol- p-cymene chemotype (32.68% and 17.82%, respectively). The EO of Lippia gracilis leaves shows antinociceptive and anti-inflammatory activities.