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Aim of the study: 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.

Materials and methods: 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.

Results: 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 x 10(6)/mL, respectively, P < 0.01), and by the compound dexamethasone (2 mg/kg, 5.34 +/- 0.33 leukocytes x 10(6)/mL, P < 0.001), as compared with the control group (16.71 +/- 0.54 leukocytes x 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).

Conclusions: The EO of Lippia gracilis leaves shows antinociceptive and anti-inflammatory activities. (C) 2010 Elsevier Ireland Ltd. All rights reserved.