Analgesic and anti-inflammatory effects of essential oils of Eucalyptus

Many species of the genus Eucalyptus from the Myrtaceae family are used in Brazilian folk medicine for the treatment of various medical conditions such as cold, flue, fever, and bronchial infections. In the current investigation, we evaluated the analgesic and anti-inflammatory effects of essential oil extracts from three species of Eucalyptus employing various standard experimental test models. Using acetic acid-induced writhes in mice and hot plate thermal stimulation in rats, it was shown that the essential oils of Eucalyptus citriodora (EC), Eucalyptus tereticornis (ET), and Eucalyptus globulus (EG) induced analgesic effects in both models, suggesting peripheral and central actions. In addition, essential oil extracts from the three Eucalyptus species produced anti-inflammatory effects, as demonstrated by inhibition of rat paw edema induced by carrageenan and dextran, neutrophil migration into rat peritoneal cavities induced by carrageenan, and vascular permeability induced by carrageenan and histamine. However, no consistent results were observed for some of the parameters evaluated, both in terms of activities and dose-response relationships, reflecting the complex nature of the oil extracts and/or the assay systems used. Taken together, the data suggest that essential oil extracts of EC, ET, and EG possess central and peripheral analgesic effects as well as neutrophil-dependent and independent anti-inflammatory activities. These initial observations provide support for the reported use of the eucalyptus plant in Brazilian folk medicine. Further investigation is warranted for possible development of new classes of analgesic and anti-inflammatory drugs from components of the essential oils of the Eucalyptus species.