Anti-nociceptive and anti-inflammatory activities of the Agastache mexicana extracts by using several experimental models in rodents

Ethnopharmacological relevance: Agastache mexicana is a plant that has long been used in large demand in Mexican folk medicine to treat pain, among others affections. Nevertheless, no scientific data confirming its use have been reported. The aim of this investigation was to examine the spectrum of antinociceptive activity of A. mexicana by using different experimental models of nociception in rodents. Material and methods: Nociceptive activity was induced 30 min post treatment of different doses of hexane, ethyl acetate and methanol extracts from A. mexicana aerial parts. The writhing test in mice, and the formalin and plantar tests as well as the pain-induced functional impairment assay in rats (PIFIR model) were the experimental nociceptive models used. Antinociceptive response of the organic extracts was compared to that observed with the analgesic drug tramadol. Results: A. mexicana organic extracts produced a dose-dependent and significant inhibition of the abdominal constrictions caused by 1% acetic acid injection (i.p.) in mice. A maximal antinociceptive effectiveness obtained with tramadol was also observed with the administration of hexane and ethyl acetate extracts in comparison to less effectiveness obtained with the methanol extract. At the same range of doses, A. mexicana organic extracts inhibited the behavioral responses in both phases of the formalin pain test, in which a more intense effect was observed in the inflammatory phase than in the neurogenic stage. With regard to the plantar test and PIFIR model, a significant but not dose-dependent antinociceptive response was observed at specific doses that depended on the organic extract evaluated. Conclusion: The antinociceptive activity of A. mexicana aerial parts depends on the intensity of the painful stimulus induced and involves different kinds of constituents. Our present results reinforce the use of this species in traditional medicine and its utility for pain treatment mainly associated with inflammation. (C) 2012 Elsevier Ireland Ltd. All rights reserved.