Antinociceptive and anti-inflammatory activities of ethyl acetate fraction from Zanthoxylum armatum in mice

Zanthoxylum armatum DC. is a traditional Chinese medicine that is prescribed to alleviate pain and treat inflammatory disorders. This species is distributed mainly in the southeast and southwest regions of China. In the present study, we found that ethyl acetate fraction of ethanolic extract of Z. armatum could significantly decrease acetic acid-induced writhing numbers, and suppress formalin induced licking times in the first phase at the highest dose and in the second phase at all tested doses. This observation revealed that Z. armatum extract possessed powerful antinociceptive activity. The mechanisms of the antinociceptive effect might be mainly involved in the periphery inflammatory analgesic. In addition, the ethyl acetate fraction also inhibited xylene-induced ear swelling in a dose-dependent manner in mice. Eight lignans [eudesmin, horsfieldin, fargesin, kobusin, sesamin, asarinin, planispine A, and pinoresinol-di-3,3-dimethylallyl] were identified as major components of the ethyl acetate fraction. Considering related studies reporting the anti-inflammatory activity for the identified lignans, lignan might be responsible for its anti-inflammatory activity. Our results confirm that the traditional use of Z. armatum in the treatment of inflammation and pain is warranted.