Background: Crude aqueous extract of the root bark of Zanthoxylum xanthoxyloides is used in folklore medicine for its anti-inflammatory activity. Although it shares the analgesic and anti-inflammatory property
of non-steroidal anti-inflammatory drugs (NSAIDs), its mechanism of action has not been well elucidated. Objective: To ascertain whether the extract decreases carrageenin-induced increase in plasma prostaglandin
E2 (PGE2) concentration with the view to shed light on the mechanism of action.

Methods: The extract was obtained by Soxhlet extraction and rotatory evaporation, followed by freezedrying. Forty Wistar rats (150g - 200g) were assigned to 8 groups of 5 rats each. The rats were given four
different treatments orally: 0.9% saline (two groups of control); two groups received indomethacin, 20mg/kg and 40mg/kg respectively; another two groups received the extract, 2000mg/kg and 4000mg/kg respectively;
and the remaining two groups, 50mg/kg and 100mg/kg nimesulide respectively. Inflammation was induced with carrageenin in one of the two groups of control. Enzyme-linked immunospecific assay was used to
measure plasma PGE2 concentration in the control and treated groups of rats. Analysis of variance was used as the statistical test. Differences in means at p