IN VIVO INHIBITION OF PROSTAGLANDIN E2 PRODUCTION BY CRUDE AQUEOUS EXTRACT OF THE ROOT BARK OF ZANTHOXYLUM XANTHOXYLOIDES

Abstract

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 extrac tion and rotatory evaporation, followed by freeze drying. 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<0.05 were considered significant. Results: Carrageenin increased plasma PGE2 concen tration which was reduced by the extract, indomethacin and nimesulide. High dose extract and indomethacin reduced plasma PGE2 concentration to a comparable extent which was much greater than that of the reduc tion caused by nimesulide. Conclusion: It was concluded that the extract might act by non-selective inhibition of cyclooxygenase 1 and 2 to decrease plasma PGE2 concentration.