Sesquiterpene fractions of plants as potent inhibitors of inducible nitric oxide synthase and cyclooxygenase-2 expression.

Objectives: species are important medicinal plants throughout the world. Some species are traditionally used for their anti-inflammatory effect. The present study was designed to isolate sesquiterpene fractions from several species and evaluate their anti-inflammatory activities on key mediators and signaling molecules involved in regulation of inflammation.

Materials And Methods: Sesquiterpene fractions were prepared from several species using the Herz-Högenauer technique. Lipopolysaccharide (LPS)-stimulated J774A.1 macrophages were exposed to isolated fractions. Their possible cytotoxic effect was examined using MTT assay. In addition, nitric oxide (NO) release was measured using Griess method and prostaglandin E2 (PGE2) level was determined by enzyme-linked immunosorbent assay (ELISA). Moreover, protein expression of pro-inflammatory enzymes, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were investigated using Western blot analysis.

Results: Nitric oxide level produced by LPS-primed macrophages was significantly decreased with all prepared fractions in a dose-dependent manner. Saturated sesquiterpene lactones-rich species ( ) showed the highest suppressive activity on NO and PGE2 production via suppression of iNOS and COX-2 expression. Fractions bearing unusual ( and ) and unsaturated sesquiterpene lactones ( ) possess less modulatory effect on PGE2 production and COX-2 expression.

Conclusion: It can be concluded that some of the medicinally beneficial effects attributed to plants may be associated with the inhibition of pro-inflammatory signaling pathways. However, these effects could be dependent on the type of their sesquiterpene content. These findings also introduce new species cultivated in Iran as a useful anti-inflammatory agents.