Unraveling immunomodulatory activities of complex Echinacea purpurea extracts

Echinacea purpurea has a long history of traditional use for the treatment of infection, but there remains considerable controversy surrounding this plant's mechanism of action. Recent studies have suggested that crude Echinacea extracts may contain a mixture of anti-inflammatory and pro-inflammatory compounds, and our goal with this research was to separate such extracts and identify specific bioactive constituents. In addition, we tested the hypothesis that in vitro pro-inflammatory effects of E. purpurea crude extracts could be caused by bacterial endophytes (bacteria living asymptomatically within the plant tissues). To test our hypothesis, E. purpurea plants with and without bacterial endophytes were grown in sterile chambers and tested for immunomodulatory effects on macrophage-type cells in vitro. Bioactivity guided fractionation was also employed to identify anti-inflammatory compounds from crude E. purpurea extracts. Our results clearly demonstrate that bacterial endophytes play a role in the in vitro pro-inflammatory activity of ethanolic E. purpurea extracts. Additionally, we have identified a previously unreported anti-inflammatory constituent of E. purpurea, 4-[(2-methylbutyl)amino-4-oxo-2-butenoic acid.