Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2007
Publication Date: 9/5/2007
Citation: Lalone, C.A., Hammer, K., Wu, L., Bae, J., Leyva, N., Liu, Y., Solco, A., Kraus, G.A., Murphy, P.A., Wurtele, E.S., Kim, O., Seo, K.I., Widrlechner, M.P., Birt, D.F. 2007. Echinacea Species and Alkamides Inhibit Prostaglandin E2 Production in RAW264.7 Mouse Macrophage Cells. Journal of Agricultural and Food Chemistry. 55:7314-7322. Interpretive Summary: Prostaglandin E2 (PGE2) is a critical mediator of inflammation in animal and human tissues. RAW264.7 mouse macrophage cells can be stimulated in a controlled manner through the addition of lipopolysaccharide to produce PGE2. This serves as a model system to study the effects of botanical supplements and selected compounds on inflammation and its control. The present study was conducted to evaluate the efficacy of Echinacea extracts in reducing inflammation through the regulation of PGE2 and in testing selected components of those extracts to see if anti-inflammatory activity could be attributed to specific constituents. Ethanol extracts from four of the six species of Echinacea we studied displayed anti-inflammatory activity at relatively low concentrations in stimulated RAW264.7 cells. Toxicity studies were conducted to verify that observed reductions in PGE2 production were not due to cellular damage or death. Selected, synthesized components found in the Echinacea extracts (and other related compounds), all classified as alkamides, were also tested on RAW264.7 cells and were found to be active at differing concentrations. Based on actual concentrations of alkamides in Echinacea extracts, we believe that alkamides may contribute toward the anti-inflammatory activity of Echinacea in a synergistic or additive manner. This research can help clarify the differences seen in bioactivity and health effects among various Echinacea extracts and contribute to our understanding of Echinacea's potential anti-inflammatory action.
Technical Abstract: Inhibition of prostaglandin E2 production in lipopolysaccharide-stimulated RAW264.7 mouse macrophage cells was assessed with an enzyme immunoassay following treatments with Echinacea extracts or synthesized alkamides. Results indicated that ethanol extracts from E. angustifolia, E. pallida, E. simulata and E. sanguinea at 15 micrograms/ml significantly inhibited PGE2 production. In further studies, PGE2 production was significantly reduced by all synthesized alkamides assayed at 50 micromolar, by Bauer alkamides 8, 12A analog, 14, Chen alkamide 2, and Chen alkamide 2 analog at 25 micromolar and by Bauer alkamide 14 at 10 micromolar. Cytotoxicity did not play a role in the noted reduction of PGE2 production in either the Echinacea extracts or synthesized alkamides. High performance liquid chromatography analysis identified individual alkamides present at concentrations below 2.8 micromolar in the extracts from the six Echinacea species (15 micrograms/ml crude extract). Results suggested that alkamides may contribute toward the anti-inflammatory activity of Echinacea in a synergistic or additive manner.