Endogenous Levels of Echinacea Alkylamides and Ketones Are Important Contributors to the Inhibition of Prostaglandin E2 and Nitric Oxide Production in Cultured Macrophages

Because of the popularity of Echinacea as a dietary supplement, researchers have been actively investigating which Echinacea constituent or groups of constituents are necessary for immune-modulating bioactivities. Our prior studies indicate that alkylamides may play an important role in the inhibition of prostaglandin E2 (PGE(2)) production. High-performance liquid chromatography fractionation, employed to elucidate interacting anti-inflammatory constituents from ethanol extracts of Echinacea purpurea, Echinacea angustifolia, Echinacea pallida, and Echinacea tennesseensis, identified fractions containing alkylamides and ketones as key anti-inflammatory contributors using lipopolysaccharide-induced PGE(2) production in RAW264.7 mouse macrophage cells. Nitric oxide (NO) production and parallel cytotoxicity screens were also employed to substantiate an anti-inflammatory response. E pallida showed significant inhibition of PGE(2) With a first round fraction, containing gas chromatography-mass spectrometry (GC-MS) peaks for Bauer ketones 20, 21, 22, 23, and 24, with 23 and 24 identified as significant contributors to this PGE(2) inhibition. Chemically synthesized Bauer ketones 21 and 23 at 1 mu M each significantly inhibited both PGE(2) and NO production. Three rounds of fractionation were produced from an E angustifolia extract. GC-MS analysis identified the presence of Bauer ketone 23 in third round fraction 3D32 and Bauer alkylamide 11 making up 96% of third round fraction 3E40. Synthetic Bauer ketone 23 inhibited PGE(2) production to 83% of control, and synthetic Bauer alkylamide 11 significantly inhibited PGE(2) and NO production at the endogenous concentrations determined to be present in their respective fraction; thus, each constituent partially explained the in vitro anti-inflammatory activity of their respective fraction. From this study, two key contributors to the anti-inflammatory properties of E angustifolia were identified as Bauer alkylamide 11 and Bauer ketone 23.