Endogenous levels of Echinacea alkylamides and ketones are important contributors to the inhibition of prostaglandin E2 and nitric oxide production in cultured macrophages

摘要

Due to 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 (PGE2) production. HPLC fractionation, employed to elucidate interacting anti-inflammatory constituents from ethanol extracts of E. purpurea, E. angustifolia, E. pallida, and E. tennesseensis identified fractions containing alkylamides and ketones as key anti-inflammatory contributors using lipopolysaccharide induced PGE2 production in RAW264.7 mouse macrophage cells. Nitric oxide (NO) production and parallel cytotoxicity screens were also employed to substantiate an anti-inflammatory response. Echinacea pallida showed significant inhibition of PGE2 with a first round fraction, containing GC-MS peaks for Bauer Ketones 20, 21, 22, 23, and 24, with 23 and 24 identified as significant contributors to this PGE2 inhibition. Chemically synthesized Bauer Ketones 21 and 23 at 1 μM each significantly inhibited both PGE2 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 PGE2 production to 83 % of control and synthetic Bauer Alkylamide 11 significantly inhibited PGE2 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.