title: Permeability studies of alkylamides and caffeic acid conjugates from echinacea using a Caco-2 cell monolayer model.
abstract: BACKGROUND
  Echinacea is composed of three major groups of compounds that are thought to be responsible for stimulation of the immune system--the caffeic acid conjugates, alkylamides and polysaccharides. This study has focussed on the former two classes, as these are the constituents found in ethanolic liquid extracts.
  
  
  OBJECTIVE
  To investigate the absorption of these two groups of compounds using Caco-2 monolayers, which are a model of the intestinal epithelial barrier.
  
  
  RESULTS
  The caffeic acid conjugates (caftaric acid, echinacoside and cichoric acid) permeated poorly through the Caco-2 monolayers although one potential metabolite, cinnamic acid, diffused readily with an apparent permeability (Papp) of 1 x 10(-4) cm/s. Alkylamides were found to diffuse through Caco-2 monolayers with Papp ranging from 3 x 10(-6) to 3 x 10(-4) cm/s. This diversity in Papp for the different alkylamides correlates to structural variations, with saturation and N-terminal methylation contributing to decreases in Papp. The transport of the alkylamides is not affected by the presence of other constituents and the results for synthetic alkylamides were in line with those for the alkylamides in the echinacea preparation.
  
  
  CONCLUSIONS
  Alkylamides but not caffeic acid conjugates are likely to cross the intestinal barrier.
authors.affiliation: MediHerb Research Laboratories, University of Queensland, Brisbane, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Matthias
authors.forename: J T
authors.initials: JT
authors.lastname: Blanchfield
authors.forename: K G
authors.initials: KG
authors.lastname: Penman
authors.forename: I
authors.initials: I
authors.lastname: Toth
authors.forename: C-S
authors.initials: CS
authors.lastname: Lang
authors.forename: J J
authors.initials: JJ
authors.lastname: De Voss
authors.forename: R P
authors.initials: RP
authors.lastname: Lehmann
mesh_terms: D000577:Amides / Q000737:chemistry / Q000493:pharmacokinetics*; D001692:Biological Transport; D018938:Caco-2 Cells; D002109:Caffeic Acids / Q000737:chemistry / Q000493:pharmacokinetics*; D002463:Cell Membrane Permeability; D020900:Echinacea / Q000737:chemistry*; D006801:Humans; D010936:Plant Extracts / Q000493:pharmacokinetics
chemical_list: D000577:Amides; D002109:Caffeic Acids; D010936:Plant Extracts