Permeability studies of alkylamides and caffeic acid conjugates from echinacea using a Caco-2 cell monolayer model
A. Matthias*, J. T. Blanchfield, K. G. Penman*, I. Toth, C.-S. Lang, J. J. De Voss and R. P. Lehmann*
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 1 104 cm/s.
Alkylamides were found to diffuse through Caco-2 monolayers with Papp ranging from 3 106 to 3 104 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.
Conclusion: Alkylamides but not caffeic acid conjugates are likely to cross the intestinal barrier.
Journal of Clinical Pharmacy & Therapeutics
Volume 29 Issue 1 Page 7 - February 2004
J Clin Pharm & Thera, 2/04
J Clin Pharm & Thera, 8/05
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