Intestinal transport and absorption of bioactive phenolic compounds from a chemically characterized aqueous extract of Athrixia phylicoides

Ethnopharmacological relevance Athrixia phylicoides, popularly known as “bush tea”, is an indigenous aromatic shrub found in mountainous and grassland areas of the northern and eastern parts of southern Africa. The plant is traditionally used for the treatment of several ailments, including coughing, treating infected wounds, treating boils and sore throat, hypertension and heart disease. Potential anti-diabetic effects have also been demonstrated in vitro. Aim of the study To investigate the intestinal transport of prominent phenolic constituents, across a fully differentiated Caco-2 monolayer, using a characterized aqueous extract of A. phylicoides, previously shown to have bioactivity. Materials and methods HPLC-DAD and LC/MS analyses were used to identify the major phenolic compounds within the extract. Intestinal transport of the phenolic compounds was assessed using a differentiated Caco-2 monolayer model in order to predict bioavailability and identify metabolite formation. Rate of transport, efflux and percentage cross-over were calculated for the respective phenolic compounds. Results Nine prominent compounds, present in the aqueous extract of A. phylicoides, were identified. Of these, three phenolic acids (protocatechuic acid, caffeic acid and para-coumaric acid), crossed the Caco-2 cell monolayer in significant amounts, with P_app values of 4.52, 4.35 (×10⁻⁶ cm/s) and 2.38 (×10⁻⁵ cm/s), respectively. para-Coumaric acid was shown to have the highest predicted bioavailability. Conclusions Para-Coumaric acid, identified for the first time in A. phylicoides, was shown to have the highest predicted bioavailability suggesting that it could play a major role in the bioactivity of A. phylicoides.