Transepithelial Transport of Rosmarinic Acid in Intestinal Caco-2 Cell Monolayers

Abstract

The absorption characteristics of rosmarinic acid (RA) were examined by measuring permeation across Caco-2 cell monolayers using an HPLC-electrochemical detector (ECD) fitted with a coulometric detection system. RA exhibited nonsaturable transport even at 30 mM, and the permeation at 5 mM in the apical-tobasolateral direction, J ap!bl , was 0.13 nmol/min/mg of protein. This permeation rate is nearly the same as that of 5 mM chlorogenic acid (CLA) and gallic acid, which are paracellularly transported compounds. Almost all of the apically loaded RA was retained on the apical side, and J ap!bl was inversely correlated with paracellular permeability. These results indicate that RA transport was mainly via paracelluar diffusion, and the intestinal absorption efficiency of RA was low. Furthermore, RA appeared to be unsusceptible to hydrolysis by mucosa esterase in Caco-2 cells. These results, together with our previous work (J. Agric. Food Chem., 52, 2518-2526 (2004), J. Agric. Food Chem., 52, 6418-6424 (2004)) suggest that the majority of RA is further metabolized and degraded into m-coumaric and hydroxylated phenylpropionic acids by gut microflora, which are then efficiently absorbed and distributed by the monocarboxylic acid transporter (MCT) within the body. The potential of orally administered RA in vivo will be further investigated.

Non-Involvement of the Human Monocarboxylic Acid Transporter 1 (MCT1) in the Transport of Phenolic Acid

“…The cells were seeded at a density of 1 Â 10 5 /cm 2 and grown in Transwell inserts with a semipermeable membrane coated with type I collagen, as previously reported. [4][5][6][7][8]12,13) The integrity of the cell layer was evaluated by measuring the transepithelial electrical resistance (TER) with Millicell-ERS equipment (Millipore, Billerica, MA, USA). A monolayer with a TER value of more than 300 Ácm 2 was used for the transepithelial transport experiments.…”

“…The amount of p-coumaric or salicylic acid in this extract was estimated by using HPLC-ECD equipment fitted with an ESA coulometric detection system (ESA, Boston, MA, USA) as described in previous studies. [4][5][6][7][8]12,13) In brief, to measure p-coumaric acid, chromatographic separation was performed in a C18 column (ODS150, MC Medical, Tokyo, Japan) with mobile phase A (solvent A) of 50 mM sodium acetate containing 5% methanol (pH 3.0) and mobile phase B (solvent B) of 50 mM sodium acetate containing 40% acetonitrile and 20% methanol (pH 3.5). Eight electrode detector potentials (from 0 to 700 mV in increments of 100 mV) were used.…”

“…The level of p-coumaric acid and salicylic acid in the extract of oocytes was determined by using a highly sensitive (detection limit < 0.5 pmol) and reproducible assay, as reported previously. [4][5][6][7][8]12,13) The retention time (RT) and dominant oxidation potential for p-coumaric and salicylic acids were respectively 14.7 min and 600 mV, and 19.4 min and 800 mV (Figs. 3A and B).…”

“…MCT-mediated absorption, partial MCT-mediated absorption, paracellular diffusion, and transcellular passive diffusion). [4][5][6][7][8] We have also established that the absorption characteristics of these compounds in the Caco-2 cell line are correlated with their absorption efficiency and bioavailability in vivo. [9][10][11] Furthermore, the microbial metabolites of poorly absorbed parent polyphenols are also thought to be absorbed and distributed by MCT, in a similar way to phenolic acids.…”

Whole Grain Consumption and Health of the Lower Gastrointestinal Tract: A Focus on Insoluble-Bound Phenolic Compounds

“…Transport of hydroxycinnamates from the intestinal lumen to the plasma involves the simultaneous transport of hydrogen ions. Studies have shown that the MCAT is involved in the transport of hydroxycinnamates and their metabolites into epithelial cells (Konishi et al, 2003, Konishi & Kobayashi, 2004, Konishi, 2005, Konishi & Kobayashi, 2005.…”