Absorption, conjugation and efflux of the flavonoids, kaempferol and galangin, using the intestinal CaCo-2/TC7 cell model

Abstract

Flavonoids are biologically active compounds in food with potential health effects. We have used the Caco-2 cell monolayer model to study the absorption and metabolism of two flavonols, a class of flavonoids, specifically kaempferol and galangin. Metabolism experiments allowed identification of 5 kaempferol conjugates: 3-, 7- and 4′-glucuronide, a sulphate and a glucurono-sulphate; and 4 galangin conjugates: 3-, 5- and 7-glucuronides, and a sulphate, using specific enzyme hydrolysis, HPLC-MS, and HPLC with post column metal complexation/tandem MS. Transport studies showed that the flavonols were conjugated inside the cells then transported across the monolayer or effluxed back to the apical side. Sulphated conjugates were preferentially effluxed back to the apical side, whereas glucuronides were mostly transported to the basolateral side. For kaempferol, a small amount of the unconjugated aglycone permeated in both directions, indicating some passive diffusion. When kaempferol-3-glucuronide and quercetin7-sulphate were applied to either side of the cells, no permeation in either direction was observed, indicating that conjugates cannot re-cross the cell monolayer. Formation of apical kaempferol-7- and 4′-glucuronides was readily saturated, whereas formation of other conjugates at the apical side and all at the basolateral side increased with increasing concentration of kaempferol, implying different transporters are responsible at the apical and basolateral sides. The results highlight the important but complex metabolic changes occurring in flavonoids during absorption.

Transport oftrans-tiliroside (kaempferol-3-β-D-(6″-p-coumaroyl-glucopyranoside) and related flavonoids across Caco-2 cells, as a model of absorption and metabolism in the small intestine

“…Kaempferol transfer from both directions was not affected by the application of inhibitors of efflux transporters MRP2. This evidence is indicative of passive transport, and is consistent with a previously published study (Barrington et al, 2009). …”

“…Metabolism of kaempferol has been studied previously in Caco-2/TC7 cells (Barrington et al, 2009), and here five metabolites were identified, including a kaempferol glucurono-sulfate.…”

Stability of Phenolic Compounds Isolated from Cocoa, Green Tea and Strawberries in Hank’s Balanced Salt Solution under Cell Culture Conditions.

“…The cell culture models were proved to be a good alternative for animal studies and have emerged as one of the standard in vitro tools to predict in vivo intestinal absorption of various substances. Subsequently, they were found to be suitable to study intestinal transport of phytochemicals [Barrington et al, 2009;Deprez et al, 2001], and nowadays, cell line models are called an indispensable tool in food science and nutrition [Langerholc et al, 2011]. The studies of epithelial transport/bioavailability are performed in conditions mimicking physiological condi-tions, involving pH 6.0-7.4.…”

The membrane transport of flavonoids from Crossostephium chinense across the Caco‐2 monolayer

“…The structurepermeability relationships of some dietary flavonoids including flavonoid agylcone and flavonoid glucoside were investigated using the Caco-2 cell monolayer [9][10][11][12][13]. Most flavonoid glucosides are impermeable to the intestinal barrier; however, flavonoid aglycones (e.g.…”