Uptake of phenolic compounds from plant foods in human intestinal Caco-2 cells.

In continuation of our studies on the bioaccessibility of phenolic compounds from food grains as influenced by domestic
processing, we examined the uptake of phenolics from native/sprouted finger millet (Eleucine coracana) and green gram
(Vigna radiata) and native/heat-processed onion (Allium cepa) in human Caco-2 cells. Absorption of pure phenolic
compounds, as well as the uptake of phenolic compounds from finger millet, green gram, and onion, was investigated in
Caco-2 monolayer model. Transport of individual phenolic compounds from apical compartment to the basolateral compartment
across Caco-2 monolayer was also investigated. Sprouting enhanced the uptake of syringic acid from both these
grains. Open-pan boiling reduced the uptake of quercetin from the onion. Among pure phenolic compounds, syringic acid
was maximally absorbed, while the flavonoid isovitexin was least absorbed. Apparent permeability coefficient P(app) of
phenolic compounds from their standard solutions was 2.02 9 10-6 cm/s to 8.94 9 10-6 cm/s. Sprouting of grains
enhanced the uptake of syringic acid by the Caco-2 cells. Open-pan boiling drastically reduced the uptake of quercetin from
the onion. The permeability of phenolic acids across Caco-2 monolayer was higher than those of flavonoids.