Effect of three edible oils on the intestinal absorption of caffeic acid: An <i>in vivo</i> and <i>in vitro</i> study

<div><p>Polyphenolic antioxidants are mainly absorbed through passive paracellular permeation regulated by tight junctions. Some fatty acids are known to modulate tight junctions. Fatty acids resulting from the digestion of edible oils may improve the absorption of polyphenolic antioxidants. Therefore, we explored the effect of three edible oils on the intestinal absorption of caffeic acid. Rats were fed with soybean oil and caffeic acid dissolved in distilled water. Caffeic acid contents in the plasma collected up to 1 hr were quantified. The experiment was repeated with coconut oil and olive oil. Component fatty acids of the oils were individually tested <i>in vitro</i> for their effect on permeability of caffeic acid using Caco-2 cell monolayers. Highest absorption of caffeic acid was observed in animals fed with coconut oil. <i>In vitro</i> transport percentages of caffeic acid in 2.5 mmol/L solutions of fatty acids were 22.01±0.12 (lauric), 15.30 ± 0.25 (myristic acid), 13.59 ± 0.35 (linoleic acid), 3.70 ± 0.09 (oleic acid) and 0.10–2.0 (all other fatty acids). Lauric acid and myristic acid are the two major fatty acids present in coconut oil. Therefore, these fatty acids may contribute to the higher absorption of caffeic acid in the presence of coconut oil.</p></div

Transport percentages of caffeic acid and lucifer yellow after 1 hr of transport through a Caco-2 cell monolayer.

<p>Transport percentages of caffeic acid and lucifer yellow after 1 hr of transport through a Caco-2 cell monolayer.</p

Ferric reducing antioxidant power (reducing power %) of plasma.

<p>Ferric reducing antioxidant power of Soybean oil and caffeic acid treated group and the Olive oil and caffeic acid treated group were significantly lower compared to the Coconut oil and caffeic acid treated group up to 1 hr after treatment (p<0.05). n = 6.</p

HPLC chromatogram of plasma after treating with de-conjugating enzymes.

<p>A, caffeic acid and B, elagic acid (Internal standard). Inset: Signal areas of caffeic acid transported through Caco-2 cell monolayers; a, caffeic acid signal in the control with no added lauric acid, b, caffeic acid signal in the sample with added lauric acid at 2.5 mmol/L.</p