ARS | Publication request: Bioaccessibility of phenols in common beans (Phaseolus vulgaris L.) and iron (Fe) availability to Caco-2 cells

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2008
Publication Date: November 1, 2008
Citation: Laparra, J., Glahn, R.P., Miller, D.D. 2008. Bioaccessibility of phenols in common beans (Phaseolus vulgaris L.) and iron (Fe) availability to Caco-2 cells. Journal of Agricultural and Food Chemistry. 56(22):10999-11005.

Interpretive Summary: A model for digestion has been developed in our lab that uses a simulated digestion and Caco-2 epithelial tissue cell culture monolayer to imitate the intestinal lining and absorption of minerals into our bodies. This model has been developed to measure Fe absorption, and is much faster and less expensive than studying iron uptake from human trials. However in some cases the cell culture system may be more sensitive to inhibitors of iron absorption, or it may simply lack processes that are present only in intact intestines. One of the compounds that inhibit Fe uptake in the in vitro system is polyphenols. This study was to determine if increased iron content, preparation methods or the color of the beans had any bearing on bioaccessability of iron with the extracted phenols in the in vitro system vs in vivo. The results indicate that there may be some factors in the in vitro system that make it more sensitive to inhibiting Fe uptake than in vivo, and may lack some physiological factors that may affect the absorption of nutrients in vivo.

Technical Abstract: Samples of common and biofortified beans (Phaseolus vulgaris), both raw and cooked (autoclaved 120 deg C, 20 min) were analyzed for their polyphenol composition. Polyphenols were identified via HPLC-UV/diode array detection. Cooking favored the extraction of polyphenols without the need of a hydrolysis step, a fact that is of interest because this is the usual form in which beans are consumed. The main differences between white and colored beans were the presence of free kaempferol (13.5-29.9 ug g-1) and derivatives (kaempferol-3-O-glucoside) (12.5-167.5 ug g-1), only in red and black beans. An in vitro digestion (pepsin, pH2; pancreatin-bile extract, pH 7) was applied to beans to estimate bioaccessibility of individual polyphenols. Caco-2 cell ferritin formation was used to evaluate Fe uptake. Cell Fe uptake was only significant from white beans. Kaempferol from seed coats exhibited high bioaccessibility (45.4-62.1%) and a potent inhibitor effect on Fe uptake at concentrations ranged 0.37-1.30 uM.