Characterization of polyphenol effects on inhibition and promotion or iron update by caco-2 cells

Authors: Hart, Jonathan; Tako, Elad; Glahn, Raymond

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2017
Publication Date: 3/31/2017
Citation: Hart, J.J., Tako, E.N., Glahn, R.P. 2017. Characterization of polyphenol effects on inhibition and promotion or iron update by caco-2 cells. Journal of Agricultural and Food Chemistry. 65(16):3285-3294.

Interpretive Summary: Iron (Fe) deficiency is the leading nutritional deficiency worldwide; therefore, factors that can influence iron absorption from foods are of keen interest to nutritionists and food scientists. Historically, polyphenolic compounds present in the seed coat of the common bean are generally known to be inhibitors of iron bioavailability (ie. absorption). Using a human intestinal cell culture model, recent studies have indeed identified specific compounds in bean seed coats that inhibit Fe absorption, and surprisingly have also identified compounds that can promote absorption of Fe. The present study advances this line of research even further as it characterizes the effects of 43 additional polyphenols on Fe absorption bioavailability; and in addition investigates the relative amounts of the promotional compounds required to negate the effects of the major inhibitory compounds on Fe bioavailability. The results indicate that the inhibitory compounds have a more potent effect that outweighs the promotional compounds effect on Fe bioavailability, even when present at only 10% of a promoter compound. A simulation of the relative concentration levels of the 8 major polyphenols (4 inhibitors, 4 promoters) found in a sample of black bean seed coats, where the inhibitors are in greater concentration, demonstrated that most (>80%) of the inhibitory compounds would need to be removed in order to reduce the negative effect on Fe bioavailability. In vivo studies are now warranted to confirm the above in vitro effects. Such work would be significant as other bean color classes exist that are likely to have polyphenolic profiles that are more favorable to Fe bioavailability.

Technical Abstract: Polyphenolic compounds present in the seed coat of the common bean are generally known to be inhibitors of iron bioavailability. Recent research identified specific polyphenols such as myricetin, quercetin, and their associated glucosides, as being potent inhibitors. Such research also identified polyphenols such as epicatechin, kaempferol and kaempferol 3-glucoside as being promoters of Fe bioavailability. The present study extends this work using a Caco-2 cell model to characterize the effects of 43 additional polyphenols on Fe bioavailability. In addition, this study investigates the relative amounts of the promotional compounds required to negate the effects of the major inhibitory compounds on Fe bioavailability. The results indicate that the inhibitory compounds have a more potent effect that outweighs the promotional compounds effect on Fe bioavailability, even when present at only 10% of a promoter compound. A simulation of the relative concentration levels of the 8 major polyphenols (4 inhibitors, 4 promoters) found in a sample of black bean seed coats, where the inhibitors are in greater concentration, demonstrated that most (>80%) of the inhibitory compounds would need to be removed in order to reduce the negative effect on Fe bioavailability. In vivo studies are now warranted to confirm the above in vitro effects. Such work would be significant as other bean color classes exist that are likely to have polyphenolic profiles that are more favorable to Fe bioavailability.