Identification of bean polyphenols that inhibit and enhance iron uptake by Caco‐2 cells

Abstract

Polyphenolic compounds present in bean seed coats are known to be inhibitors of Fe bioavailability; however, the specific polyphenols in bean seed coats that inhibit Fe bioavailability have not been identified. In addition, the antioxidative properties of some polyphenols may actually promote Fe absorption. The objective of this study was to identify the major polyphenols that affect Fe bioavailability in black beans. Extracts of white beans and black beans were evaluated for effect on Fe uptake using a Caco‐2 cell model. LC/MS was then used to identify compounds present in active extracts. As expected, Iron uptake was inhibited by extracts from black bean seed coats relative to that of white beans. Examination of the effect of individual polyphenols present in black bean seed coats showed varying dose related Fe uptake responses, ranging from inhibition to stimulation. Myricetin, quercetin and quercetin 3‐glucoside inhibited iron uptake; ferulic acid and salicylic acid had no effect; and caffeic acid, epicatechin, gallic acid and kaempferol stimulated iron uptake in Caco‐2 cells. The results clearly indicate that not all polyphenols inhibit iron uptake and that some are promoters. Targeting these compounds in breeding and or processing of beans could yield improvements of Fe bioavailability. Funded by USDA‐ARS.