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United States Department of Agriculture

Agricultural Research Service

Title: Screening of iron bioavailability patterns in eight bean (Phaseolus vulgaris L.) genotypes using the Caco-2 cell in vitro model

Authors
item Ariza-Nieto, Magnolia - CORNELL UNIVERSITY
item Blair, Matthew - CIAT, CALI, COLOMBIA
item Welch, Ross
item Glahn, Raymond

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 2007
Publication Date: September 19, 2007
Citation: Ariza-Nieto, M., Blair, M., Welch, R.M., Glahn, R.P. 2007. Screening of iron bioavailability patterns in eight bean (Phaseolus vulgaris L.) genotypes using the Caco-2 cell in vitro model. Journal of Agricultural and Food Chemistry. 55:7950-7956.

Interpretive Summary: Beans represent a significant source of Fe in the diets of many developing regions. Therefore, it is critical to evaluate the nutritional characteristics of the parental lines used by many plant breeders. The goal of this research was to use a cell culture model to study iron bioavailability in 8 bean genotypes (three Mesoamerican and five Andean) that represent diversity of grain types in the crop. We also measured the distribution of both iron and phytate (an inhibitor of iron bioavailability) in different bean grain tissues (cotyledon, seed coats and embryos). Bioavailability tests were conducted on cooked, lyophilized and ground beans with or without seed coats. The cotyledons represented 88-92% of the grain weight, and their iron concentration ranged from 45-83 ug/g while the seed coats represented between 8-10% of grain weight and their iron concentration ranged from 28-156 ug/g. The embryo represented the smallest fraction of the entire grain weight 0.64-1.82% but their iron concentration was among the highest 88-146 ug/g. In whole beans, iron concentration ranged from 48-74 ug/g and was similar to previous reports for some of the genotypes. Phytate concentration was found to be higher in the embryo than in the seed coat or cotyledons but at most represented only 3% of the total phytate in the grain. Seed coats were confirmed to be the exclusive tissue containing polyphenols; thus, the removal of seed coat improved iron bioavailability from the bean samples from an overall mean response of 3.7 to 20.3 ng ferritin/mg protein. The highest cell iron uptake correlated with the highest cotyledon iron concentration. These results suggest that iron accumulation varies among bean genotypes and confirmed the importance of polyphenols compared to phytates in their influence on iron bioavailability in a cell culture model.

Technical Abstract: The primary goal of this research was to use an in vitro digestion/Caco-2 model to study iron bioavailability in 8 bean genotypes (three Mesoamerican and five Andean) that represent diversity of grain types in the crop. Complementing this goal, we measured the distribution of both iron and phytate in different bean grain tissues (cotyledon, seed coats and embryos). Bioavailability tests were conducted on cooked, lyophilized and ground beans grains with or without seed coats. The cotyledons represented 88-92% of the grain weight, and their iron concentration ranged from 45-83 ug/g while the seed coats represented between 8-10% of grain weight and their iron concentration ranged from 28-156 ug/g. The embryo represented the smallest fraction of the entire grain weight 0.64-1.82% but their iron concentration was among the highest 88-146 ug/g. In whole bean grains, iron concentration ranged from 48-74 ug/g and was similar to previous reports for some of the genotypes. Phytate concentration (measured as umols phytate g-1) was found to be higher in the embryo than in the seed coat or cotyledons but at most represented only 3% of the total phytate in the grain. Seed coats were confirmed to be the exclusive tissue containing polyphenols; thus, the removal of seed coat improved iron bioavailability from the bean samples from an overall mean response of 3.7 to 20.3 ng ferritin/mg protein. The highest Caco-2 cell iron uptake was observed from the genotypes G19833 and Radical Cerinza, which were also the genotypes with the highest cotyledon iron concentration. These results suggest that iron accumulation varies among bean genotypes and confirmed the importance of polyphenols compared to phytates in their influence on iron bioavailability to Caco-2 cells.

Last Modified: 9/10/2014
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