Phytate and cation binding activity
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Since O'Dell and Savage, reported in 1960 that phytate decreased the bioavailability of zinc, the negative, antinutrient properties of phytate have been well documented. But the chemical activities of phytate remain largely unknown. Recently, under the perception of weight control and healthy life, Americans increasingly have chosen diets containing foods of plant origin. Phytate intake has increased substantially. Understanding of the influence of phytate on the absorption of di(poly)valent cations and the interactions between phytate and divalent cations have become more important. In this study, phytate-cation(s) complexation interaction were studied in the relation to the pH, the concentration of the available cation(s), and the atomic weight of the cation. The affinity of these 5 cations in phytate-cation complexations are in the order of Pb+2 > Zn+2 > Cu+2 > Ca+2 > Mg+2 at pH 6. Ca+2 and Mg+2 have lower affinity for phytate than P+2^ Zn+2^ and Cu+2 while these 5 cations compete with each other to bind withe phytate. These results lead us to propose that there may be two different binding arrangements or models in phytate-cation(s) complexation. Ca+2 and Mg+2, both with atomic weights < 40.08, may complex with phytate in an intermolecular arrangement. In opposite, Pb+2, Zn+2, and Cu+2, all with atomic weights > 63.54, may complex in an intramolecular arrangement. The synergistic effect was observed when two different atoms were bound for phytate.