Eugene R. Morris

Quantitative determination of phytate in the presence of high inorganic phosphate

Abstract The review on the determination of phytate and inositol phosphates by Oberleas (1) indicates that most methods for the determination of phytate are derived from the method of Heubner and Stadler (2). This method is based on the principle that ferric ion forms a stable complex with phytate in dilute acid solution and is the only phosphate compound, at least in significant concentration in nature, with this property. However, the phytate values were high when we applied the procedure of Oberleas (3) to samples with high inorganic phosphate content such as rat feces or semipurified rat diets. This appeared to be a result of inorganic phosphate coprecipitating with ferric phytate. As a preliminary step to study phytate balance in rats, a modified procedure of the Oberleas (3) method was developed that appears to free the ferric phytate precipitate of inorganic phosphate. The procedure and its efficiency are reported in this communication.

Ascorbate Offsets the Inhibitory Effect of Inositol Phosphates on Iron Uptake and Transport by Caco-2 Cells

Abstract Differentiated monolayer cultures of Caco-2 human intestinal cells were used as a model to examine interactions between various dietary factors related to the intestinal uptake and absorption of nonheme Fe. Caco-2 cells accumulated 91–98 pmol Fe/mg protein from uptake buffer containing 12 nmol of Fe(III)-nitrilotriacetate during a 1-hr incubation at 37°C. Addition of a 10-fold molar excess of inositol hexa-phosphate (IP6) and its lesser phosphorylated derivatives (IP3, IP4, and IP5) decreased cellular uptake and transport of Fe from the lumenal compartment. Addition of ascorbic acid (AA) to the solution containing IPs stimulated Fe uptake and transport in a manner dependent upon the ratio of AA to IP and inversely proportional to the degree of phosphorylation of inositol (i.e., IP3 > IP4 > IP5 > IP6). A mixture of essential amino acids had minimal impact on Fe uptake in either the absence or presence of IPs. Cellular acquisition of Fe from solutions containing IPs was further enhanced by simultaneous addition of essential amino acids and AA. The stimulatory influence of ascorbic acid on Fe uptake from solutions containing IP6 was associated with an increase in the level of ferrous ion. These data further support the usefulness of Caco-2 cells as a model for investigating the effects of various dietary factors on mineral bioavailability.

Mineral balance of adult men consuming whole or dephytinized wheat bran

Abstract Ten men consumed for 15 days each, 36 g daily of either whole or dephytinized wheat bran. Mineral intakes were the same for each dietary regimen. Phytic acid intake was 2 or 0.2 g and the phytate/zinc molar ratio was 12 or 1.2 when eating whole or dephytinized bran, respectively. Apparent absorption (intake-fecal excretion) of iron, zinc, copper, managenese, magnesium, and calcium tended to be lower when whole bran was consumed. However, balances (intake-[fecal+urinary excretion]) for the last 10 days were for the most part positive regardless of which type of bran and more positive when whole bran was eaten. The whole wheat bran did not have a deleterious effect on mineral nutriture of adult men under the conditions of this study.

Bioavailability to rats of iron and zinc in calcium-iron-phytate and calcium-zinc-phytate complexes

Abstract The bioavailability of iron in Fephytate and Ca 3 Fephytate and of zinc in Zn 2 phytate and Ca 4 Zn 2 phytate was assayed in rats. Hemoglobin response was the same to the iron of Fephytate as the reference iron compound, Fe(NH 4 ) 2 (SO 4 ) 2 .6H 2 ) but the response to iron of Ca 3 Fephytate was significantly less than to both Fephytate and the reference. The zinc of Zn 2 phytate and Ca 4 Zn 2 phytate promoted growth as effectively as did ZnSO 4 . The femur bone zinc response to Ca 3 Zn 2 phytate and Zn 2 phytate did not differ significantly but the femur zinc responses to both complexes were significantly less than to ZnSO 4 . In contrast to iron, calcium in a preformed calcium-zinc-phytate complex appears to have no significant effect on the bioavailability to rats of the zinc in the complex.