Analysis of iron chelates in commercial iron fertilizers by gel chromatography

A gel chromatographic method for the quality control of iron chelate fertilizers is described. The iron chelates are separated on a column of Sephadex G-10 and the eluates are analysed for iron. Using a sample quantity of 25 mg in a volume of 5 ml water and eluting with 0.15 M soidum chloride solution, a separation was achieved of commercial products of Fe-EDDHA or Fe-EDDHMA. The chromatographic analysis of Fe-EDTA or Fe-DTPA calls for a better resolution. This was obtained by decreasing the sample quantity and eluting with 0.035 M calcium chloride solution of pH 7.0. In this way it is possible to eliminate the interference of iron chelates of moderate stability which can be present in commercial products containing Fe-EDTA or Fe-DTPA.     

Peptides isolated from in vitro digests of milk enhance iron uptake by caco-2 cells

Milk proteins, during digestion, produce a range of biologically active peptides. Among those are peptides that may enhance iron absorption. The objective of this project was to investigate the effect of isolated milk peptides on iron uptake. Cow's milk, 0% fat, was subjected to a modified in vitro digestion process. The milk digest was further fractionated by gel filtration. All eluted fractions as well as beta-casein synthetic peptides (a tripeptide and a hexapeptide) were subsequently tested for effects on iron uptake with Caco-2 cell monolayers. Fractions of milk digests obtained through Sephadex G-25 gel filtration had a significant enhancing effect on iron uptake in Caco-2 cells compared to nonfractionated milk digests. Two fractions (P = 0) and the hexapeptide (P < 0.0001) enhanced iron uptake by up to 3-fold, whereas others and the tripeptide had no effect. These results suggest that selected peptides produced during the in vitro digestion of milk may enhance iron absorption; however, it remains to be demonstrated whether this effect may be nutritionally significant.     

Isolated glycosaminoglycans from cooked haddock enhance nonheme iron uptake by Caco-2 cells

This study continues previous research to confirm that glycosaminoglycans (GAGs) exert a positive effect on promoting iron uptake by Caco-2 cells. Cooked haddock was digested with papain, and GAGs were further purified on the basis of their sulfur content. Reverse phase chromatography (RP-HPLC) and digestion with chondroitinase ABC (Chase) (50 mU/mg) were used to approach the identification of the GAGs. FeCl 3 was mixed with the purified GAGs, and Fe uptake was measured by ferritin formation using an in vitro digestion/Caco-2 cell model. The identificative analyses suggest that chondroitin/dermatan sulfate-related structures promote Fe uptake by Caco-2 cells; however, this effect was lower (40%) than that observed with whole fish muscle. Chase eliminated the positive effect on Fe uptake. These results indicate that specific GAGs may contribute to the enhancing effect of meat on Fe absorption. Further in vivo studies addressing these aspects of the meat factor are needed.     

Calcium, iron, and zinc uptake from digests of infant formulas by Caco-2 cells.

Our aim was to estimate the bioavailability of calcium, iron, and zinc from infant formulas using a model that includes in vitro digestion and a Caco-2 cell culture to estimate the uptake. The cell culture conditions were selected, and uptake assays were carried out first with calcium, iron, and zinc standard solutions, and then with the soluble fraction of enzymatic digests of an adapted milk-based and a soy-based infant formula. It was not possible to measure the uptake of calcium, iron, and zinc from standard solutions added to the cell cultures in amounts similar to those present in infant formula digests with our method. The fact that it was, however, possible in the case of enzymatic digests suggests the presence of components in the digests that enhance mineral uptake. When mineral uptakes were expressed as percentages of the mineral present, statistically significant differences were found in the case of calcium between the uptake from the milk- and the soy-based formulas. For iron and zinc no such differences were observed.     

The stability of iron chelates in calcareous soils

The stability of Fe-EDTA and Fe-CDTA was investigated in order to evaluate their effectiveness under calcareous soil conditions. To accomplish this evaluation the reaction rate of fixation, K, the adsorption coefficient, K_d, and the retardation factor, S, of the iron chelate were determined through column experiments at pH 7.8 and two ionic strengths, I, of CaCl₂. The results indicated that iron in Fe-EDTA was more fixed than in Fe-CDTA. The fixation increased by increasing the ionic strength. Also it increased linearly with increasing CaCO₃ content of the soil. The values of retardation factor, S, showed that this parameter depended more on the surface area of the soil than on I or CaCO₃ content. The product KS depends on CaCO₃ content, surface area of the soil, ionic strength and chelating agent used. It can be taken as an index for the efficiency of the iron chelate under different conditions. Fe-EDTA was more adsorbed than Fe-CDTA, the adsorption increased with increasing ionic strength and surface area of the soil.     

Combined impact of pH and organic acids on iron uptake by Caco-2 cells

Previous studies have shown that organic acids have an impact on both Fe(II) and Fe(III) uptake in Caco-2 cell. However, to what extent this effect is correlated with the anion of organic acids per se, or with the resulting decrease in pH, has not yet been clarified. Therefore, we studied the effect of five organic acids (tartaric, succinic, citric, oxalic, and propionic acid) on the absorption of Fe(II) and Fe(III) in Caco-2 cells and compared this with sample solutions without organic acids but set to equivalent pH by HCl. The results showed that the mechanisms behind the enhancing effect of organic acids differed for the two forms of iron. For ferric iron the organic acids promoted uptake both by chelation and by lowering the pH, whereas for ferrous iron the promoting effect was caused only by the lowered pH.     

Organic acids influence iron uptake in the human epithelial cell line Caco-2

It has previously been suggested that organic acids enhance iron absorption. We have studied the effect of nine organic acids on the absorption of Fe(II) and Fe(III) in the human epithelial cell line Caco-2. The effect obtained was dose-dependent, and the greatest increase (43-fold) was observed for tartaric acid (4 mmol/L) on Fe(III) (10 micromol/L). Tartaric, malic, succinic, and fumaric acids enhanced Fe(II) and Fe(III) uptake. Citric and oxalic acid, on the other hand, inhibited Fe(II) uptake but enhanced Fe(III) uptake. Propionic and acetic acid increased the Fe(II) uptake, but had no effect on Fe(III) uptake. Our results show a correlation between absorption pattern and chemical structure; e.g. hydroxyl groups, in addition to carboxyls, were connected with a positive influence. The results may be important for elucidating factors affecting iron bioavailability in the small intestine and for the development of foods with improved iron bioavailability.     

Inositol phosphates influence iron uptake in Caco-2 cells.

Phytate, inositol hexaphosphate (InsP(6)), may be hydrolyzed to inositol phosphates with lower degree of phosphorylation, i.e., inositol penta- to monophosphates (InsP(5)-InsP(1)), during food processing. Each of these lower inositol phosphates exists in different isomeric forms. The objective of this study was to determine if different isomers of InsP(3)-InsP(5) (Ins(1,2,4)P(3), Ins(1,2,3)P(3), Ins(1,2,6)P(3), Ins(1,3,4)P(3), Ins(1,2,3,4)P(4), Ins(1,2,5,6)P(4), Ins(1,2,4,5,6)P(5), and Ins(1,3,4,5,6)P(5)) and InsP(6) affect the uptake of iron. We studied the iron absorption in vitro using the human intestinal epithelial cell line, Caco-2. Addition of a 2-fold molar excess of InsP(6) or InsP(5) in proportion to Fe (1 h incubation at 37 degrees C) reduced iron uptake by 46-52% (p < 0.001). Neither InsP(4) isomers nor InsP(3) isomers affected iron uptake significantly at 1 h incubation with a molar InsP:Fe level of 2:1. Iron uptake was shown to not be a function of the isomeric form of inositol phosphates. The inositol phosphate isomers did not seem likely to interact with each other through iron to form more stable iron complexes. At a molar InsP:Fe level of 20:1 an inhibitory effect of InsP(4) was found, while InsP(3) did not affect the iron absorption even at a 20-fold molar excess.     

Xanthohumol uptake and intracellular kinetics in hepatocytes, hepatic stellate cells, and intestinal cells

Xanthohumol (XN) is the major prenylated chalcone of hops and hence an ingredient of beer. Despite many advances in understanding of the pharmacology of XN, one largely unresolved issue is its low bioavailability in the human organism. Also, not much is known about its actual concentrations and pharmacokinetics in liver and intestinal cells. Therefore, the uptake, intracellular distribution, and kinetics of XN were studied in various cell types, namely, hepatocellular carcinoma cells (HuH-7), hepatic stellate cells (HSC), primary cultured hepatocytes, and colorectal adenocarcinoma cells (Caco-2). Fluorescent microscopy allowed for the first time visualization and tracing of the uptake and intracellular distribution of XN. A rapid accumulation of XN concentrations that were up to >60-fold higher than the concentration present in the ambient culture medium was observed. Fluorescence recovery after photobleaching experiments revealed that most XN molecules are bound to cellular proteins, which may alter properties of cellular factors.     

Inulin affects iron dialyzability from FeSO4 and FeEDTA solutions but does not alter Fe uptake by Caco-2 cells

The in vitro effects of inulin on the fluxes of Fe (F(Fe)) and uptake by Caco-2 cells from FeSO4 and FeEDTA were evaluated. Cell ferritin formation was used as a measure of Fe uptake. Mitochondrial (MTT test) and lysosomal activities were monitored as biomarkers of the changes of cellular metabolism. Changes in mRNA expression of Fe transporters, DMT1 and Dcytb, were evaluated. Inulin decreased dialyzability and F(Fe) from FeSO4 solution, suggesting a mineral binding effect, but increased those from FeEDTA. Cultures exposed to FeEDTA solutions exhibited higher ferritin values and MTT conversion percentages. Regardless of Fe source, cell Fe uptake and mRNA expression of Fe transporters were similar with or without inulin, suggesting that inulin did not impair Fe uptake. These observations might indicate a faster cellular Fe internalization from FeEDTA solutions. From a physiological perspective, the decreased F(Fe) from FeSO4 might be reflected in a decreased Fe uptake.     

Digestive Stability, micellarization, and uptake of beta-carotene isomers by Caco-2 human intestinal cells

While isomeric profiles of carotenoids found in food often differ from those in body fluids and tissues, insights about the basis for these differences remain limited. We investigated the digestive stability, relative efficiency of micellarization, and cellular accumulation of trans and cis isomers of beta-carotene (BC) using an in vitro digestion procedure coupled with human intestinal (Caco-2) cells. A meal containing applesauce, corn oil, and either water-soluble beadlets (WSB) or Dunaliella salina (DS) as a BC source was subjected to simulated gastric and small intestinal digestion. BC isomers were stable during digestion, and the efficiency of micellarization of cis-BC isomers exceeded that of all-trans-BC isomers. The cellular profile of carotenoids generally reflected that in micelles generated during digestion, and intracellular isomerization was minimal. These data suggest that cis isomers of BC are preferentially micellarized during digestion and transferred across the brush-border surface of the enterocyte from mixed micelles with similar efficiency as all-trans-BC at the concentrations of the carotenoids utilized in this study.     

The use of iron chelates in compound fertilizers containing trace elements

Abstract

The chemical behaviour of iron chelates, incorporated in compound fertilizers with inorganic micronutrient compounds, was studied. Pot experiments were conducted to evaluate the effectiveness of these products in controlling iron deficiency. A commercial compound fertilizer, containing 0.09% Fe as Fe‐DTPA, 0.12% Cu, 0.16% Mn and 0.04% Zn as sulfates, proved to be ineffective in preventing iron chlorosis in Chamaecyparis lawsoniana ’Alumii’, growing on sphagnum peat at two lime levels. The same fertilizer formulation with 0.09%‐ Fe as Fe‐EDDHA did prevent iron chlorosis at both lime levels. Fe‐EDTA, incorporated in the compound fertilizer, gave good results at the lower but not at the higher lime level, due to the low stability of Fe‐EDTA at high pH. Data from laboratory experiments showed that copper replaced the chelated iron in the compound fertilizer containing Fe‐DTPA, causing the iron to precipitate. The strong competition between copper and iron for the organic ligand is due to a specific affinity of copper for DTPA, resulting in a copper chelate with high stability constant and a molar ratio of copper to chelating agent of 2 : 1.

In the case of Fe‐EDDHA and Fe‐EDTA the competition between iron and copper is much weaker. In contrast to Fe‐DTPA, these chelates remain rather stable when incorporated in fertilizers containing micronutrients.     

Effectiveness of iron chelates and FeSO4 for correcting iron chlorosis of peanut on calcareous soils

The effectivenness of different Fe chelates to correct lime induced chlorosis of peanut (Arachis hypogaea) was tested on calcareous soils in Cyprus. Among the chelates tested, Fe‐DTPA and Fe‐EDTA were less effective than Fe‐EDDHA. In one experiment. Fe‐EDDHMA Was less effective while in another experiment was equally effective compared to Fe‐EDDHA . Three different commercial chelates of the form Fe‐EDDHA were equally effective in correcting iron chlorosis. The stability of the Fe‐EDDHA chelate in the soil does not affect its efficiency in curing chlorosis of peanut due to the short growing season for this crop. Ferrous sulfate applied without an acidifying soil amendment was not effective to correct iron chlorosis of peanut.     

Removal of metal ions from aqueous solutions by Penicillium biomass: Kinetic and uptake parameters

The uptake and binding of Ni, Zn, Cd, and Pb by the mycelium of Penicillium digitatum are highly pH-sensitive, being severely inhibited below pH 3. In the case of Ni, Zn, and Cd, H⁺ inhibits competitively. The Cu-ion, like UO₂ ²⁺ studied previously, is nearly pH-insensitive. All of these cations except Pb are taken up to a greater extent by mycelial preparations preheated at 100° C for 5 min. Other activators include alkali and dimethyl sulfoxide (DMSO) pretreatment, but formaldehyde inhibits, Combining current and previous data, the ion-selective character of uptake is reflected, on a molar basis by the rank order Fe³⁺, Ni²⁺ Zn²⁺ > Cu²⁺ > Pb²⁺ UO₂ ²⁺ ? MoO₄ ^2?. P. digitatum appears to act like a mixture of neutral and acidic glycans with no real evidence for cationic amino-functional sites. In addition to the technological applications in water treatment, we suggest that fungal biosorption may be of natural geochemical importance in the concentration of metals and formation of minerals.     

Applications of fertilizer cations affect cadmium and zinc concentrations in soil solutions and uptake by plants

A pot experiment was conducted to study changes over time of Cd and Zn in soil solution and in plants. Radish was grown in a soil which had been contaminated with heavy metals prior to 1961. Constant amounts of a fertilizer solution (NH₄NO₃, KNO₃) were added daily. Soil solution was obtained at intervals by displacement with water. The cumulative additions of small amounts of fertilizers were made equal to the plants' requirements at the final harvest but were found to exceed them during most of the experiment. Excess fertilizers caused substantial increases of major (K, Ca, Mg) and heavy-metal (Cd, Zn) ions in soil solutions and a decrease in soil pH, probably due to ion-exchange mechanisms and the dissolution of carbonates. Uptake of Cd and Zn into leaves was correlated with the mass flow of Cd (adjusted r²= 0.798) and Zn (adjusted r²= 0.859). Uptake of K, Ca and Mg by the plants was independent of their concentrations in solution. It is concluded that, in order to study effects of plants on heavy-metal availability and obtain soil solution that has not been altered by fertilizer ions, nutrients must be added according to the needs and growth of the plants. This could be achieved by linking fertilizer additions to the rate of transpiration, as nutrient uptake and transpiration were closely correlated in this experiment.     

Characterization of commercial iron chelates and their behavior in an alkaline and calcareous soil

Iron deficiency is a common problem for many plants grown in alkaline and calcareous soils. To correct this problem, iron is supplied to plants as chelates. Several iron chelates are sold under diverse trademarks with different characteristics. This work evaluated 18 commercial products containing the most representative chelated iron sources used in agricultural practice in Spain when the study was done, namely the ferric chelates of EDDHA, EDDHMA, EDDCHA, EDDHSA, EDTA, and DTPA. The chelates were comprehensively characterized and quantitated by several techniques, including several chromatographic methods. Iron and chelate dynamics in soil were also studied in a model alkaline and calcareous soil. Results indicate that, in this model soil, among the different iron compounds studied only FeEDDHA and analogues have the capacity to maintain soluble iron in soil solution over time. These results are in agreement with general experience under field conditions. Furthermore, among the different ortho-ortho isomers of FeEDDHA's, FeEDDHSA and FeEDDCHA showed greater capacity than FeEDDHA and FeEDDHMA to maintain the chelated iron in soil solution over time.     

Effect of mono- and divalent cations on sorption of water-extractable organic carbon and microbial activity

Biology and Fertility of Soils - Sorption is an important process for retention of organic carbon (C) in soils. The effect of Na+ and Ca2+ on sorption of organic C has been studied in salt-affected...     

Green tea polyphenols inhibit the sodium-dependent glucose transporter of intestinal epithelial cells by a competitive mechanism

Intestinal glucose uptake is mainly performed by the sodium-dependent glucose transporter, SGLT1. The transport activity of SGLT1 was markedly inhibited by green tea polyphenols, this inhibitory activity being most pronounced in polyphenols having galloyl residues such as epicatechin gallate (ECg) and epigallocatechin gallate (EGCg). Experiments using brush-border membrane vesicles obtained from the rabbit small intestine demonstrated that ECg inhibited SGLT1 in a competitive manner, although ECg itself was not transported via SGLT1. The present results suggest that tea polyphenols such as ECg interact with SGLT1 as antagonist-like molecules, possibly playing a role in controlling the dietary glucose uptake in the intestinal tract.