Chelated forms of inorganic minerals are very similar to biologically active substances. This property is used in agriculture for the production of fertilizers and valuable pet food additives. In medicine, such compounds are used as antidotes and dietary supplements.
What does chelate form mean?
Chelates are a complex that appears as a result of the interaction of positively charged metal ions (the central atom of the complexing agent) with ligands that form chemical compounds with various types of biomolecules. Simply put, chelates are a combination of a mineral and a complex organic compound. Ligands include amino acids, peptides, proteins, purines, porphyrins, macrolides, as well as their synthetic analogues (crown ethers, cryptands).
Chelating ligands must have more than 2 functional groups capable of creating covalent bonds and a ring structure with a metal. The word "chelate" comes from the Latin chela ("claw"). Outwardly, the form of these chemical compounds is similar to the claws of a crab holding a mineral.
In nature, the most striking representatives of this type of porphyrin-based compounds are human hemoglobin, where Fe (iron chelate) and chlorophyll (magnesium chelate) act as the center of the complexing agent. Modern biochemical technologies make it possible to obtain various forms of such substances.
Examples
3 groups of chelate forms are distinguished (depending on the ratio of the charge of the ligand to the metal ion).
- Cationic. The most common representatives are compounds of polyamines with metal ions. The liganding agent in this case is neutral, therefore, the total charge of the compound is determined by the central ion.
- Anionic. Typical anionic chelates are complexes based on ethylenediaminetetraacetic acid (EDTA).
- Neutral (intra-complex connections). The central positive charge is neutralized by the addition of an equal number of negatively charged ligands, and an “internal salt” is formed.
Many metals form stable chelates that are capable of combining into high molecular weight substances. This effect is used for the synthesis of multicomponent highly dispersed oxide materials used for the production of dielectrics, high-temperature superconductors and coatings.
Biological properties
Chelated minerals are substances that have a number of valuable characteristics, such as:
- High stability with various acidity of the medium and under the influence of microorganisms.
- Good adsorption and solubility in water.
- The biological activity of metals, unusual for them in a free state.
- Less toxic than other forms of compounds.
- High bioavailability, that is, good digestibility for both plants and animals.
- Lack of insoluble precipitate.
The absorption of minerals mainly occurs in the small intestine, and a more stable form of chelating compounds protects them from destruction by hydrochloric acid in the stomach. This property is used in medicine and animal husbandry to fill the deficiency of trace elements.
Production
Chelated forms of the compounds are obtained by chelation (or chelation). This term is not universally recognized in chemical science. The simplest way is to mix solutions of metal salts with chelating agents. As the latter, organic substances such as:
- nitrilotriacetic, ethylenediaminetetraacetic and ethylene glycoltetraacetic acid;
- tris (carboxymethyl) ethylenediamine;
- hydroxyethylidene diphosphonic acid;
- lysine;
- methionine and others.
Amino acids and small peptides are prepared under the influence of enzymes in the laboratory. When implementing the chelation process, the following parameters are taken into account:
- acidity of the medium (add alkali if necessary);
- temperature;
- ratio of substances;
- amino acid solubility.
The chelate complex in the form of a precipitate is washed in distilled water, and then dried.
Application in agronomy
Chelated fertilizers have the following advantages:
- Close affinity with biological structures, due to which substances easily penetrate through the cell membranes of plants.
- Improved solubility.
- Lower consumption of chelated fertilizers compared to conventional salts.
- Possibility of both root and foliar top dressing.
- Increase seed germination.
- Low phytotoxicity.
- Stability at various levels of soil acidity.
- Good compatibility with other chemicals, pesticides.
Chelated iron is of the greatest importance, since this element is contained in plant tissues in a more significant amount than other metals. Its deficiency leads to the development of many diseases, including chlorosis. Other chelates are also used - copper, zinc, boron, which stimulate plant growth and the formation of ovaries. In the early stages of the growing season, it is advisable to feed with calcium chelate, which contributes to the development of the root system.
Use in livestock
Chelated forms of trace elements are used to fortify the nutrition of all types of farm animals and birds. These substances in low concentrations are able to replace up to 40% of inorganic minerals and have the following effect:
- increase of immune forces during illness, pregnancy of females or in adverse conditions;
- improvement of reproductive function;
- reduction in the number of somatic cells in milk, which increases its quality (thermal stability and other technological properties);
- accelerated growth of young animals.
Chelated iron, unlike its sulfate, can easily penetrate the placental barrier. According to studies, the addition of this vitamin in the diet of sows further contributes to the birth of piglets with high weight and prevent them from developing iron deficiency.
As a result of the use of magnesium chelate, an improvement in the quality of carcasses of animals and a decrease in body fat are noted. Copper and manganese compounds help in the prevention of bone chondromatosis and damage to the cardiovascular system in poultry.
Medications
In medicine, chelated forms of the compounds are used for the following purposes:
- Antidotes for acute and chronic poisoning with heavy metals and other poisons (Unitiol, Tetatsin-calcium). When they are taken, the binding of harmful substances into closed complexes of the chelate type occurs.
- Antineoplastic agents ("Cisplatin" and others). Drugs penetrate the nuclei of affected cells, form a stable connection with DNA, which prevents their self-reproduction.
- Vitamin preparations (most often chelated calcium and iron).
Unlike free metal ions, these substances do not form compounds with other chemical elements in the stomach and intestines, so they are better absorbed in the human body. In this regard, on the basis of chelates, it is possible to create medicines and dietary supplements of a new generation.