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 food supplements for pets. In medicine, such compounds are used as antidotes and dietary supplements.
What does "chelated 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 the metal. The word "chelate" comes from the Latin chela ("claw"). Outwardly, the shape of these chemical compounds is similar to the claws of a crab holding a mineral.
In nature, the brightestrepresentatives 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
There are 3 groups of chelate forms (depending on the ratio of the charge of the ligand and the metal ion).
- Cationic. The most common representatives are compounds of polyamines with metal ions. The liganding agent in this case is neutral, so the total charge of the compound is determined by the central ion.
- Anionic. Typical anionic chelates are complexes based on ethylenediaminotetraacetic acid (EDTA).
- Neutral (intra-complex compounds). The central positive charge is neutralized by adding an equal number of negatively charged ligands, thus forming an "inner s alt".
Many metals form stable chelates that are capable of combining into macromolecular substances. This effect is applied to 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 resistance to various acidity of the environment and under the influence of microorganisms.
- Good adsorption and solubility in water.
- Biological activity of metals, unusual for them in the free state.
- Less toxicity compared to other forms of compounds.
- High bioavailability, i.e. good digestibility for both plants and animals.
- No insoluble sediment.
Minerals are mostly absorbed in the small intestine, and the more stable chelate form protects them from being destroyed by hydrochloric acid in the stomach. This property is used in medicine and animal husbandry to compensate for micronutrient deficiencies.
Production
Chelated forms of compounds are obtained by chelation (or chelation). This term is not generally recognized in chemical science. The simplest method is mixing solutions of metal s alts 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 environment (if necessary, add alkali);
- temperature;
- substance ratio;
- amino acid solubility.
The precipitated chelate complex is washed in distilled water and then dried.
Agronomic applications
Chelated fertilizers have the following benefits:
- Close affinity with biological structures, due to which substances easily penetrate plant cell membranes.
- Improved solubility.
- Less consumption of chelated fertilizers compared to conventional s alts.
- Possibility of both root and foliar feeding.
- 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 found in plant tissues in greater quantities 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 chelated calcium, which promotes the development of the root system.
Animal use
Chelated forms of microelements are used to fortify the nutrition of all types of farm animals and birds. These substances in small concentrations can replace up to 40% of inorganic minerals and have the following effect:
- boost immunestrength during illness, pregnancy of females or in adverse conditions;
- improvement of reproductive function;
- decrease in the number of somatic cells in milk, which improves its quality (thermal stability and other technological properties);
- acceleration of growth of young animals.
Chelated iron, unlike its sulfate, can easily cross the placental barrier. Studies have shown that adding this vitamin to the diet of sows promotes later birth of piglets with a large weight and prevents them from developing iron deficiency.
As a result of the use of magnesium chelate, there is an improvement in the quality of animal carcasses, a decrease in body fat. Copper and manganese compounds help prevent bone chondromatosis and cardiovascular disease in poultry.
Drugs
In medicine, chelate forms of compounds are used for the following purposes:
- Antidotes for acute and chronic poisoning with heavy metals and other poisons ("Unithiol", "Tetacin-calcium"). When they are taken, harmful substances are bound into closed chelate-type complexes.
- Antineoplastic drugs ("Cisplatin" and others). Drugs penetrate the nuclei of affected cells, form a stable connection with DNA, which prevents them from self-reproducing.
- Vitamin preparations (most often chelated calcium and iron).
Unlike free metal ions, these substances do not formcompounds with other chemical elements in the stomach and intestines, so they are better absorbed in the human body. In this regard, based on chelates, it is possible to create medicines and dietary supplements of a new generation.
