The preparation of special formulations which allow for a controlled release of the formulation constituents, jointly with the protection of said constituents against interaction with the environment in order to minimise their degradation and optimise their efficiency, is of great interest. This fact is particularly evident in the field of trace element nutrition in plants and animals, as well as humans.
Thus, in the area of vegetable nutrition, in the case of plants cultivated in basic and calcareous soils, the rapid precipitation of metal trace elements, primarily iron, copper, manganese, zinc and cobalt, due to the alkaline pH and the formation of insoluble salts, such as carbonates, makes it necessary to carry out nutrition of these trace elements by means of special compounds—organic chelates—which have the capacity to protect the trace elements against the soils' blocking reactions (Abadía, J., Álvarez-Fernández, A., Rombola, A. D., Sanz, M., Tagliavini, M., Abadía, A., 2004. Technologies for the diagnosis and remediation of Fe deficiency. Soil Sci Plant Nutr 50, 965-972). These chelates are formed by synthetic molecules, the most efficient and widely used being EDDHA chelates, for Fe(III), and EDTA chelates for the other trace elements (Abadía, J., Álvarez-Fernandez, A., Rombola, A. D., Sanz, M., Tagliavini, M., Abadía, A., 2004. Technologies for the diagnosis and remediation of Fe deficiency. Soil Sci Plant Nutr 50, 965-972). However, these compounds raise significant problems.                From a nutritional standpoint, the co-absorption of the chelate through the root causes metabolic changes in the plants, which, in turn, cause significant problems in the quality of the fruit (Bienfait, F., García-Mina, J. Ma, Zamarreño, A Ma, 2004. Distribution and secondary effects of EDDHA in some vegetable species. Soil Sci. Plant Nutr., 50, 1103-110).        From an environmental standpoint, the low or null biodegradability of the chelates used leads to significant soil and water pollution problems (Abadía, J., Álvarez-Fernández, A., Rombola, A. D., Sanz, M., Tagliavini, M., Abadía, A., 2004. Technologies for the diagnosis and remediation of Fe deficiency. Soil Sci Plant Nutr 50, 965-972).        From the standpoint of product efficiency, the product's high solubility in water favours lixiviation and losses.        
In the area of animal and human nutrition, special compounds are needed which improve or favour the adequate bioassimilation of the trace elements provided. This is particularly important in ruminants, the microbiological activity whereof involves the immobilisation of a significant concentration of the trace elements provided, since they are used by the ruminant's microorganisms. Currently, these formulations primarily consist of trace element chelates with amino acids and peptides (Ashmead, H. D., 1993. The roles of amino acid Chelates in Animal Nutrition. Noyes Publication. New Jersey, USA). However, the large problem that these compounds raise is the high biodegradability of the amino acids, as well as the low stability constant of the complexes which they form (Ashmead, H. D., 1993. The roles of amino acid Chelates in Animal Nutrition. Noyes Publication. New Jersey, USA).
This invention offers a solution to the above-mentioned problems by using a formulation that contains compounds present in nature, which are innocuous for the environment, capable of protecting the trace element against the soils' blocking reactions (formation of hydroxides and carbonates), and which facilitate a gradual release, thus controlling lixiviation phenomena and leading to a beneficial effect on the plant's development; moreover, it intends to protect, in both monogastric animals and in humans, the trace elements provided against reacting in the intestine with compounds that might lead to the precipitation thereof (for example, through the formation of phytates), by means of formulating chelates/compounds which improve their bioassimilation in the intestine.
Similar inventions are already known in the state of the art, but they are substantially different from the solution offered in this application. U.S. Pat. No. 6,080,220 describes the obtainment of a special humic-acid-iron complex and its use in correcting iron chlorosis. This complex describes the use of pyrophosphate in order to reduce aggregation processes during preparation of the complexes.
U.S. Pat. No. 5,354,350 discloses the obtainment of a water-insoluble humic acid-Fe(III) complex which is prepared in the presence of an inorganic phosphate.
U.S. Pat. No. 4,786,307 discloses the preparation of chelated micronutrients by mixing fulvic acids with different EDTA hydroxy acids and analogous acids. This invention excludes fulvic acids for two main reasons: (i) when mixed with hydroxy acids with chelating capacity, the low stability of the fulvic-acid-metal complexes/chelates leads to the formation of the complex with the hydroxy acid and not to the mixed complex involving fulvic acid and the hydroxy acid; (ii) fulvic acids are highly degradable by microorganisms, therefore, their complexes do not provide protection against microbial degradation.
U.S. Pat. No. 4,425,149 discloses the preparation of a chelating agent by mixing leonardite (32%) with citric acid (3%), nitric acid (1%) and methanol (64%). This treatment of leonardite in an acidic alcoholic medium will generate the extraction of fulvic acids from leonardite (Stevenson, F. J., 1994, Humus Chemistry, Second Edition. Wiley. New York); therefore, the final chelating agent (once the methanol has been eliminated) would be formed by fulvic acids and citric acid. As noted above, this invention does not consider fulvic acids due to the low stability constant of their metal complexes and their high susceptibility to being attacked and degraded by microorganisms.
U.S. Pat. No. 4,698,090 considers a method of extracting humic substances from leonardite by means of reaction with different substances, including inorganic acid salts. In no case does this patent disclose the formation of mixed or heteromolecular complexes of the type disclosed in this invention, nor are the reaction conditions (primarily stoichiometry) adjusted in order for these complexes to form. Likewise, the high reaction pHs (highly basic) disclosed in this patent would prevent the formation of the complexes.
Finally, U.S. Pat. No. 6,649,566 considers the preparation of mixtures of humic substances with salicylic acid and chitosan, but in no case does it consider the formation of humic acid-metal-salicylic acid complexes or formulations designed for the gradual release of salicylic acid.