Mechanism of the action of humic substances on living cells
The mechanism of the interaction of living cells with polymers with irregular structures of the humic acid type began to be formed in the earliest stages of the development of living organisms.
Polymers with irregular structure were formed before living organisms and later existed alongside them. These connections are capable of hydrophilic-hydrophobic cooperation, have their own antiradical, antioxidant and radiation-protective action and can act as ligands for metal ions. Irregular polymers bear parts that organisms can employ as a source of energy or as a building block in the synthesis of cellular components. Hypotheses have been formulated that elucidate the action of natural humic substances as a complex of effects that, as a consequence, lead to the action of humic acids as immediate participants in the metabolic processes in living cells.
Kristian de Duve (1964) elucidated the mechanism of transfer of molecules of humic acids into cells as a transfer pathway based on intracellular conversion of large molecules and particles. The theory of this kind of transfer, and this is very important, does not permit direct contact of the humic acid molecule with the cell components. The acceptance of large molecules by the cells occurs as a result of endocytosis and they are further changed in the digestive vacuoles, formed following combination of endocytic vesicles with lysosomes. All the basic classes of biopolymers that enter the “peripheral part” of humic acid molecules or that are bonded to them non-covalently (proteins, polysaccharides, nucleic acids, lipids) are decomposed by ferments contained in the lysosomes. Fermentation hydrolysis leads to the formation of amino acids, sugars and nucleotides, which diffuse into the cytoplasm and participate in metabolic processes. Unaccepted residues of humic acids (in principle, the “nucleus”) leave the cell during exocytosis.
The frequent positive results of experiments to discover labeled humic acids within the cell can be explained particularly by the process of partial intracellular conversion.
The biological action of humic acids on living organisms is based on the fact that the intact molecules of humic acids and high-molecular residues of their intracellular conversion are localized in the cell walls or the outer layers, which immediately combine with the cytoplasmic membrane. In this way, an analogue of an active filter capable of fulfilling the following functions is formed in this way:
- combining with heavy metal ions and converting them into stable chelate-type complexes;
- combining with xenobiotic molecules;
- combining free radicals formed in the plasmatic membrane as a consequence of oxygenation of lipids.
It cannot be excluded that low-molecular-weight parts of humic substances can be formed during the intracellular conversion of humic acids and also during their passage through the cell walls, and that these substances are independent, biologically active connections acting on the living cell.
Consequently, the effect of humic preparations on the living organism is derived directly from the content of its low-molecular part. A higher content of fulvic acids is desirable.
A general consequence of the described joint effects of the action of humic substances on living cells is the release of energy that, instead of being wasted in compensation of the negative effects of the external environment, can be used by the cell for growth and reproduction.