LECTINS OF SAMBUCUS NIGRA AS BIOLOGICALLY ACTIVE AND DNA-PROTECTIVE SUBSTANCES

The human genome is affected by diverse environmental pollution factors and this is particularly acute for Ukrainians who have suffered from the Chernobyl radiation disaster. At the same time many natural compounds, especially from medicinal plants, are known as agents that prevent DNA lesions which often result in increasing mutagenesis and carcinogenesis. The aim of our work was to study the DNA-protective potential of biologically active compounds found in Sambucus nigra called lectins, a very large group of universally occurring proteins that recognize and specifically bind to carbohydrates/glycoconjugates. Various physiological activities of lectins based on protein-carbohydrate interactions have been demonstrated in all living forms. For example, lectins participate in host defense in plants against stress-related conditions, the attack of phytopathogens and phytophagous insects, as well as modulation of immune response, mitogenic stimulation or induction of apoptosis in animals. Antiviral, immunomodulating, antioxidant and insulin-stimulating properties of S. nigra fruit and flower extracts have been described in scientific literature. Also the elderberry lectins were found in roots, leaves, bark, seeds and fruits, the latter (SNA-IV) being the predominant protein in the juice. In Ukraine, various parts of S. nigra plants are used in folk medicine. Using methods of isoelectric focusing and chromatography, we determined that elderberry flowers and pollen contain rather high levels of lectins agglutinating animal and human erythrocytes, which differ from a commercial preparation of S. nigra bark lectin (SNA-I). The major lectin found in inflorescences, named SNAflu-I, is GalNAc/Gal specific and is supposed to be a heterotetramer with subunits of about 30 and 33 kDa. Sambucus nigra lectins demonstrated protective effects against heavy metals (nickel ions) in soil bacteria Bacillus subtilis. Also it was shown that lectins under study can modulate, in a concentration-dependent manner, the frequency of mutations and genotoxic activity of alkylating agents in eukaryotic cell cultures. Studies focused on the elucidation of cell targets sensitive to S. nigra lectins and demonstrated that at least one of the targets may be the DNA-dependent synthesis of RNA – the way to modulate gene expression. The results obtained lead to the conlusion that the protective functions of lectins both in pro- and eukaryotes involve complex mechanisms including components of the DNA repair system.