Novel Thionins from Black Seed (Nigella sativa L.) Demonstrate Antimicrobial Activity

Black seed (Nigella sativa) is known as a good source of various biologically active compounds which possess antimicrobial properties. One of our objectives was to elaborate methods of obtaining and extracting peptides from plants. In the current study, we discovered some biological effects of thionins from black seed, such as bactericidal and fungicidal effects. Isolation of thionins performed by combining acidic extraction and fractionation with various liquid chromatography methods. The N-terminal amino acid sequences were revealed using automated Edman degradation. The antimicrobial activity of thionins were evaluated by a microdilution broth assay. A fluorescent spectroscopy and an atomic force microscopy allow to investigate the features of mode of action of the thionins. The two novel peptides from black seed (N. sativa L.), a plant endemic to Central Asia. These peptides, named NsW1 and NsW2, have a high affinity with heparin, a polysaccharide glycosaminoglycan. These molecules were indentified as thionins, a well-known family of plant antimicrobial peptides. These thionins effectively inhibit viability of Bacillus subtilus, Staphylococcus aureus and Candida albicans that has been confirmed using a bacteriological and some biophysical techniques. Obtained data indicate that black seed thionins are biologically active molecules that may be considered to be perspective antibacterial agents.