Antibacterial and Antifungal Activity of Ethanol Extracts from Centaurea montana, Centaurea macrocephala and Psephellus dealbatus, Depending on the Phases of Their Phenological Development

Background: Plants are an important source of biologically active compounds that can be used as crop protection agents. When using them, it is important to take into account the period when these biologically active substances accumulate in the plant to the maximum level. This article presents the results of a study on the antibacterial and antifungal activity of ethanol extracts obtained from Centaurea montana, Centaurea macrocephala and Psephellus dealbatus at different stages of their development. Methods: Plants of Centaurea montana, Psephellus dealbatus and Centaurea macrocephala were grown in the experimental fields of the Tatar Research Institute of Agriculture in the Republic of Tatarstan, Russian Federation. Extracts were prepared from the freshly harvested biomass using single maceration with stirring. In experiments, the minimum inhibitory concentration (MIC) of bacterial and fungal extracts from C. montana and P. dealbatus and C. macrocephala were determined using a double sequential dilution method in a liquid medium. To determine the minimum bactericidal and fungicidal concentrations (MBC and MFC), 10 μl of an inoculum (or a piece of fungal mycelium) was added to agarized nutrient media in Petri dishes using a bacteriological loop, taken from test tubes without visible growth. Result: Extracts from the buds, flowers, leaves and stems of these plants exhibited the greatest antimicrobial activity during the budding and early flowering stages. Bacterial growth was inhibited at an extract concentration of 625 µg/ml and fungal growth at a concentration of 312 µg/ml. The data obtained demonstrates the potential of using these ethanol extracts as herbal preparations for combating plant pathogens during the budding and early flowering periods.