Drugs based on plants of the Asteraceae family are broadly used against microorganisms that are pathogenic to people and animals. However, their potentials in this aspect have not been fully researched. In our in vitro experiment, we tested alcohol tinctures of 12 species of plants of the Asteraceae family against 10 species of bacteria, one species of fungi, and the larval stages of three species of nematodes – parasites of ruminants (L1 Muellerius capillaris, L1–3 Strongyloides papillosus, L3 Haemonchus contortus). The growth inhibition zone larger than 8 mm was observed after using ethanol extracts of the aboveground parts of several plants against the colonies of various microorganisms: Solidago canadensis showed activity against five species – Klebsiella pneumoniae, Proteus mirabilis, Shigella flexneri, Clostridium perfringens, and Candida albicans; Cyclachaena xanthiifolia was effective against five species – Escherichia coli, P. mirabilis, Enterococcus faecalis, C. perfringens, and C. albicans); Jurinea arachnoidea inhibited four species – K. pneumoniae, P. mirabilis, Pseudomonas аeruginosa, and Bacillus subtilis); Scorzoneroides autumnalis acted against four species – P. mirabilis, Sh. flexneri, C. perfringens, and C. albicans; Helichrysum arenarium demonstrated activity against four species – P. mirabilis, Sh. flexneri, E. faecalis, and Listeria monocytogenes; and extracts from the fruits of Echinops ritro were active against four species – K. pneumoniae, P. mirabilis, Staphylococcus aureus, and B. subtilis, while extracts from the flowers of Echinops ritro were effective against four microorganisms – K. pneumoniae, P. mirabilis, Sh. flexneri, and Р. аeruginosa. However, we observed no expressed nematocidal action of ethanol extracts of the studied species of plants. After 24 h exposures to 0.1% solutions of those extracts, over 95% of the nematode larvae of ruminants were found to be vital. Nonetheless, as a result of the study, those plants were recognized the most promising for further in vivo research of antibacterial activity. During the search for antibacterial and antifungal activities, the following plants were found to be the less promising: the aboveground parts of Artemisia austriaca, Lactuca serriola, Ambrosia artemisiifolia, Solidago virgaurea, roots of Artemisia vulgaris, Echinops ritro, Lactuca serriola, Solidago canadensis, Ambrosia artemisiifolia, Scorzoneroides autumnalis, and leaves of Echinops ritro.
