Screening of the Antimicrobial Potential of Aqueous Extracts of Some Plants Collected from the City of Narafominsk, Moscow, Russia

Background: The antimicrobial properties of medicinal plants, including those from Russian flora, can be a considerable asset in the fight against antibiotic resistance and the search for new antimicrobials. The present work aimed at assessing the antimicrobial properties of plants collected from the Narafominsk's flora, a city located on the outskirts of Moscow, Russia.

Methods: The plants were collected from June to August 2021, the extraction was carried out with water as a solvent and the antimicrobial activity of the extracts was tested on 3 referenced microorganisms from the American Type Culture Collection (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538 and Candida albicans ATCC 10231). We determined the inhibition diameters by the well diffusion method, the minimum inhibitory concentrations (MIC) & minimum bactericidal concentrations (MBC) by the microbroth dilution method.

Results: A total of 59 samples from 33 plants were extracted and included 44.1% of leaves (n=26), 32.2% of flowers (n=19), 8.5% of barks (n=5), 5.1% of whole plant (n =3) and 1 stem and 1 root (1.7%). Inhibition diameters ranged from 0 to 28 mm, MICs and MBCs from 0.5< to >128 mg/ml. 69.49% (n=41) of the plants showed an inhibition diameter greater than zero (>0 mm) against S. aureus, 42.37% (n=25) against E. coli and only 23.72% (n=14) against C. albicans. The plant parts ranked in decrease order of antimicrobial activity were as follows: flower < bark < leaf < whole plant < root < stem < fruit. The plants having shown a noteworthy antimicrobial (MIC ≤0.5 mg/ml) activity against at least 1/3 microorganisms tested and which deserve to be investigated in depth were: flowers of Epilobium angustifolium, Spirea japonica, Heracleum mantegazzianum and Saponaria officinalis, bark of Picea abies and the whole plant extract of Rumex obtusifolius. The second group (1≤ MIC ≤ 4 mg/ml) of plants with no less worthy antimicrobial abilities were flowers of Angelica sylvestris, Arctium minus, Centaurea jacea, Convallaria majalis, Melampyrum nemorosum and Physocarpus opulifolius, leaf of Achillea millefolium and Heracleum mantegazzianum, and bark of Quesrcus robur.

Conclusion: Flower extracts of Epilobium angustifolium, Spirea japonica, Heracleum mantegazzianum, Saponaria officinalis against are highly recommended for further studies since they presented the best MIC and inhibitions diameters.