Antibacterial properties of commercially available plant extracts containing tannins against Escherichia coli

Abstract Escherichia coli is a gram-negative bacterium that exists as commensal microorganism and can diversify into pathogenic strains that cause illnesses in humans and animals. Whilst antibiotics are the most commonly used compounds against E.coli , many other compounds, such as polyphenols, demonstrate strong antibacterial activity. In this work, the antibacterial potential of five commercially available plant compounds: chestnut extract, mimosa extract, quebracho extract, ellagic acid and gallic acid against E.coli was investigated. In the studies, standard microbiological tests, including MIC (minimal inhibitory concentration) and MBC (minimum bactericidal concentration), were performed. Also, to better study and explain the antibacterial potential of analyzed compounds against E.coli , additional investigations involving cell membrane fluidity analyses, Zeta potential measurements, and activity against hemolysis induced by E.coli toxins has been conducted. Our results demonstrated that all five compounds have antibacterial activity, but the strongest activity is observed for ellagic acid and chestnut. Investigated compounds possess the potential to modulate E.coli membrane fluidity and to inhibit the sheep erythrocytes hemolysis evoked by E.coli toxin.