Medicinal plants with significant activity against important pathogenic bacteria

Abstract

Interest in the study of medicinal plants as a source of pharmacologically active compounds has increased worldwide. This study is a broad screening of 31 plant species against a wide range of pathogenic bacteria, including Acinetobacter baumannii, Bacillus cereus, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella spp., Shigella flexneri, Staphylococcus aureus, Streptococcus mutans, and Streptococcus pyogenes. The agar disk diffusion method showed that most plants were more active against gram-positive than gram-negative bacteria. Streptococcus pyogenes was the most sensitive organism inhibited by nearly all of the extracts (97.6%), followed by Bacillus cereus (63.4%) and Staphylococcus aureus (61.0%). The ethanol extracts of Rhodomyrtus tomentosa (Aiton) Hassk. (Myrtaceae) (leaf) and Eleuterine americana Merr. (bulb) exhibited good antibacterial activity against gram-positive bacteria. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of Rhodomyrtus tomentosa ranged from 3.9 to 7.8 and 7.8 to 125 μg/mL, respectively, while those of Eleuterine americana were 120–125 and 250–1000 μg/mL, respectively. Quercus infectoria G. Olivier (Fagaceae) and Piper betle L. (Piperaceae) showed a broad spectrum of activity. The ethanol extract from the nut galls of Quercus infectoria demonstrated significant activity against all important pathogens. It inhibited the growth of all pathogens, with MIC values of 62.5–1000 μg/mL. The MBC ranged from 125 to 1000 μg/mL in most species, except Enterococcus faecalis. The ethanol extract from Piper betle (leaves) demonstrated antibacterial activity against almost all species with the same MIC and MBC values, ranging from 125 to 500 μg/mL.