Comparative study of plant extracts as broad-spectrum antibacterial agents

Plants with an established history of medicinal uses were tested against various microorganisms in this study. We compared the antibacterial activity of methanol, ethanol, and water extracts of three plant species, including Origanum syriacum, Thymus vulgaris, and Carica papaya, which commonly grow in open habitats or mountainous areas with well-drained soil. The methanol and ethanol extracts of the three plants had high antibacterial activity against Escherichia coli, Campylobacter jejuni, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pyogenes, and Shigella sonnei. Water extracts of O. syriacum and T. vulgaris showed an inhibitory effect against the tested bacteria, while the water extract of C. papaya was less effective. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were reflected in the inhibitory activity with MICs of 2 μL after treating with O. syriacum and T. vulgaris extracts, and MBCs of 4 and 8 μL with O. syriacum and T. vulgaris extracts. An assay of secondary compounds revealed the presence of alkaloids, flavonoids, glycoside, cardiac glycoside, terpenoids, anthraquinones, and tannins. We conclude that O. syriacum, T. vulgaris, and C. papaya have bioactive compounds that combat a broad spectrum of bacteria.