EFFECT OF PLANT EXTRACTS ON BACTERIAL GROWTH AND POTENTIAL MECHANISM OF ACTION

Abstract

Mentha piperita and Melissa officinalis are both well-known medicinal plants that have applications in traditional medicine. In this research the antibacterial activity of the ethanol extracts of M. piperita and M. officinalis was examined against 14 bacterial strains via the microdilution method. Minimum inhibitory concentrations of ethanol extracts of both plant species ranged from 0.312 to 20 mg/mL. Standard strains of Staphylococcus aureus ATCC 25923 at a concentration of 0.312 mg/mL and Bacillus subtilis ATCC 6633 at a concentration of 1.25 mg/mL showed the highest sensitivity to the ethanol extract of M. piperita. Ethanol extract of M. officinalis showed antibacterial activity on standard strains of S. aureus ATCC 25923 and B. subtilis ATCC 6633 at a concentration of 0.625 mg/mL. In addition to the mentioned standard strains, it showed activity on the isolate from the food Proteus spp. at a concentration of 0.312 mg/mL and isolate from the wound Proteus mirabilis at a concentration of 0.625 mg/mL. Mechanism of action of the ethanol extract of M. officinalis was examined on the permeability of the bacterial cell membrane. The effect of the extract on the increased permeability of the cell membrane was measured based on the release of proteins and the percentage of crystal violet binding. Ethanol extract of M. officinalis has been shown to act at the level of the cell membrane in the following bacterial strains of Pseudomonas aeruginosa, S. aureus and Enterococcus spp.