BACKGROUND AND OBJECTIVE: Diversity of plants and the increasing tendency to use them for therapies has increased the significance of screening herbal extracts. Several researches have reported the antibacterial effects of plants. Therefore, the present study aims to investigate the antibacterial effects of methanol extract of Ammi majus.

METHODS: After preparing methanol extract (0.5, 1 and 2%), the antibacterial effects of the plant were measured according to minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), disk diffusion method (determining the zone of inhibition) and well diffusion method on Staphylococcus aureus and Escherichia coli.

FINDINGS: In well diffusion method, the lowest concentration (0.5%) created a 9±0.000 mm inhibition zone diameter, while the highest concentration (2%) created a 12.3±0.57 mm inhibition zone diameter (p<0.001). The photometric tests revealed that the methanol extract of the plant (0.5 to 1%) with mean difference of 0.04 had antibacterial effects on Escherichia coli (p<0.001). However, as the concentration increased (2%), adverse non-inhibitory effects could be observed. The tests based on colony counting method demonstrated that Ammi majus extract 0.5, 1 and 2% have antibacterial effect on Staphylococcus aureus (p<0.001). However, only the 2% extract had inhibitory effects on Escherichia coli (p<0.01).

CONCLUSION: Results of the study demonstrated that methanol extract of Ammi majus has more antibacterial effect on Staphylococcus aureus compared with Escherichia coli.