In-vitro antibacterial effects of methanolic extract of peppermint (Mentha Piperita Lamiaceae) on standard Staphylococcus aureus, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa strain

Microbial resistance to antibiotics is one of the most common problems in the health care system. Therefore, many efforts have been performed to find new compounds as antimicrobial compounds. This study carried out to investigate the in-vitro antibacterial effect of methanolic extract of peppermint on standard Staphylococcus aureus, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa strain.

In this experimental laboratory study, after collecting and performing pharmacognosy evaluations, methanolic extract of the peppermint plant was prepared and its antimicrobial effects on several bacteria were determined at concentrations of 20 to 400 mg/ml using the agar well diffusion method, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC)  methods. The test was repeated five times for each bacterium and the collected data were analyzed using SPSS software.

It was revealed that the methanolic extract of peppermint had antimicrobial effects against standard Staphylococcus aureus, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa. The highest effect was observed in S. aureus and the least in P. aeruginosa.  MIC and MBC of methanol extract on S. aureus, B. cereus, E. coli, and P. aeruginosa were 6.5-15.5, 15.5-25, 50-100, and 100-200 mg/ml, respectively.

The results of this study reveal that peppermint can be considered as an antibacterial medicinal herb and that if the concentration of the extract is higher, its antibacterial properties will also increase. Thus, it can be used as an alternative to the usual chemical drugs in the treatment of infections after evaluating their effects in vitro.