Determining the Efficacy of Ethanolic, Ethyl Acetate and Chloroform Extracts of Thymus Vulgaris and Nepeta Binaloudensis Medicinal Plants on the Inhibition and Removal of Standard Bacteria from Aquatic Environments

Investigating the antimicrobial effects of medicinal plant extracts is important in terms of efficiency in removing or reducing water and wastewater bacteria. Plant extract can be used as a natural and affordable disinfectant. This study aims to determine the minimum inhibitory concentration (MIC) and minimum lethal concentration (MBC) based on the extracts of Thymus vulgaris and Nepeta binaloudensis medicinal plants.

The type of study in this research was experimental and of laboratory type. Water samples containing bacteria were used as the studied population. To carry out this research, three types of ethanolic, chloroform and ethyl acetate extracts related to the aerial parts of two medicinal plants, Thymus vulgaris and Nepeta binaloudensis, were prepared using rotary and seven standard bactericidal strains relating to water and wastewater were investigated. Five different concentrations of 3.1, 6.25, 12.5, 25 and 50 ppm were used on bacteria to determine the minimum inhibitory concentration (MIC) and minimum lethal concentration (MBC) by microdilution method. SPSS16 software and a one-way variance test were used for data analysis.

The results showed that for the Thymus vulgaris plant, the lowest inhibitory concentration and the lowest lethal concentration are related to all three types of extracts. Therefore, Listeria monocytogenes and Shigella dysenteriae bacteria were inhibited and eliminated at concentrations of 3.1 ppm and 6.25 ppm, respectively. The lowest inhibitory concentration and the lowest lethal concentration were related to the extract of chloroform and ethyl acetate, which inhibited and eliminated Shigella dysenteriae and E. coli bacteria at concentrations of 3.1 and 6.25 ppm, respectively. The ethanolic extract of St. John's wort did not affect Shigella dysenteriae bacteria.

This study showed that the Thymus vulgaris plant has better potential for antibacterial properties and disinfection for water and wastewater. Therefore, the compounds of this plant can be used for future studies to design an antimicrobial agent as an alternative to chemical disinfectants.