Comparison of Antimicrobial Effects of Melissa Officinalis and Impatiens Walleriana Extracts against Several Species of Pathogenic Bacteria

Emergence of resistance to antimicrobial medications has led to the use of medicinal herbs for the treatment of infections. In this regard, this study aimed to investigate the antimicrobial effects of three extracts (i.e., ethanol/methanol, water, and acetone) of Melissa officinalis and Impatiens walleriana on four species of bacteria.

The selected bacteria, including Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Enterococcus were first activated in the culture medium of broth neutrinos. Subsequently, a suspension equivalent to half McFarland was prepared from the activated bacteria. Antimicrobial activities of the extracts were evaluated by microdilution broth and disc diffusion methods to determine the minimum inhibitory and bactericidal concentration values.

Based on the results, the Impatiens walleriana acetone extract had the most antimicrobial effects on all four species of bacteria. Moreover, acetone and ethanol/methanol extracts of Impatiens walleriana had more antimicrobial effects on E. coli than ethanol/methanol and water extracts of Melissa officinalis. In case of S. aureus, the water and ethanol/methanol extracts of both plants had almost the same minimum bactericidal and inhibitory concentration values. Finally, it can be said that all three Melissa officinalis extracts had better antimicrobial effects on Enterococcus and B. subtilis than the three Impatiens walleriana extracts.

Among all extracts, acetone extract of Impatiens walleriana showed the highest antibacterial property. Given the results and the increasing resistance of bacteria to antibiotics, it is suggested to use antibacterial compounds of plants for the treatment of infectious diseases; nevertheless, further studies should be carried out in this regard.