Antibacterial activity of different parts of Peganum harmala L. growing in Iran against multi-drug resistant bacteria

Peganum harmala L. (Zygophyllaceae) is one of the most famous medicinal plants used in traditional medicine of Iran. The aim of this study was to consider antibacterial effects of the methanolic extract of different parts of P. harmala including root, stem, leaf, flower and seed against some important human pathogenic bacteria. Antibacterial properties of methanolic extract of mentioned parts were assessed by disc diffusion method. Active extract was fractioned using Thin Layer Chromatography; also their synergism activity in combination with synthetic antibiotic was evaluated. Among the evaluated parts of P. harmala, the root and seed extracts presented antibacterial activity against all of tested bacteria even at the lowest concentration. Antibacterial effect of leaf part was moderate while stem and flower extracts showed relatively poor activity. Antibacterial activity of root extract against most of the tested Gram positive bacteria was better than seed extract. Tested against Gram negative bacteria the obtained results were inconsistent. MIC (Minimal Inhibitory Concentration) and MBC (Minimal Bactericidal Concentration) values for both extracts against MRSA (Methicillin Resistant Staphylococcus aureus) and for seed extract against E. coli and S. typhi were equal (0.625 mg/ml). TLC (Thin Layer Chromatography) results revealed that seed and root extracts were different in terms of nature and content of their constituents. Furthermore, these two extracts showed an excellent stability to temperature and pH treatment. Also, the seed and root extracts showed synergism in combination with novobiocin, colistin and carbenicillin. In conclusion, P. harmala can be assigned as a source of antibacterial compounds for treatment of infections caused by multi-drug resistant (MDR) bacterial pathogens.