Antimicrobial Activity of Different Extracts and Fractions of Marrubium parviflorum

Background and purpose: Marrubium plants have long been used as a traditional medicine in treatment of diseases. The aim of this study was to evaluate the antimicrobial effects of Marrubium parviflorum extracts and fractions. Materials and methods: In this experimental study, solvent extraction from aerial parts of the plant was done by Soxhlet method. The antimicrobial effect of the extracts was evaluated on six strains of gram-positive bacteria, four strains of gram-negative bacteria, and one strain of fungus. Also, effective extracts were fractionated by various chromatographic methods and their antimicrobial effects were investigated. Results: Chloroform extract of M. parviflorum was found to be effective against Micrococcus luteus, Staphylococcus epidermidis, and Bacillus cereus with a growth inhibition zone diameter (DIZ) of 16.6, 14.6, and 11.6 mm, respectively, and MBC 100 mg/ml. Methanolic extract also showed considerable antimicrobial effects against Proteus mirabilis and Psudomonas aeruginosa. Among the fractions obtained, 10%, 20%, 40%, and 60% fractions of the chloroform extract and 20% and 40% fractions of the methanolic extract showed the highest antimicrobial effect. The superior values ​​of MBC and DIZ in fractions indicate the condensation of certain antimicrobial compounds in some fractions and higher sensitivity of gram-positive bacteria compared with gram-negative bacteria. Conclusion: Among the extracts studied, the chloroform and the methanolic extracts of M. parviflorum exhibited the strongest antimicrobial effect and Micrococcus luteus was the most sensitive microorganism.