In Vitro Antimicrobial Activity of 80% Methanol Extract and Solvent Fractions of Urtica simensis Hochst. ex. A. Rich. (Urticaceae) Leaves against Pathogenic Bacteria and Fungi

Abstract

Medicinal plants have been used for the treatment of infectious diseases since a long time. Urtica simensisHochst. ex. A. Rich. is one of the endemic medicinal plants used for the treatment of bacterial and fungalinfections in Ethiopian folklore medicine. The aim of this study was to investigate the antimicrobial activityof 80% methanol extract and solvent fractions of the leaves of U. simensis. The 80% methanol extract wasprepared by maceration and the solvent fractions were obtained by successive fractionation of the 80%methanol extract with chloroform, ethyl acetate, n-butanol and distilled water. The antimicrobial activity ofthe extracts was evaluated on eight bacterial and two fungal species using agar well diffusion method atconcentrations of 200, 400 and 800 mg/ml. Minimum inhibitory concentrations (MICs) were determined bybroth microdilution method. From the gram positive bacteria tested, the most susceptible species wasStreptococcus pneumoniae (MIC of 1.36 mg/ml), while Klebsiella pneumoniae and Aspergillus niger weremost susceptible gram negative bacterial and fungal species with MIC values of 2.54 and 3.13 mg/ml,respectively. The least values of MIC, MBC and MFC were 1.36, 5.21 and 6.25 mg/ml, respectively. Resultsof the present study revealed that the 80% methanol extract and solvent fractions, of the leaves of U.simensis, with the exception of the aqueous fraction, possess activity against the growth of selected pathogenic bacterial and fungal species. Among the solvent fractions, the n-butanol fraction was the most active fraction against the gram positive bacteria tested, while the ethyl acetate fraction was the most active fraction against the other tested organisms. Further studies are needed to isolate the active principles, elucidate the mechanism of antimicrobial action, determine in vivo antimicrobial activity and effect of the extracts on other pathogens including clinical isolates.