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 simensis
Hochst. ex. A. Rich. is one of the endemic medicinal plants used for the treatment of bacterial and fungal
infections in Ethiopian folklore medicine. The aim of this study was to investigate the antimicrobial activity
of 80% methanol extract and solvent fractions of the leaves of U. simensis. The 80% methanol extract was
prepared 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 of
the extracts was evaluated on eight bacterial and two fungal species using agar well diffusion method at
concentrations of 200, 400 and 800 mg/ml. Minimum inhibitory concentrations (MICs) were determined by
broth microdilution method. From the gram positive bacteria tested, the most susceptible species was
Streptococcus pneumoniae (MIC of 1.36 mg/ml), while Klebsiella pneumoniae and Aspergillus niger were
most 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. Results
of 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.