Evaluation of the antimicrobial activity of Zanthoxylum zanthoxyloides root bark extracts

The development of resistance to antibiotics by infectious agents has been a continuous challenge. Thus, in this study, the aim was to evaluate the antimicrobial activities of Zanthoxylum zanthoxyloides, a potential plant source for novel antibiotics. Toward this end, dried powdered samples of the root barks of Z. zanthoxyloides were extracted successively to obtain Crude Petroleum Ether (CPE), Defatted Ethanol Ether (DEE) and Defatted Ethanol Chloroform (DEC) extracts. The antimicrobial activities indicated by the size of the Zone of Inhibition (ZOI) of each extract at concentrations 5, 10, 15, 20 and 30 μg μL -1 were evaluated against Escherichia coli (E. coli), methicillin-susceptible Staphylococcus aureus (MSSA), Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VREF) using disc diffusion method. Two sets of Analysis of Variance (ANOVA) were performed. The first set comprised separate ANOVAs for each microorganism because the positive controls were different for each microorganism, although the negative control (DMSO) was the same for all. The second set was a single combined ANOVA with all microorganisms included with their positive controls excluded. The first set of analysis showed that DEE had significantly (p\u3c0.001) higher antimicrobial activity than DMSO, CPE, or DEC. No significant interaction between extract and concentration was detected. The second set indicated a significant (p\u3c0.01) interaction effect between extract and microorganism. Although no significant differences in ZOI were observed for microorganisms exposed to DMSO, CPE and DEC; one particular microorganism VREF was found to be the most susceptible to DEE. In addition, findings of this study show the potential of Z. zanthoxyloides as a source of broad-spectrum antimicrobial compounds. © 2012 Academic Journals Inc