Author(s):

Mai Abdalla Ali, Weshahshrafaldein Taha Mohammed, Awad M Abd El-Rahim, Yassir Mohamed Hassan and Ivan Kahwa

Abstract: Guava (Psidium guajava) and Eucalyptus camaldulensis are phytotherapeutic plants used in folk medicine, either as a single plant or mixed to treat and manage various diseases like diarrhea and coughs. This study aimed to determine the antimicrobial potential of guava and Eucalyptus camaldulensis leaf extracts against gram-negative bacteria (Escherichia coli) which are some of the foodborne and spoilage bacteria, occasionally responsible for causing diarrhea. The study was carried out at the Plant Pathology Center, the University of Gezira during the period. The efficacy of these extracts was tested against this bacteria through the disc diffusion and well diffusion methods. Aqueous extract of plant material (DW) powder (50g/500ml) was used to prepare different concentrations (25, 50 and 100% the extract). Both water and antibiotic (Ampiclox) were used as control. According to the results of the antibacterial assay, the aqueous extract of the guava leaves showed inhibitory activity against the E.coli, with mean zones of inhibition of (11 And 14 mm) by the disc diffusion method and the well-diffusion method respectively, whereas, the aqueous extract of the E. camaldulensis leaves showed mean zones of inhibition of (11mm and 13mm) on both methods respectively. According to the results, no significant differences were found between the two plants at the different concentrations (P value= 0.846). The combination of (P. guajava and E. camaldulensis) at different concentrations showed relatively synergistic antimicrobial activity with inhibition zone range between (15mm and 17mm) compared to the controls that gave means of inhibitions range between (13 mm and 14mm). On the high of the obtained results, guava and E. camaldulensis leaf-extract might be a good candidate in the search for a natural antimicrobial agent against E.coli. Further studies showed to be done, to determine the antimicrobial activities against other types of bacteria and investigate other pharmacological properties of the two plants.

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