Extracts of leaves of Eucalyptus camaldulensis and Eucalyptus torelliana were screened phytochemically for the presence of secondary metabolites and for in vitro antibacterial properties. Methanol and dichloromethane extracts of leaves of Eucalyptus camaldulensis and Eucalyptus torelliana were studied for their antibacterial activity against 8 clinically isolated organisms of gastrointestinal origin viz., Klebsiella species UCH 2101, Proteus mirabilis UCH 2102, Proteus mirabilis UCH 2204, Salmonella typhi UCH 2201, Escherichia coli CHO 3101, Escherichia coli UCH 2103, Pseudomonas aeruginosa CHO 3102 and Pseudomonas aeruginosa UCH 2203. The result of the phytochemical screening showed that both extracts contained tannins, saponins, cardiac glycosides but in addition to these, E. torelliana was found to contain anthraquinones. Both extracts were also found to inhibit all the isolates at 10mg mL-1 concentration. The diameter of zones of inhibition exhibited by the extracts was between 10mm and 22mm. The methanol extracts compared favorably with gentamycin used as a standard control. The minimum inhibitory concentrations determined by the agar dilution method were between 0.04mg mL-1 and 10mg mL-1.
The results obtained from this study reveals that extracts of Eucalyptus camaldulensis and Eucalyptus torelliana possess antibacterial activities against enteric pathogens and the extracts may be a potential source of new antimicrobials against enteric organisms
