Phytomedicines mark the major component of health care as natural medicines have always provided the strong foothold for the discovery and manufacturing of synthetic drugs. So plants are a rich source of bioactive compounds having many therapeutic activities and majority of them are still untapped. Eucalyptus globulus is a medicinal plant known for its value to cure asthma, respiratory infections, cough and allergic reactions. The antimicrobial activity, insecticidal and hypoglycemic activity have also been credited to the plant. Most of the studies have been conducted on the essential oils of Eucalyptus globulus and little work has been reported on extracts. Whereas, sequential extracts has not been employed yet.
Hexane, chloroform and ethanol, aqueous extracts were prepared by the sequential extraction on Soxhlet apparatus and antibacterial activity was evaluated against Staphylococcus aureus, Escherichia coli, Salmonella enterica, Clostridium perfringens type A and Haemophilus paragallinarum by agar well diffusion and micro broth dilution method. The zones of inhibition and minimum inhibitory concentration were determined. The extracts showing antimicrobial activity were further evaluated for cytotoxicity by using MTT assay on Vero cell line. The cell culture media was prepared and cell lines were propagated to form monolayer then monolayer was exposed to plant extract dilutions. After 24-48 hours, MTT dye was introduced and cell survival percentage was calculated.
The statistical analysis was conducted with help of Statistic Package for Social Sciences (SPSS for windows version 16, SPSS inc, Chicago, IL, USA) and results were compared using one way ANOVA.
Summary
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The zones of inhibitions showed by hexane, chloroform, ethanol and aqueous leaf extracts of Eucalyptus globulus against Staphylococcus aureus were 0.0, 19.3, 20.3 and 23.3mm; against Clostridium perfringens type A were 14, 22.3, 14.0 and 15.3mm; against Escherichia coli were 0.0, 12.6, 13.3 and 15.6mm; against Salmonella enterica were 10, 12.3, 18.6 and 21mm; against Haemophilus paragallinarum were 0.0, 8.6, 14 and 18mm respectively. Hexane extract showed no zone of inhibition against Staphylococcus aureus, Escherichia coli and Haemophilus paragallinarum.
The MICs values of hexane, chloroform, ethanol and aqueous leaf extracts of Eucalyptus globulus against Staphylococcus aureus were 0.00, 104.1, 32.55 and 312.5 μg/ml; against Clostridium perfringens type A were 52.08, 39.06, 16.27 and 312.5 μg/ml; against Escherichia coli were 0.00, 78.12, 260.4 and 625.0 μg/ml; against Salmonella enterica were 13.02, 104.1, 130.2 and 416.6 μg/ml; against Haemophillus paragallinarum were 0.00, 104.1, 260.4 and 416.6 μg/ml respectively. MIC was not performed against Staphylococcus aureus, Escherichia coli and Haemophilus paragallinarum for hexane extract as no zone of inhibition was observed against them.
Hexane extract of Eucalyptus globulus was cytotoxic at concentration ≥ 312.5μg/ml, chloroform extract at concentration ≥ 375μg/ml, ethanol extract at concentration ≥ 625μg/ml and aqueous extract was cytotoxic at concentration ≥312.5 μg/ml.
The indigenous plant Eucalyptus globulus has antibacterial activity against common poultry pathogens and can be helpful for development of new drugs of plant origin.