Antibacterial activity of Senna siamae leaf extracts on Salmonella typhi


Doughari J. H and Okafor N. B

The aqueous and organic leaf extracts of the plant Senna siamae, traditionally used for the treatment of infectious disease, were tested for their activity against clinical isolates of Salmonella typhi using the disc diffusion method. The ethanol extracts showed the highest activity (zone of inhibition 10 ± 0.01 mm), followed by acetone extracts (zone of inhibition 8 ± 0.01 mm), while the aqueous extracts showed the lowest activity (zone of inhibition 3.5 ± 0.01 mm) at 40 mg/ml concentration. Preliminary phytochemical studies revealed the presence of alkaloids, saponins, tannins and glycosides. The activities of the extracts were comparable to those of ampicillin, chloramphenicol, cotrimoxazole and ciprofloxacin antibiotics (t-test; p < 0.05) . The antibacterial activities of the extracts against S. typhi did not change significantly when treated at 4, 30, 60 and 100°C for 1 h, but reduced significantly at pH 6 to  10. The MIC and MBC values of the crude extracts (1 - 3 mg/ml) were comparable to those of the tested antibiotics (0.3 - 1 mg/ml) (t-test; p < 0.05). Preliminary purification of the ethanol extracts with hexane, ethyl acetate, chloroform and n-butanol showed that the ethyl acetate fraction possessed the highest activity (zone of inhibition 15 mm), followed by n-butanol fraction (zone of inhibition 2 mm), while the chloroform fraction did not show any activity at 20 mg/ml. 

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