Abstract:
Plant materials continue to play a major role in the primary health care as therapeutic remedies
in many developing countries. Three medicinal plants: Moringa oleifera, Azadirachta indica,
and Lepidium sativum which were traditionally believed to have medicinal values for the
treatment of various infectious diseases were investigated for their antibacterial activities
against Staphylococcus aureus, Salmonella Typhi, streptococcus agalactiae and Shigella boydii.
Two solvent types (methanol and distilled water) were used for extraction by maceration. The
susceptibility of the pathogen to the antibacterial substances was determined using the disc
diffusion method. Minimum Inhibitory Concentration was determined by the broth dilution
method. The results of the antibacterial activities revealed that both methanol and aqueous leaf
extracts had inhibitory activities against the selected gram-positive and gram-negative test
pathogens. Methanol extract of Moringa oleifera had the highest antibacterial activity (13.3 mm)
against Staphylococcus aureus and Salmonella Typhi, while Azadirachta indica exhibited the
least zone of inhibition (8.2 mm) against Shigella boydii at a concentration of 150 mg/mL.
Aqueous extracts of Moringa oleifera showed the highest antibacterial activity (10.6 mm)
against Staphylococcus aureus and the lowest antibacterial activity (6.6 mm) against Shigella
boydii at a concentration of 150 mg/mL. The Antibacterial activities of heat treated crude
extracts against the test pathogens were also determined at varying temperature (45-55ºC) for a
period of 30 and 60 minutes. The results revealed that at higher temperature and exposure time,
there was a decrease in the zone of inhibitions. The Minimum Inhibitory Concentrations of the
methanol extracts ranged from 1.25 mg/ml - 5 mg/mL; whereas, for aqueous extracts ranged
from 2.5 mg/mL -10 mg/mL. In general, this study provides base line information for further
work on the search for specific active compounds from the selected plant leaf extracts against
two Gram negative and Gram positive pathogenic bacteria
