Antimicrobial Activity of Citrullus Lanatus (Watermelon) Seeds on Some Selected Bacteria

Plants are reservoirs of different kinds of phytochemicals used for treatment of infections and other diseases. This study was aimed at evaluating the phytochemical and antimicrobial activity of Citrullus lanatus (watermelon) seeds against some selected bacteria. Water and ethanol were used to obtain the extracts and they were analyzed for the presence of alkaloids, flavonoids, glycosides, tannins and saponins. Out of the phytochemicals screened, only saponins were not detected in both aqueous and ethanolic extract. Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae were selected for antibiotic susceptibility testing. Antibacterial activity revealed that S. aureus, E. coli, and P. aeruginosa were most susceptible to the extracts at concentrations ranging from 6.25mg/ml to 50mg/ml. Klebsiella pneumoniae was observed to be resistant especially to the ethanolic extract. Largest zone of inhibition (8 mm) was produced against P. aeruginosa using aqueous extract at 50mg/ml. Higher concentrations were generally efficacious than the lower concentration whereas, ciprofloxacin (control) exert better activity than either of the extracts. Results for the MIC and MBC suggest that the constituents of the extract could be bactericidal as they were in close range. The findings of this study showed that seeds of C. lanatus contained bioactive compounds with potent antibacterial activity and thus could be used as herbal preparations just as the other parts of the plant.