Comparative Investigation of the Antibacterial and Antifungal Potentials of the Extracts of Watermelon (Citrullus lanatus) Rind and Seed

Abstract

Aim: To investigate the antibacterial and antifungal potentials of the crude ethanol and aqueous extracts of watermelon (Citrullus lanantus) rind and seed.  Study Design: The fruits were purchased from a local market and identified in the Department of Plant Science and Biotechnology, Michael Okpara University of Agriculture Umudike, Nigeria by a taxonomist. The rind and seed samples were extracted using ethanol (95%) and water and the crude extracts screened for antibacterial and antifungal potentials. Place and Duration of Study: Department of Biochemistry, Michael Okpara University of Agriculture Umudike, Nigeria and National Root Crops Research Institute Umudike, Nigeria, between August, 2014 and November, 2014. Methodology: The ethanol and aqueous extracts of watermelon (Citrullus lanantus) rind (EER and AER) and seed (EES and AES), each at a concentration of 100 mg/ml, were investigated by well-diffusion method for activity against ten pathogens. Results: The EER exhibited the highest activity against the bacterium, Esherichia coli (6.0) and the fungus, Candida albican (4.0). The least activity was in the EES against the fungus, Trichosporo bepelli (0) followed by EER and AES against the bacterium, Staphylococcus aureus (1.0). For the bacterial strains, the highest mean activity (4.0) and mean susceptibility (4.50), respectively was in the EER and Esherichia coli whereas the least mean activity (3.0) and mean susceptibility (1.50), respectively was in AES and Staphylococcus aureus. For the fungal strains, the highest mean activity (2.5) and mean susceptibility (3.0), respectively was in the EER, AER, AES and Candida albican whereas the least mean activity (1.25) and mean susceptibility (1.25) was in EES and Trichosporo bepelli. The activity against the studied pathogens however was higher in the EE than in the AE of the rind and seed, suggesting the preference to the EE for higher pharmacologic activity. Conclusion: The extracts (EER, AER, EES and AES) exhibited activity against the tested strains, especially Escherichia coli and Candida albicans. The study underscores the overriding potency of EER against the bacterium, Escherichia coli and the fungus, Candida albicans, and the non-susceptibility of the fungus, Trichosporo bepelli to EES. Further works, however are needed to validate reliability and possible exploitation in nutraceutical formulations and in ethnomedication.