Antibacterial activities of watermelon (Citrullus lanatus) rind and seed extracts against selected gram-positive and gram-negative bacteria

The aim of this research was to study the antibacterial effects of watermelon [Citrullus lanatus] rind and seed extracts against selected Gram-positive and Gram-negative bacteria. Watermelon rind and seed extract were prepared using Soxhlet and cold extraction with either ethanol or water. Zones of inhibition against specific bacterial species using the extracts demonstrated varying degrees of antimicrobial activities against both groups of bacteria. However, the zones of inhibition from seed extracts were larger compared with those from rind extracts with most of the examined bacteria and were most pronounced with Staphylococcus aureus. The zones of inhibition against Streptococcus pneumoniae and Escherichia coli with ethanol extracted rind and seed were superior when compared with those extracted with water. Watermelon seed extract produces a greater zone of inhibition when compared with rind extract suggesting that highly active antimicrobial components are present in watermelon seed. Further investigation is warranted to improve the extraction methods and to identify the minimum inhibitory concentration of the extracts.