Chemical composition and antibacterial activity of extracts and compounds isolated from Citrullus colocynthis (L.) Schrad

The aim of this study was the phytochemical screening of different extracts of leaves and stems prepared with three increasing polarity solvents (n-hexane, ethyl acetate and methanol) of Citrullus colocynthis. Our main goal was to investigate the antibacterial activity of different extracts and compounds isolated from ethyl acetate extract of leaves using the agar disc well-diffusion method. rnFounded results showed that ethyl acetate extracts of leaves and stems possess potential antibacterial activity compared to other extracts against tested Gram-positive and negative bacterial strains. A bioguided isolation of the ethyl acetate extract obtainded from the leaves led to the identification of Cucurbitacin E and the Gluco-Cucurbitacine E. Moreover, a LC-MS analysis of ethyl acetate leaf extract of C. colocynthis permitted the identification of eight other cucurbitacins. Antibacterial activities of the isolated compounds emphasize the importance of sugar moiety. The most important minimum inhibitory concentrations (MIC) values were obtained for the ethyl acetate extract 0.625 mg/mL against Bacillus cereus and Glucocucurbitacin E 1.25 mg/mL against both Bacillus cereus and Enterococcus faecalis.