Phytochemical screening and antibacterial activity of Citrullus colocynthis (Linn.) Schrad against Staphylococcus aureus.

Citrullus colocynthis (Linn.) Schrad (CCT) is an important medicinal plant belonging to the family of Cucurbitaceae. It is a well recognized plant in the traditional medicine and was used by people in rural areas as a purgative, antidiabetic and insecticide. In the present investigation, after phytochemical screening of CCT through standard experimental procedure, antibacterial properties of this plant were studied. The antibacterial activity of CCT leaves and fruits extracts (water and ethanolic) against standard (ATCC 25923) and hospitalisolated strains of Staphylococcus aureus from novobiocin treatment patients were evaluated using disc diffusion method. The inhibitory effects of this extracts were compared with standard antibiotic, novobiocin. Phytochemical screening of CCT revealed the presence of tannins, saponins, alkaloids, flavonoides and glycosides. The ethanolic extract showed inhibitory activity against S. aureus more than water extract and this effect was dose dependent manner. Results indicated that 5 mg/mL fruits ethanolic extract have a similar inhibitory effect with novobiocinagainst standard strain. We suggest one of the chemical components that exist in ethanolic extract such as alkaloids, flavonoides and glycosides can have a powerful antibacterial effect even more than novobiocin, especially against hospital isolated strains. The study scientifically validates the use of plant materials in traditional medicine.   Key words: Citrullus colocynthis, Staphylococcus aureus, phytochemical screening.