Inhibitory effect of Ficus racemosa leaf extract on Staphylococcus aureus

Abstract

Current antimicrobial research does not only focus on the identification of new chemical antibiotics but also on the identification of natural compounds present in plant-based traditional medicines. In Thailand, Ficus racemosa is an excellent representative of medicinal plants that provides health benefits in several diseases. Preliminary evaluation of the antibacterial activity of Ficus racemosa leaf extract against Staphylococcus aureus. Fresh leaves of F. racemosa were collected and extracted in methanol. The methanolic extract of F. racemosa was diluted in sterile distilled water and analyzed for contained phytochemical agents. Antibacterial activity against D-test negative and D-test positive S. aureus was evaluated by agar disk diffusion and broth dilution methods to determine inhibition zone, minimum inhibitory titer, and minimum bactericidal titer, respectively. Stability of active agents against S. aureus was tested on the day of extract preparation and 15 days later. Chemical analysis suggested the presence of flavonoids and tannins in the methanolic extract of F. racemosa. Inhibition of bacteria was dose dependent and not different between the two tested S. aureus strains at day 1 and day 15. Higher concentrated F. racemosa extract showed higher antibacterial activity than lower concentrated extract in all measurements. Agar disk diffusion seemed not to be suitable to evaluate antibacterial activity of the F. racemosa methanolic extract as it showed only a very narrow inhibition zone. However, the broth dilution assay allowed to determine an inhibitory titer. Our data indicates that methanolic F. racemosa leaf extract contains potent antimicrobial compounds. The ability to inhibit the growth of two different drug-susceptible strains of S. aureus suggests that these plant-derived compounds are alternative antimicrobial drugs.