The spread of new infections and the emergence of multidrug resistant strains of microorganisms necessitate the search for new antimicrobials with focus on plant extracts. In this study, the antimicrobial activity of the extracts (aqueous and ethanolic) of lemon grass known usually for bioactive essential oil (Cymbopogon citratus) was investigated in-vitro, against selected clinical isolates (Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans). Antimicrobial efficacy of the extracts was assessed using the agar-well diffusion and broth-dilution techniques. The aqueous extract of C. citratus was more efficacious as it showed higher antimicrobial activity against all the test isolates at all tested concentrations. In contrast, only two of the test isolates; P. aeruginosa and S. aureus were susceptible to the ethanolic extract with minimum inhibitory (MIC) concentrations of 2 mg/ml (against S. aureus) and 12.5 mg/ml (against P. aeruginosa). The MIC of the aqueous extract were (mg/ml): 2, 6.25, 12.5, 25 and 50 against S. aureus, E. faecalis, P. aeruginosa, E. coli and C. albicans respectively. Meanwhile, both the aqueous and ethanolic extracts of C. citratus exerted only a bacteriostatic effect against the five test isolates at all concentrations. Quantitative phytochemical screening of the two extracts revealed the presence of more concentration of active compounds in the aqueous extract than the ethanolic extract which plausibly accounts for its greater antimicrobial activity. This study has shown that, in difference to the use of its conventional essential oil, solvent extraction of Cymbopogon citratus is also a potent source of efficacious antimicrobials. Further works to determine the respective mechanisms of action(s) of the extracts’ active principle is being projected.
Keywords: Lemon grass, clinical isolates, antimicrobial efficacies, bioactive compounds
In vitro antimicrobial activity of essential oil of Cymbopogon citratus (lemon grass) on Streptococcus mutans biofilm