SUCCESSIVE EXTRACTION AND ANTIBACTERIAL SCREENING OF Cymbopogon citratus (LEMON GRASS) AGAINST SOME GRAM POSITIVE AND GRAM NEGATIVE PATHOGENS

Methods of extraction, types of solvents and types of microorganisms have been reported to play important roles in the quest for plant-based drugs against microbial infections. The antibacterial activity of Cymbopogon citratus leaf crude extract against Salmonella enterica, Klebsiella pneumoniae and Streptococcus species was determined by agar well diffusion method while the crude extract was obtained by successive reflux extraction method using n-hexane, ethyl acetate, ethanol and water as extraction solvents. Preliminary qualitative phytochemical screening of the extract for 11 phytochemical constituents reveals the presence of 10 constituents namely phenols, tannins, flavonoids, cardiac glycosides, anthraquinones, terpenes, alkaloids, steroids, saponins and volatile oils while resins were absent. All the solvent extracts exhibited antibacterial activity with mean zones of inhibition (MZI) ranging from 0.00 mm to 13.00±1.53 mm against the test organisms except for ethanol extract that was not active on Salmonella enterica. Ethyl acetate extract was the most active, having MZI ranging from 9.33±0.66 mm to 13.00±1.53 mm while ethanol extract was the least active with MZI ranging from 5.66±0.33 mm to 8.00±0.00 mm. The minimum inhibitory and bactericidal concentration (MIC and MBC) of the plant extract was 7.5 mg/ml and 120 mg/ml respectively while the MBC of ethanol extract against Salmonella enterica was above 120 mg/ml. The activity of the plant extract was low when compared to the activity of the standard positive control drugs. Based on the result of this study, it can therefore be concluded that antibacterial drugs can be formulated from extract of Cymbopogon citratus to treat infections caused by the test organisms.