Abstract

Olgica Stefanovic*and Ljiljana Comic

In vitro antibacterial activity of ethanol, ethyl acetate and acetone extract from Cytisus nigricans and Cytisus capitatus and their synergistic interaction with gentamicin and cephalexin were studied. Antibacterial efficacy of the extracts was defined by determining minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). The values were in the range from 1.25 mg/ml to >20 mg/ml. The most sensitive bacteria were: Staphylococcus aureus ATCC 25923, Bacillus subtilis and Pseudomonas aeruginosa ATCC 27853. Herb-drug interactions tested by checkerboard method and expressed as fractional inhibitory concentration (FIC) index showed indifferent and synergistic effects. Synergism was observed only in combination between antibiotics and ethanol, ethyl acetate extract of C. nigricans. In the presence of subinhibitory concentrations (1/4 MIC, 1/8 MIC) of the extracts the activity of gentamicin and cephalexin were increased up to 16-fold. The highest amount of flavonoids was measured in acetone extracts while the highest amount of total phenols had ethanol extract of C. nigricans and acetone extract of C. capitatus