Antibacterial activities of Fagara macrophylla, Canarium schweinfurthii, Myrianthus arboreus, Dischistocalyx grandifolius and Tragia benthamii against multi-drug resistant Gram-negative bacteria

Bacterial infections caused by multidrug resistant phenotypes constitute a worldwide health concern. The present study was designed to evaluate the in vitro antibacterial activities of the methanol extracts of five medicinal plants: Fagara macrophylla, Canarium schweinfurthii, Myrianthus arboreus, Dischistocalyx grandifolius and Tragia benthamii against a panel of 28 multidrug resistant Gram-negative bacterial strains. The liquid broth microdilution was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the extracts. The best activity was recorded with Canarium schweinfurthii bark extract, MIC values ranging from 32 to 1024 µg/mL being recorded against 85.7 % tested bacteria. Broad spectra of antibacterial activities were also obtained with both bark and leaf extracts from Myrianthus arboreus (78.6 %) as well as the bark extract from Fagara macrophylla (75.0 %). The lowest MIC value of 32 µg/mL was obtained with Canarium schweinfurthii bark extract against Klebsiella pneumoniae KP63 strain. The results of this work provide baseline information for the use of the studied plants, and mostly Fagara macrophylla, Canarium schweinfurthii and Myrianthus arboreus in the treatment of bacterial infections including multidrug resistant phenotypes.