Antimicrobial Activity and Isolation of Methylated Flavanone from Methanol Stem-bark Extract of Nauclea diderrichii

The antimicrobial activities of the crude methanol fraction of the stem bark extract of Nauclea diderrichii was investigated using agar diffusion and broth dilution techniques. Clinical isolates obtained from the Department of Medical Microbiology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria were used for the studies. The crude fraction showed activity against Staphylococcus aureus, Streptococcus pyrogenes, Pseudomonas aeruginosa, Klebsiella pneumonia and Samonella typhi, but were below detectable limits (BDL) in methicillin resistant S. aureus, Bacillus subtilis, Corynobacterium ulcerans, Escherichia coli and the fungus Candida albicans. Low values for minimum inhibitory concentration (MIC, 1.25 μg/ml), and minimum bactericidal concentration (MBC, 2.25 μg/mL), suggested that the crude extract had a good antimicrobial activity against the susceptible organisms. The minimum fungicidal concentration MFC, was 5.00 μg/mL.Chromatographic separation using a combination of silica and sephadex LH-20 led to the isolation of a methylated flavanone. The structure of this isolated compound was determined using different spectroscopic techniques including both 1 and 2D nuclear magnetic resonance (NMR). All the above validates the ethno medicinal uses of the N. diderichii in the treatment of various bacterial infections.