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The emergence of multi-drug resistance in bacteria has led to call for research and development of new leads as antibiotics from medicinal plants. Acacia nilotica (Linn) is a plant of multipurpose medicinal uses, three bioactive flavonoids (methyl gallate, gallic acid and catechin) were isolated from its fruit pulps through a bioassay guided fractionation technique and characterized based on High Performance Liquid Chromatography, Liquid Chromatography-Mass Spectra and Nuclear Magnetic Resonance spectra. Antibacterial activity of these compounds was determined by microplate tetrazolium dye assay of broth microdilution technique against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and clinical isolates of Salmonella typhi, Klebsiella pneumonia, Candida albicans and Bacillus subtilis. Catechin, methyl gallate and gallic acid at 19.5, 39 and 39 µg/ml respectively caused a significant bio-reduction in cells of test organisms. Time kill kinetic study of the extract shows that there was percentage of growth reduction in test organisms at 2, 4, 6, 8 and 12 hrs of contact. The extent and rate of killing of the organism by the extract at 2 x MIC followed the same trend as rate of killing was time dependent. Antibacterial effects of these compounds are within the breakpoint of control drug chloramphenicol and could serve as leads in new drug development.

The microorganisms associated with fermented African oil bean (Pentaclethra macrophylla Bentham) seed during ugba production was studied. Only bacteria were isolated from the ugba samples used. Although the bacteria included Bacillus spp., Lactobacillus spp., Staphylococcus spp., Micrococcus spp. and members of the family Enterobacteriaceae, only the Bacillus spp. were found to ferment African oil bean seeds to ugba. Bacillus spp. were the predominant microorganisms present, constituting over 95% of the total microbial population density. An increase in the number of Bacillus cells of about 2 log units daily, which attained a maximum density of log10 9.00 - log10 11.90 cfu/g after 3 days was observed. Contrarily, the Lactobacillus spp. increased minimally and attained a maximum value of log10 4.20 - log10 6.35 cfu/g within the same period. The Staphylococcus spp., Micrococcus spp. and the members of the family Enterobacteriaceae remained fairly steady in number for 24h, increased slightly till the 3rd day followed by exponential increases which attained maximum values of between log10 9.20 - log10 11.00, about the 7th day. Bacillus spp. cells also had the highest protease activities which were significantly (p < 0.05) higher than the values for the other bacterial isolates. The Bacillus spp. responsible for the fermentation of African oil bean seeds to ugba were identified as Bacillus coagulans, B. macerans, B. megaterium, B. pumilis and B. subtilis.

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