Antibacterial Activity of Bioflavonoid from Fruit Pulps of Acacia nilotica Willd

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.