Abstract

The cold extraction method was used to obtain the methanol extract of the leaf ofCombretum mucronatum. The extract was analyzed for antibacterial activities, using some pathogenic bacteria namely: Klebsiella pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Bacillus cereus, Salmonella typhi and Bacillus subtilis. The antibacterial bioassay was carried out in-vitro and it revealed that the methanol leaf extract inhibited the growth of the tested organisms at a concentration of 25.0 mg/ml except K. pneumoniae and S. pyogenes which were resistant. The extract exhibited the highest inhibitory potential on S. aureus with a zone of inhibition value of 35.0 mm at a concentration of 25.0 mg/ml. This was followed by E. coli and P. aeruginosa which were inhibited with zones of inhibition values 30.0 mm and 25.0 mm respectively. B. cereus was the least inhibited with a zone of inhibition of 16.0 mm. Result of the phytochemical screening tests revealed that the extract contains saponin, tannins, anthraquinone and cardiac glycoside. The rate at which the extract was able to kill the test organisms showed that the organisms decreased with increased time of exposure to the extract. P. aeruginosa decreased to zero at the 24th hour. The minimum inhibitory concentration (MIC) of the leaf extract ranged from 25.0 to 3.12 mg/ml. The result of the antibiotic sensitivity test compared well with the commercial antibiotics.

Key words: Antibacterial, zone of inhibition, phytochemical screening, extracts, rate of killing.