Evaluation of antimicrobial potentials of stem bark extracts of Erythrina senegalensis DC

Abstract

Antimicrobial activity of organic (methanol and chloroform) and aqueous stem back extracts of Erytrina senegalensis against some pathogenic microorganisms was investigated using the filter paper disc diffusion method. Phytochemical studies revealed the presence of saponins, tannins, glycosides, phenols and alkaloids. The extracts demonstrated antimicrobial activity against both bacteria (Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa) and fungi (Aspergillus flavus, Aspergillus fumigatus, Candida albicans, Penicillium notatum). For the bacteria, the highest activity (14 mm zone diameter of inhibition) was demonstrated against E. coli and the lowest activity (4 mm zone diameter of inhibition) against S. aureus and P. aeruginosa, while for the test fungi, the highest activity of 8 and 6 mm (zone diameter of inhibition) was demonstrated against C. albicans and A. flavus respectively, and the lowest activity of 4 mm against P. notatum. The methanol extracts demonstrated the highest activity while, the aqueous extracts demonstrated the lowest activity against all the test organisms. The activity of the extracts increased with increase in temperature (4 - 100oC) and acidic pH, but decreased as the pH was adjusted toward alkalinity (pH 8 - 10). The MIC (7.5 - 30 mg/ml) and MMC (8.0 - 30.0) for bacteria, and MIC (7.5 - 40) and MMC (8.0 - 30.0) shows that E. senegalensis stem bark, if further purified can be used to source novel antibiotic substances for drug development against infections such as typhoid fever, urinary tract and wound infections, dysentery and mycotic infections. Key words: Antimicrobial activity, antibiotic substance, bacterial infections, disc diffusion method, Erythrina senegalensis, phytochemicals, MIC, MMC, mycotic infections.