Antimicrobial activities of Alstonia boonei stem bark, a Nigerian traditional medicinal plant

Abstract

To determine the in vitro antimicrobial activities of various solvent extracts of stem bark of Alstonia boonei, a Nigerian traditional medicinal plant against some microorganisms of food and clinical importance. The antimicrobial activities of crude solvent extracts of stem bark were determined using well in agar diffusion method against Escherichia coli (E. coli), Staphylococcus aureus, Salmonella typhi, Pseudomonas aeruginosa, Saccharomyces cerevisiae and Kluyveromyces sp. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration were determined to establish the antimicrobial potential of extracts. The antimicrobial results revealed that ethanol extract produced maximum zone of inhibition (23.73 mm) against E. coli. All the extracts had no inhibitory activity on Salmonella typhi and Pseudomonas aeruginosa at the lowest concentration tested (3.2 mg/mL). MIC was determined at various concentrations and the least MIC (5.8 mg/mL) was produced by the crude ethanol extract on E. coli, while the least minimum bactericidal concentration (20 mg/mL) was also produced by the ethanol extract on E. coli. Ethanol and chloroform extracts had the highest and least inhibitory effects on the isolates, respectively. The present study has revealed that the solvent extracts of Alstonia boonei stem bark possess potent antimicrobial activity that can be harnessed. It may also be a new source of antimicrobial compounds that could be used to combat drug resistance which has become a global challenge.