Phytochemical Screening and Antimicrobial Effect of Ethanolic Leaf Extract of Alstonia boonei De Wild (Apocynaceae) on some Selected Pathogenic Micro-organisms

Abstract

Antibiotics usage in animal production has been restricted by World Health Organization (WHO) due to their negative effects leading to the development of antibiotics resistant bacteria (superbugs) in animals and humans. The search for alternatives to antibiotic growth promoters has led to various researches in phytomedicine. An in-vitro experiment was therefore conducted to evaluate the antibacterial effect of ethanolic leaf extract of Alstonia boonei De Wild (Apocynaceae) on the following selected bacterial isolates: Escherichia coli, Salmonella typhi, Proteus mirabilis, Staphylococcus aureus and Pseudomonas aeruginosa. The antimicrobial effect was performed by agar well diffusion method. Preliminary phytochemical screening of the extract of Alstonia boonei indicated the presence of tannins, cardiac glycosides, flavonoids, saponnins, steroids and terpenoids while phlobatannins and anthraquinones were absent. The extract produced significant inhibitory effect on S. aureus and P. aeruginosa with inhibition zones of 19mm, 16mm, Minimum Inhibitory Concentration (MIC) of 6.25mg/ml and 12.50mg/ml respectively. E. coli, S. typhi and P. mirabilis were not sensitive to the extract. It was concluded that Staphylococcus aureus and Pseudomonas aeruginosa were highly sensitive to ethanolic leaf extract of Alstonia boonei.