Antimicrobial potency of extracts from selected medicinal plants towards Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa

Abstract

Antibiotic resistance has become a very big threat to the existing first line antibiotics. Some of the infectious pathogens are becoming multidrug resistant including Mycobacterium tuberculosis. This has necessitated social, scientific and financial interventions from key players. The strain this puts on the fragile health care systems of developing nations is frustrating. Scientific interventions have involved campaigns for improved hygiene, use of combination therapies and revived search for new drugs with different modes of action. It is on this basis that this research was conducted as phase I into the search for antibiotic agents from nature. This was done by screening several plant extracts to identify bioactive extracts that can be developed into drugs or purified for better active single molecules in the second phase. Extracts were obtained by cold percolation of pulverized samples of different dried plant parts using different mono-solvents. Agar diffusion and froth floatation were used to measure the potency of the extracts. Many of the screened extracts had good to moderate activities. Five of the plant species; Zanthoxylum chalybeum and gilletii, Diospyros abyssinica, Prunus africana, Peptadeniastrum africana and Blighia unijugata showed very promising activities (1.9 to 9.4 mg/mL) against Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. The other species had moderate activity (10.6 to 47.5 mg/mL). The species (Albizzia coriaria, Maytenus senegalense and Kigellia africana) that inspired this research from literature only demonstrated moderate activity against all the tested organisms, probably due to antagonistic effect of the active compounds within the extracts. In conclusion, Z. chalybeum and gilletii, D. abyssinica, P. africana, Peptadeniastrum. africana and B. unijugata have a very strong potential for drug development and are recommended for use in the management of infections caused by the tested microbes and purification to isolate the individual active compounds for better formulation, standardization and drug acceptability.