Combined activity of Azadirachta indica and Dodonea viscose leaves extract on some selected pathogens

The study was undertaken to investigate the antimicrobial activity both individually and in combination of two Nigerian plants (Azadirachta indica and Dodonea viscosa) against a variety of pathogenic bacteria. Five bacterial species namely; Staphylococcus aureus, Escherichia coli, Salmonella typhi, Klebsiella pneumoniae and Pseudomonas aeruginosa were selected for the assays. The powdered plant materials of the two plants were extracted using sohxlet extraction technique with methanol water and petroleum ether as solvents. The crude extracts of the two plants were subjected to phytochemical screening for qualitative detection of plant secondary metabolites. The extracts were further tested for antibacterial activity against the selected pathogens singly and then combined using agar well diffusion method. Antibacterial activity of the two plants singly indicates that the methanolic extract possess the highest antibacterial activity at a concentration of 50mg/ml with an inhibition zone of 23.3±0.5mm compared to aqueous extract with 21.7±0.5mm inhibition zone at a concentration of 50mg/ml. The least activity was observed with the petroleum ether extract with an inhibition zone of 7.3±0.5mm at a concentration of 12.5mg/ml. Combination of the plants extracts exhibited lower antibacterial activity on the test isolates compared to single plants as evidenced by the production of lower inhibition zones. Key words: Azadirachta indica, Dodonea viscosa, pathogens, antimicrobial activity, synergistic effec