Antibacterial Screening of Leaves Extracts of Annona muricata (Annonaceae) and Jatropha tanjorensis (Euphorbiaceae) against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa

The crude extracts of Annona muricata and Jatropha tanjorensis leaves were investigated with the aim of determining the antibacterial activity, qualitative and quantitative properties, the best solvent used for extraction, the most active ingredients and the organism that is most susceptible to them. Ethanol, petroleum ether and water (warm) were used as solvents. Agar well diffusion method was used for the susceptibility testing of extracts against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, with ciprofloxacine as positive control and sterile water as negative control. Ethanol and petroleum ether extracts of the plant, either alone or in combination, showed activities against test organisms. P. aeruginosa was more susceptible to ethanolic extract of A. muricata extract with 11.33±0.33 mm zone of inhibition while E. coli was the least susceptible with 9.83 mm.  E. coli was more susceptible to ethanolic extract of J. tanjorensis with 10.0±0.00 mm zone of inhibition while P. aeruginosa was the least susceptible with 9.0±0.0 mm diameter. Using petroleum ether, E. coli was the most susceptible to A. muricata extract with 7.33±0.33 while S. aureus was the least susceptible with 7.00±0.58 mm diameter. For J. tanjorensis petroleum ether extract, E. coli was the least susceptible with 7.33.0±0.33 mm zone of inhibition while S. aureus was the most susceptible with 8.0±0.0.58 mm diameter. The combination of petroleum ether extracts of both plants gave zones of inhibition of 7.67±0.67 mm and 8.33±0.67 mm for E. coli and S. aureus respectively. The combination of ethanolic extracts of both plants gave zones of inhibition of 14.33±0.67 mm, 12.60±0.6 mm and 7.67±0.33 mm E. coli, S. aureus and P. aeruginosa respectively, which suggest a synergistic effect. The minimal inhibitory concentration of the extracts against test organisms ranged between 25 mg/mL and 100 mg/mL while the minimal bactericidal concentration ranged between 50 mg/mL and 100 mg/mL. This study reveals that the ethanol and petroleum ether extracts of A. muricata and J. tanjorensis have antibacterial effect on E. coli, S. aureus and P. aeruginosa.