Abstract:Aims: To evaluate antibacterial activity of aqueous, methanol, dichloromethane, and hexane extracts of Artocarpus nobilis Thw. leaves and stem bark against Escherichia coli and Staphylococcus aureus using agar well diffusion method. Methodology: Matured fully expanded leaves and stem bark parts of Artocarpus nobilis were collected, air-dried, and grounded. The extraction was obtained using a decoction extraction method. Antibacterial activity was performed against Staphylococcus aureus (ATCC® 25923TM) and Escherichia coli (ATCC® 25922TM) using agar well diffusion method and gentamicin was used as a positive control. The whole experiment was done in triplicates and the diameter of the inhibition zone (in mm) was measured and recorded. Results: Results showed that aqueous bark extract (EC₅₀ 4.286 mg/mL) showed the highest efficacy and potency against E. coli while methanol bark extract (EC₅₀ 4.427 mg/mL) showed the highest efficacy and potency against S. aureus. R² and P values for aqueous, methanol, dichloromethane, and hexane extracts indicated that there was a strong, statistically significant correlation (P ≤ 0.05) between concentration and zone of inhibition for all extracts of A. nobilis against E. coli and S. aureus. Conclusion: This study showed that aqueous and methanol bark extracts of Artocarpus nobilis have marked in vitro dose-dependent antibacterial activity against E. coli and S. aureus respectively. Further studies are necessary to ascertain the mechanism and the active constituents responsible for the antibacterial activity of the of plant parts of Artocarpus nobilis.