Background: Annona squamosa is used in different places such as India as a general tonic to enrich blood, relieve vomiting, cancer, as a vermicide, for skin complaints and also applied to wounds and ulcers. The purpose of the study was to evaluate the antibacterial and antioxidant properties from of the alkaloidal fraction of A. squamosa. Methods: Well diffusion assay, minimum inhibitory concentration and the minimum bactericidal concentration (MBC) were used to evaluate antibacterial activity against Staphylococcus aureus, Escherichia coli, Bacillus cereus, Pseudomonas aeruginosa, MRSA and Helicobacter pylori. DPPH and SOD assays were used to evaluate antioxidant activity. LC-MS analysis was used to identify alkaloids and scanning electron microscopy studies that revealed mode of action. Results: Alkaloidal fraction of A. squamosa exhibited significant inhibition against the tested bacteria. Extracted alkaloids from the leaves of A. squamosa showed high level of antioxidant activities. LC-MS analyses of alkaloids of the plant were identified as corydine, sanjoinine, norlaureline, norcodeine, oxanalobine and aporphine in the leaves of A. squamosa. SEM analysis of the interaction of these substances with the bacteria showed morphological changes of cell wall and lysis of the targeted bacterial cells. Conclusions: It could be concluded that the alkaloids isolated from A. squamosa showed good antibacterial and antioxidant activity. The results suggest the alkaloids can be a new source of antimicrobial agents against pathogenic bacteria and antioxidant source
