A new aporphine alkaloid, (-)-arcabucoine [(6aR)-N-formyl-1,2-methylenedioxy-9,10-dimethoxy-5,6,6a,7-tetrahydro-4H-dibenzo[de,g]quinoline] 1 was isolated from the leaves of Talauma arcabucoana (Magnoliaceae), along with the known compounds (-)-erythro-saccharinic acid lactone 2 and (-)-shikimic acid 3. Furthermore, the known aporphine alkaloids (-)-dicentrine 4, (-)-nordicentrine 5 and dicentrinone 6 were isolated from the stem bark. The alkaloids 4 and 5 were found to be the most active compounds in a brine shrimp lethality assay. In addition, alkaloids 1, 4 and 5 showed moderate growth inhibition against Staphylococcus aureus and Candida albicans.