Bioassay guided fractionation of the methanol extract of Magnolia grandiflora L. (Magnoliaceae) leaves led to the isolation and characterisation of four aporphine alkaloids, magnoflorine, lanuginosine, liriodenine and anonaine. The cytotoxicities of the pure compounds magnoflorine and lanuginosine were determined in a cell viability assay with the tumour cell lines Hela (cervix tumour cell line), HEPG2 (hepatocellular carcinoma cell line) and U251 (brain tumour cell line). Magnoflorine was more cytotoxic (IC50 0.4 mu g mL-1) than lanuginosine (IC50 2.5 mu g mL-1) against HEPG2 in comparison with the standard doxorubacin (IC50 0.27 mu g mL-1). In addition, magnoflorine and lanuginosine exhibited cytotoxicity against U251, with IC50 of 7 and 4 mu g mL-1, respectively. The two compounds were found to be inactive against the Hela cancer cell. On the other hand, the methanol extract showed high antiviral activity against the herpes simplex virus (HSV-1), 76.7% inhibition at 1.1 mu g mL-1, whereas the extract exhibited a moderate antiviral activity against poliovirus type-1 (47% inhibition at the same concentration). This chemical and biological investigation has not been studied previously.