Magnolol has the ability to induce apoptosis in tumor cells.

We previously found that multiple intraperitoneal administration of magnolol from Magnolia obovata inhibited tumor metastasis and growth in vivo, and that the anti-metastatic effect of magnolol was due to the inhibition of the tumor cell invasion. The purpose of this study was to clarify the inhibitory mechanism of magnolol on the growth of tumor cells, and we expect that magnolol may have the ability to induce apoptosis in tumor cells. In an in vitro proliferation assay, 100 microM of magnolol inhibited the proliferation of B16-BL6, THP-1, BAE and HT-1080 cells, but 30 microM of magnolol did not affected cells proliferation. In addition, 100 microM of magnolol induced apoptotic cell death within 24 h in three tumor cell lines, B16-BL6, THP-1 and HT-1080, not BAE cells, and then up-regulated the activity of caspase-3 and caspase-8. The up-regulation of caspases activity by 100 microM of magnolol was suppressed by the inhibitor of all caspases, z-VAD-fmk. These data suggest that magnolol possesses ability to inhibit tumor growth, and the ability is due to the induction of apoptosis with the activation of caspases.