Tulbaghia violacea inhibits growth and induces apoptosis in cancer cells in vitro

Abstract

Methanol extracts of Tulbaghia violacea leaves and bulbs inhibited growth of MCF-7, WHCO3, HT29 and HeLa cancer cell lines. At 250 µg/ml, bulb extracts exhibited higher growth inhibition than leaf extracts in MCF-7 (49.6 ± 2.6%), HT29 (26.0 ± 4.5%) and HeLa cells (54.7±5.9%) relative to untreated controls. In WHCO3, the leaf extract was more active, inhibiting growth by 30.3 ± 1.8%. The growth inhibitory activity of T. violacea was due to induction of apoptosis in all four cell lines. This was shown by the staining of cells with Hoechst 33342, indicating fragmented nuclear material and condensed chromatin. HeLa and MCF-7 cells treated with bulb extract had higher apoptotic indices than the other two cell lines (HeLa, 25.8 ± 3.9%; MCF-7, 19.0 ± 4.3%). Treated cells stained with Annexin V but not with propidium iodide (PI), indicating that the extract induced apoptosis and not necrosis. Using Western blotting, cleavage of Poly [ADP-ribose] polymerase-1 (PARP) was shown in HeLa cells upon exposure to T. violacea bulb extract. These findings provide evidence for anticancer activities in T. violacea. The induction of apoptosis by the extract is promising for anticancer therapy as it is desirable for anticancer agents to induce apoptosis.