Effects of alpha-hederin and thymoquinone, constituents of Nigella sativa, on human cancer cell lines.

The separate effects of alpha-hederin and thymoquinone, the two principal bioactive constituents of Nigella sativa, on four human cancer cell lines [A549 (lung carcinoma), HEp-2 (larynx epidermoid carcinoma), HT-29 (colon adenocarcinoma) and MIA PaCa-2 (pancreas carcinoma)] were investigated. Alpha-hederin was also examined as a pro-drug. Each assessment quantified both cytotoxic and apoptotic/necrotic effects. Alpha-hederin and thymoquinone separately induced a dose- and time-dependent effect on the cell lines tested. HEp-2 cells were the most sensitive, exhibiting apoptosis with a higher incidence following thymoquinone treatment. Pre-treatment of cells with alpha-hederin, followed by thymoquinone or cisplatin, did not enhance the cytotoxicity or apoptosis induced by either drug. So, the membrane-perforating properties associated with saponins, here represented by alpha-hederin, enhance neither cytotoxicity nor apoptosis of these cancer cells.