Cytotoxic effects of a decoction of Nigella sativa, Hemidesmus indicus and Smilax glabra on human hepatoma HepG2 cells

A decoction of Nigella sativa seeds, Hemidesmus indicus root and Smilax glabra rhizome is used by traditional medical practitioners in Sri Lanka to treat cancer and has been shown to prevent chemically induced carcinogenesis in rats. The cytotoxicity of the decoction and the individual plant extracts were tested on the human hepatoma HepG2 cell line. The effects of 24 h incubation with different concentrations (0-50 mg/ml) of the extracts on HepG2 cells were determined. Results from MTT and SRB assays, and [14C]-leucine and [3H]-thymidine uptake demonstrated that the decoction had a strong dose-dependent cytotoxic activity. The greatest inhibitory effects were observed on DNA synthesis with both the decoction (91 ± S.E. 3.7% inhibition) and N. sativa plant extract (88 ± 3.8%) even at low concentrations (5 mg/ml). The three individual plant extracts were cytotoxic in the order of potency N. sativa > H. indicus > S. glabra. Flow cytometric analysis using Annexin V and propidium iodide staining showed that after 24 h exposure to the decoction, cells were in the late stage of apoptosis and/or necrosis. Further experiments are worthwhile to determine the anticancer potential of this plant decoction and its components.