Cytotoxic activity of steroidal saponins against human oral tumor cell lines.
Three steroidal saponins showed higher cytotoxicity against human oral squamous cell carcinoma cell lines (HSC-2), as compared with normal human gingival fibroblasts HGF. Tumor specificity of saponins exceeded that of tannins and flavonoids. Agarose gel electrophoresis showed that saponins failed to induce internucleosomal DNA fragmentation, but produced large DNA fragments in both HSC-2 cells and human promyelocytic leukemic HL-60 cells. In contrast to epigallocatechin gallate or gallic acid, cytotoxic activity of saponins was not significantly affected by metals (Co2+, Cu2+, Fe3+) nor by antioxidants (sodium ascorbate, N-acetyl-L-cysteine, catalase). Furthermore, saponins did not produce radicals (detected by ESR spectroscopy) nor oxidation potential (measured by NO monitor). These data suggest that an oxidation-mediated mechanism is not involved in the cytotoxicity induced by steroidal saponins.