AbstractThe effects of soybean saponins (SS) and gypsophilla saponin (GS) on the growth and viability of colon tumor (HCT‐15) cells in culture were investigated. Cells were incubated in various concentrations of saponins for 1 hour (short term) or 48 hours (long term). Cell growth and viability were monitored at 24 and 48 hours. SS and GS inhibited cell growth and reduced cell viability in a dose‐dependent manner in long‐term treatment. The viability of cells was also reduced by short‐term treatment with GS. The saponins differed in their effects on cell surface morphology: GS induced a rough and granular cell surface, whereas SS‐treated cells displayed only minor morphological alterations. Changes in membrane permeability were assessed by measuring leakage of the cytoplasmic enzyme lactate dehydrogenase from cells. GS showed a concentration‐dependent increase in lactate dehydrogenase leakage, whereas SS did not exhibit this effect. These results suggest that SS and GS have a significant growth‐inhibitory effect on colon tumor cells in culture. However, it would appear that they are acting through different mechanisms.