Structural requirements of quassinoids for the inhibition of cell transformation

The effects of eleven quassinoids on Rous sarcoma virus induced cell transformation and on growth of normal cells were examined. At concentrations of 0.15-1 μg/ml they inhibited foci formation (76–99 %) without toxic effects on normal cells. The most active compounds also affected virus production by transformed cells. In intact normal and transformed cells, protein and DNA synthesis was equally affected after 3 hours of exposure to quassinoids of both cell types. RNA synthesis was not inhibited. This study has shown that the structural requirement of a C-15 ester in the quassinoids for antileukemic activity $\text{in vitro}$ and $\text{in vivo}$ is not essential for their antitransforming activity.