Terpenoids. LIII. Antitumor activity of trichorabdals and related compounds

Among the three types, enmein-, oridonin-, and trichorabdal-type, of diterpenoids from Rabdosia trichocarpa, the latter showed the highest antitumor activity against Ehrlich ascites carcinoma in mice. Their potent activities were attributed to synergistic increase arising from the presence of two active sites in one molecule. In vitro activity against HeLa cells and in vivo activity against P 388 lymphocytic leukemia of diterpenoids and related compounds were also determined, but no synergistic increase in activity due to plural active sites was observed in those cases.