New substances with cytotoxic and antitumor effects. IV. In vitro effect of some veratrum alkaloids and their derivatives on leukemia P388 cells.

Some Veratrum alkaloids and their derivatives exhibited an in vitro cytotoxic effect on leukemia P388 cells, depending on the structure of the skeleton of the molecule, particularly on the type of the heterocycle attached to C-20. Veracintine and 20-(2-methyl-1-pyrrolin-5-yl)-4-pregnen-3-one, which proved to be the most effective, inhibited incorporation of uridine, and to a lesser extent that of L-valine into P388 cells fractions. After a brief reaction (15 min), these substances became irreversibly bound in the P388 cells and stopped their further in vitro proliferation. The cytotoxic effect of veracintine became enhanced by sublethal doses of tubercidine (phase of maximum lethality of G1).