ISOLATION OF A NEW VINCA ALKALOID FROM THE LEAVES OF ERVATAMIA-MICROPHYLLA AS AN INHIBITOR OF RAS FUNCTIONS

A new vinca alkaloid was isolated from a chroloform extract of Ervatam ia microphylla leaves as a potent inhibitor of ras functions. The stru cture of the new alkaloid was elucidated by spectroscopic analysis to be a dimer of aspidosperma-class indoles. The new inhibitor, named III -121C, induced normal morphology in K-ras(ts)-NRK cells at around 0.3 mu g/ml. It also inhibited DNA, RNA, and protein synthesis weakly at 0 .3 mu g/ml. It inhibited the growth of K-ras(ts)-NRK cells with IC(50) s Of 0.29, and 0.20 mu g/ml at 33 degrees C and 39 degrees C, respecti vely. III-121C is the first vinca alkaloid that inhibits ras functions .