Plants have proved to be significant natural sources for effective chemotherapeutic agents and offering a broad spectrum of activity with great emphasis on preventive action. The present study shows that the leaves of Cathranthus roseus constituent the only source which is a starting material for semisynthesis of anticancer drug Vinblastine have been used for the treatment of Hodgkins disease ,Neuroblastoma ,and in Acute Leukemia..The extraction of dried leaves of Cathranthus roseus with aqueous acidic solution of HCl and alkaline solution of Embonic acid gives the alkaloid embonate precipitate which mainly consist of Cathranthine. The determination and elucidation of Cathranthine were done by IR spectra and High Performance liquid chromatography of C-18 column with a mobile phase of Acetonitrile :0.1M Phosphate buffer:Glacial Acetic Acid(38:62:0.3). The acute toxicity of drug against some pathogens i.e bacteria and fungi were determined by microbial study .The In vitro and In vivo Pharmacological study of drug have also been done on B16F10 Melanoma Cancer Cells. The result of analysis demonstrates that the Cathranthus roseus is major source of Cathranthine which is a viable source of anticancer activity.