Development of C-20 modified betulinic acid derivatives as antitumor agents.

Chemical modifications were performed on C-20 position of betulinic acid for a structure-activity relationship study. The evaluation of the compounds using human colon carcinoma HCT-116, human prostate adenocarcinoma PC3, and human melanoma cell lines M14-MEL, SK-MEL-2, and UACC-257 did not show any selective cytotoxicity towards melanoma cells. The results from both MTT reduction assay and SRB staining assay were comparable that no remarkable differences in cytotoxicity profile of the compounds were noticed. The C-20 position was found to be sensitive to the size and the electron density of the substituents in retaining the cytotoxicity of betulinic acid and was found to be undesirable position to derivatize.