Targeting cancer cells with oleanolic and ursolic acid derived hydroxamates

Oleanolic and ursolic acid derived hydroxamates were easily obtained from their parent compounds; they were screened for their cytotoxicity applying SRB assays employing several human tumor cell lines. Low EC50 values were determined for compounds in which the nitrogen as well as the oxygen in the hydroxamic acid part still holds acidic hydrogens. Thus, ursolic acid derived compounds having at least an OH and/or NH moiety in the hydroxamate part of the molecule showed good cytotoxicity but they are significantly less selective for the tumor cells than oleanolic acid derived compounds. Good results were determined for oleanolic acid derived 7 for tumor cell lines 518A2 (melanoma, EC50=3.3 μM), A2780 (ovarian carcinoma, EC50=3.4 μM) and HT29 (colon adenocarcinoma, EC50=5.6 μM) while being significantly less cytotoxic for fibroblasts (EC50=20.4 μM).