Modification at A-Ring and Cytotoxic Activity of Betulonic Acid and its N-Methylpyperazinyl Amide

Abstract Since cancer remains one of the most prevalent diseases today, there is an urgent need for the development of new agents. Triterpenoids may act in multiple pathways displaying antiproliferative, antiangiogenic, anti-inflammatory, and pro-apoptotic activities that place them as promising multifunctional agents in treating cancer. In this paper a series of betulonic acid and its N-methylpyperazinyl amide derivatives, especially holding C2-nicotinoylidene/furfurylidene/fluorobenzylidene fragments, have been synthesized and evaluated for their cytotoxic activity against the NCI-60 cancer cell line panel. N-Methylpiperazinyl amides of betulinic acid 11 and 4-pyridinoylidene-betulinic acid 9 as well as betulonic acid C2-4-pyridinoylidene- 14 or furfurylidene 16 derivatives were found to be the leading compounds with GI50 values of 0.49 μM for leukemia CCRF-CEM, 1.60 μM and 1.36 μM for colon cancer HCT-116 and 1.66 μM for melanoma LOX IMVI cell lines, respectively. The activity displayed for these compounds was higher than for the standard drug doxorubicin against colon cancer HCT-15 and ovarian cancer NCI/ADR-RES cell lines. Cell cycle analysis indicates that compound 11 promotes cytotoxic activity through the apoptosis induction both in conditionally normal (HEK293) and in cancer (A549, MCF-7) cells, whereas compound 14 exhibits both cytostatic and cytotoxic activity, dependently on cell line evaluated. In particular, in HEK293 cells the compound 14 induces mainly apoptotic cell death, while in A549 and MCF-7 cells cytostatic effect is dependent on cell cycle arrest in G2/M phase.Our results suggest that betulinic acid N-methylpyperazinyl amide 11 is the promising compound for the future drug development antitumor studies.