Synthesis and biological investigation of new carbonic anhydrase IX (CAIX) inhibitors.

In this report, we describe the synthesis, characterization, in vitro anticancer activity and Carbonic anhydrase IX (CAIX) inhibition of new sulfamate conjugates of Betulin and Betulinic acid (BA). The betulinyl sulfamates were subjected to inhibit carbonic anhydrases (CA), e.g. CAIX, an attractive target for tumor-selective therapy strategies in cancer cells. Data on combined in vitro antitumor activity with CAIX inhibition are very rare. The betulinyl sulfamates were tested against five tumor cell lines and normal human skin fibroblasts. The mode of cell death on MCF7 breast cancer cells induced by the most active compounds CAI1, CAI3 and CAI6 was investigated by Fluorescence Activated Cell Sorting (FACS) experiments. The compounds showed inhibitory activity towards CAIX, which was determined via in vitro enz-yme assay. Our preliminary investigations revealed that all compounds showed potent anticancer properties with IC50 values below 20 µM against all tumor cells. Interestingly, among the panel of sulfamate conjugates, CAI3 found to be highly cytotoxic (average IC50 = 5-10 µM) and possess high inhibitory activity (Ki = 1.25 nM) towards CAIX. Our results suggest that betulinyl sulfamates seem to be attractive substances, due to their possibility of targeted drug delivery they deserve to be proceeded for further pre-clinical (kinetic studies) and in vivo investigations.

Synthesis and studies of anticancer properties of lupane-type triterpenoid derivatives containing a cisplatin fragment.

Both betulinic acid 1 and cisplatin are promising antitumor agents, which induce apoptotic cell death of cancer cells. In the present investigation a new series of betulinic acid-cisplatin conjugates were synthesized and cytotoxicity and selectivity were assessed against five different tumor cell lines. The aim was to combine two structural units, both related with apoptosis induction. The derivatives exerted a dose-dependent antiproliferative action at micromolar concentrations and the effect of these structural variations on anticancer activity was studied and discussed. Several compounds revealed significant antitumor activity, as the most active substance 3-O-acetylbetulinic (2-(2-aminoethyl)aminoethyl)amide (IC50=1.30-2.24 µM). Interestingly, Betulinic acid-cisplatin conjugates were less cytotoxic than the precursors.