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Organoantimony(III) halide complexes with azastibocine framework as potential antitumor agents: Correlation between cytotoxic activity and N→Sb inter-coordination.
The relationship between chemical structure and in vitro cytotoxic activities of a series of azastibocine-framework organoantimony(III) halide complexes against cancerous (HepG2, MDA-MB-231, MCF-7 and HeLa) and nonmalignant (HEK-293) cell lines was studied for the first time. A positive correlation between cytotoxic activity and the length of N→Sb coordinate bond on azastibocine framework of same nitrogen substituent was observed. By comparison, the organoantimony(III) complex 6-cyclohexyl-12-fluoro-5,6,7,12-tetrahydrodibenzo[c,f][1,5]azastibocine (C4) exhibited the highest selectivity index, giving a IC50(nonmalignant)/IC50(cancerous) ratio of up to 8.33. The results of cell cycle analysis indicated that the inhibitory effect of C4 on the cellular viability was caused by cell cycle arrest mainly at the S phase. The necrosis induced by C4 was confirmed by the Trypan blue dye exclusion test and the increase of lactic dehydrogenase (LDH) released in the culture medium. Furthermore, evaluation of the levels of intracellular reactive oxygen species (ROS) in MDA-MB-231 cells, by quantifying the relative fluorescence units (RFU) using spectrofluorometer, indicated that cytotoxic activity of C4 is dependent on the production of ROS. This work established the correlation between cytotoxic activity and N→Sb inter-coordination, a finding that provided theoretical and experimental basis for in-depth design of antimony-based organometallic complexes as potential anticancer agents.
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