Tempicol-3, a novel piperidine-N-oxide stable radical and antioxidant, with low toxicity acts as apoptosis inducer and cell proliferation modifier of Yoshida Sarcoma cells in vivo.

The novel nitroxyl, Tempicol-3 (nitroxide-N-oxide) was synthesized and its capacity to act as a scavenger of hydroxyl radicals was tested. The concentration-dependent reducibility of this novel compound was also examined and compared with those of previously characterized nitroxides, Tempo and Tempace. The cytotoxicity of Tempicol-3 in vitro was measured by the modified tetrazolium assay (MTT), using, model cells for neoplastic phenotype (mouse NIH 3T3 fibroblast line). The ability of Tempicol-3 to act as an antitumor agent in vivo was also investigated in a pharmacological test, using rats bearing 3-day old Yoshida Sarcoma (promotion phase of the disease). Our results clearly indicated that Tempicol-3 acts as an effective and promising hydroxyl radical scavenger-antioxidant. Structure- and concentration-dependent bioreduction of Tempicol-3 by ascorbic acid may account for some of its biological effects, causing modulation of the antioxidant status of cells. The presence of one nitrone moiety per molecule of Tempicol-3 caused a significant decrease in nitroxide cytotoxicity as compared with Tempo, in vitro. The results clearly confirmed that the toxic effect could result either from the presence or structure of substituent(s) at position 4 of the free radical piperidine moiety. It can be stated that Tempicol-3 is a lowtoxicity nitroxide, which could be effective in providing antioxidative activity. We have also observed that lowtoxic Tempicol-3, at m.e.d. (minimal effective dose) suppressed tumorigenesis, acting as a cell proliferation modifier and apoptosis inducer in vivo. This work provides the base for further investigations on nitroxide-N-oxide derivatives since the serious question remains to be solved as to what is the molecular mechanism of action of the nitroxide-N-oxides.