Tempicol-3, a novel piperidine-N-oxide stable radical and antioxidant, with low toxicity acts as apoptosis inducer and cell proliferation modifier ofYoshida 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 concent ration - dependent reducibility of this novel compound was also examined an d compared with chose of previously characterized nitroxides, Tempo and Tem pace. 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 b earing 3-day old Yoshida Sarcoma (promotion phase of the disease). Our resu lts clearly indicated that Tempicol-3 acts as an effective and promising hy droxyl radical scavenger-antioxidant. Structure- and concentration-dependen t bioreduction of Tempicol-3 by ascorbic acid may account for some of its b iological effects, causing modulation of the antioxidant status of cells. T he presence of one nitrone moiety per molecule of Tempicol-3 caused a signi ficant decrease in nitroxide cytotoxicity as compared with Tempo in vitro. The results clearly confirmed that the toxic effect could result either fro m the presence or structure of substituent(s) at position 4 of the free rad ical piperidine moiety. It can be stated that Tempicol-3 is a lowtoxicity n itroxide, which could be effective in providing antioxidative activity. We have also observed that lowtoxic Tempicol-3 at m.e.d. (minimal effective do se) suppressed tumorigenesis, acting as a cell proliferation modifier and a poptosis inducer in vivo. This work provides the base for further investiga tions on nitroxide-N-oxide derivatives since the serious question remains t o be solved as to what is the molecular mechanism of action of the nitroxid e-N-oxides.