A series of new 8-[(2H-tetrazol-5-yl)methoxy]quinoline derivatives, their sugar hydrazones, and their N-glycoside derivatives were synthesized. Furthermore, the 1,2,4-triazole-3-one derivatives 3 and 4 were synthesized from the amidrazone derivative 2. Some of the newly prepared compounds demonstrated inhibitory effects on the growth of MCF-7 human breast cancer cells as compared with the activity of the commonly used anticancer drug, cisplatin. The results of antitumor evaluation revealed that compounds 2-5, 8b, and 12 inhibited the growth of cancer cells through their effect as free-radical regulators by increasing the activity of superoxide dismutase and depletion of intracellular levels of reduced glutathione, catalase and glutathione peroxidase activities, accompanied with a high production of hydrogen peroxide, nitric oxide, and other free radicals causing the killing of tumor cells. The results suggested that the prepared compounds possess significant anticancer activity comparable to cisplatin and the antitumor activity of these prepared compounds was accompanied with a reduction in the levels of protein and nucleic acids.