A novel complex, Rutoxyl [rutin/4-acetamide-1-hydroxy-2,2,6,6-tetramethylpiperidinium] was synthesized and its structure and anticancer activity were investigated. The results reported here are consistent with our idea, that the formation of such a complex of two biologically active molecules: polyphenolic flavonoid antioxidant (Rutin) and nitroxylamine of nitroxide antioxidant (Tempace), stabilized by hydrogen bond(s) can result in a supra-additive properties.