Nitrogen-and Sulfur-Containing Heterocycles as Dual Anti-oxidant and Anti-cancer Agents

Cancer derives from a multi-step process in which tumor cells establish the ability to proliferate and disseminate. Other non-oncogenic pathways can be influenced as an adaptive response, being the oxidative stress the most affected. Indeed, reactive oxygen species act as pivotal mediators of oxidative stress and are involved in cancer initiation and development. Medicinal chemists have directed their efforts toward the concurrent inhibition of the cancer cell growth and the modulation of the upregulated oxidative stress level. Furthermore, anti-cancer drugs can exert their cytotoxic effects by displaying pro-oxidative damage in cancer cells. This pleiotropic activity has been largely investigated among the heterocyclic scaffolds with particular interest in those containing both sulfur and nitrogen atoms. In this chapter, we collected an up-to-date overview of this topic demonstrating the importance of these heterocycles categorizing the discussion on acyclic (isothiosemicarbazones), monocyclic (thiazoles, thiazolidines, thiadiazoles, thiazines, thiazepines), bicyclic (benzothiazoles and benzothiazines), and tricyclic (phenothiazines) compounds. Moreover, natural compounds and metal complexes containing such structures were considered and described. Structure-activity relationships and the most promising agents were provided as well as their results in terms of anti-proliferative and antioxidant activities.