**Abstract**

This chapter is intended to describe the main antioxidants used in the design and construction of functional foods. Defining the role of antioxidants, in the main redox processes in which certain oxidoreductases are involved, the best way of monitoring the activity of certain coenzymes of these oxidoreductases, will be established the main criteria in the design of sustainable functional foods. In addition, the importance of some coenzymes (FMN, FMNH + H <sup>+</sup> , NAD, NADH + H+ ) in preserving the activity of some valuable bio-compounds (with the role of antioxidants) in functional foods will be highlighted. Antioxidants are good diseasefighters, protecting our bodies from free radicals' attacks that would otherwise damage of the human cellular structures. Knowing and supporting the activity of the main compounds (with antioxidant activity) are operations that improve the reaction mechanisms of redox processes and can significantly contribute to achieving good functional foods - able to regulate the acid–base balance of the body and improve the metabolic processes from the consumer body.

**Keywords:** main antioxidants, functional foods, bio-compounds, coenzymes NAD and FMN, oxidoreductases, healthy products
