Chapter 6. Exogenous Antioxidants Derived from Plants, Fungi, and Other Taxa

The equilibrium between reactive species formation and antioxidant defenses (endogenous and exogenous) is essential for normal organism functioning. The oxidation–reduction reactions responsible for this equilibrium are critical to maintaining many cellular processes and cell survival mechanisms. However, under specific biotic and abiotic stresses, this balance is disturbed, leading to an oxidative challenge. In this situation, excess reactive species may damage cellular lipids, proteins, and DNA; affecting the normal body function. The endogenous defense system (enzymatic and non-enzymatic) is an evolutionary response to this continuous exposure. However, this system requires uptake of exogenous antioxidants to boost its activity and enhance the cellular body defense against oxidative damage. The exogenous antioxidants can be obtained mainly from plants, but also fungi and other taxa. This chapter explores the overall literature concepts regarding oxidative stress and the organism antioxidant defense systems, together with an overview of the main exogenous antioxidants from plants and other taxa. Additionally, a critical assessment of the analytical procedures for antioxidant properties measurement, with a particular emphasis on the antioxidant properties of plant phenolic compounds, is provided in the present chapter.