Nonenzymatic Exogenous and Endogenous Antioxidants

*Ziad Moussa, Zaher M.A. Judeh and Saleh A. Ahmed*

## **Abstract**

Nonenzymatic exogenous and endogenous antioxidants play an important role in human health and act as preservatives for cosmetics, pharmaceuticals, and food products. This chapter will discuss the chemical structure and mechanism of action of the most important nonenzymatic small exogenous and endogenous organic molecules that act as antioxidants. The chapter will focus on the structural features, functional groups, properties, biosynthetic origin, and mechanism of action of such antioxidants. It also covers damages that free radicals create and the mechanisms by which they are neutralized by the various antioxidants. The scope of this chapter will be limited to nonenzymatic exogenous and endogenous antioxidants since enzymatic antioxidants have been discussed extensively in several reviews.

**Keywords:** antioxidants, nonenzymatic, endogenous, exogenous, low-molecular weight antioxidants, mechanism
