ABSTRACT
A nutrient is defined as any substance that has nutritious qualities, i.e., that
nourishes or promotes growth, and one that can be metabolized by an organism to
give energy and build tissue. In this chapter a nutrient is assumed to be an amino
acid, carotenoid, vitamin C, vitamin E, and other antioxidants such as polyphenols
(Fig. 1 shows the structures of some important antioxidants discussed in chapter).
While carotenoids, vitamin E, and vitamin C are often regarded as our most
important dietary antioxidants, little is known of their possible interactions. The
aim of this chapter is to discuss such interactions and to suggest how these may
explain possible synergistic protective effects as well as how deleterious effects
could arise. The carotenoids we consume, from our foods, food colorants, and
possibly as dietary supplements, are thought to be antioxidants both by quenching
singlet oxygen and by scavenging free radicals. This chapter concerns free radical
reactions; readers interested in singlet oxygen may consult recent reviews (1,2) and
the recent study of singlet oxygen quenching by carotenoids in liposomes (3).
