38] Antioxidant effects of carotenoids in Vivo and in Vitro: An overview

Abstract

This chapter discusses the antioxidant effects of carotenoids in vivo and in vitro state. It describes their role as biological antioxidants in radical-initiated processes, both in vitro and in vivo. Biological antioxidants are compounds that protect biological systems against the potentially harmful effects of processes or reactions that can cause excessive oxidations. Several mechanisms have been suggested for carotenoid protection in biological systems, which include the deactivation of electronically activated species, such as singlet oxygen and the deactivation of reactive chemical species, such as peroxyl or alkoxyl radicals that can be generated within cells and might otherwise initiate harmful oxidative reactions. Antioxidant action is well documented in a number of in vitro studies, including lipids in homogeneous solutions, liposomes, isolated membranes, and intact cells. This antioxidant activity is related to the chemical structures of the carotenoids and it has been reported to be particularly effective at low oxygen tensions. Antioxidant action of the molecules seems a likely basis for the effects of carotenoids, and this chapter evaluates the available evidence for this explanation of in vivo biological activity.