INSTITUTO DE BIOQUIMICA Y MEDICINA MOLECULAR PROFESOR ALBERTO BOVERIS
Unidad Ejecutora - UE
capítulos de libros
Thermodynamics and kinetics: limitations for biochemical actions of plant polyphenols
C. G. FRAGA; G. SAGDICOGLU CELEP; M. GALLEANO
Plant Phenolics and Human Health: Biochemistry, Nutrition, and Pharmacology
The benefits of polyphenols on human health are very often ascribed to their potential ability to act as antioxidants. This assumption is based on polyphenol chemical structures supporting scavenging of free radical and chelation of redox-active metals. In this chapter we will use physical chemistry tools to analyze the antioxidant actions of polyphenol from a physiological perspective. Thermodynamic analysis predicts that both antioxidant actions are energetically favored, stressing the chemical feasibility of flavonoids as potential free radical scavengers and/or metal chelators. Nevertheless, the actual concentrations reached by polyphenols in animal and human tissues are incompatible with the kinetic requirements necessary to reach reaction rates of physiological relevance. Alternative biochemical mechanisms can explain the observed in vitro and in vivo antioxidant effects, such as the associated to polyphenol-lipid and polyphenol-protein interactions. These mechanisms do not completely preclude a direct free radical or metal chelating action, but are more consistent with polyphenol levels found in tissues.