Chapter 25 - Galloylation and Polymerization: Role of Structure to Antioxidant Activity of Polyphenols in Lipid Systems

Abstract

Many polyphenols are present in foods and nature as individual congeners, but also polymerized in oligomeric and polymeric entities. Flavanols and their condensed polymers, proanthocyanidins, are widespread components in green tea, red wine, cocoa, grape seeds and pine bark, with an extremely variable number of polyphenolic residues (polymerization degree) and galloyl moieties (galloylation). Polymerization and galloylation are key structural elements in the healthy outcome and antioxidant activity of polyphenols. The present chapter résumés how size and composition diversity, particularly polymerization and galloylation, influence the physicochemical properties relevant for the antioxidant activity of polyphenols in foods and biological systems: the radical scavenging ability, chelation on redox active metals, interfacial partitioning, redox capacity to regenerate, or to be regenerated by co-antioxidants and to inactivate/active pro-oxidants. To evaluate these structural-activity relationships, the physicochemical properties of polyphenols, evaluated either in vitro or in situ in biological systems, will be assessed together with their antioxidant efficiency in food and biological lipid systems.