1 - Overview of polyphenols and their properties

Abstract

Today, polyphenols represent one of the most well-known secondary plant metabolites characterized by a large and diverse array of unique bioactive properties, which makes them highly appreciated for their beneficial effects on both plants and humans. Polyphenols are compounds that are structurally extremely different, but essential for a variety of functions in plants, responsible for organoleptic and nutritional properties of plant-derived foods, and useful for numerous practical applications. In this introductory chapter, the basic information on polyphenols is presented, covering their historical background, evolution of the chemical definition of polyphenols, and different ways of their classification. The structural diversity of polyphenols is elaborated and related to their common food sources. The basic physicochemical properties of polyphenols, especially the reducing capacity and binding properties (metal chelating activity and protein–polyphenol complexation), are thoroughly elaborated. Different mechanisms of the main bioactive feature of polyphenols and their antioxidant properties are outlined, as well as mechanisms governing their oxidation, reactivity with dioxygen (autoxidation), and modulation of oxidative damage. Additionally, recent progress in the models for probing the antioxidant activity of polyphenols in the gastrointestinal tract and the effects of controlled polyphenol-rich foods on selected parameters of oxidative stress after consumption are presented.