Polyphenols

Abstract

Polyphenols are a very diverse and multi-functional group of phytochemicals, widely found throughout the plant kingdom. Their basic monomer chemical structure comprises a phenolic ring-a benzene ring(s) with at least one hydroxyl group attached to it. The main classes of polyphenols are tannins, lignans, phenolic acids, phenolic alcohols, flavonoids, stilbenes, coumarins and chalcones. Flavonoids are the most plentiful classes of polyphenols, since they represent ≈4000 out of 8000 polyphenols already identified. Polyphenols are also classified, merely, as flavonoids and non-flavonoids. Flavonoids are chemically composed of backbone of two benzene rings linked by a 3 carbon atoms in a chain from the pyran ring. The oxidation state of central carbon can be used to subclassify them (flavonoids): flavanones, flavanols, flavonols, isoflavonoids, flavones, and anthocyanidins. Rich sources of phenolic compounds include grape pomace, apple, berries, oranges, pomegranate, tomatoes, coffee, tea, wine, olive oil, among others. The remarkable chemical structure of polyphenols leads to their biological and physiological activities, mainly due to their antioxidant activity. Regarding the effects of polyphenols on human health, the phenolics have many health-promoting benefits, including antimutagenic, antihypertensive, hypoglycemic and antihyperglycemic, anticancer and antiapoptotic, antimicrobial, and inflammatory effects. Furthermore, when the phenolic antioxidants are added in food products, they can delay the generation of toxic products (oxidation), to act as rancidity regulator and maintaining nutritional quality of foods, among others. This chapter describes the principal sources of poly-phenols and then correlated their properties (health), particularly absorption (bioavailability), metabolism, gut flora, chronic disease (cardiac health, obesity, diabetes, cancer, among others).