Polyphenols from Root, Tubercles and Grains Cropped in Brazil: Chemical and Nutritional Characterization and Their Effects on Human Health and Diseases

Abstract

Throughout evolution, plants have developed the ability to produce secondary phenolic metabolites, which are important for their interactions with the environment, reproductive strategies and defense mechanisms. These (poly)phenolic compounds are a heterogeneous group of natural antioxidants found in vegetables, cereals and leguminous that exert beneficial and protective actions on human health, playing roles such as enzymatic reaction inhibitors and cofactors, toxic chemicals scavengers and biochemical reaction substrates, increasing the absorption of essential nutrients and selectively inhibiting deleterious intestinal bacteria. Polyphenols present in some commodity grains, such as soy and cocoa beans, as well as in other vegetables considered security foods for developing countries, including cassava, taro and beetroot, all of them cropped in Brazil, have been identified and quantified in order to point out their bioavailability and the adequate dietary intake to promote health. The effects of the flavonoid and non-flavonoid compounds present in these vegetables, their metabolism and their effects on preventing chronic and degenerative disorders like cancers, diabetes, osteoporosis, cardiovascular and neurological diseases are herein discussed based on recent epidemiological studies.

Keywords: beetroot; cassava; cocoa nibs; soybeans andantioxidant activity; taro.

Figure 1

Schematic representation of the main classes and subclasses of phenolic compounds and their respective chemical structure backbone, where C6 corresponds to the aromatic ring and C1, C2 or C3 refers to side chains or intermediate chains.

Figure 2

Chemical structures of phenolic acids, adapted from the database “Polyphenol content in foods” (http://phenol-explorer.eu). Gallic acid and vanillin acid belongs to benzoic acids subclass, characterized by a backbone composed of 7 carbons (C6-C1). Caffeic acid, ferric acid and p-coumaric acid represent the cinnamic acids subclass and exhibit a backbone composed of 9 carbons (C6-C3) [1].

Figure 3

Representative chemical structures of the main subclasses and basic structure of the majority of flavonoids, adapted from the database “Polyphenol content in foods” (http://phenol-explorer.eu) [1].

Figure 4

Chemical structures of the stilbene and lignan classes, adapted from the database “Polyphenol content in foods” (http://phenol-explorer.eu) [1].

Figure 5

Polyphenolsfrom vegetables popularly consumed in Brazil—taro, beetroot, cassava, soybean and cocoa—and their effects on human health promotion and diseases.