Protective effects of dietary polyphenols in human diseases and mechanisms of action

Abstract

More than 8000 polyphenols have been identified from plants, and several hundreds of dietary polyphenols were characterized in foods, such as fruits, vegetables, grains, dry legumes, chocolate, and plant-derived beverages such as fruit juices, tea, coffee, and red wine. Polyphenols have potent antioxidant capacity because of the presence of hydroxyl groups in their structures and thus they can directly scavenge reactive oxygen species (ROS). Based on their structural characteristics, dietary polyphenols are divided into phenolic acids, flavonoids, stilbenes, tannins, and miscellaneous dietary polyphenols. There is evidence that consumption of foods and beverages rich in polyphenols plays a role in the prevention of inflammation-related diseases, cancer, cardiovascular diseases, neurodegenerative diseases, diabetes, obesity, and osteoporosis. Modulation of multiple cell signaling pathways, including transcription factor NF-E2-related factor 2, nuclear factor-?B, mitogen-activated protein kinases, cytokines, cyclooxygenases, lipoxygenases, apoptosis-related proteins, and cell cycle proteins could explain the antioxidant actions of dietary polyphenols. Their diverse pharmacological functions suggest that dietary polyphenols are compounds with good preventive potential in human diseases. In this chapter, we illustrate the predominant members of dietary polyphenols and their protective effects and mechanisms of action against ROS-induced oxidative stress and associated noncommunicable diseases.