Bioactive Polyphenols and Carotenoids

Abstract

Previously considered as anti-nutritional compounds, polyphenols have now gained a significant status in the functional foods industry as important health-promoting factors. Polyphenols can be in the form of simple phenolic acids with one aromatic ring or complex compounds that contain several rings joined together. Typical examples include caffeic acid, flavonoids, flavanols, anthocyanins, and proanthocyanidins. Polyphenols can be present in the free form or as covalently or non-covalently linked complexes with polysaccharides. The health benefits of polyphenols have been ascribed mainly to the antioxidant capacity, which is conferred by the presence of several electron-donating groups (e.g., -OH, –SH, and NH). Polyphenols can donate electrons to free radicals, which inactivates the toxic potential reactive oxygen and reactive nitrogen species. Inactivation of these reactive species helps to protect lipids and DNA from radical-induced damages, which can reduce the potential for development of chronic diseases like atherosclerosis and cancer. Polyphenols are also known to upregulate cellular production of antioxidant enzymes (e.g., catalase, glutathione peroxidase, superoxide dismutase) to enhance natural ability of tissues to deal with toxic compounds. As an agent against obesity, polyphenols upregulate cellular signaling to promote increased fatty acid oxidation and reduced lipid synthesis. Specific groups of polyphenols known as phytosterols are useful ingredients for the formulation of functional foods and nutraceuticals aimed at reducing plasma cholesterol contents.