**1. Introduction**

The growing resistance of pathogenic bacterial isolates against the traditional chemical antibiotics as well as the resurgent of old disappeared diseases associated with the constant consumers' demanding of healthier, nutritious and safe food has led the researchers to focus on searching for new, safe and effective molecules. One class of such molecules is the class of polyphenols. Polyphenols are a ubiquitous class of compounds largely present in plants as their secondary metabolites, which are synthesized during their normal development [1] in response to several stressful biotic and abiotic factors [2, 3]. This class of compounds are a much diversified group derived from the amino acids phenylalanine and tyrosine and

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© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

comprise simple phenols, hydroxybenzoic acids and cinnamic acid derivatives, flavonoids, coumarines, stilbenes and tannins, among others [4–6].

The results from the last decade's research have shown that polyphenols have important beneficial properties for human health, including antioxidative, antiaging, antibacterial and antimutagenic [7–11]. Moreover, the recent evidence of their interaction with proteins, DNA and other biological molecules has enhanced their exploitation for the production of new natural product-derived therapeutic agents. Despite these advantages, several limitations still persist, particularly those related with their extraction efficiency, which affects the large-scale use of some of these substances. The difficulties in screening, extracting, separation and purifying these compounds have increased the development of new and modern methods to address these limitations. In this context, the aim of this chapter is to present an updated review about sources, technologies and methods that have been developed until now to improve the extraction, detection, separation and full characterization of such beneficial compounds, with special emphasis to their possible application in the design of nutraceuticals and functional food products.
