Natural polyphenols as versatile materials for applications in biomedical and food sectors : powering their potential by chemical manipulation and green methodologies

In the last decade the versatility of polyphenol chemistry and the unparalleled bioactivities exhibited by many of these compounds has increasingly been appreciated and largely translated into advanced biomedical and technological applications. The activity of natural phenols is primarily associated to their antioxidant potential, but is ultimately expressed in a variety of biological effects. Molecular scaffold manipulation of this large class of compounds is a currently pursued approach to boost or modulate their properties. These strategies that include conjugation with biological thiols, selenylation, and polymerization will be presented [1,2] together with other examples showing how to impart biological activities to phenolic polymers, e.g. sulfation of polymers from tyrosol providing a new class of non-saccharidic heparin mimetics anticoagulants (figure, panel A ). [3] Nowadays, the remarkable antioxidant properties have also prompted the use of natural phenolic compounds not only as food supplements, but also as additives for the development of functional materials. The presentation will be therefore focused on relevant examples of how natural phenols can be exploited as multifunctional compounds in the food, cosmetic, and biomedical sectors. Particular attention will be paid to phenolic compounds from agri-food wastes such as spent coffee grounds (figure, panel B), exhausted woods from tannin industrial production, and nut shells, which are rich in phenolic polymers including lignin and tannins, endowed with very potent antioxidant properties. [4,5] The possibility to further improve these antioxidant properties through chemical manipulation will also be presented, together with efficient and green strategies for the recovery of phenolic compounds based on the use of ball milling and/or deep eutectic solvents (DES). [6]