Ultrasound-Assisted Functionalization of Polyphenols

Natural polyphenols are a class of compounds that is available in quantities from renewable resources. Natural polyphenols, and among them especially lignins and tannins, thus represent important precursors for a variety of valorisations, ranging from the production of biofuel via the use as source for bulk aromatic chemicals to applications in material science areas. Ultrasonication has been used both for isolating and for subsequently valorising natural polyphenols. This chapter introduces important structural characteristics of lignins and tannins in order to set the background for a series of applications of ultrasound in connection with polyphenols; these applications comprise isolation methods as well as valorisation approaches.