Glycoside hydrolases for extraction and modifi cation of polyphenolic antioxidants

Antioxidants are important molecules that are widely used by humans, both as dietary supplements and as additives to different types of products. In this chapter, we review how flavonoids, a class of polyphenolic antioxidants that are often found in glycosylated forms in many natural resources, can be extracted and modifi ed using glycoside hydrolases (GHs). Glycosylation is a fundamental enzymatic process in nature, affecting function of many types of molecules (glycans, proteins, lipids as well as other organic molecules such as the fl avonoids). Possibilities to control glycosylation thus mean possibilities to control or modify the function of the molecule. For the fl avonoids, glycosylation affect both the antioxidative power and solubility. In this chapter we overview results on in vitro deglycosylation and glycosylation of fl avonoids by selected GHs. For optimal enzymatic performance, desired features include a correct specificity for the target, combined with high stability. Poor specifi city towards a specifi c substituent is thus a major drawback for enzymes in particular applications. Efforts to develop the enzymes as conversion tools are reviewed