Analytical approaches for investigating functional properties of polyphenols

Polyphenols are phytochemicals that are raising great interest in the scientific world for their potential health-promoting effects. These compounds are characterized by a wide range of molecules, classified as flavonoids (i.e. flavonols, flavanols, flavones, flavanones, isoflavones, and anthocyanins) and non-flavonoids (i.e. phenolic acids, hydroxycinnamic acids, lignans, stilbenes, and tannins), depending on their chemical structure. In the last years, polyphenols deriving from different food matrices, including food wastes and by-products, are being investigated for a broad spectrum of positive biological activities. Several studies have shown polyphenols ability in reducing oxidative stress and inflammation, that are common conditions mainly in chronic diseases such as type-2 diabetes, cardiovascular and inflammatory bowel diseases. These effects can be evaluted by several methods, starting with in vitro assays. The aim of this lesson is to give an overview of the main methods that can be used to assess: 1-antioxidant activity (e.g. spectrophotometric methodologies such as 2,2-diphenyl-1-picrylhydrazyl radical scavenging- (DPPH), Folin-Ciocalteu, or ferric reducing antioxidant power (FRAP) assay, etc.); 2- anti-inflammatory activity (e.g. using in vitro models of gastric inflammation); 3- biological activity on key enzymes involved in diabetes mellitus pathway (e.g. dipeptidyl-peptidase IV). These methods could be useful to understand the potentiality of food polyphenols in human health and to the select the most promising molecules to formulate functional foods or dietary supplements.