Flavonoid-bearing probes have been designed and synthesized to explore their ability to selectively capture target proteins or biosynthetic enzymes under oxidative activation. A proof-of-concept study using biotinylated (epi)catechin-bearing affinity-based probes herein demonstrates the ability of these probes to capture the LDOX flavonoid enzyme using sodium periodate as the oxidant.

As election of bioactive polyphenols of different structural classes, such as the ellagitannins vescalagin and vescalin, the flavanoidsc atechin, epicatechin,e pigallocatechin gallate (EGCG), and procyanidin B2, and the stilbenoids resveratrol and piceatannol, were chemically modified to bear ab iotin unit for enabling their immobilization on streptavidin-coateds ensor chips. These sensorc hips were used to evaluate in real time by surfacep lasmon resonance(SPR) the interactionso fthree different surface-bound polyphenolic ligandsp er sensorc hip with variousp rotein analytes, including human DNA topoisomerase IIa,f lavonoid leucoanthocyanidin dioxygenase, B-cell lymphoma 2a poptosis regulator protein,a nd bovine serum albumin. The types and levels of SPR responses unveiled major differences in the association,o rl ack thereof,a nd dissociation between ag iven protein analyte and different polyphenolic ligands. Thus,t his multi-analysis SPR technique is av aluablem ethodology to rapidly screena nd qualitatively compare various polyphenol-protein interactions.

Interactions between plant polyphenols and biomacromolecules such as proteins and pectins have been studied by several methods in solution (e.g. isothermal titration calorimetry, dynamic light scattering, nuclear magnetic resonance and spectrophotometry). Herein, these interactions were investigated in real time by Surface Plasmon Resonance (SPR) analysis after immobilization of flavan-3-ols onto a sensor chip surface. (−)-epicatechin, (+)-catechin and flavan-3-ol oligomers with an average degree of polymerization of 2 and 8 were chemically modified using N-(2-(tritylthio)ethyl)propiolamide in order to introduce a spacer unit onto the catecholic B ring. Modified flavan-3-ols were then immobilized onto a carboxymethylated dextran surface (CM5). Immobilization was validated and further verified by evaluating flavan-3-ol interaction with bovine serum albumin (BSA), poly-l-proline or commercial pectins. BSA was found to have a stronger association with monomeric flavan-3-ols than oligomers. SPR analysis of selected flavan-3-ols immobilized onto CM5 sensor chips showed a stronger association for citrus pectins than apple pectins, regardless of flavan-3-ol degree of polymerization.