Collagen-Catechin Interactions: a NMR Approach

This work focuses on understanding at molecular level the mechanism of interaction between collagen and catechin. Interactions were investigated by NMR measurements both in solution and in solid state. It was also explored the possibilities offered by NMR to characterize the effect of catechin on the stability of collagen to oxidation. Collagen type I fibres were used throughout the study. Collagen was treated with two different concentration of catechin. Oxidation was carried out by incubation of collagen solution with three different oxidation systems (Fe(II)/H2O2; Cu(II)/H2O2; NaOCl/H2O2). High resolution 1D 1H and 2D spectroscopy were recorded at 30°C on Bruker Avance 400. Solid state NMR experiments were performed by a Bruker spectrometer equipped with a CP-MAS accessory. Data obtained from 1D and 2D proton NMR and 13C CP MAS spectroscopy pointed out that interactions between collagen and catechin preferentially occurred between catechin B ring and the amino acids proline and hydroxyproline. Oxidation studies carried out by metal/H2O2 systems on collagen showed that both iron and copper were able to interact with collagen by site specific attak. Oxidation studies performed on collagen in interaction with catechin pointed out that the ligand was able to protect collagen proline from oxidation by metal/H2O2 systems. The protective effect of catechin towards collagen oxidation was markedly evident for the copper oxidation system