Role of dietary antioxidant (-)-epicatechin in the development of ?-lactoglobulin fibrils

Under specific physico-chemical conditions ?-lactoglobulin is seen to form fibrils structurally highly similar to those that are formed by the amyloid-like proteins associated with neurodegenerative disorders, such as Alzheimer and Parkinson diseases. In the present study we provide insights on the possible role that the dietary flavonoid (-)-epicatechin plays on ?-lactoglobulin fibril formation. Fibril formation is induced by keeping ?-lactoglobulin solutions at pH 2.0 and at a temperature of 80 °C for 24 h. Atomic Force Microscopy measurements suggest that, by adding (-)-epicatechin in the solution, fibrils density is visibly lowered. This last observation is confirmed by Fluorescence Correlation Spectroscopy experiments. With the use of Fourier Transform IR spectroscopy we monitored the relative abundances of the secondary structures components during the heating process. We observed that in the presence of (-)-epicatechin the spectral-weight exchange between different secondary structures is partially inhibited. Molecular Dynamics simulations have been able to provide an atomistic explanation of this experimental observation, showing that (-)-epicatechin interacts with ?-lactoglobulin mainly via the residues that, normally in the absence of (-)-epicatechin, are involved in ?-sheet formation. Unveiling this molecular mechanism is an important step in the process of identifying suitable molecules apt at finely tuning fibril formation like it is desirable to do in food industry applications.