(-)-epicatechin Biology Criollo cocoa Food Maillard reaction Nrf2 PPAR-γ Research Social aspects antioxidant activity antioxidant capacity antioxidants apoptosis borderline hypertensive rats catechin cherry extract chocolate cocoa cocoa by-products cocoa extract cocoa polyphenols conching enzyme inactivation epicatechin flavan-3-ol flavonoids fourier transform infrared spectroscopy heat treatment human endothelial cell inflammatory markers