Identification of Roasting Reaction Products of Catechin Exhibiting Xanthine Oxidase Inhibitory Activity

Food processing and cooking methods that involve high-temperature heating (such as roasting) alter the composition of raw food materials. Even polyphenols, which are generally considered thermally stable, undergo changes in their chemical structure during roasting. This study investigated the roasting reaction of catechin, a functional polyphenol, at a temperature of approximately 200ºC and found that it enhanced xanthine oxidase inhibitory activity. Purification and separation of the products derived from the catechin roasting reaction revealed two types of moderately active compounds: dimeric products with a linkage between the C and A rings, and an aurone-like benzofuran product. Additionally, several fractions containing oligomeric products were identified as highly active fractions. These results suggest that catechin enhances xanthine oxidase inhibitory activity by transforming into dimeric, aurone-type, and probably oligomeric products.