THE ROLE OF (-)-EPICATECHIN AND POLYPHENOL OXIDASE IN THE COUPLED OXIDATIVE BREAKDOWN OF THEAFLAVINS

An enzymic in-vitro model tea fermentation system has been used in com bination with gradient elution reversed-phase HPLC to study the oxidat ive breakdown of black tea theaflavins in the presence and absence of (-)-epicatechin. It was found that theaflavin, theaflavin-3-monogallat e, theaflavin-3'-monogallate and theaflavin-3,3'-digallate were not su bstrates for tea polyphenol oxidase (EC 1.14.18.1) whereas (-)-epicate chin alone, or mixtures of (-)-epicatechin and a theaflavin were rapid ly converted to a complex mixture of thearubigin-like substances. Whil e the chromatographic profiles varied with the identity of the theafla vin precursor each resembled the equivalent profile obtained with a wh ole black tea liquor. It is concluded that theaflavins are degraded by a coupled oxidation with (-)-epicatechin-quinone. It is suggested tha t thearubigins may form via these pathways during black tea manufactur e.