IN-VITRO STUDIES ON THE EFFECT OF POLYPHENOL OXIDASE AND PEROXIDASE ON THE FORMATION OF POLYPHENOLIC BLACK TEA CONSTITUENTS

Flavanols (catechins and gallocatechins) isolated from green tea leaves (Camellia sinensis (L) O Kuntze) were treated in vitro with polyphenol oxidase, peroxidase and a combination of both. The flavanol levels and those of the products formed were monitored by reversed-phase high-performance liquid chromatography (HPLC) using spectrophotometric detection at 280 and 380 nm. Flavanols and theaflavins were quantified, whilst integrated peak areas are given for the remaining compounds. After fermentation in the presence of polyphenol oxidase higher levels of theaflavins and resolved thearubigins were obtained, whilst peroxidase produced higher amounts of chromatographically unresolved thearubigins of higher molecular weight, observed as a rise in the HPLC baseline. In the presence of peroxidase a significant decrease in the levels of all flavonol glycosides was observed, whilst in the presence of polyphenol oxidase only myricetin glycoside levels decreased.