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 combination with gradient elution reversed-phase HPLC to study the oxidative breakdown of black tea theaflavins in the presence and absence of (−)-epicatechin. It was found that theaflavin, theaflavin-3-monogallate, theaflavin-3′-monogallate and theaflavin-3,3′-digallate were not substrates for tea polyphenol oxidase (EC 1. 14. 18. 1) whereas (−)-epicatechin alone, or mixtures of (−)-epicatechin and a theaflavin were rapidly converted to a complex mixture of thearubigin-like substances. While the chromatographic profiles varied with the identity of the theaflavin precursor each resembled the equivalent profile obtained with a whole black tea liquor. It is concluded that theaflavins are degraded by a coupled oxidation with (−)-epicatechin–quinone. It is suggested that thearubigins may form via these pathways during black tea manufacture.

[1]  Shaun C Opie.  Black tea thearubigins , 1992 .

[2]  H. Nursten,et al.  Isolation and analysis of a polymeric thearubigin fraction from tea , 1992 .

[3]  A. Robertson.  The chemistry and biochemistry of black tea production — the non-volatiles , 1992 .

[4]  G. E. Who,et al.  IARC monographs on the evaluation of carcinogenic risks to humans. v. 51: Coffee, tea, mate, methylxanthines and methylglyoxal , 1991 .

[5]  H. Nursten,et al.  Comparative study of the reversed-phase high-performance liquid chromatography of black tea liquors with special reference to the thearubigins , 1991 .

[6]  M. Clifford,et al.  Black tea thearubigins—their HPLC separation and preparation during in‐vitro oxidation , 1990 .

[7]  U. Engelhardt,et al.  Theaflavins in black tea Comparison of the flavognost and HPLC analysis — preliminary in results , 1989 .

[8]  T. Tsushida,et al.  Effects of (-)-Epicatechin on Oxidation of Theaflavins by Polyphenol Oxidase from Tea Leaves , 1987 .

[9]  D. Bendall,et al.  Production and HPLC analysis of black tea theaflavins and thearubigins during in vitro oxidation , 1983 .

[10]  A. Robertson.  Effects of catechin concentration on the formation of black tea polyphenols during in vitro oxidation , 1983 .

[11]  D. Frost,et al.  The theaflavins of black tea , 1973 .

[12]  P. Coggon,et al.  Formation of epitheaflavic acid and its transformation to thearubigins during tea fermentation , 1971 .

[13]  D. Bendall,et al.  The purification and some properties of the polyphenol oxidase from tea (Camellia sinensis L.). , 1966, The Biochemical journal.

[14]  E. A. H. Roberts,et al.  The chemistry of tea manufacture , 1958 .

[15]  E. Roberts.  The phenolic substances of manufactured tea. II. — Their origin as enzymic oxidation products in fermentation , 1958 .

[16]  D. J. Wood,et al.  A study of the polyphenols in tea leaf by paper chromatography. , 1951, The Biochemical journal.