Sc. Opie et al., THE FORMATION OF THEARUBIGIN-LIKE SUBSTANCES BY IN-VITRO POLYPHENOL OXIDASE-MEDIATED FERMENTATION OF INDIVIDUAL FLAVAN-3-OLS, Journal of the Science of Food and Agriculture, 67(4), 1995, pp. 501-505
An enzymic in-vitro model tea fermentation system has been used in com
bination with gradient elution reversed-phase high-performance liquid
chromatography to study the formation from individual flavan-3-ols of
resolvable and unresolvable thearubigin-like substances. It has been f
ound that in 30 min at pH 5.6 tea polyphenol oxidase (EC 1.14.18.1) pr
oduces a distinctive range of resolvable thearubigin-like products fro
m each flavan-3-ol substrate examined ((+)-catechin, (-)-epicatechin,
(-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin
gallate). However, (-)-epicatechin, and to a much lesser extent (+)-c
atechin, were the only flavan-3-ols converted to an unresolvable thear
ubigin-like hump under these conditions. In addition, it was demonstra
ted that varying the pH of incubation in the range 5.0-6.0 had little
effect on the profile of products obtained from the simple catechins,
but a pronounced effect in the case of the gallocatechins. It is concl
uded that the combination of (-)-epicatechin and polyphenol oxidase is
the simplest model of tea fermentation that can be used to generate i
n quantity thearubigin-like materials for structure elucidation.