title: Reaction of the black tea pigment theaflavin during enzymatic oxidation of tea catechins.
abstract: Degradation of the black tea pigment theaflavin was examined in detail. Enzymatic oxidation of a mixture of epigallocatechin and epicatechin initially produced theaflavin, while prolonged reaction decreased the product. Addition of ethanol to the reaction mixture at the point when theaflavin began to decrease afforded four new products, together with theanaphthoquinone, a known oxidation product of theaflavin. The structures of the new products were determined by spectroscopic methods. One of the products was an ethanol adduct of a theanaphthoquinone precursor, and this reacted with theaflavin to give two further products. A product generated by coupling of theaflavin with epicatechin quinone was also obtained. The structures of the products indicate that oxidation and coupling with quinones are key reactions in the degradation of theaflavins. The degradation of theaflavin probably contributes to production of thearubigins.
authors.affiliation: Laboratory of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, Bunkyo-Machi 1-14, Nagasaki 852-8521, Japan.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Akane
authors.initials: A
authors.lastname: Shibahara
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Matsuo
authors.forename: Takashi
authors.initials: T
authors.lastname: Tanaka
authors.forename: Isao
authors.initials: I
authors.lastname: Kouno
mesh_terms: D044946:Biflavonoids / Q000737:chemistry / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D013662:Tea / Q000737:chemistry*
chemical_list: D044946:Biflavonoids; D013662:Tea; C056068:theaflavin; D002392:Catechin; C057580:gallocatechol