Titre du document / Document title

Elucidation of the partial structure of polymeric thearubigins from black tea by chemical degradation

Auteur(s) / Author(s)

OZAWA T. ⁽¹⁾ ; KATAOKA M. ⁽¹⁾ ; MORIKAWA K. ⁽¹⁾ ; NEGISHI O. ⁽¹⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Iharaki 305, JAPON

Résumé / Abstract

Butanol-soluble neutral and acidic thearubigins were prepared by a combination of solvent extraction, fractional precipitation, and Toyopearl column chromatography. These pigments showed similar properties to those of Roberts' thearubigins on the paper chromatogram, and a convex broad band with several peaks on reversed-phase HPLC. The thearubigins were methylated, degallated, and chemically degraded with KMnO₄ under alkaline conditions. From the degradation products, methyl esters of 4-methoxy benzoic acid, 3,4-dimethoxy benzoic acid, 3,4,5-trimethoxy benzoic acid, 3,4-dimethoxy-1,2-benzenedicarboxylic acid, 3,4-dimethoxy-1,5-benzenedicarboxylic acid, 3,4-dimethoxy-1,6-benzenedicarboxylic acid, 3,4,5-trimethoxy-1,2-benzenedicarboxylic acid, 4,5,6-trimethoxy-1,2,3-benzenetricarboxylic acid, 4,5,4',5'-tetramethoxy-2,2'-diphenic acid, and 3,4,5,3',4',5'-hexamethoxy-2,2'-diphenic acid were detected by using GC-MS and GC-SIM. The butanol-soluble neutral thearubigins, which had been purified by Toyopearl column chromatography, were hydrolyzed by treating with HCl-BuOH. Cyanidin and delphinidin were identified in the reaction mixture. These results suggest that thearubigins are heterogeneous polymers of flavan-3-ols and flavan-3-ol gallates which have a bond at C4, C6, C8, C2', C5', and C6' in the flavan-3-ol units. In addition to the C4-C8 or C6 interflavanoid linkage, a C6'-C6' linkage was also found, and a possible partial structure for thearubigin is proposed.

Revue / Journal Title

Bioscience, biotechnology, and biochemistry    ISSN  0916-8451 

Source / Source

1996, vol. 60, n^o12, pp. 2023-2027 (27 ref.)

Langue / Language

Anglais

Editeur / Publisher

Japan Society for Bioscience Biotechnology and Agrochemistry, Tokyo, JAPON  (1992) (Revue)

Mots-clés anglais / English Keywords

Vegetal tannin

;

Tea

;

Purification

;

Structural analysis

;

Molecular structure

;

Polyphenol

;

Mots-clés français / French Keywords

Tanin végétal

;

Thé

;

Purification

;

Analyse structurale

;

Structure moléculaire

;

Théarubigine

;

Polyphénol

;

Mots-clés espagnols / Spanish Keywords

Tanino vegetal

;

Té

;

Purificación

;

Análisis estructural

;

Estructura molecular

;

Polifenol

;

Localisation / Location

INIST-CNRS, Cote INIST : 8935, 35400006333877.0200