Stereochemistry of the Black Tea Pigments Theacitrins A and C
2016
Matsuo, Yosuke | Okuda, Keita | Morikawa, Hitomi | Oowatashi, Ryosuke | Saitō, Yoshinori | Tanaka, Takashi
Theacitrins A–C are yellow pigments of black tea that are produced by oxidative coupling of gallocatechins, i.e., flavan-3-ols with pyrogallol-type B-rings. However, their stereostructures have not yet been determined. In this study, DFT calculations of NMR chemical shifts of theacitrin C (1) and TDDFT calculations of the ECD spectra of theacitrinin A (5), a degradation product of theacitrin C (1), were used to determine the stereostructure of the theacitrins. Furthermore, the preparation of theacitrins A (4) and C (1) by enzymatic oxidation of an epigallocatechin (7) and epigallocatechin-3-O-gallate (2) mixture confirmed their structural relationship.
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