Structural Annotation and Elucidation of Conjugated Phenolic Compounds in Black, Green, and White Tea Extracts

Advanced analytical approaches consisting of both LC-LTQ-Orbitrap
Fourier transformed (FT)-MS and LC-time-of-flight-(TOF)-MS coupled
to solid-phase extraction (SPE) NMR were used to obtain more insight
into the complex phenolic composition of tea. On the basis of the
combined structural information from (i) accurate mass fragmentation
spectra, derived by using LC-Orbitrap FTMSn, and (ii) proton NMR spectra, derived after LC-TOFMS triggered SPE
trapping of selected compounds, 177 phenolic compounds were annotated.
Most of these phenolics were glycosylated and acetylated derivatives
of flavan-3-ols and flavonols. Principal component analysis based
on the relative abundance of the annotated phenolic compounds in 17
commercially available black, green, and white tea products separated
the black teas from the green and white teas, with epicatechin-3,5-di-O-gallate and prodelphinidin-O-gallate
being among the main discriminators. The results indicate that the
combined use of LC-LTQ-Orbitrap FTMS and LC-TOFMS-SPE-NMR leads to
a more comprehensive metabolite description and comparison of tea
and other plant samples.