CHARACTERIZATION OF FLAVONOIDS BY LIQUID-CHROMATOGRAPHY TANDEM MASS-SPECTROMETRY

Thermospray LC-MS-MS was used to study a catechin mixture extracted from the tea plant Camellia sinensis. Four major catechins, (-)-epicatechin, (-)-epipllocatechin, (-)-epicatechin 3-0-gallate, and (-)-epigallocatechin 3-0-gallate were quickly recognized in the mixture by their [M + H]+ ions. Collission-induced dissociation (CID) spectra of the [M + H]+ ions gave simple fragmentation patterns, which permitted characterization of the substituents and the ring structures of the molecules. Several representative flavonoids and their glycosides were also studied by thermospray LC-MS-MS. Their CID spectra showed three types of ring cleavages in the pyran ring of the flavonoids, and differentiation among flavanone, flavone, and flavonol was made. LC-MS-MS appears to be the method of choice for the analysis of plant flavonoids including their glyosides.