Comprehensive characterization by LC-DAD-MS/MS of the phenolic composition of seven Quercus leaf teas

A complete characterization of the phenolic profile of leaves infusions from seven Mexican Quercus species was developed using different LC-DAD-MS/MS methodologies. The main families of phenolic compounds identified and quantified were: hydrolyzable tannins and flavonol glycosides, based on their fragmentation patterns and UV spectra, proanthocyanidins analyzed after acid-catalysis in the presence of phloroglucinol, and phenolic acids evaluated using UPLC-triple quadrupole mass spectrometer (QqQ). White oak species showed the largest amount of total phenols (830-2956 mg/L) with hydrolyzable tannins as the predominant group (60-96%), mainly vescavaloninic acid, vescalagin, and castalagin. Red species (total phenolics 129-280 mg/L), showing proanthocyanidins as the dominant family, consisted of units of catechin, gallocatechin and in less amount epicatechin gallate and epigallocatechin gallate and larger percentages of phenolic acids (10-19%).