LC-MSn study of the chemical transformations of hydroxycinnamates during yerba maté (Ilex paraguariensis) tea brewing.

Yerba maté is one of the most popular beverages in South American countries and its consumption is associated with a wide array of health effects. In this study, we used advanced HPLC-ESI-MSn and HPLC-ESI-HRMS methods for the identification and characterization of hydroxycinnamates and their derivatives formed during the brewing process of yerba maté. We report on the hydroxylation of the hydroxycinnamates cinnamoyl substituent by conjugate addition of water to form 3-hydroxy-dihydrocinnamic acid derivatives using a series of model compounds, including caffeoylglucoses, dicaffeoylquinic acids, methyl caffeoylquinate and mono caffeoylquinic acids. The regiochemistry of conjugate addition was determined by targeted tandem MS experiments performed on authentic standards. It was interesting to note that hydroxylation of hydroxycinnamates produced cis and acyl-migration isomers, which is in line with previously reported data.