Dynamic Profiling of Phenolic Acids during Pu-erh Tea Fermentation Using Derivatization Liquid Chromatography–Mass Spectrometry Approach

Pu-erh tea, a famous traditional Chinese tea with multiple health benefits, is produced by microbial fermentation. It has been reported that major known bioactive compounds in green tea, e.g. epicatechin, epigallocatechin gallate, and theanine, decreased during fermentation. Then which components account for the benefits of Pu-erh tea? Phenolic acids are aromatic secondary metabolites and possess various biological properties. In this research, phenolic acids in Pu-erh tea were investigated qualitatively and quantitatively to reveal the influence of fermentation and their potential effects using 5-(diisopropylamino)amylamine (DIAAA) derivatization-ultrahigh performance liquid chromatography-quadrupole-time-of-flight/mass spectrometry (UHPLC-Q-TOF/MS) approach. A total of 33 phenolic acids were determined, and most of them were detected in Pu-erh tea for the first time. Moreover, gallic acid and theogallin were the major components in ripened and raw Pu-erh tea, respectively. Dynamic profiling revealed the increase of simple phenolic acids and the decrease of most of phenolic acid esters during Pu-erh tea fermentation. These results provided firm basis for practical fermentation and quality control of Pu-erh tea.