Change in tea polyphenol and purine alkaloid composition during solid-state fungal fermentation of postfermented tea

The aim of this study was to evaluate tea polyphenol and purine alkaloid contents of pu-erh tea (Camellia assamica) in a fermentation solid system with Aspergillus niger and Aspergillus fumigatu. In addition, the objective was to find the major intermediate product during fermentation by HPLC-MS(n) analysis. The results showed the change of catechin, ester-catechins and gallic acid by quantitative analysis. In the early stages, the contents of ester-catechins were lightly increased. Then, ester-catechins were gradually degraded to produce catechins and gallic acid. Furthermore, a major metabolic intermediate compound of catechins was observed and elucidated by HPLC-DAD-MS(n) analysis. This study provided a reliable dynamic data description and metabolic pathway of tea polyphenols for postfermented pu-erh tea.