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-MSn 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-MSn analysis. This study provided a reliable dynamic data description and metabolic pathway of tea polyphenols for postfermented pu-erh tea.