The Effect of Storage Time on Tea Polyphenols, Catechin Compounds, Total Flavones and the Biological Activity of Ya’an Tibetan Tea ( Camellia Sinensis )

The content of tea polyphenols (TPP), tea total flavones (TFS) and tea catechin compounds in Ya'an Tibetan tea after different storage times was investigated, and the alpha-glucosidase inhibition activity and antioxidative activity of tea were measured. Moreover, the correlation between the levels of tea catechins in Ya'an Tibetan tea with different storage years and their bioactivities were evaluated. During the period of storage, the content of Tibetan tea polyphenols decreased, and the content of Tibetan tea flavonoids increased significantly. Five catechins were identified in Ya'an Tibetan tea using UPLC-QqQ-MS/MS, and the Ya'an Tibetan tea had diverse antioxidant activities and alpha-glucosidase inhibitory activities over different storage years, due to the various tea catechin components. (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC) were found to be responsible for its strong antioxidant activity and alpha-glucosidase inhibitory activity, indicating Ya'an Tibetan tea has potential as a functional food. Practical applications Ya'an Tibetan tea, also called as Kangzhuan brick tea, is a typical Chinese dark tea with a dark brown color. The change of the main active substances and its bioactivity in Ya'an Tibetan tea during a long-term storage was obtained in this study. These findings have provided important reference basis for people to have a better understanding of the chemical constituents and bioactivity of Ya'an Tibetan tea which store for a long time. Moreover, our study showed Ya'an Tibetan tea has high antioxidant activity and alpha-glucosidase inhibitory activity. These findings will improve product quality and upgrade Ya'an Tibetan tea industry, and promotes Tibetan tea economic development.