In the present study, different tea samples were scientifically classified
based on their antioxidant activities and their antioxidant activities
were comprehensively evaluated by the combination of principal
component analysis, hierarchical clustering analysis and the on-line
HPLC–DPPH assays.The bioactive compounds which contributed
to the antioxidant activity of tea were found out, and their Trolox
equivalent antioxidant capacities (TEACs) and contributions to the
antioxidant activity were investigated. We found that catechin components
especially EGCG contributed greatly to the antioxidant activity
of tea, they decreased during tea fermentation and led to the
reduction of antioxidant activity. Moreover, we established a simple
and rapid method for simultaneous capture of chemical quantitative
analysis and bioactivity evaluation by determining contents of the
bioactive compounds for the first time. This method could provide a
comprehensive evaluation of tea and its derived products