Abstract: This study was conducted to investigate the chemical composition and potential bioactivity of fermented dark tea with Pericarpium Citri Reticulatae in comparison with those of raw dark tea. The differences in the contents of the main chemical components between raw dark tea from two manufacturers and fermented dark tea with Pericarpium Citri Reticulatae made with each of them. The influence of fermentation on the chemical composition of fermented dark tea with Pericarpium Citri Reticulatae was observed using ultra-high performance liquid chromatography coupled with Q-exactive quadrupole/electrostatic field orbitrap mass spectrometry (UPLC-Q-Exactive-MS) combined with principal component analysis (PCA). Furthermore, the inhibitory effect of the boiling water extract from fermented dark tea with Pericarpium Citri Reticulatae on α-amylase and α-glucosidase was tested. The results showed that the content of tea polysaccharides decreased after fermentation. The content of flavonoids did not change significantly remaining in the range between 2.69% and 3.29%. After fermentation, the content of tea polyphenols decreased from 14.96% to 8.99%–12.44%. The score plot of PCA indicated that fermented dark tea with Pericarpium Citri Reticulatae could be separated from raw dark tea because of the significant variation in the main components between them. A total of 31 compounds that greatly differed between the fresh and aged samples of fermented dark tea with Pericarpium Citri Reticulatae including phenolic acids, flavanols and flavonoids were identified by comparison with the database library. These compounds were detected in all samples of fermented dark tea with Pericarpium Citri Reticulatae and they showed the same trend with aging time, among which, the relative contents of 13 compounds increased, while those of 17 compounds decreased and the remaining one remained basically unchanged. The inhibiting or activating effect of fermented dark tea Pericarpium Citri Reticulatae on α-amylase differed between the two kinds of raw dark tea. Sample 1-1 showed high inhibitory effect on α-amylase at three concentrations tested and its effect increased with increasing concentration. Sample 1-2 had a strong inhibition effect on α-amylase only at low concentration. All samples had inhibitory effect on α-glucosidase; the inhibitory effect of sample 2-1 was weak, while that of the other samples was strong. The half-maximum inhibitory concentration (IC50) of fermented dark tea with Pericarpium Citri Reticulatae for lipase was high, indicating its weak anti-lipase effect.

Key words: fermented dark tea with Pericarpium Citri Reticulatae; high-resolution mass spectrometry; chemometrics; material basis; α-amylase; α-glucosidase; lipase