*2.2. Sample Preparation*

The 30 common Chinese teas are widely consumed and famous in China. The basic information of these teas is presented in Table 1. The fat-soluble, water-soluble, and bound-insoluble fractions of these teas were acquired using tetrahydrofuran, methanol-acetic acid-water (50:3.7:46.3, *v*/*v*/*v*), and diethyl ether-ethyl acetate (1:1, *v*/*v*) with alkaline digestion according to the procedures described in the literature [16–18]. All extracts were preserved at −20 ◦C before being subjected to relevant tests.

#### *2.3. Ferric-Reducing Antioxidant Power (FRAP) Assay*

The ferric-reducing antioxidant power (FRAP) assay was conducted according to the method established by Benzie and Strain [19]. FeSO4 was used as the standard, and the value was presented as μmol Fe(II)/g dry weight (DW) of the tea.

#### *2.4. Trolox Equivalent Antioxidant Capacity (TEAC) Assay*

The Trolox equivalent antioxidant capacity (TEAC) assay was performed based on the procedure reported by Re et al. [20]. Trolox was applied as the standard, and the value was displayed as μmol Trolox/g DW of the tea.

#### *2.5. Determination of Total Phenolic Content (TPC)*

Determination of total phenolic content (TPC) was carried out as described by Singleton et al. [21]. Gallic acid was adopted as the standard, and the value was described as mg gallic acid equivalent (mg GAE)/g DW of the tea.

#### *2.6. Detection of Phytochemicals by High-Performance Liquid Chromatography (HPLC)*

Ca ffeine, theaflavine, and polyphenols in the extracts were detected by HPLC based on the literature reported by Cai et al. [22] with small alterations. Briefly, the testing system was comprised of a Waters (Milford, MA, USA) 1525 binary HPLC pump separation module with an auto-injector, a Waters 2996 photodiode array detector (PDAD) and an Agilent Zorbax Extend-C18 column (250 × 4.6 mm, 5 μm, Santa Clara, CA, USA). Gradient elution was performed at 35 ◦C with the mobile phase composed of methanol (solution A) and 0.1% formic acid solution (solution B), which were routinely delivered at a flow rate of 1.0 mL/min according to the procedure: 0 min, 5% (A); 10 min, 20% (A); 15 min, 22% (A); 20 min, 25% (A); 40 min, 40% (A); 50 min, 42% (A); 60 min, 50% (A); 70 min, 95% (A); 70.10 min, 5% (A); 75 min, 5% (A). A 20 μL of extract sample was injected for HPLC analysis. The spectra were recorded between 200 and 600 nm, and the targeted compounds were identified by retention time and UV-Vis spectra in comparison with the standards and quantified based on the peak area under the maximum absorption wavelength. The value was expressed as mg/g DW of the tea.


**Table 1.** Basic information about the 30 Chinese teas.
