2 2 diphenyl 1 picrylhydrazyl (dpph)

Cellulose acetate (CA, Mn ~30,000) was provided by Sigma-Aldrich (St. Louis, MO, USA). Acetone was purchased from Hengfa Chemical Reagent Co., Ltd. (Tianjin, China). Methanol anhydrous, anhydrous citric acid, sodium citrate, sodium chloride, sodium hydroxide, N, N-Dimethylacetamide (DMAc), and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) were obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Anhydrous ethanol was provided by Kermel Chemical Reagent Co., Ltd. (Tianjin, China). Hydrochloric acid was purchased from China Pingmei Shenma Group Kaifeng Dongda Chemical Co., Ltd. (Kaifeng, China).

Theaflavins (TF), theaflavin-3-gallate (TF2A), theaflavin-3′-gallate (TF2B), and theaflavin-3,3′-digitate (TF3), all with purities of 98%, were purchased from Chengdu Munster Biotechnology Co., Ltd. (Chengdu, China). Gallic acid, pyrogallol, 4-hydroxybenzoic acid, 3-hydroxyphenylacetic acid, phenylacetic acid, and 3-(3′,4′-dihydroxyphenyl) propanoic acid, all with purities of at least 98%, were purchased from Shanghai Yuanye Biotechnology Co., Ltd. (Shanghai, China).
2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,4,6-Tris(2-pyridyl)-s-triazine (TPTZ) were purchased from Sinopharm Chemical (Shanghai, China). Acetonitrile (LC/MS grade) was obtained from Merck (Darmstadt, Germany). Formic acid (LC/MS grade) was purchased from Fisher Scientific (Loughborough, UK). Deionized water (18.2 MΩ/cm) was prepared by distilling water through a Milli-Q water purification system (Millipore, Billerica, MA, USA). Other reagents were all of analytical grade.

All chemicals and reagents used were of analytical grade. The water was double distilled (ddH₂O). Methanol and acetonitrile of chromatographic purity were purchased from Sigma-Aldrich (St. Louis, MO, USA). N-hexane, ethyl acetate, gallic acid, NaOH, Folin–Ciocalteu, Na₂CO₃, Trolox, 2,2-diphenyl-1-picrylhydrazyl (DPPH), FeCl₃, HCl, NaAc, and 2,4,6-tris (2-pyridyl)-s-triazine (TPTZ) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).

In this study, most of the chemicals and reagents were analytical grade. Ethanol, ferric chloride, hydrogen peroxide, salicylic acid, sodium carbonate catechin, 2,2′-diphenyl-1-picrylhy-drazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) were purchased from Sinopharm Chemical Reagent Co. Ltd (Shanghai, China). Chemical standards including rutin (purity > 98%), luteolin (purity > 98%), apigenin (purity > 98%), quercetin (purity > 98%), luteolin-7-O-glucoside (purity > 98%) and kaempferol (purity > 98%) were purchased from Yuanye Biotechnology Co., Ltd. (Shanghai, China). HPLC grade reagents including methanol, acetonitrile and formic acid were purchased from Thermo Fisher Scientific (San Jose, CA, USA).

Instant dark tea was provided by Hunan Tea Industry Group Co. Ltd. (Changsha, China) with the fermentation of Eurotium Cristatum. Carboxylic acid (Trolox) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonicacid) diammonium salt (ABTS) were purchased from Shanghai Maclin Biochemical Reagent Co., Ltd. (Shanghai, China). Rutin, 2,2-diphenyl-1-picrylhydrazyl (DPPH), and phosphate buffer were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). Fluorescein and 2,2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH) were purchased from Aladdin Reagent Co. Ltd. (Shanghai, China). Folin-Ciocalteu reagent was purchased from Beijing Solarbio Science and Technology Co. Ltd. (Beijing, China). (-)-Epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-gallocatechin gallate (GCG), (-)-epicatechin gallate (ECG), (-)-epicatechin (EC), (-)-gallocatechin (GC), (-)-catechin gallate (CG), (+)-catechin (C), theobromine (TB), theacrine, and gallic acid were purchased from Aladdin Industrial Co. Ltd. (Shanghai, China) with the HPLC purity ≥98%. Simvastatin was purchased from Tianjin Huairen Pharmaceutical Co. Ltd. (Tianjin, China).

3-hexanone (chromatographic grade, Sigma-Aldrich); C8-C20 alkane mixture (Sigma-Aldrich); n-hexane (chromatographic grade, Ron); chloroform (AR, Sinopharm); Acetone (AR, Sinopharm); Folin-Ciocalteu (AR, Sinopharm); Gallic acid (AR, Sinopharm); Ascorbic acid (AR, Sinopharm); 2,2-diphenyl-1-picrylhydrazyl (AR, Sinopharm); 2,6-dichlorophenolindophenol (AR, Sinopharm); (+)-Catechin (AR, Sinopharm). 30 authentic volatile compound standards (Sigma-Aldrich).