2 2 azino bis 3 ethylbenzothiazoline 6 sulfonic acid abts

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.

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).